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Quantitative estimation of extracellular enzyme activities of bacterial strains isolated from mangrove sediments in Puttalam Lagoon, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Narampanawa, D.A.; Weerasinghe, K.E.; Halmillawewa, A.P.
Mangrove ecosystems provide habitats for diverse bacterial populations with extensive abilities to produce various secondary metabolites and extracellular enzymes such as amylases, proteases, cellulases, and lipases. These secondary metabolites and extracellular enzymes are known to harbour great biotechnological potential making them good candidates for various industrial applications. The present study was focused on the quantitative estimation of extracellular enzyme production capabilities of eight bacterial strains isolated from mangrove habitats located in the Puttalam lagoon, Sri Lanka. In a previous study, these bacterial isolates were screened qualitatively for the production of amylase, protease, and cellulase enzymes, and isolates positive for each of the selected enzyme production were quantitatively analyzed using the spectrophotometric methods. Out of the four amylase-positive bacterial isolates, the highest amylase activity was observed with PUTS1_2 (1.397 ± 0.055 U/ ml), whereas the minimum amylase activity was given by the PUTS2_10 (0.573 ± 0.032 U/ ml). According to the qualitative screening, seven isolates produced protease, while the highest and the lowest protease activities were detected with PUTS1_1 (1.743 ± 0.010 U/ ml), and PUTS2_12 (0.093 ± 0.011 U/ ml), respectively. The highest cellulase activity was given by the PUTS2_6 (3.229 ± 0.081 U/ ml), whereas PUTS2_5 had the lowest activity (0.792 ± 0.042 U/ml) among the five cellulase-positive isolates. Isolate PUTS2_2 exhibited comparatively higher activities for all the three enzymes quantified. Further studies are needed to understand the potential use of these extracellular enzymes in various large-scale industrial applications.
Toxicity of terminalia arjuna (combretaceae) using brine shrimp assay
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Madhuranga, H.D.T.; Farween, M.R.K.; Ilangage, J.I.M.K.; Rupasena, W.H.Y.P.S.; Samarakoon, D.N.A.W.
Terminalia arjuna (Kumbuk) is a herbaceous, ever-green tree, standing 20 - 30 m above ground level, in the Family Combretaceae. The plant has shown many medicinal and antimicrobial properties in previous studies. Even though the medicinal value of T. arjuna has been extensively studied, there are no toxicity assays. The objective was to identify the minimum toxic concentration of the crude extract of T. arjuna using a brine shrimp assay. The brine shrimp lethality assay of the aqueous extracts of the T. arjuna plant was used to determine the toxicity of the T. arjuna bark aqueous extract. The air-dried plant material was powdered and extracted into distilled water in a 1:3 ratio using the laceration technique. The dilution series was prepared with two-fold dilution, one gram of bark aqueous extract powder dissolved in 4 ml of distilled water, starting from 1g/ml to 1.9 ×10⁻³ g/ml concentration. Their ability to kill a cultured larva (nauplii) was observed. Ten larvae were exposed to plant extract for 24 h. The number of live larvae was observed using the naked eye, and the mortality percentage and LC₅₀ (the median lethal concentration) were calculated using GraphPad Prism software. The study was triplicated. The mortality percentage and LC₅₀ were calculated using GraphPad Prism according to a log concentration and percentage mortality graph and compared with Meyer’s or Clarkson’s toxicity scale (if LC₅₀ < 1,000 μg/ml is considered toxic if LC₅₀ > 1,000μg/ml is considered as non-toxic). The resulting LC₅₀ was = 0.0083 g/ml for the aqueous extract. The results confirmed that the plant extract is nontoxic, and the minimum toxic concentration of T. arjuna in the brine shrimp assay was 0.0083 g/ml.
Plant–pollinator interactions in residential gardens in the Kandy Municipal Council area
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Herath, H.M.D.N.; Yakandawala, K.; Minor, E.S.
Residential gardens provide a significant component of urban landscapes, but their relative contribution to pollination remains largely un-quantified. Vegetation in these gardens plays a vital role in conserving pollinators. Hence, the present study aimed to investigate the contribution of garden flora to insect pollinator conservation. Six Grama Niladhari Divisions (GND) were randomly selected in the Kandy Municipal Council area, and a cluster of 10 adjacent residential gardens was selected in each GND (n=60). In each front garden, vegetation was identified. The gardens were visited once a month for three months to quantify floral resources and pollinator visitations. Pearson’s correlation analysis was used to investigate the relationship between the abundance of floral resources and pollinators. Data were analyzed using R- studio software. The garden flora belonged to 92 families represented by 321 species. The majority of species belonged to the family Arecaceae (7%), followed by Fabaceae (6%), Poaceae and Asteraceae (5%). Overall, we recorded 3,153 pollinator visits. Among them, bees were dominated (54%), followed by flies (22%) and butterflies (15%). Arecaceae recorded the highest number of plant-pollinator interactions, followed by Asteraceae and Fabaceae. A significant moderate correlation was observed between floral abundance and pollinator abundance (p<0.05; Correlation coefficient[r]=0.36), suggesting that increasing floral abundance could support the attraction of pollinators. Hence, we recommend maintaining residential garden flora with abundant floral resources to support the pollinators. Based on the study, planting designs of the residential gardens could be enriched with the members of the families Arecaceae, Asteraceae and Fabaceae.
In vitro antimicrobial activity of traditional mouthwash preparations: a preliminary study
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Rohini, P.; Panagoda, G.J.
Antimicrobial agents administered systemically or locally can help to suppress periodontal pathogens. In Siddha medicine, Padikkaraneer (PN), Panchathuvarpikasayam (PT) and Mayakaaineer (MN) are used as mouthwashes in treating oral diseases. In this study, the herbal mouthwash preparations (HMP) were tested for their antimicrobial activity (AMA) against oral ulcer-causing pathogens viz, Candida albicans, Escherichia coli, Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive). Recommended guidelines in the Siddha texts were used to prepare the mouthwashes. AMA of each HMP was checked using the agar well diffusion method. Each experiment was carried out in duplicate and repeated thrice. Significant differences among HMP were analyzed using one-way ANOVA. HMPs showed significant antimicrobial activity (p<0.001) against tested strains. It was observed that PN was the most effective among the three HMPs. The inhibitory effect of the three HMPs and the positive control on the standard organisms and clinical isolates demonstrated that PN contains higher antimicrobial activity. MN showed a zone of inhibition against E.coli, P.aeruginosa and S.aureus. No activity was reported against the fungi. PT was less effective against both Gram-negative and Gram-positive bacteria and fungi. This study revealed a potent in vitro activity of HMP on certain oral ulcer- causing pathogens. Results scientifically validate the inhibitory capacities of PN and MN in Siddha medicine, and the findings contribute towards developing new treatment options based on herbal mouthwashes.
Biological control of podosphaera sp., the causal agent of eggplant powdery mildew disease by Iilleis cincta (coleoptera: Coccinellidae)
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Ekanayake, E.M.D.; Karunaratne, W.A.I.P.; Jayasuriya, K.M.G.G.; Hemachandra, K.S.; Karunarathne, A.K.; Athukorala, A.D.S.N.P.; Edirisinghe, E.S.M.
Eggplant, Solanum melongena L. is infected by many diseases, including powdery mildew caused by Podosphaera spp. (Family: Erysiphaceae), which seriously affects yield. The mycophagous coccinellids play an important role as biocontrol agents in controlling powdery mildew disease. The present study investigates the efficacy of the coccinellid beetle, Illeis cincta (Fabricius), in controlling powdery mildew disease in eggplant. The study was conducted at Meewathura farm, Peradeniya, Sri Lanka from December 2021 to April 2022. The 100 m² cultivation area had 76 one-square-meter plots, each with an eggplant. As symptoms of powdery mildew disease appeared on leaves, a survey was conducted to determine the abundance of associated coccinellid beetles. Randomly selected 16 plots were sampled twice a week for five weeks; both sides of all leaves from top to bottom of each plant were observed for symptoms. The number of infected and healthy leaves per plant per plot was also recorded. Plant disease incidence was determined using a disease index and severity scale. The abundance of I. cincta larvae and adults was quantified per plot. Identification revealed Podosphaera sp. as the causal agent of powdery mildew. During the flowering stage, I. cincta population density positively correlated to disease severity while disease incidence negatively correlated with I. cincta population density. Illeis cincta abundance is significantly higher (p < 0.05) in the voracious larval stage than in the adult stage and the larvae had more negative impact on the disease. Initially, the total abundance of I. cincta increased with time but started decreasing by the second week with decreasing disease severity. The present study revealed that I. cincta abundance was positively related to the damage severity of powdery mildew. Increase in I. cincta abundance with disease severity may lower further spread of the disease. Overall, I. cincta is a vital biocontrol agent to control powdery mildew disease on eggplants. Biodiversity enhancement within agroecosystems by conserving natural enemies will be an effective alternative for pesticide usage and managing pests/diseases in eco-friendly cropping systems.