The aim of the present study was to investigate biosurfactant-producing culturable bacteria inhabiting the coast of the Arabian Sea at Karachi. Overall, 15 seawater samples were collected from the Arabian Sea coast of Karachi. Isolation, characterization, and screening for 89 biosurfactant-producing bacterial strains were conducted through 8 conventional screening tests. Through GSP agar plate method 22 strains were found to be Pseudomonas aeruginosa and Gram reaction revealed 70% of the isolates to be gramnegative. Furthermore, 24% of the isolates showed hemolytic activity, 44% exhibited positive results for oil-spreading test, 54% showed emulsification to at least 1 of the 3 hydrocarbons tested, BATH assay results indicated maximum adhesion for hexane, 52.8% produced positive results for CTAB agar plate assay, drop-collapse activity was found in 84% of the isolates, and emulsification assay revealed highest emulsification for xylene. Findings revealed none of the isolates to be negative for every screening test conducted, while only one gram-negative isolate, DGHE65, identified as Pseudomonas aeruginosa, was positive for all the tests for biosurfactant production. Results indicate that these isolates have potential for future environmental friendly applications such as bioremediation and industrial biotechnology.

Sclerotium rolfsii is a polyphagous soil borne fungus infecting more than 500 plant species across the world that is causing vast losses. Although the fungus is soil and seed borne, soil borne inoculum is most vital in infection-causing and syndrome development. Treating soil borne pathogens with fungicides is not reasonable due to very high costs. Environmental hazards are also involved. Therefore, integrated management of pathogens using biological controlling agents is the paramount alternative. Extracts of higher plants have demonstrated a wide range of activity against plant pathogenic organisms. The present research work was carried out to manage the pathogen and disease in vitro by using plant extracts. The antifungal activity of the methanolic leaf extract of two medicinally important indigenous plants, Alstonia scholaris and Azadirachta indica, against the fungal pathogen S. rolfsii was evaluated. In vitro antifungal bioassay was conducted against the S. rolfsii using different concentrations (0, 1, 2 and 5) of the methanolic leaf extract of A. scholaris and A. indica using malt extract (ME) broth as a culture medium. Different concentrations of A. indica leaf extract appreciably reduced the fungal biomass growth up to 76% as compared to the control. In the same manner, various concentrations of the leaf extract of A. scholaris significantly decreased fungal biomass up to 70% as compared to the control. Higher fungal growth was reduced by a 2% concentration of both plants. The present study concludes that the methanolic extract of A. indica has more active antifungal components and can be effectively used to manage phyto-pathogens.

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A bacterium, Pseudomonas lubricans, isolated from heavy metal laden industrial wastewater, has been shown to tolerate multiple heavy metals suggesting its importance in bioremediation of industrial effluents. P. lubricans tolerated As(III) up to 3 mg ml-1 , Cu 2+ up to 0.7 mg ml-1 , Hg 2+ up to 0.4 mg ml-1 , Ni 2+ up to 0.4 mg ml-1 and Cr 6+ up to 0.5 mg ml-1. P. lubricans showed optimum growth at pH 7 while optimum temperature for growth was 30°C. P. lubricans could oxidize As(III) 42% (42 µg mg-1 of protein), 78% (78 µg mg-1 of protein) and 95% (95 µg mg-1 of protein) from the medium after 24, 48 and 72 h of incubation at optimal conditions, respectively. The arsenite oxidizing ability shown by P. lubricans indicates its potential application in biological treatment of wastewaters contaminated with arsenic.