Category Archives: Publications

Authors: Sumaiya Idroos and Pathmalal Manage
Journal: Asian Journal of Microbiology, Biotechnology & Environmental Sciences.

Microcystins (MCs) are a group of cyclic heptapeptide hepatotoxins produced by cyanobacteria. Among 70 analogues of MCs, Microcystin-LR (MC-LR) is the dominant type in Sri Lankan water bodies. Contamination of MC-LR in drinking water is a serious health issue. Thus, the present study was carried out to identify freshwater bacteria, which are capable of degrading MC-LR. BIOLOG MT2 plate assay was employed to confirm MC-LR biodegradation by the bacterium Bacillus cereus and Rahnella aquatilis which were isolated from Girandurukotte reservoir and form Ulhitiya reservoir respectively. Classic batch culture experiments showed that B. cereus and R. aquatilis removed 100% of MC-LR at 28oC within 8 and 10 days of incubation respectively. Optimized biodegradation conditions for MC-LR by B. cereus and R. aquatilis were recorded at 320C when phosphates and nitrate concentrations were 0.01ppm and 0.4 ppm respectively in experimental medium. Moreover, B. cereus andR. aquatilis were capable of degrading other MCs analogues; Microcystin-LF (MC-LF), Microcystin –LW (MC-LW), Microcystin –RR (MC-RR) and nodularin (NOD) as well. Molecular studies confirmed that B. cereus and R. aquatilis harbored MC degrading mlrA, mlrB, mlrC and mlrD genes. This is the first record for degradation of MCs and NOD by R. aquatilis.

Authors: Sonali Garg, Gayani Senevirathne, Nayana Wijayathilaka, Samadhan Phuge, Kaushik Deuti, Kelum Manamendra-Arachchi, Madhava Meegaskumbura, SD Biju

Journal: Zootaxa

Based on a recent molecular phylogenetic study, the South Asian microhylid genus Uperodon (subfamily Microhylinae) currently comprises of 12 valid species that are largely restricted to India and Sri Lanka. Considering the revised generic-level status of its various members, here we review the taxonomy of all known species in this genus and clarify their nomenclatural status and geographical distribution, by integrating evidence from genetics, adult and tadpole morphology, breeding ecology, and bioacoustics. Our molecular analyses of a mitochondrial 16S rRNA gene fragment combined with external and internal morphological studies also revealed a distinct new species in the genus. This species, formally described as Uperodon rohani sp. nov., is endemic to Sri Lanka and widely distributed at lower elevations in the island. For nomenclatural stability of various previously known members, the following actions are also undertaken: (1) redescription of the poorly-defined species Ramanella anamalaiensis Rao (= Uperodon anamalaiensis) and Hylaedactylus montanus Jerdon (= Uperodon montanus); (2) neotype designation for Ramanella anamalaiensis Rao (= Uperodon anamalaiensis), Ramanella minor Rao, Ramanella mormorata Rao (= Uperodon mormorata), and Ramanella triangularis rufeventrisRao; (3) lectotype designation for Callula variegata Stoliczka (= Uperodon variegatus); and (4) synonymization of Ramanella minor Rao with Uperodon anamalaiensis.

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Authors: Yong Chang Jang, R.R.M.K.P. Ranatunga, Jin Yong Mok, Kyung Shin Kim, Su Yeon Hong, Young Rae Choi, A.J.M. Gunasekara

Journal: Marine Pollution Bulletin

This study provides the first assessment of marine debris washed ashore on 22 beaches along the coast of Sri Lanka. There was an average of 4.1 large (>25 mm) and 158 small (5–25 mm) pieces of debris per square meter of beach. Classified by use, packaging material (55%) dominated the debris, followed by consumer products (25%) and fishing gear (20%). In terms of materials, plastic was the greatest contributor (93%) to marine debris. Beaches near a river mouth or city and those with a barrier had greater debris accumulations. The east coast had significantly greater small debris density, possibly due to strong northeastern monsoon currents. Large spatial heterogeneity was observed in the amount of debris. Long-term monitoring is imperative to better understand the temporal changes in, and the pathways and possible management of, marine debris.

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Authors: Kosala Ayantha Sirisena, Steven Ramirez, Andrew Steele, Mihaela Glamoclija
Journal: Microbial Ecology

Lake Lucero is a gypsum-rich, hypersaline, ephemeral playa located on the southern part of the Alkali Flat at the White Sands National Monument (WSNM), New Mexico, USA. This modern playa setting provides a dynamic extreme environment that changes from a freshwater lake to a hypersaline dry desert during the year. We investigated the microbial diversity (bacteria, archaea, and microbial eukaryotes) of the Lake Lucero sediments using 16S- and 18S-based amplicon sequencing approach and explored the diversity patterns in different geochemical microenvironments. Our results indicated that similar microbial communities, in particular bacterial communities colonized, were remarkably consistent across our depth profiles. Therefore, these communities show a first-order relevance on the environmental conditions (moisture content, oxygen content, and mineral composition). We found that Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Gemmatimonadetes were the major bacterial phyla, while Cyanobacteria were present in relatively low abundances and appeared only at the surface. Genus level assessment reflected that Truepera, Delftia, and Pseudomonas were the predominant bacterial genera across all samples. Euryarchaeota was the major archaeal phylum in all the samples, while Candidatus Halobonum and Candidatus Nitrososphaera were the main genera. Diatoms were the dominant eukaryotic group in surface samples and Fungi, Ciliophora, Metazoa, and Nematodes were the other major groups. As expected, metabolic inference indicated that aerobic microbial communities were near surface colonizers, with anaerobic communities dominating with increasing depth. We demonstrated that these microbial communities could be used to characterize unique geochemical microenvironments enabling us to extrapolate these results into other terrestrial and possibly extraterrestrial environments with comparable geochemical characteristics.