Rhizosphere Bacteria with the Potential of Forming Biofilm and Plant Growth Promotion Under Salt Stress

Abstract

Bacteria develop microbial communities as biofilm under different environmental stress factors like salinity, temperature, pH and antimicrobial agents and help in the adherence of bacteria to different surfaces. The growth of microorganisms is inhibited in the presence of salinity. An objective of the present research work was to check the growth response and biofilm behavior of indigenous bacteria isolated from plant rhizosphere in the presence of salt. Bacterial strains were named as TAK, TAF and SY. Biofilm formation response was also observed at different molar concentration (0M, 1M, 2M and 3M) of NaCl following test tube assay after 24, 48 and 72 hours of culture incubation. Results showed that TAK has the best biofilm forming ability on abiotic surface as compared to isolate TAF and SY, however, isolate SY showed growth and form biofilm under saline conditions. Bacterial plant growth promoting response was also determined on the basis of improvement in seed germination, shoot length and root length. In general, bacterial biofilm was best at 1M to 3M NaCl stress and 72 hours of culture incubation . Inoculation with SY improved (shoot length 3 % and root length 10.41 %) at 100 mM when compared to inoculated seedlings at 0 mM NaCl stress. It was concluded that among all three isolates, isolate SY used for broad perspective to increase soil fertility. While working to strive for the most promising isolates involved in plant growth promotion, the indigenous isolates showed the promising ability to improve germination of seeds in saline soil while helping the seeds to grow in salt stress conditions.