Morphological, physiological and biochemical characterizations of some soil isolates of Bacillus cereus group from Algeria

Bacillus cereus is a group of bacteria frequently found in soil, widely distributed in the environment. They are a group of ubiquitously facultative anaerobic spore-forming Gram-positive rods and are of health and economic benefits. The present study was conducted to identify, characterize about 36 B. cereus and examined for their potential plant growth promoting (PGP), which was tested in vitro. Parameters assessed were indole acetic acid (IAA) production, phosphate solubilization, starch hydrolysis, proteolytic activity and biofilm formation. Multiple B. cereus were isolated from several soil plots from South-Western region of Algeria and characterized by using phenotypic methods including fatty acid methyl ester. Ten bacterial isolates were examined in this study. Fatty acid profiles showed that bacterial isolates were classified into B. cereus group, three isolates were B. cereus Subgroup "A" and seven isolates were B. cereus Subgroup "B". Temperature effect on the maximal specific growth rate was studied in B. cereus between 10 and 50°C, no growth was observed in 10°C, all B. cereus isolates grown from 15 to 45°C and no grown observed in 20 to 50°C. This study demonstrates adaptation of isolates of the B. cereus group to different habitats. The ability to solubilize precipitated phosphate was positively exhibited by three isolates, five isolates showed ability to produce IAA. All the isolated bacterial isolates had amylolytic and proteolytic activity. All isolates did not form a biofilm in the microtiter plate assays, while all B. cereus in our study formed biofilm in tubes at air-liquid interfaces.