Browsing by Author "Rathnayake, I.V.N."

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Chromium accumulation in Cr (VI) resistant bacteria
(Book of Abstracts, Annual Research Symposium 2014, 2014) Abewickrama, J.H.G.; Jayarathne, D.L.; Rathnayake, I.V.N.; Gunawardane, M.M.
Accumulation of Cr(VI) is one of the methods used in bacteria to overcome elevated chromium concentrations. These hyperaccumulators of Cr(VI) are important in bioremediation of Cr (VI) containing wastes. Accumulation of Cr(VI) has been previously reported in Alcaligenes eutrophus CH34, Bacillus subtilis and some Pseudomonas sp. During this study Chromium accumulation of a Cr (VI) resistant Psuedomonas sp., Escherichia coli JM109 and the transformant E.coli JM109 with plasmids extracted from the Cr(VI) resistant Pseudomonas sp. were compared. Cr (VI) accumulation was estimated at 0, 5, 10, 15 mg/L Cr (VI) concentrations after 72 hour exposure time. The cells were subjected to acid lysis and the chromium concentrations were estimated using Atomic Absorption Spectrometry. Cr (VI) accumulation percentages of Cr (VI) resistant Pseudomonas sp. under 5, 10, 15 mg/L Cr (VI) concentrations were 51.38%, 37.46% and 43.13% respectively. Those percentages were 2.6%, 1.54%, and 1.12% for E.coli JM109 while they were 35.58%, 20.06% and 34.03% for the transformant. There is a possibility of chromium accumulation being regulated by Cr (VI) resistant genetic determinants found on plasmids. In addition, the nature of the host that bears the plasmid is also important for the Cr (VI) accumulation mechanism.These hyperaccumulators of Cr (VI) showed potential use in bioremediation of Cr(VI) containing wastes.
Comparison of Sensitivity of Tropical Freshwater Microalgae to Environmentally Relevant Concentrations of Cadmium and Hexavalent Chromium in Three Types of Growth Media
(Bull Environ Contam Toxicol, 2020) Munagamage, T.; Rathnayake, I.V.N.; Pathiratne, A.
Sensitivity of tropical freshwater microalgae (Mesotaenium sp., Chlorococcum sp. and Scenedesmus sp.) to environmentally relevant concentrations of hexavalent chromium (Cr6+) and cadmium (Cd2+) was compared individually in three growth media viz. Bold’s Basal Medium (BBM), Test Medium 1 (TM1) and Test Medium 2 (TM2) based on fluorescence reduction. Free metal content of growth media was determined by Visual MINTEQ (version 3.1). After 24 h, relative fluorescence of microalgae in the three media decreased with increased metal concentration showing a concentration dependent graded toxicity response. All microalgae were more sensitive to the metals when grown in TM1, when compared, more sensitive to Cr6+ than Cd2+. Metal speciation indicated that TM1 and TM2 media have higher percentage of bioavailable Cd2+ than BBM, and chromium was present mainly as CrO42− and HCrO4−. The results suggest that the TM1 medium is more suitable under short term exposure of microalgae to metals in environmental monitoring.
Medium composition affects the heavy metal tolerance of microalgae: a comparison
(Journal of Applied Phycology, 2021, 2021) Rathnayake, I.V.N.; Megharaj, M.; Beer, M.; Naidu, Ravi
Tolerance of the three metals cadmium (Cd), copper (Cu), and zinc (Zn) by four microalgal species was investigated in three different culture media available in the literature together with a modified version in order to ...
Microbiological quality of ballast water discharged from ships arriving in Colombo inner harbour
(Marine Environment Protection Authority, 2015) Jayasundera, C.D.; Rathnayake, I.V.N.
Plant and Plant Associated Microflora: Potential Bioremediation Option of Indoor Air Pollutants.
(Nepal Journal of Biotechnology, 2021, 2021) Gunasinghe, Y. H. K. I. S.; Rathnayake, I.V.N.; Deeyamulla, M. P.
Indoor air pollution is a significant problem today because the release of various contaminants into the indoor air has created a major health threat for humans occupying indoors. Volatile Organic Compounds (VOCs) are ...
Plasmid mediated Chromium resistance of bacteria
(Book of Abstracts, Annual Research Symposium 2014, 2014) Abewickrama, J.H.G.; Jayarathne, D.L.; Rathnayake, I.V.N.; Gunawardane, M.M.
Plasmid-mediated Cr(VI) resistant bacteria are naturally found in environments contaminated with chromium releasing industrial effluents. These envirnments may contain microorganisms those have genetically regulated mechanisms to overcome elevated Cr(VI) levels. Such mechanisms could be regulated by genes found either in chromosomal DNA or plasmid DNA. In order to understand the exact mechanism and for the possible use of such mechanisms in monitoring and control of heavy metal pollution, it is important to determine whether the resistance is plasmid borne or controlled by chromosomal DNA. There are certain plasmids which contain genes to resist highly toxic hexavalent chromium (chromates and dichromates). Resistance to chromate is determined by decreased chromate transport by the resistant cells. The genes for a hydrophobic polypeptide, ChrA, have been identified in Cr(VI) resistance plasmids of Pseudomonas aeruginosa and Alcaligenes eutrophus.
Sensitivity of Four Cyanobacterial Isolates from Tropical Freshwaters to Environmentally Realistic Concentrations of Cr6+
(Springer US., 2016) Munagamage, T.; Rathnayake, I.V.N.; Pathiratne, A.; Megharaj, M.
Sensitivity of four tropical cyanobacteria viz. Coelosphaerium sp., Synechococcus sp., Oscillatoria sp. and Chroococcus sp. to environmentally relevant concentrations of Cr6+, Cd2+ and Zn2+was assessed based on fluorescence change as a proxy for growth reduction. At 24 h exposure, the growth reduction inthe cyanobacteria followed the order: Zn2+ < Cr6+ ≤ Cd2+. Of the four cyanobacteria, Synechococcus was the most sensitive for Cr6+, where as Chroococcus was the most sensitive for Cd2+and Zn2+. Sensitivity was gradually decreased by 96 h implying the acquisition of tolerance by cyanobacteria to heavy metal ions with prolonged exposure.
Sensitivity of freshwater organisms to cadmium and copper at tropical temperature exposures: Derivation of tropical freshwater ecotoxicity thresholds using species sensitivity distribution analysis
(Ecotoxicology and Environmental Safety, 2021, 2021) Arambawatta Lekamge, S. H.; Pathiratne, A.; Rathnayake, I.V.N.
Tropical freshwater ecosystems are increasingly influenced by chemical stressors including heavy metals posing threats to biodiversity. Adequate ecotoxicity data are not available for native tropical freshwater species for ...
Survival of Skin Resident Bacterial Flora (SRBF) in the presence of facial cleansers
(Ruhuna International Science & Technology Conference University of Ruhuna, Matara, Sri Lanka, 2021, 2021) Balasooriya, B.A.Y.B.; Rathnayake, I.V.N.
Human skin has a balanced Skin Resident Bacterial Flora (SRBF) which is beneficial for healthy skin maintenance and different factors are responsible for their well-being. Since facial cleansers are such potential factors ...
Toxicity of selected facial cleansers to soil bacterial flora.
(International Conference of the Biotechnology Society of Nepal (ICBSN), 2021, 2021) Balasooriya, B.A.Y.B.; Rathnayake, I.V.N.
Facial Cleansers are widely used Personal Care Products containing complex mixtures of different substances. Large quantities of these substances enter the environment in unaltered form through regular usage of these ...