Browsing by Author "Wickramasinghe, P. M. T. B."

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Exposure to environmentally relevant concentrations of acetaminophen increases the vitellogenin expression in juvenile Danio rerio (zebrafish)
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Ishara, A. A. A. P.; Perera, K. D. C.; Gunathilaka, N.; Gunasekera, D.; Wickramasinghe, P. M. T. B.; Rajapaksa, G.
Non-Steroidal Anti Inflammatory Drug acetaminophen has become the most common pharmaceutical pollutant in aquatic ecosystems. Recently a non-classical pathway of endocrine disruption is suggested with acetaminophen. Early life stages account for a significant level of hormone-regulated development therefore, it is important to assess whether early life exposure to acetaminophen could result in endocrine disruption in aquatic organisms. Vitellogenin (Vtg) is an egg precursor protein produced in response to estrogen and serves as a reliable molecular marker to assess the xenoestrogen-induced endocrine disruption. Therefore, this study was carried out to investigate the effects of long-term juvenile exposure to environmentally relevant concentrations of acetaminophen on vitellogenin expression in model organism, zebrafish (Danio rerio). Zebrafish of 25 days post fertilization were maintained under environmentally relevant acetaminophen concentrations of 10 μg/L, and 75 μg/L, and in control tanks for 60 days in triplicate with 18 fish in each tank. Vtg-1, the most predominant type of Vtg mRNA produced in zebrafish liver was analyzed using qRT-PCR with β-actin as the housekeeping gene. Furthermore, hepatic vitellogenin expression has been observed with hematoxylin and eosin staining of zebrafish hepatic sections. According to the results, acetaminophen-exposed zebrafish showed higher Vtg-1 gene expression than the fish of control treatment. 10 μg/L acetaminophen showed the highest Vtg-1 expression followed by 75 μg/L of acetaminophen in fish. Hematoxylin and eosin staining of the liver of male zebrafish from control treatments appeared eosinophilic indicating the absence of Vtg while hepatocytes of control female fish were more basophilic indicating Vtg expression. However, under 10 μg/L of acetaminophen exposure, male and female fish hepatocytes appeared more basophilic than the control treatment indicating acetaminophen-induced Vtg secretion. However, 10 μg/L concentration shows a higher basophilic nature compared to 75 μg/L, especially in female fish. The lowered Vtg expression in 75 μg/L can be due to the increased hepatotoxicity caused by the higher doses of acetaminophen which overrides the physiological activity in acetaminophentreated fish, dilated capillaries were observed compared to fish in the control treatment. It has been demonstrated that estrogenic xenobiotics stimulate the synthesis of Vtg by acting on the liver's estrogen receptors. Increased Vtg -1 mRNA in low acetaminophen concentration as shown in qRT- PCR and liver histopathology postulate an “estrogen-like activity of acetaminophen”. The results indicate that acetaminophen has the potential to increase vitellogenin expression in zebrafish even under environmentally relevant low concentrations indicating an endocrine disruption effect during juvenile exposure.
Isolation and screening of synthetic dye degrading bacteria from textile effluents in Western Province, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Fernando, W. P. E. M.; Wijesinghe, L. H.; Wickramasinghe, P. M. T. B.; Senarath, G. L. C. N. T.; Efrem, S. M.
Synthetic dyes in the textile industry contribute significantly to environmental pollution, particularly through effluents. Numerous chemical and physical methods have been developed during the past few decades to eliminate toxic dyes from wastewater. Most of these techniques have limitations, such as the generation of sludge and additional negative environmental and economic effects caused by increased chemical demand. This study aimed to isolate and characterise the bacterial strains from textile effluents with the ability to degrade synthetic dyes, which could serve as a solid basis for establishing viable bioremediation techniques. The focus was directed on efficiently recycling wastewater containing textile dye effluents. The effluent samples were collected from industrial discharge points in Negombo and Biyagama, and the bacterial strains were isolated using a modified nutrient agar medium containing dye. The isolated strains were characterised by observing their morphological and biochemical characteristics, which included gram staining, catalase test, and the triple sugar iron test. An initial test for dye degradation was carried out using two synthetic dyes, Acid red 88 and Methylene blue, at 37 ˚C for 72 hours. The degradation efficiency was quantitatively measured using a UV-visible spectrophotometer in a dye decolourization assay. The bacterial isolates with higher efficiency in dye degradation were further tested for the effect of environmental changes, such as pH and dye concentration variations. The isolates were tested in duplicates for their growth and decolourising ability in a dye-containing media at pH 5 and pH 9 and at 5 mg/l and 20 mg/l dye concentrations. Most of the selected isolates showed decolourisation of 53-66% at pH 5 and 65-94% at pH 9 for acid red 88 within 48 hours. Among the selected isolates, acid red 88 containing media, L2(06) achieved the highest decolourisation of 93.93 ± 0.92 % after 48 hours of incubation at pH 9 (p=0.0001). Several isolates decolourised methylene blue 68-83% at pH 5. Isolate L2(07) was identified to decolourise in methylene blue in both pH levels, achieving decolourisation of 82.28 ± 7.56 % in pH 5 (p=0.02) and 92.33 ± 1.48 % in pH 9 (p=0.01). Moreover, most isolates showed decolourisation above 95% at 5 mg/l and 84% at 20 mg/l in acid red 88 media. For methylene blue, all selected isolates showed decolourisation above 70% in both concentrations. The results revealed the successful isolation of several bacterial strains capable of degrading two different acid red 88 and methylene blue concentrations within a pH range of 5-9, suggesting their adaptability to diverse industrial effluent settings. This research contributes important new understandings of the microbial ecology of synthetic dye degradation in textile effluents and lays the groundwork for creating environmentally friendly and long-lasting bioremediation techniques.