Isolation and characterization of bacteria from two soil samples and their effect on wheat (Triticum aestivum L.) growth promotion

Since ancient times, soil bacteria play an important role on crop growth and yield by genetic transformation naturally. But the continuous use of chemical fertilizers reduces their number and proper environment for multiplication. Seed treatment with beneficial bacteria provides nutrients for the growth of crop plants. Thus, soil bacteria were isolated, their growth characteristics and effect on wheat growth were observed. The maximum growth of Isolate A and Isolate B was observed at pH 5.5, 7.0 and 33°C, 35°C respectively. Morphological characteristics indicated that Isolate A and Isolate B were gram-positive. But both bacteria were non-motile. In Biochemical test, both of them showed positive result in the methyl red test, catalase test, urea test, starch hydrolysis test, and negative in TSI (Triple Sugar Iron) test, mannitol salt test. Isolate B showed positive result in BSA, MacConkey test and EMB (Eosin Methylene Blue) test and Isolate A showed negative result in BSA (Bismuth Sulphite Agar), MacConkey test and EMB test. Besides, both of the bacteria were multi-drug resistance showing resistance to penicillin, amoxicillin, ampicillin cefuroxime, and ceftazidime.16S rRNA gene sequencing identified the isolate A and Isolate B as Bacillus thuringiensis and Bacillus anthracis. After 6 hours of wheat seed treatment germination percentage, fresh root and shoot weight, root and shoot dry weight, relative water content of both root and shoot, and plant growth was enhanced by Bacillus thuringiensis and Bacillus anthracis. Bacillus anthracis was more capable than bacillus thuringiensis for increasing germination rates, both root and shoot growth of wheat. It indicated that Bacillus anthracis and Bacillus thuringiensis mediated growth improvement of wheat is possibly originated in roots.