Browsing by Author "Sirisena, D.M."

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A preliminary investigation on proteins produced by iron resistant and iron sensitive rice varieties
(Proceedings of the Annual Research Symposium 2005-Faculty of Graduate Studies, University of Kelaniya, 2005) Attanayake, K.P.R.N.; Sirisena, D.M.
K.P.R.N. Attanayake and D.M. Sirisena
Analysis of naphthalene and phenanthrene degradation catabolic genes of phyllosphere bacterial strains, Alcaligenes faecalis and Alcaligenes sp. DN25
(2015) Kannangara, B.T.S.D.P.; Undugoda, L.J.S.; Sirisena, D.M.
The bacterial strains, Alcaligenes feacalis and Alcaligenes sp. DN25 which were isolated from the phyllosphere of four ornamental plant species, Ixora chinensis, Ervatamia divaricata, Hibiscus rosa-sinensis and Amaranthus cruentus in five highly polluted sites in Sri Lanka, showed the highest phenanthrene and naphthalene degradation ability. Transformation and plasmid curing results of them revealed, naphthalene and phenanthrene degradation ability of these bacterial strains were plasmid encoded character. The occurrence of naphthalene specific (nahR and nahU) genes and phenanthrene specific (phnAc and phnG) genes of these catabolic plasmids were analyzed by PCR using degenerate primers. According to the amplification results, plasmids of Alcaligenes faecalis and Alcaligenes sp. DN25 harbour nahR, nahU and phnG genes but, lack of phnAc gene. RFLP and sequence data of nahU and nahR amplicons revealed, both of these genes were homologous to these two bacterial strains. But, phnG gene of two phenanthrene and naphthalene degrading phyllosphere bacterial strains was coexistence as two distinct copies of alleles.
Aromatic hydrocarbon degrading Phyllosphere Fungi
(University of Sri Jayawardhanapura, 2013) Undugoda, L.J.S.; Kannangara, S.; Sirisena, D.M.
Aromatic hydrocarbon degrading phyllosphere microorganisms
(University of Kelaniya, 2013) Undugoda, L.J.S.; Kannangara, S.; Sirisena, D.M.
Pyrogenic nature of the most recalcitrant aromatic hydrocarbons elevates their persistency in the environment and rapid bioaccumulation in living organisms. Therefore, air pollution by aromatic hydrocarbons is one of the current concerns. It has been shown that utilization of phyllosphere microorganisms as bioremediators is an efficient means of remediating these air pollutants. This study was carried out to isolate aromatic hydrocarbon degrading phyllosphere fungi and bacteria from selected plants; Ixora sp., Hibiscus sp., Ervatamia sp., and Amaranth sp., which are highly abundant in roadsides around the oil refinery at Sapugaskanda and high traffic areas. Phenanthrene, naphthalene, xylene and toluene degradation ability of the isolated bacteria and fungi was then examined using plate assays and spectrophotometric analysis. The best degraders were selected for further identification and characterization. Phenanthrene, naphthalene, toluene and xylene utilization rates of identified phyllosphere fungi; Penicillium sp. Aspergillus sp. and Trichoderma sp. were comparatively higher than that of isolated phyllosphere bacterial species; Pseudomonas sp., Paracoccus sp., Klebsiella sp. and Alcaligenes sp. Penicillium janthinellum utilized more than 90% of polyaromatic hydrocarbons in the medium during seven days’ incubation, but Pseudomonas sp. required 14 days of incubation to achieve that level. Moreover, the best toluene degrader Aspergillus niger degraded toluene very efficiently compared to Pseudomonas sp. The best xylene degrader Aspergilus flavus utilized only 57.35% of xylene in the medium in seven days, but 90% degradation was observed in 14 days. Therefore, xylene degradation ability of fungi was comparatively less but significantly higher than that of bacteria. Bioremediation is a very economically and environmentally friendly strategy used in cleaning of AH contaminated sites. According to the results, Penicillium spp. and Aspergillus spp. could be considered as the best fungal candidates for bioremediation. Pseudomonas sp. was able to degrade all tested AHs at relatively high efficiencies. Therefore, it can be considered as a general AH degrader. Therefore, ability of these microorganisms to degrade AH while surviving under environmental stress makes them very suitable candidates for bioremediation.
Cytotoxic and genotoxic effects of aromatic hydrocarbons on Allium cepa
(Sri Lanka Association for the Advancement of Science, 2014) Seneviratne, W.S.J.M.S.L.; Sirisena, D.M.
Isolation and characterization of cellulolytic bacteria from decomposing rice straw
(Natural Resources, Energy and Science Authority of Sri Lanka, 1995) Sirisena, D.M.; Manamendra, T.P.
Isolation of aromatic hydrocarbon degrading phyllosphere bacteria
(Sri Lanka Association for the Advancement of Science, 2013) Undugoda, L.J.S.; Kannangara, S.; Sirisena, D.M.
Potential use of blood-fed mosquitoes as evidence in forensic casework
(Sri Lanka Association for the Advancement of Science, 2007) Marasinghe, M.P.L.R.; Sirisena, D.M.; Bandara, K.B.A.T.; Hapuarachchi, H.A.C.; Abeyewickreme, W.
Medico - criminal entomology has been an important source of evidence in forensic investigations for many years. However, it has not been widely used to provide direct evidence for personal identification in forensic casework so far. In this study, we made an attempt to determine the usefulness of human DNA extracted from blood-fed mosquitoes as evidence in forensic casework. Approximately 1500 adult female mosquitoes of same age from four different species, i.e. Culex quinquefasciatus, Armigerus sabalbatus, Aedes aegypti and Anopheles tessellatus were fed with the same volume of human blood and maintained under the same environmental conditions. Three batches (N=1, 5 and 10) of randomly selected blood-fed mosquitoes were crushed and blotted onto filter paper strips separately at two hour intervals subsequent to blood meals up to 48 hours to determine the longitudinal variation in the extraction of polymerase chain reaction (PCR) amplifiable human DNA from mosquitoes. Human DNA was extracted from filter papers using a chelex-100 extraction protocol and amplified by PCR technique using human primers. Amplified products were run in 1.5% agarose gels. PCR amplifiable human DNA could be extracted from mosquitoes of Cx. quinquefasciatus and An. tessellatus up to 48 hours subsequent to blood meals. However, this duration was up to 46 and 42 hours in Ae. aegypti and Ar. Sabalbatus, respectively. The amount of amplifiable DNA was inversely proportionate to the post-feeding duration, but increased with number of mosquitoes at each time interval. Amplifiable human DNA could be extracted even from a single mosquito of four different species even after 48 hours from a blood meal with slight variation among species. However, as the amount of DNA decreases with time interval, more mosquitoes will have to be used for extraction in late sample collections. Similarly, it may be required to use a highly sensitive PCR protocol when analyzing such samples. Blood-fed mosquitoes collected even after 2 days from a crime scene may be used as a source of direct evidence for personal identification in forensic casework.