Browsing by Author "Magana-Arachchi, D.N."

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Co-occurrence of Geogenic, Microbial, and Anthropogenic Emerging Contaminants: Ecotoxicity and Relative Environmental Risks
(Springer, 2022) Magana-Arachchi, D.N.; Wanigatunge, R.P.
Heavy metals, 1,4-dioxane, cyanotoxins, bacteria with antibiotic-resistant genes, pharmaceuticals, nanoparticles, and many more are listed as emerging contaminants due to their toxicity whether their origin is geogenic, microbial, or anthropogenic. These specific types of environmental impurities, at present, are excluded from regular scrutinizing programs but are potential nominees for future supervision and management subjected to their hazardous nature, community awareness, incidence, and depending on the amount present in distinct environments. A chemical or an organism does not need to be novel to be groped as an emerging contaminant. Primarily, these impurities had been in nature for decades, but their impact is being assessed only now. When these three types of pollutants coexist together the adverse impact they create on Mother Nature is enormous. With increasing population growth and with rapid urbanization, release of these contaminants gets accelerated and considered as a global issue. Due to their perseverance, in aquatic environments, they get accumulated in biota thereby contaminating the food web and humans and animals mostly get exposed through the food chain or by drinking the contaminated waters. This chapter focuses on emerging contaminants of geogenic, anthropogenic and microbial origin, their coexistence in the environment, ecotoxicity, and relative environmental risks.
Culture-Dependent Characterization of Marine Bacteria from Ussangoda Coast, Sri Lanka
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Hettiarachchi, H.H.; Wanigatunge, R.P.; Magana-Arachchi, D.N.
Marine bacteria play a vital role in marine ecosystem structure and ocean biogeochemistry. Ussangoda has identified as a serpentinite site, situated along the Southern coastal zone of Sri Lanka. In the past, few studies have focused on biodiversity and soil chemistry of this unique habitat. However, marine bacterial diversity in the Ussangoda coast is largely unexplored. Thus, the present study was conducted to isolate and identify marine bacteria in Ussangoda coast. Water, sand and soil samples were collected from 14 sites of the beach which were located approximately 1 m distance representing foreshore, shore line, backshore and upland. Bacteria were isolated by inoculating a 10 μl of each water sample, soil and sand suspension into tryptone soya agar, nutrient agar (NA), and seawater nutrient agar (SNA) and were incubated at 27 ± 2 oC for 3 days. Pure cultures were obtained after 1-2 consecutive sub-culturing on to fresh media plates by streaking. In order to obtain halophilic bacteria, isolates were inoculated into saline nutrient agar media with the concentrations of 10% and 20% of NaCl for moderate halophiles and extreme halophiles respectively and were incubated at 27 ± 2 oC for 7 days. 198 bacterial pure cultures were initially isolated and among them 152 were Gram-positive bacteria (76.8%). Based on colony morphology and Grams’ staining, bacterial isolates were identified as Bacillus, Staphylococcus, Micrococcus, Pseudomonas, Klebsiella, Escherichia coli and Stenotrophomonas,which have been previously reported in coastal zones of other countries. Among the tested 102 isolates, 35 isolates (34%) were reported as moderately halophilic and 14 isolates (13%) were reported as extremely halophilic bacteria. Halophilic bacteria were recorded from shoreline as well as in the upland soil and it may be due to the soil chemistry of the area. Bacterial isolates should be further confirmed by the 16S rDNA sequencing to confirm their identity. This study provides foundational data on the microbial diversity of the Ussangoda coast and further studies are needed to identify the association of microbial community structure with the environmental factors in this region.
Diversity of Firmicutes in selected hot water springs of Sri Lanka by 16S metagenomic sequencing
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Samarasinghe, D.G.S.N.; Wanigatunge, R.P.; Magana-Arachchi, D.N.
Thermophiles have the ability to survive in environments with very high temperatures. Hot springs provide unique natural environments for these thermophilic microorganisms. In recent years, hot water springs and thermophilic microorganisms have gained attention due to their industrial and biotechnological importance. Among the thermophilic bacteria, a large number of metabolites can be found in the phylum Firmicutes. Different species of Firmicutes show various ecological optima. Even though Sri Lanka harbors many hot springs, majority of them are not yet explored and require comprehensive studies to unravel the inhabitant microbial diversity, specially the phylum Firmicutes. This study was focused into uncovering the resident thermophilic Firmicutes which could be unculturable and their diversity in four major hot springs namely, Mahapelessa, Wahawa, Maha Oya and Nelumwewa using 16S rRNA metagenomic sequencing. Water samples were collected from the four hot springs in which the surface temperature ranged from 44.2 to 53.8 °C. Further, a water sample from a natural spring located in Digana (26.9 °C) was used as the control. Genomic DNA was extracted from the water samples using modified Boom’s method and was subjected to 16S rRNA metagenomic sequencing (16S V3-V4 region) using Illumina platform. The results were analyzed using GAIA: Metagenomics data analysis software to identify Firmicute bacteria (Operational taxonomic units/ OTU) and to determine their relative abundance. OTU analysis was carried out with a cut-off similarity value at 97%. The relative abundance of Firmicutes in each spring is as follows: Mahapelessa (23.7%), Wahawa (0.8%), Maha Oya (0.9%), Nelumwewa (5.8%) and Digana natural spring (4.2%). The class Clostridia and Bacilli were the most abundant classes observed in hot springs. A total of twenty-one species were affiliated with the phylum Firmicutes, among which 18 species were only detected in hot water springs while the rest of the three species (Clostridium sp., Flintibacter butyricus and Oscillibacter sp.) were only detected in the natural spring. Nine different bacterial species were unique to Mahapelessa hot spring including; Bacillus licheniformis and Bacillus thuringiensis belonging to class Bacilli, Caldanaerocella colombiensis, Desulfotomaculum reducens, Geosporobacter sp., Geosporobacter subterraneus, Pelotomaculum isophthalicicum, Salimesophilobacter vulgaris and Tepidibacter sp. belonging to the class Clostridia. The two bacterial species; Carboxydocella manganica and Faecalibacterium prausnitzii were only recorded from Maha Oya while Clostridium islandicum was reported from Maha Oya and Nelumwewa hot springs. Bacillus pumilus and Sporacetigenium mesophilum were present in Mahapelessa and Wahawa hot springs. Anaerosolibacter carboniphilus was found in both Mahapelessa and Nelumwewa while Anaerobacterium chartisolvens was detected in all hot water springs except Wahawa. Bacillus sp. and Paenibacillus sp. were common in all the hot water springs. When compared to the natural spring, the four hot water springs showed high bacterial species diversity (85%). Results from this study confirm the uniqueness of bacterial species belonging to phylum Firmicutes in hot water springs than in the natural springs. More comprehensive studies on these Firmucutes are needed to identify their potential to be used in industrial and biotechnological applications.