An antibiotic, heavy metal resistant and halotolerant Bacillus cereus SIU1 and its thermoalkaline protease

Abstract

BackgroundMany workers have reported halotolerant bacteria from saline conditions capable of protease production. However, antibiotic resistance and heavy metal tolerance pattern of such organisms is not documented very well. Similarly, only a few researchers have reported the pattern of pH change of fermentation medium during the course of protease production. In this study, we have isolated a halotolerant Bacillus cereus SIU1 strain from a non-saline environment and studied its antibiotic and heavy metal resistance pattern. The isolate produces a thermoalkaline protease and changes the medium pH during the course of fermentation. Thermostability of protease was also studied for 30 min.ResultsSeventy bacterial strains isolated from the soils of Eastern Uttar Pradesh, India were screened for protease production. All of them exhibited protease activity. However, 40% bacterial isolates were found good protease producers as observed by caseinolytic zones on milk agar plates. Among them, culture S-4 was adjudged as the best protease producer, and was identified as Bacillus cereus by morphological, biochemical and 16 S rDNA sequence analyses. The isolate was resistant to heavy metals (As2+, Pb2+, Cs1+) and antibiotics (penicillin, lincomycin, cloxacillin, pefloxacin). Its growth behavior and protease production was studied at 45°C and pH 9.0. The protease units of 88 ml-1 were noted in unoptimized modified glucose yeast extract (GYE) medium during early stationary phase at 20 h incubation period. The enzyme was stable in the temperature range of 35°-55°C.ConclusionsAn antibiotic and heavy metal resistant, halotolerant Bacillus cereus isolate is capable of producing thermoalkaline protease, which is active and stable at pH 9.0 and 35°-55°C. This isolate may be useful in several industrial applications owing to its halotolerance and antibiotic and heavy metal resistance characteristics.

Antibiotic and Heavy Metal Tolerance of Some Indigenous Bacteria Isolated From Petroleum Contaminated Soil Sediments with A Study of Their Aromatic Hydrocarbon Degradation Potential

“…cereus showed resistance / intermediate resistance against 6 of the 9 antibiotics whereas rest of the isolates showed resistance only against 2 antibiotics (Penicillin and Cefuroxime). Multiple resistance against heavy metals and antibiotics of B. cereus isolates has also been reported by Singh et al (2010). Since several genes responsible for degradation of aromatics and for heavy metal/antibiotic resistances are located on plasmids which are key vectors of horizontal gene transfer, the members of the bacterial community gained opportunity to expand their chromosome encoded resistance and catabolic potential with those encoded on plasmids.…”

Microbial Characterization and Optimization of Protease Production by Bacillus SP. Isolated from Soil

“…Thereafter, the stationary phase was initiated. The bacterium exhibited minimal growth rate at 60C, which may be due to the inhibition in protease production [30][31][32]. Microbes exhibited higher growth rate at optimum pH.…”

Extreme Environments: Goldmine of Industrially Valuable Alkali-stable Proteases

“…Also, ground water available in different Indian geoclimatic regions is saline [186], which may be detrimental for the cleaning potential of detergents. Hence, the presence of halotolerant alkaline protease in detergents can make the washing efficient and effortless [187].…”