Physiological properties of facultative and obligate alkalophilic Bacillus sp. strains isolated from Saudi Arabia

Abstract

Isolation and identification of new alkalophilic Bacillus strains have increasing interest due to their possessing valuable and commercially interesting enzymes. To date, several researchers have studied the identification and characterization of alkalophilic Bacillus strains based on the phenotypic characterization as phylogenetic analysis of 16SrRNA. In the present study, six obligate and facultatively alkalophilic isolates were purified from dessert soil around Al-qunfotha city, in Saudi Arabia. All isolates were phenotypically and genotypically characterized. Among these isolates, AS3, AS4, AS5 and AS6 could grow at pH 9, 10, 11 and 12, but could not grow at pH 7 indicating that this isolates are obligate alkalophiles while, isolates AS1 and AS2 grew at pH range from 7 to 10, but could not grow at pH 11 and 12, suggesting that they could be facultative alkalophiles. All isolates could hydrolyze casein and starch, indicating that they possess interesting amylase and protease enzymes. Comparative sequence analysis of 16s rRNA of  the six alkalophilic Bacillus strains indicated that these isolates share 99% identity  with the previously isolated genes and belong to Bacillus cohnii at the full length gene nucleotide sequence level. The nucleotide sequences of 16SrRNA gene for the six isolates were given Gene-bank accession numbers: KP053301, KP053302, KP053303, KP053304, KP053305 and KP053306, respectively.

Key words: Bacillus cohnii, 16SrRNA, obligate alkalophiles, facultative alkalophiles.