Browsing by Author "Randika, J.L.P.C."

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    Effect of Temperature on Mono and Dual Species Biofilms Formed by Salmonella, E. coli and Proteus spp.
    (Uva Wellassa University of Sri Lanka, 2021) Pathiranage, S.U.; Hasintha, K.V.D.M.; Nadishani, H.C.; Madushanka, D.N.N.; Randika, J.L.P.C.; Fernando, G.C.P.; Jayaweera, T.S.P.; Ruwandeepika, H.A.D.
    Biofilms are microbial communities encased with self-producing extracellular matrix, composed with polysaccharide, DNA and protein. Persistent survival capability of these biofilms in food contact surfaces cause contamination of food batches and pose health risk among the public. The biofilm formation is affected by several environmental factors such as temperature and humidity etc. This study was conducted to investigate the effect of temperature on biofilms formed by Salmonella, E. coli and Proteus spp. when they are present as mono species and in combinations. Organisms were incubated at two different temperatures (280C and 370C) for 120 hr and biofilm formation was quantified using microtiter plate method at different time points as 24 hr, 48 hr, 72 hr, 96 hr and 120 hr. Biofilm formation at 24 hr by Proteus spp. with Salmonella and E. coli (i.e. Proteus with E. coli and Proteus with Salmonella) were higher in the temperature of 280C compared to 370C. There was no significant effect of temperature on mono species biofilm at 24hr incubation period. At 48 hr, biofilm formation by Salmonella together with Proteus and E. coli (Salmonella with E. coli and Proteus with Salmonella) and by Salmonella alone was higher at 280C than that of at 370C. At 48 hr, Proteus and E. coli alone did not exhibit significant (p > 0.05) difference in biofilm formation at 280C and 370C. At 72 and 96 hr, the biofilm formation by Proteus and Salmonella alone and Salmonella together with Proteus (Proteus with Salmonella) showed higher biofilm formation at 280C than at 370C. But Proteus with E. coli, Salmonella with E. coli or E. coli alone did not exhibit any significant (p > 0.05) effect of temperature. At 120 hr, all the organisms alone and their combinations showed significantly higher biofilm formation at 280C than at 370C. This study concluded that temperature and time significantly (p < 0.05) affect on biofilm formation by Salmonella, E. coli and Proteus spp. individually and as combinations. This study revealed that biofilm formation at 280C is higher than their optimal growth temperature (370C). Keywords: Biofilm; E. coli; Proteus; Salmonella; Temperature
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    Isolation of Fenobucarb Resistant Bacteria from Agricultural Soils in Belihuloya, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2020) Randika, J.L.P.C.; Bandara, P.K.G.S.S.; Soysa, H.S.M.; Ruwandeepika, H.A.D.; Gunatilake, S.K.
    Pesticides are extensively used in controlling pests globally as well as in Sri Lanka, and many of these pesticidal compounds are nuisances of the natural ecosystem. But, some soil microbes immensely help in biodegrading the pesticide residues, enabling the pesticides to be less harmful. Fenobucarb is one of the extensively used carbamate insecticides in Sri Lanka. The objective of this study was to isolate resistant soil bacteria against Fenobucarb in agricultural soils. Three pooled soil samples were collected from three selected farming lands located in the Belihuloya area where Fenobucarb is used continuously in crop cycles. Each sample was grown on M9 minimal salt medium supplemented with 100 ppm Fenobucarb at 28 °C for 2-3 days. Seven well-grown single colonies were isolated and subcultured on the same medium supplemented with 100, 150, 200, 300 ppm Fenobucarb separately. Four out of the seven isolates were able to grow in all the concentrations of the pesticide. From the other three isolates, one was able to grow in 100 and 150 ppm while the other two showed their growth only in 100 ppm concentration of the pesticide. One out of four isolates that grew in all the pesticide concentrations didn't show any growth on control (M9 minimal salt medium without the pesticide). One out of two isolates that grew only in 100 ppm concentration also did not show any growth in control. However, the other five isolates exhibited very small colonies on control as well. These results support the fact that some soil bacteria can utilize pesticides as their sole carbon source. According to the above results, the study concludes that some isolated soil bacteria can resist up to the concentration of 300 ppm Fenobucarb being potential bioremediation agents for decontaminating the polluted sites. Keywords: Fenobucarb, Bioremediation, Soil Bacteria, M9 minimal salt medium