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PHENOL RESISTANT BACTERIA FROM SOIL: IDENTIFICATION-CHARACTERIZATION AND GENETICAL STUDIES

MUNAZZA AJAZ, NABEELA NOOR, SHEIKH AJAZ RASOOL AND SHAKEEL A. KHAN

Abstract: Phenol and its derivatives are highly toxic and a source of serious environmental concern. The present study was undertaken to isolate and characterize the phenol resistant bacteria from indigenous soil (rhizosphere). Thirty soil bacterial isolates were identified and screened for phenol resistance. Four of these strains (belonging to genera Staphylococcus, Corynebacterium, Bacillus, and Proteus) were found resistant to 15mM of phenol. Growth kinetic patterns and generation time of these phenol resistant strains were determined. At extremely stressful conditions (glucose starved minimal medium with different molarities of phenol) the generation time was considerably extended. However, Bacillus subtilis found an optimum C:N ratio in minimal medium with 0.1mM phenol with a generation time of 174 minutes (several times shorter than the generation time of other sister resistant strains). Location of phenol resistant genes was determined by acridine orange mediated plasmid curing. Interestingly, all the resistant isolates lost the characteristic (to resist phenol) after curing thereby indicating the plasmid genes being responsible for this property. Plasmid DNA isolated from the uncured strains was transferred into the cured competent recipient cells. Stable intrageneric transfer of phenol resistance plasmid gene(s) was observed.
 

Department of Microbiology, University of Karachi, Karachi-75270, Pakistan.