Characterization of indigenous bacillus isolates from stabilized sludge in petrochemical industry

Abstract

Bacillus species are rod-shaped, endospore-forming aerobic or facultatively anaerobic, Gram-positive bacteria; in some species cultures may turn Gram-negative with age. The many species of the genus exhibit a wide range of physiologic abilities that allow them to live in every natural environment. The spores are resistant to heat, cold, radiation, desiccation, and disinfectants. Bacillus species are used in many medical, pharmaceutical, agricultural, and industrial processes that take advantage of their wide range of physiologic characteristics and their ability to produce a host of enzymes, antibiotics, and other metabolites. Certain Bacillus species are important in the natural or artificial degradation of waste products. We isolated 15 indigenous Bacillus isolates from stabilized sludge in petrochemical plant in Serbia (FOV – HIP “Petrohemija”, Pancevo) and investigated their morphological and biochemical characteristics, emulsification activity and sensitivity to antibiotics and heavy metals. In addition, we estimated the genetic diversity of isolates by RAPD and rep-PCR. Three of 15 isolates showed very strong emulsification ability of xylol (E24 from 95 to 100). Six isolates showed strong emulsification of mineral oil (E24 from 78 to 100). All isolates were tolerant to 100μg/ml of Zn and Co, 10μg/ml of Hg and Mo, while eleven isolates showed tolerance to 10μg/ml of Cd and six isolates to 100μg/ml Hg. Only one isolate was sensitive to trimethoprim (5 μg). All isolates were sensitive to bacitracin (40U), cephalexin (30 μg), clindamycin (2 μg) and neomycin (120μg), while five isolates were resistant to novobiocin (5μg) and two to bacitracin (40U). Based on PCR analysis, we assessed genetic similarity of investigated Bacillus isolates.