Isolation and Characterization of Bacteria of Mangrove Rhizosphere in the Mekong Delta,

Abstract

Total of 125 rhizospheric bacterial isolates were isolated from 18 rhizospheric soil samples of mangrove at Ca Mau Peninsula (Ca Mau province, Mekong Delta of Vietnam). Although all of them had the abilities of ammonium synthesis and phosphate solubilization, the isolated strains had excellent phosphate solubilizing potential. The sequences from selected nitrogen-fixing and phosphate-solubilizing bacteria (22 isolates) showed high degrees of similarity to those of the GenBank reference strains (between 97% and 99%). From 22 isolates, 16 strains belonged to Bacilli, and 6 strains were Gamma-Proteobacteria. Whereas our results showed that there were some good strains for nitrogen fixation as Bacillus subtilis DLB4b, Bacillus sp. VAB2b, Enterobacter sp. MABlb and Bacillus sp. MDBlc and strains for phosphate solubilation as Bacillus subtilis MLNlb, Bacillus sp. MLNlc, Bacillus subtilis VDNlf and Bacillus subtilis MDNlc, all of them tolerated at a concentration of 4% NaCl. However, the strain Bacillus subtilis MAB2b revealed as a promising candidate with multiple beneficial characteristics (both good nitrogen fixation and phosphate solubilization). Besides, the isolated bacterial strain has the potential for application as inoculants adapted to poor, soil salinity as well many kinds of crop because it is not only famous strain but also safe strain for sustainable agriculture in “sea level rise” condition.