Science
Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/1
Browse
4 results
Search Results
Item Production of certain extracellular enzymes by some bacteria and amplification of cellulase gene from Bacillus species(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Jayasinghe, J. A. S. M.; Medhavi, P. I. H. R.; Magana-Arachchi, D. N.; Wanigatunge, R. P.; Herath, H. M.Bacteria have received attention, due to their ability to produce extracellular enzymes beneficial in various industries. In the present study, extracellular enzyme production by two thermophilic bacteria (Meiothermus ruber, Tepidimonas ignava) and eight other bacterial isolates (Bacillus thuringiensis, Bacillus amyloliquefaciens, Bacillus pumilus, Bacillus aryabhattai, Pseudomonas stutzeri, Pseudomonas aeruginosa, Sphingomonas sp., Burkholderia lata) was investigated. Extracellular amylase, protease, pectinase and cellulase production was studied in vitro in media containing starch, skimmed milk, citric pectin and carboxymethylcellulose respectively, at 28 °C, 35 °C, 45 °C and 55 °C. Hydrolyzing Capacity Index (HCI) at day seven was calculated to identify the isolates, which hydrolyzed a substrate with minimal colony formation. Such isolates would have a higher potential in industrial applications. HCI values were analyzed using one-way ANOVA and Tukey’s multiple comparison tests. All isolates, except thermophilic M. ruber, produced at least one extracellular enzyme within 1-3 days. T. ignava, B. thuringiensis and P. aeruginosa produced amylases. All isolates except B. aryabhattai and M. ruber produced proteases. B. thuringiensis, Sphingomonas sp., B. amyloliquefaciens and P. stutzeri produced cellulases. Pectinases were produced only by B. lata. Thermophilic T. ignava produced amylases and proteases at 28 oC and 35 oC but did not produce any enzyme at 55 °C, the temperature of the Maha Oya hot springs from which it was isolated. B. amyloliquefaciens, P. stutzeri, P. aeruginosa, B. pumilus, Sphingomonas sp. and B. lata produced proteases, which were stable at higher temperatures; 45 °C and 55 °C. It was the only enzyme to be produced at those temperatures. According to the HCI values, B. thuringiensis and P. stutzeri were the most efficient degraders of starch and cellulose, respectively. P. stutzeri, Sphingomonas sp. and B. lata were the best protein degraders. A gene coding for glycoside hydrolase (a cellulase) was amplified from bacteria by PCR using primers designed for Bacillus licheniformis ATCC 14580. Although expected amplicon size was ~1683 bp, amplicons of apporiximately 500 bp, 600 bp and 1000 bp were generated from cellulase producing B. thuringiensis. According to the information available in NCBI, B. thuringiensis has glycoside hydrolase gene of 738 bp suggesting that those amplicons could also be some glycoside hydrolase genes of different lengths. This should be confirmed by DNA sequencing. PCR product was generated by the same primers for B. aryabhattai as well, although it did not produce cellulases in vitro. It could be due to non-expression of the particular gene at the experimental conditions used in this study. These Bacillus species are perceived as sources of purified cellulases and the particular genes would be useful also in transformation of other organisms for industrial purposesItem Isolation and identification of thermophilic bacteria and cyanobacteria from Maha Oya hot springs in Sri Lanka(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Medhavi, P.I.H.R.; Samarasinghe, D.G.S.N.; Herath, H.Hot springs are a rich source of thermophilic microorganisms such as bacteria, cyanobacteria and archaea. Though, there are several hot springs recorded in Sri Lanka, a comprehensive community analysis of thermophilic microorganisms in these springs is inadequate. Therefore, the present study was conducted to isolate and identify the thermophilic bacterial and cyanobacterial diversity in Maha Oya hot springs. Water samples were collected from the surface and the bottom of the seven wells of Maha Oya hot water springs, which showed temperatures ranging from 42 to 59.80C and pH ranging from 6.89-7.63. Water samples treated with Lugol’s iodine as well as microbial mats growing on water surface and attached to the surface of wells, were observed under a light microscope to determine the presence of cyanobacteria. Thermophilic bacteria were isolated by inoculating a dilution series (100, 10-2 and 10-4) of water samples separately into nutrient agar medium and incubating at 550C for 48 hours. Water and microbial mat samples were inoculated into cyano-specific BG11 and BG110 media and incubated at 550C and 12:12 hours dark:light cycle to isolate culturable thermophilic cyanobacteria. Based on morphological (colony morphology, Gram staining, endospore staining and motility test) and biochemical (oxidase activity, catalase activity, H2S production, citrate utilization, glucose fermentation) characteristics, the isolated bacteria were identified as Bacillus thermoamylovorans, Meiothermus sp. and Bacillus schlegelii which have been previously reported as thermophiles. Morphological identification of both uncultured and cultured cyanobacteria revealed the presence of eight different cyanobacterial genera. The most abundant genus was Oscillatoria . Additionally, Calothrix, Synechococcus, Gloeocapsa, Gloeothece, Cylindrospermopsis, Lyngbya and Pseudanabaena were observed. The isolation and identification of these thermophiles could be useful in mass scale production of thermostable enzymes and other bioactive compounds with biotechnological and industrial applications.Item Rumen microbiome: Exploring the adaptive roles of viruses and bacteria in the rumen.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Anderson, C. L.; Fernando, S.C.Complex and diverse microbial communities mediate the cycling of nutrients within ruminants. The structure of this complex microbial community is shaped by the highly variable physical, chemical and predatory environment. In turn, the microbial community regulates the environment and nutrient cycling including the export of energy to the host in the form of volatile fatty acids. The diversity of the enteric microbial community is both ecologically and biochemically important. In addition to the important role of the rumen microbiome on its host, the anaerobic conversion of complex organic matter to methane in ruminants is an essential link in the global carbon cycle, and has a significant contribution towards global warming and climate change. However, our understanding of the rumen microbial community structure and function is in its infancy and we are just starting to understand microbial community structure within ruminants. As a first attempt to better understand the influence of viruses on host bacterial populations, we investigated viral and total, microbial community structure and function using metagenomic shotgun sequencing under changing dietary conditions. When a shared read approach and protein clusters were used, the structure of total microbial communities significantly differed based on diet and host, while viral metagenomes differed only by diet. Using community level metabolic networks, we further explored why different diets enrich phage communities for specific metabolic pathways. Enzymes differentially abundant in the total metagenome and virome were more centrally located and a shorter path length compared to non-differential genes in the network. This ongoing work begins to suggest diet, rather than host factors, has a strong influence on the structuring of rumen phage populations and that phages encode for an adaptive repository of central metabolic functions related to selection pressures driven by altering environmental conditions. Current efforts are focused on better understanding what governs, why certain central metabolic genes are enriched and how this is related to the flow of information through metabolic networks.Item Endophytic bacterial diversity of mangrove leaves.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Gunathunga, S.U.; Rathnayake, V.N.Endophytes are by definition, the microorganisms that reside in the plant tissues, colonizing locally as well as systemically, without causing any harm to the particular plant. Both the plant and its endophytes have benefits for each other, hence this is called a mutualistic relationship, where both species gain advantage. Considering the scarcity of records regarding mangrove endophytic bacteria in Sri Lanka, a preliminary study was carried out using four true mangrove species from “Kadol kale” mangrove forest (Negombo, Sri Lanka). There are two groups of mangroves; major mangrove species and mangrove associates. Major mangroves are true mangrove species that grow only in mangrove environment, while mangrove associates are found in within or in peripheral areas of mangrove forests. Mangrove species, namely Avicennia marina, Brugeira gymnorhiza, Lumnitzera racemosa and Rhizophora mucronata were selected with the objective of isolating and determining endophytic bacterial diversity of mangrove leaves. For the isolation of endophytes, the healthy mature leaves were surface sterilized, and bacteria from inner tissues were extracted using a buffer and inoculated in to Tryptone Soy Agar medium using spread plate technique and plates were incubated for 1 week at 30 °C. Fifty bacterial isolates were obtained according to their phenotypical attributes. Morphological, cultural and some biochemical characteristics of these isolates were studied and according to Bergey’s manual of determinative bacteriology, isolates were grouped in to their generic level. A total of 17 isolates from Avicennia marina (AM), 17 isolates from Brugeira gymnorhiza (BG), 11 isolates from Lumnitzera racemose (LR) and 5 isolates from Rhizophora mucronata (RM) were obtained. Majority of the isolates were belonged to the genus Bacillus and rest of the isolates belonged to genus Aerococcus, Corynebacterium, Staphylococcus, Enterobacter, Rothia and Micrococcus.