RESCON 2024

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A morphological character-based taxonomic review of the genus Sargassum C. Agardh (phaeophyta) in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Palihawadana, D. K.; Kariyawasam, I. U.
Sargassum C. Agardh (1820) is the most species-rich genus within the family Sargassaceae. It is abundantly distributed in tropical and subtropical regions of the world. In Sri Lanka, Sargassum is recognized as the most economically important seaweed genus. However, the current taxonomic status of the genus Sargassum in Sri Lanka remains uncertain, as no valid taxonomic literature has been published with species-level identification since 1961. Therefore, this study aimed to address the six-decade gap in Sargassum taxonomy by analysing the morphological characters of Sargassum specimens collected from various coastal localities around Sri Lanka. The coastal regions of Sri Lanka; Southern, Northern, Western, and Eastern were explored for sample collection, resulting in the collection of nine specimens of Sargassum. For each collected specimen, 30 morphological characters were recorded, and photographs of the thallus morphology were taken. Voucher herbarium specimens were prepared for each collected specimen. Of the nine collected specimens, seven were identified as distinct species based on their unique morphological characters. Those seven species include Sargassum aquifolium (Turner) C. Agardh, S. cymosum C. Agardh, S. vulgare C. Agardh, S. siliquosum J. Agardh, S. oligocystum Montagne, S. carpophyllum J. Agardh and S. natans (Linnaeus) Gaillon. The other two specimens could not be differentiated due to their similar morphology. These results were confirmed by the Multiple Correspondence Analysis (MCA) based on the recorded morphological characters of the collected specimens. For the accurate identification of those two specimens, molecular characterization is needed. This study serves as a preliminary guide for understanding the morphological diversity of the Sargassum species in Sri Lanka, which will be important in future taxonomic research and for using Sargassum species in various economic aspects. However, further research is needed for more accurate identification and a comprehensive review of the genus Sargassum in Sri Lanka.
A preliminary morphological study on the diversity of the spider genus Mallinella (Zodariidae) in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Dayananda, D. N. G.; Benjamin, S. P.
The zodariid genus Mallinella Strand, 1906, is represented by 228 species globally, including a single species, Mallinella redimita, from Sri Lanka, which is indicative of underestimated species diversity. This study aims to identify and describe species of Mallinella on the island based on their morphology. Fieldwork was conducted from 2023 to 2024 in 20 localities across 12 districts, covering all climatic zones of Sri Lanka. All spiders were collected from litter by sieving and hand collection. The collected spider specimens were preserved in 70% ethanol, identified, photographed, and illustrated using Olympus SZX7, Leica M205C, and Leica DM3000 microscopes using standard methodology. A total of 34 males and 33 females were collected. Five new species of Mallinella were recognized based on the differences in their genital morphology (Provisionally named Mallinella sp. A, Mallinella sp. B, Mallinella sp. C, Mallinella sp. D, and Mallinella sp. E). Mallinella sp. A is widespread across Central, Eastern, Northern, North Central, and North Western provinces, whereas Mallinella sp. B was specifically recorded from Galle District. Mallinella sp. C, Mallinella sp. D, and Mallinella sp. E were reported from Kandy, Badulla, and Rathnapura Districts, respectively, suggesting localized distributions for these species. The five new species belong to three currently recognized species groups of Mallinella, namely redimita (Mallinella sp. A), annulipes (Mallinella sp. B, Mallinella sp. D, and Mallinella sp. E), and fasciata (Mallinella sp. C). All five species of Mallinella are new to science and will be formally described in a future publication.
A preliminary study of nocturnal beetle diversity and their functional groups across habitat types in deenston, knuckles, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Wijerathna, W.M.H.U.; Ranasinghe, U.G.S.L.; Benjamin, S.P.
Beetles represent a significant portion of Sri Lanka's biodiversity, with 115 families (ca. 3,033 species) documented, making them the largest faunal group on the island. However, little is known about their habitat preferences, related to their functional groups, which determine the assemblage structure of these mega diverse nocturnal beetles (Coleoptera) in the tropics. Here, we examined the diversity of nocturnal beetle assemblages in Deenston, Southeastern Knuckles region, and investigated the influence of different habitat types on their diversity. Additionally, we explored how these habitat types affect their general feeding groups. Field surveys were conducted in Deenston area during 2019 and 2020 including dry and rainy seasons (total 72 trapping events). Specimens were sampled using six UV-light traps, encompassing habitat types including central forest (CF), forest edge (FE) and abandoned plantation (AP). Beetles were identified up to family level and grouped according to feeding type (Herbivore, Predator, Scavenger, Fungivore, Moss feeders, Xylophagous). Assemblages were assessed for compositional similarity, diversity, and abundance within habitats. Overall, 1183 beetles were examined across 39 families. Beetle abundance and family richness were highest in the CF (49.79% and 39 families), followed by the FE (31.70% and 38 families) and AP (18.51% and 31 families). Family Chrysomelidae was the most abundant in both CF and FE habitats, while the abundance of Staphylinidae was higher in the AP habitat. The beetle assemblages in the CF and FE ecosystems exhibited less similarity to those found in the AP habitat. Shannon diversity value (H’) and Evenness (E) resembled variation among different habitat; AP (H’:2.60, E:0.75), FE (H’:2.36, E:0.65), CF (H’:2.43, E:0.66). Herbivorous and predators exhibited the highest diversity and abundance at 55.62% and 26.64%, respectively. The predominant composition of herbivorous beetles might be due to anthropogenic actions, with their occurrence higher in the less disturbed CF and decreases from the FE to the AP habitat. Predatory, fungivorous, and scavenger beetles were higher in the disturbed AP ecosystem. This indicates a loss of beetle abundance and richness and changes in beetle composition in disturbed environments.
A preliminary study on the potential of using freshwater flora as an indicator in aquatic environmental risk assessment
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Prasadika, H. K. A. E.; Gamage, S. G.; Thayaparan, M.; Weerasinghe, T. K.
This study explored the potential of using freshwater flora to assess heavy metal and pesticide pollution in water bodies. A survey on agrochemical usage was conducted in five Grama Niladhari divisions in Matara, Sri Lanka, through direct interviews with one hundred farmers. The study was carried out in the Thihagoda canal by collecting samples of Salvinia natans, Hydrilla verticillata, Nelumbo nucifera, and water from surface (10 cm), mid (65 cm), and bottom (100-120 cm) depths. Composite water and plant samples were analysed for pesticides using HPLC and for heavy metals using ICP-MS. The heavy metal pollution index for As, Cu, Zn, Cd, Ni, Pb, Cr, and Mn in water and the plants' Bio-Concentration Factor (BCF) were calculated using standard formulas. The most commonly used fertilisers at the site were mixed fertiliser (65%) and organic liquid fertiliser (55%), while the predominant herbicide and pesticide were Satunil (75%) and Gaucho-Imidacloprid (100%), respectively. Both pesticides were detected in all water and plant samples. Organic liquid fertiliser contained As (0.05 mg/L), Cr (13.13 mg/L), and Pb (0.56 mg/L), while mixed fertiliser also showed As (0.74 mg/kg), Cr (3.93 mg/kg), and Pb (6.75 mg/kg). Salvinia and Hydrilla exhibited a BCF > 5000 for As, Cr, and Pb, indicating strong bioconcentration potential. The heavy metal pollution index for As, Cu, Zn, Cd, Ni, Pb, Cr, and Mn in water and the plants' Bio-Concentration values below 100 at all three water depths suggested the absence of significant risk of heavy metal pollution in the canal. However, the high BCF values in plants highlighted the bioaccumulation of most metals. These results underscore that pollution assessments should not rely solely on water analysis and emphasize the importance of incorporating aquatic flora as key indicators in water quality assessments to better evaluate environmental risks in water bodies.
Abundance and diversity of plankton in Mamunugama tank cascade system
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Amarasinghe, D. A. N. M.; Batugedara, B. D. I. M.; Handapangoda, H. M. K. D.; Senanayake, S. A. M. A. I. K.
Plankton are critical biological indicators used to assess the water quality in aquatic ecosystems. The objectives of the study were to identify the phytoplankton and zooplankton and estimate their diversity and abundance in the Mamunugama Tank Cascade System (TCS), located in the Kurunegala District, Sri Lanka. This TCS consists of six interconnected tanks: Ulpath tank, Athaudagama tank, Ihala Thimbiriyawa tank, Mamunugama tank, Kandubodagama tank and Weera tank. Plankton samples were collected from August 2023 to February 2024, covering both wet and dry months. At each visit, three samples were collected from each tank using a 55 μm mesh size plankton net. Planktons were identified based on the morphological features using standard keys, and their abundance was estimated using a Sedgewick-Rafter counting cell. The Simpson and Shannon-Wiener diversity indices were calculated. A total of forty-five phytoplankton species from seven groups were identified, with chlorophytes accounting for 40%, making them the dominant group, while Chrysophyta represented the lowest abundance of 2.2%. Twenty-four species of zooplankton were recorded representing four groups, with Rotifera being the most abundant group, accounting for 45.5%, and Cladocera being the least abundant group, accounting only for 9.1%. Plankton abundance was higher during wet months compared to dry months. The Simpson index indicated a high degree of diversity (D = 0.81-0.99) in all tanks during both dry and wet months. The Shannon-Wiener index values ranged from H = 2-3 in the dry months and H = 3-4.5 during the wet months. The dominance of chlorophytes and rotifers suggests favourable conditions for these groups. Seasonal variations in plankton abundance and diversity highlight the seasonal dynamics in aquatic ecosystems.
Activity pattern variations of large mammals during the 'paada yaathra' pilgrimage in Kumana national park, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Anawarathna, M. A. D. C. K.; Weerasinghe, H. M.; Rodrigo, B. K. P. D.; Dhananjani, D. M. T.; Jayasekara, E. G. D. P.; Mahaulpatha, W. A. D.
Human activities inside protected areas can have an impact on wildlife. We conducted a camera trap survey to study the temporal variation of large mammal activity during varying human disturbances within Kumana National Park (KNP). Data were collected using seven camera traps placed along the traditional road used by the pilgrims attending the “Paada Yaathra” (PY) annual pilgrimage. A systematic random sampling method was followed to install the camera traps. The study site was divided into 2 × 2 km² plots, and traps were placed randomly within 300 m from the road inside the plot. All traps were placed 30 cm above the ground, approximately 3 m away from animal trails. Cameras were active 24 hrs a day for 48 days, from 27ᵗʰ May 2023 to 13ᵗʰ July 2023. This period was divided into three 16-day segments; before, during and after the PY period. Activity time was collected using the timestamp on the camera trap recordings. Collected data were used to generate activity graphs (overlap package in R 4.3.3) and calculate the activity overlap of each species before and during the PY, as well as after and during the PY. The activity overlap of detected Panthera pardus kotiya, Melursus ursinus, Elephas maximus, Cervus unicolor, Axis axis, Sus scrofa, and Bubalus sp. were analysed during the study. Among them, the lowest activity overlap was recorded for Panthera pardus kotiya in both comparisons: an activity overlap of 0.04 before and during the PY and 0.02 after and during the PY. This indicates a change in their activity that was not recovered even after the PY. The Axis axis, and E. maximus exhibited a high activity overlap in both comparisons. However, all large mammal species displayed reduced diurnal activity and increased nocturnal activity during the PY period compared to before and after PY. Understanding these changes in activity patterns during the PY period can help implement conservation efforts to reduce the negative interactions between large mammals and human pilgrims due to temporal activity overlaps.
Adverse psychological effects of Kameshwari Modaka: a case study in Colombo district using the challenging experience questionnaire via online survey
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Manohara, M. G. R. K.; Sandunka, A. G. G.; Munasinghe, D. A. L.
“Kameshwari Modaka” (KM), an Ayurvedic drug traditionally used for its aphrodisiac properties, has recently been misused in Sri Lanka, particularly among youth seeking ecstasy-like effects. This study investigated the psychedelic experiences, specifically "bad trips", associated with KM misuse using the Challenging Experience Questionnaire (CEQ). From January to March 2024, an online survey gathered responses with a snowball sampling technique from 102 participants in the Colombo district (average age: 28.59 years; 96% male, 4% female). Results showed KM induces mild challenging experiences, including fear, isolation and, physical distress, with an average CEQ score of 21.31%. Most participants (60.8%) reported no or mild bad trip symptoms, but 13.7% experienced severe bad trips. Paranoia was significantly elevated compared to other serotonergic psychedelics (p < 0.05), suggesting potential psychological risks. KM's psychoactive effects are attributed to its high cannabis content, which can lead to acute psychosis and addiction in chronic use, especially with doses surpassing the therapeutic range of 3-6 g. Findings highlight the need for caution and regulatory measures in KM use, especially among younger demographics, despite the limitations of small sample size, lack of brand-specific data, recall bias, and variations in KM dosage of the present study. Further research is essential to explore demographic, psychological, and dosage-related factors influencing these adverse reactions. Clinical studies should validate findings and clarify KM's pharmacological mechanisms.
Agave americana as a promising green biosorbent for Ni(II) remediation
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Wickramasinghe, W. R. M. N. R.; Karunathilaka, R. M. M. K.; Priyantha, N.
The heavy metal content in the environment has been rising due to industrial advancement. Nickel (Ni) poses adverse health impacts, such as gastrointestinal distress, pulmonary fibrosis, and skin dermatitis, when present in excess, although it is a micronutrient essential for cellular functions. Excess Ni(II) concentrations can also induce ecological damage by disrupting the cellular functions of flora and fauna. Therefore, Ni remediation from industrial effluent is essential to safeguard human quality of life and ecosystem health. Fibrous biosorbents present promising green alternatives compared to other biosorbent types, offering advantages such as ease of surface modification to attract intended contaminants and simple removal. This study aimed to conduct a comprehensive investigation of the adsorption characteristics of Ni(II) on Agave americana fibres as a value-added product. Batch experiments were conducted under optimal parameters; 40 min shaking time, 20 min settling time, and ambient pH, which indicated a significant removal rate of 90.39% at an agitation speed of 150 rpm and room temperature with an optimum dosage of 20 g/L of the sorbent. Kinetic studies validated the pseudo-second-order model for the adsorption of Ni(II) on Agave americana fibre, with regression coefficients of 0.9968 and 0.9726 at ambient pH and initial solution pH of 4, respectively, suggesting that chemisorption is the rate-limiting factor in adsorption. Moreover, the fitting of kinetic data to the Weber-Morris intra-particle diffusion model at ambient pH and initial solution pH of 4 implied that both intra-particle diffusion and the boundary layer can affect the rate of adsorption. Further studies could expand the scope of Ni remediation from industrial effluent on a larger scale.
Air quality assessment using gas sensors in urban traffic areas in Peradeniya, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Prasadani, S. A. N.; Ranathunga, R. J. K. U.; Thalpavila, T. K. N. D.; Navarathne, J. M. S. G. B.; Wijesinghe, M. B.
The issue of air quality is a pressing environmental concern, as 99% of the global population resides in areas where air quality standard levels are not met. Onsite and real-time air quality monitoring is required to ensure the respiratory health of the urban population. However, air quality monitoring is difficult to achieve using benchtop equipment such as gas chromatography and mass spectrometry. The primary emphasis of this research was to systematically explore and assess pollution levels by using portable gas sensors in urban areas in Peradeniya, thereby contributing valuable insights to the existing body of knowledge on environmental monitoring in this area. The study analysed NO₂, CO₂, and CO gas levels at designated monitoring locations. The analysis examined the effects of traffic density, time variability, road infrastructure, and environmental conditions. The monitoring device was developed by integrating hardware components with Arduino IDE software. The results implied that emissions from road traffic have a greater influence on CO₂, CO, and NO₂ concentrations than meteorological conditions. The levels of pollution were found to be elevated by approximately 100% in traffic locations, which is a 25% increase compared to normal traffic conditions. The observed trends showed a 20% increase in pollutant gasses in the afternoon and evening. Galaha junction had an approximate 40% increment than Gatambe, and it demonstrates that the pollution levels have varied significantly within short distances. The levels of all three gases were higher at the Galaha and Gatambe junctions compared to the reference location, University ground. Afternoon hours showed higher pollution levels, which were affected by high ambient temperature. Analysis of the present study was limited to a specific area, which may limit the generalizability of the results to overall air pollution and potentially restrict the applicability of findings to urban traffic areas. Further investigations, including multiple geographic locations in the Kandy and Peradeniya areas, are being conducted to calibrate the developed detection system to measure gas concentrations in ppm.
Analysing the need for building classification based on land deformation Sri Lanka: a case study from the Kandy district
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Hettikankanama, H. K. S. R.; Welikanna, D. R.
Land deformation poses significant challenges to buildings in Sri Lanka, particularly in urban areas with older, potentially vulnerable structures. This study highlights the necessity of a building classification system to evaluate risks from urban deformation, aiding decisions on rebuilding or modifying buildings for safety and resilience. Given Sri Lanka's ageing infrastructure and susceptibility to geophysical changes, systematic risk assessment is crucial. The research aimed to develop a classification system for buildings based on their vulnerability to urban deformation, enhancing urban planning and disaster preparedness. Utilizing remote sensing data and Geographic Information System technology, the study assessed land deformation impacts in Kandy, Sri Lanka. Sentinel-1 Synthetic Aperture Radar data was processed using Interferometric Synthetic Aperture Radar techniques to generate a deformation map. Concurrently, Sentinel-2 multispectral data, analysed using the Support Vector Machine method, produced a detailed building footprint map. The integration of these datasets, including building age and material type, facilitated the classification of buildings into risk categories. The Geographic Information System database, incorporating building numbers, deformation classification, and construction era, was developed using historical records and correlation analysis. Correlating deformation and building maps allowed the classification of buildings into high, moderate and low-risk categories based on deformation values. Findings revealed that 16.67% of buildings are high-risk, requiring immediate action; 50% are moderate-risk, needing structural upgrades, and 33.33% are low-risk, requiring minimal intervention. This classification system offers a clear framework for prioritizing resources and planning, which is crucial for urban development and disaster management. However, it is limited by the availability of high-resolution data, which may affect the precision of risk assessments. The database allows authorities to model scenarios, prioritize actions and plan for sustainable urban growth, improving disaster preparedness and response. This system aids in selecting building methods and designs resilient to deformation, enhancing urban resilience in Sri Lanka through data-driven risk assessment.
Anti-corrosion performance of electrochemically synthesized polyaniline-graphene nanocomposite
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Peradeniya ,Sri Lanka, 2024-11-01) Lakhari, G. D. R.; Rathuwadu, N. P. W.; Koswattage, K. R.
Polyaniline (PANI) is known as one of the best candidates for corrosion protection. In its conductive emeraldine salt form, it provides anodic protection by passivating the metal surface and promoting the formation of the metal oxide layer. However, the corrosion protection performance of PANI is constrained by its limited electrical conductivity. Therefore, further enhancing the anti-corrosion performance of PANI is a challenge. Graphene is an advanced carbon material having good electrical conductivity. Therefore, to improve the electrical conductivity and thereby ensure improved electron transfer for better anti-corrosion performance, a graphene-PANI nanocomposite was synthesised. In this study, a facile electrochemical approach was proposed to synthesize the nanocomposite. This method involved electrochemical polymerization of aniline using cyclic voltammetry (CV) by applying ten cycles in 0.1 M H₂SO₄ in the presence of electrochemically synthesized graphene. Synthesised material was structurally characterized using UV-visible and FTIR spectroscopy. The UV-visible data showed a characteristic band at ~265 nm, confirming the presence of graphene, and FTIR analysis confirmed the presence of PANI. The electrochemical characterization was carried out in 0.1 M HCl to illustrate the anti-corrosion performance. Potentiodynamic polarization data showed that corrosion potentials significantly shifted to the anodic region by 280 mV in the presence of PANI–graphene nanocomposite compared to bare stainless steel, indicating enhanced corrosion protection. The corrosion rate decreased significantly from 0.36 mm/yr for the bare stainless steel to 0.02 mm/yr. The electrochemical measurements, therefore, indicated that the inhibition efficiency for PANI-graphene nanocomposite was 95% compared to bare stainless steel. Electrochemical impedance spectroscopy data showed improved anticorrosive performance for nanocomposite. These findings indicate that the PANI-graphene nanocomposite synthesised via a facile method demonstrates significant anticorrosion performances. Therefore, the PANI-graphene nanocomposite is an ideal candidate for anti-corrosion application having enhanced barrier protection with improved electrical conductivity.
Anti-diabetic, anti-inflammatory and GC-MS profile analysis of Schleichera oleosa (Kon) seed extract
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Senaweera, Y. T.; Darmasiri, N. H.; Shanuke, D. S.; Molagoda, M. N.; Ranasinghe, P.; Jayasooriya, P. T.; Samarakoon, K. W.
The medicinal properties of Schleichera oleosa (Lour.) Oken, commonly called “Kon”, has been acknowledged and utilised in traditional medicine for its wide-ranging therapeutic effects. This study was carried out to determine the fatty acid content in S. oleosa seeds. Gas Chromatography-Mass Spectroscopy (GC-MS) was employed to identify and quantify fatty acid content, while its biological activities were determined using Alpha-amylase inhibition using the dinitrosalicylic acid (DNS) method. Anti-inflammatory activity was assessed by bovine serum albumin method for the methanolic extract, as well as for the hexane, ethyl acetate and aqueous fractions. The results were expressed as mean ± SD using GraphPad Prism 7.4 (n = 3). The results were analysed by one-way ANOVA followed by Tukey’s multiple comparison tests, and p < 0.05 was considered statistically significant. The analysis identified 13 major fatty acids, with Eicosanoic acid exhibiting the highest significant percentage (39.16 ± 5.64). 9-Octadecenoic acid, Hexadecanoic acid and 9,12-Octadecadienoic acid were also detected as 36.81% ± 2.39, 10.84% ± 1.40 and 6.98% ± 2.29, respectively. The anti-inflammatory potential of S. oleosa seed extract was significant, while no antidiabetic activity was observed against the alpha-amylase enzyme. The crude methanolic seed extract exhibited better anti-inflammatory activity at 81.68 ± 0.45 due to the presence of Eicosanoic acid and other fatty acid derivatives, with 82.34 ± 0.22 for Diclofenac as the standard. Our results suggest that S. oleosa seed extract is a promising source of natural compounds with anti-inflammatory properties, making it suitable for potential therapeutic, nutraceutical, and functional food applications.
Antibacterial and antifungal activities of locally available four duckweed varieties in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Prasadini, H. R. P.; Madhujith, T.; Jayawardena, B. C.; Wijesundara, S.; Liyanage, R.
The overuse of synthetic antibiotics has caused multidrug-resistant pathogens, a major health issue. Secondary metabolites of plants are effective alternatives to combat antimicrobial resistance. This study aimed to evaluate and compare the antibacterial and antifungal properties of plant extracts (water, 60% EtOH, and 70% EtOH) obtained from four duckweed varieties, including Spirodella polyrhiza (SP), Landoltia punctata (LaP), Lemna purpusilla (LP), and Lemna minor (LM) owing to their rich content of secondary metabolites. The antimicrobial effectiveness of the extracts was assessed using the agar disc diffusion method. Each extract (20, 10, 5 mg/mL) was tested against bacteria; Staphylococcus aureus and Escherichia coli as well as fungi; Aspergillus niger and Candida albicans. Zones of inhibition were compared with amoxicillin for antibacterial activity and itraconazole for antifungal activity as reference standards. The SPSS MANOVA analysis showed significant differences (p < 0.05) in zones of inhibition against examined microbes among solvent extracts and duckweed varieties. The results indicated that the most effective inhibition (p < 0.05) of A. niger growth was observed (10.667 ± 0.577 mm) in SP 70% EtOH at 20 mg/mL. For C. albicans, the highest (p < 0.05) inhibition (31.000 ± 1.000 mm) was observed in LaP 70% EtOH at both 5 mg/mL and 20 mg/mL concentrations. These values were comparable to the inhibition by itraconazole at 0.125 mg/mL (33.000 ± 1.000 mm). The most notable (p < 0.05) antibacterial effectiveness against S. aureus (23.000 ± 1.000 mm) was observed with LaP 70% EtOH at 20 mg/mL. In contrast, SPW at 20 mg/mL demonstrated the highest inhibition activity against E. coli (17.333 ± 1.155 mm), which is comparable to the effectiveness of amoxicillin at 0.5 mg/mL (18.333 ± 0.577 mm). The results show that SP and LaP exhibited significantly greater (p < 0.05) antimicrobial activity compared to other duckweed varieties. Future studies could focus on isolating and identifying the active compounds responsible for these activities.
Antibacterial potential of Azadirachta indica and Curcuma longa extracts against some selected multidrug-resistant bacteria
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Thilakarathna, R. D. S. M.; Thathsarani, M. P. M.; Hettiarachchi, T. S.; Sandamini, K. M. N.; Kumari, E. A. K. I.; Kowshalya, Y.; De Silva, R. M.; Rathnayake, G.
The emergence of multidrug-resistant bacteria has become a major global challenge to public health. Therefore, attention has been paid to explore alternative antimicrobial agents to overcome this challenge. This study aimed to compare the antibacterial efficacy of neem leaf (Azadirachta indica) and turmeric rhizome (Curcuma longa) extracts against selected multidrug-resistant bacteria; Acinetobacter species, Coliform species, Methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The antibacterial efficacy of neem and turmeric was evaluated by performing disk diffusion and broth dilution methods. The plant extracts were prepared using the maceration method using 95% ethanol. The organisms were inoculated onto Muller Hinton agar plates with 0.5% McFarland turbidity standard for the selected microorganisms. Ciprofloxacin and Gentamicin discs were used as controls and applied along the plant extracts on the agar plates, which were then incubated at 37 °C for 24 hrs. The procedure was repeated three times to obtain the mean inhibition zone for each strain in the disc diffusion method. The minimum inhibitory concentration (MIC) of neem against MRSA was determined by the broth dilution method. An antibiotic sensitivity test was performed for control organisms in conjunction with these methods. Inhibition zones both in disc (± 8 mm) and well diffusion (± 9 mm) indicated a significant antibacterial activity of neem extract against MRSA. However, neem extract exhibited a MIC and minimum bacterial concentration of 20 mg/mL against MRSA, while turmeric showed no significant inhibitory activity. Other selected multidrug-resistant bacteria showed no significant inhibitory zones for both plant extracts. The results indicated that neem leaf extract has a significant antimicrobial effect against selected multidrug-resistant MRSA, whereas turmeric extract shows no significant effect on the aforementioned microorganisms. Further studies should focus on the impacts of neem extract concentration on its antimicrobial efficacy as it may serve as an effective alternative anti-microbial agent against multidrug-resistant MRSA.
Antibiotic resistance in Pseudomonas spp. from Kinniya and Wahawa hot springs, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Gunathilaka, H. M. S. A. T.; Samarasinghe, D. G. S. N.; Samarakoon, T. M. U. E. K.; Wanigatunge, R. P.; Magana-Arachchi, D. N.
Pseudomonas are opportunistic pathogens that can cause human diseases. Hot springs are rich sources of thermophilic microorganisms adapted to natural geothermal environments. This study focused on identifying antibiotic-resistant genes (ARG) in selected Pseudomonas species isolated from the two hot springs, Kinniya (KY) and Wahawa (WH), Sri Lanka. Antibiotic sensitivity tests (n = 17) were conducted using the Kirby-Bauer disk diffusion method for aminoglycosides (kanamycin, gentamycin, and streptomycin) and quinolone ciprofloxacin. A real-time PCR technique was employed to detect resistance genes associated with aminoglycosides, phosphotransferase and acetyltransferase genes (aph(3')-VI, aac(6')-I, and aac(3')-II), as well as quinolone resistance genes (gyrA, and parC). Of the 17 strains (Pseudomonas sp., n = 11; Pseudomonas aeruginosa, n = 6), Pseudomonas sp. from KY displayed resistance to all antibiotics, while WH only resisted gentamycin and streptomycin. Pseudomonas sp. (75.54%) exhibited resistance to multiple drugs more frequently than Pseudomonas aeruginosa (25.33%). The most frequently identified ARG was gyrA (66.66%), particularly in KY isolates. Notably, aac(3')-II and gyrA were detected in 100% of WH isolates, whereas gyrA is the commonly found quinolone-resistance gene, and aac(3')-II is the aminoglycoside resistance gene. Findings reveal that antibiotic-resistant Pseudomonas isolates were less common in the WH than in the KY. The KY hot spring is more urbanized and populated by tourists than the WH. The KY isolates carry antibiotic-resistance genes, including all aminoglycoside-modifying enzymes and fluoroquinolone-resistant enzymes. However, WH isolates carry the aminoglycoside-modifying enzymes aac(3')-II and enzymes responsible for fluoroquinolone resistance: gyrA and ParC. The gyrA gene was commonly found among the selected two quinolone-resistance genes and aac(3')-II for aminoglycoside resistance. Monitoring anthropogenic activities regularly and thoroughly is critical to prevent the spreading of antibiotic resistance among environmental microbial communities.
Antibiotic resistance pattern of biofilm producing bacteria isolated from water plumbing systems
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Thevashayinath, S.; Vivehananthan, K.; Abeygunawardena, I.
Microbial biofilm is a three-dimensional complex community of microbial cells enclosed in a self-produced matrix that protects the microbes from the harsh environment, including antibiotics. As a result, biofilm bacteria could exhibit resistance to antibiotic treatments, leading to persistent infections that contribute significantly to morbidity and mortality rates. The objective of this study was to assess the antibiotic resistance of biofilm bacteria in water plumbing systems, i.e. distribution line (drinking water and scrapings) and drain line (wastewater and scrapings). Bacterial isolates were confirmed for biofilm production using the Tissue Culture Plate method, Congo red agar method and Tube method. The biofilm bacteria were classified into four groups i.e. group 1: coliform group bacteria excluding Escherichia coli; group 2: Escherichia coli; group 3: Pseudomonas aeruginosa and group 4: Staphylococcus aureus based on morphological and biochemical tests. These bacteria were tested for antibiotic susceptibility using the Kirby-Bauer disc diffusion method, with the following recommended antibiotics; Amoxicillin/Clavulanic acid, Ceftriaxone, Ciprofloxacin, Gentamicin, Tetracycline, and Cotrimoxazole. The results revealed that all the bacteria screened in this study were resistant to Amoxicillin/Clavulanic acid. Bacteria from groups 1 and 3 primarily exhibited resistance to Tetracycline and Cotrimoxazole, respectively. Meanwhile, bacteria from group 2 and group 4 showed resistance to both Gentamicin and Tetracycline. Additionally, some bacteria from all four groups demonstrated resistance to both Ciprofloxacin and Ceftriaxone. The antibiotic sensitivity patterns varied among each group based on the location of isolation (distribution line and drain line). However, no consistent correlation was observed within each group, likely due to their isolation from different areas of the water plumbing system, variations in nutrition levels, differences in biofilm formation efficiencies, and the presence of different strains of the same bacteria. These findings highlight the challenge posed by biofilm formation in water plumbing systems and the need for strategies to combat infections associated with biofilms.
Antifungal effect of green synthesized zinc oxide nanoparticles against plant pathogens Fusarium spp.
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Madusanka, H. K. S.; Aruggoda, A. G. B.; Chathurika, J. A. S.; Weerakoon, S. R.
This study evaluated the antifungal potential of green-synthesized zinc oxide nanoparticles (ZnO NPs) against plant pathogens of the Fusarium species. The synthesis process utilised Mimosa pigra leaves, which were dehydrated, pulverized, and extracted by mixing 8 g of dried leaf powder with 100 mL of double-distilled water. Zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) served as the precursor salt for the eco-friendly synthesis of ZnO NPs. The formation of ZnO NPs was confirmed through UV-visible spectroscopy, revealing a characteristic absorption peak at 356 nm. Scanning electron microscopy indicated a heterogeneous distribution of particle shapes and sizes, with an average particle size of 81 nm (range: 35-164 nm). The antifungal efficacy of the synthesized ZnO NPs was assessed using the poisoned food technique. ZnO NP concentrations of 0 (negative control), 50, 100, 500, and 1000 mg/L were incorporated into potato dextrose agar (PDA) plates. Fusarium species mycelial plugs (8 mm diameter) were inoculated into 9 cm diameter Petri dishes. All treatments were incubated at 28 ± 2 °C for seven days, with three replicates per treatment. Mycelial growth was measured, and statistical analysis was performed using one-way ANOVA, yielding a significant F-value of 43.93 (p < 0.001). Duncan’s Multiple Range Test (DMRT) was applied as a post hoc analysis to identify significant differences in growth inhibition between treatments. ZnO NPs exhibited concentration-dependent inhibition of Fusarium species, with the highest inhibition (61.52%) observed at 1000 mg/L and 22.21% inhibition at 500 mg/L compared to the control. These findings indicated that green-synthesized ZnO NPs could be a sustainable approach for managing Fusarium infections in agricultural systems. Further research is warranted to elucidate the mechanisms of action and evaluate their potential for field applications.
Antioxidant potential of bark column fractions of Stereospermum suaveolens
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Thanusika, N.; Aluthge, D. C.
Antioxidants are molecules that primarily slow down or prevent oxidation reactions. Their application in pharmacology is valuable to improve current treatments for diseases. Medicinal plants are a rich source of biologically active compounds such as flavonoids, phenolic compounds, etc., which may be responsible for their antioxidant activities. This study aimed to investigate the antioxidant activity of the column chromatographic fractions of crude extracts of Stereospermum suaveolens bark. The extraction was performed using ultrasound sonication, followed by fractionation with silica gel column chromatography. The antioxidant activity test was carried out using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay with 200 μg/mL fraction solutions, and L-Ascorbic acid was used as the standard. Thin-layer chromatography was performed to analyse the chemical profile. Methanolic bark extracts of S. suaveolens yielded seven fractions, with radical scavenging percentages ranging from 13.22% to 82.51%. The test results further depicted that the third and fourth fractions possessed high antioxidant activities with the percentage radical scavenging activity of 82.51% and 56.27%, respectively, whereas other fractions showed weak antioxidant activities. However, the standard L-Ascorbic acid exhibited the highest antioxidant activity compared to bark fractions (92.83%). However, the radical scavenging activities of all active bark fractions were lower than that of L-Ascorbic acid as a positive control. The study concluded that most active fractions demonstrated good antioxidant activity, worthy for further study to isolate specific compound/s which is/are responsible for antioxidant activity.
Antioxidant, antidiabetic, cytotoxic and phytotoxic properties of two medicinal plants, Buchanania axillaris and Curcuma longa
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Premasiri, H. A. K. D.; Siriwardhane, U.; Piyasena, N. P.; Adikaram, N. K. B.; Marikkar, N.; Jayasinghe, U. L. B.
Medicinal plants are a rich source of bioactive compounds with potential applications in pharmaceuticals, nutraceuticals, and agrochemicals. This study aimed to assess the bioactivities of extracts from Buchanania axillaris leaves and rhizomes of Curcuma longa. They were collected domestically within the Kandy District, Sri Lanka. Plant material was air-dried and ground to obtain a homogenous powder using a grinder. The powdered samples were extracted into methanol by sonicating for 30 min. This procedure was repeated twice, and the filtrates were combined and evaporated to dryness using a rotary evaporator. The crude extracts were evaluated for antioxidant activity using triplicates for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, enzyme inhibitory activity against α-amylase, α-glucosidase, and lipase, and 10 nauplii for cytotoxicity through the brine shrimp lethality assay, and 10 seeds for phytotoxicity by the lettuce seed germination assay. The results demonstrated that B. axillaris exhibited potent antioxidant activity, with an IC₅₀ value of 0.03 ± 0.07 mg/L for DPPH radical scavenging activity, than C. longa (61.49 ± 0.57 mg/L). Positive control was ascorbic acid (IC₅₀ = 3.47 ± 0.45 mg/L). Both extracts displayed α-glucosidase inhibitory activity, with 100% inhibition at 1000 mg/L, indicating their potential in managing diabetes. Curcuma longa showed moderate α-amylase inhibitory activity, with an IC₅₀ of 465.81 ± 23.31 mg/L (Positive Control-Acarbose IC₅₀ = 8.87 ± 1.21 mg/L). Neither extract exhibited significant lipase inhibitory effects within the tested concentration range. The cytotoxicity assay revealed potent brine shrimp lethality for C. longa, with a LC₅₀ of 20.01 ± 3.14 mg/L, against the positive control, atropine, LC₅₀ = 88.60 ± 8.11 mg/L. Buchanania axillaris exhibited phytotoxic potency with IC₅₀ values of 520.97 ± 15.14 mg/L and 665.14 ± 20.54 mg/L, while C. longa exhibited IC₅₀ values of 625.29 ± 12.76 mg/L and 586.53 ± 9.32 mg/L, compared to the positive control, abscisic acid (IC₅₀ = 1.46 ± 0.19 mg/L and 1.85 ± 0.31 mg/L) for root and shoot inhibition, respectively, suggesting potential applications as natural herbicides. The findings indicate promising bioactivities of B. axillaris and C. longa extracts, suggesting further exploration for potential applications in pharmaceuticals, nutraceuticals, and agriculture.
Application of Kruskal’s algorithm in finding basic feasible solutions for transportation problems
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Ekanayake, E. M. T. D. K.; Ekanayake, E. M. U. S. B. K.; Rodrigo, W. N. P.
Transportation problems (TPs) are prevalent in logistics and operational research optimization challenges. The structure of the transportation problem consists of multiple shipping routes connecting various sources to different destinations, with the objective of minimizing the overall transportation cost. The literature describes the development of many traditional methods to address transportation problems. Some methods, such as the Stepping Stone Method and the Modified Distribution Method (MODI), are intended to find an optimal solution to TP, while the Northwest, Least Cost, and Vogel’s Approximation techniques are concentrated on identifying a basic feasible solution. The proposed algorithm was based on a graphical method and has proven to provide initial basic feasible solutions to a reasonable degree of satisfaction, regardless of the scale of TPs. The modified Kruskal’s algorithm was adjusted to select edges that minimize transportation costs, subject to the constraints imposed by the demands and supply chains. This includes sorting the edges in ascending order of their cost and adding them to the solution iteratively until all nodes are connected and the constraints are satisfied. This study suggested an algorithmic approach simpler than the well-known heuristic algorithms.

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