Journal of Environmental Biology

Influence of salinity variations on exocellular polysaccharide production, biofilm formation and flocculation in halotolerant bacteria

B.H. Hong¹, M.M Joe¹,3, G. Selvakumar¹, K.Y. Kim¹, J.H. Choi² and T.M. Sa¹*?

¹Department of Environmental and Biological Chemistry, Chungbuk National University, Cheongju, Chungbuk, 361 763, Republic of Korea

²Department of Food Science and Biotechnology, Wonkwang University, Iksan, 54538, Korea

³Department of Microbiology, School of Life Sciences, VELS University, Chennai-600 117, India

*Corresponding Author E-mail: tomsa@chungbuk.ac.kr

Key words

Biofilm,

Exopolysaccharide,

Flocculation,

Halotolerant bacteria,

Salinity

Publication Data

Paper received : 04.03.2016

Revised received : 14.11.2016

Accepted : 22.12.2016

Abstract

Aim: The present study was carried out to evaluate the exopolysaccharide (EPS) production, biofilm formation and flocculation in four halotolerant plant growth promoting (PGP) bacterial strains i.e., Brevibacterium iodinum RS16, Micrococcus yunnanensis RS222, Bacillus aryabhattai RS341, B. licheniformis RS656 under different salt levels.

Methodology: Four halotolerant plant growth promoting bacterial strains namely B. iodinum RS16, M. yunnanensis RS222, B. aryabhattai RS341 and B. licheniformis RS656 were studied for their exopolysaccharide (EPS) production, biofilm formation and flocculation efficiency under different NaCl levels. EPS production of halotolerant plant growth promoting strains was quantified in terms of dry weight and glucose content. Biofilm formation of the plant growth promoting halotolerant strains was quantified based on a micro titer plate assay. Plant growth-promoting efficiency of halotolerant strains was quantified in red pepper plants in terms of vigor index and fresh weight.?

Results: Among the strains, strain B. aryabhattai RS341 recorded the highest EPS dry weight (5.80 g l^-1), while the highest floc yield (0.60 g l^-1 dry weight) was recorded by B. licheniformis RS656 at 2 mM NaCl concentration. Regression analysis revealed that EPS content, expressed in terms of dry weight, and flocculation in terms of floc yield, correlated positively with NaCl levels. The highest biofilm formation in Canola root surfaces was observed in the strain B. iodinum RS16 in all NaCl concentrations. All the halotolerant strains promoted plant growth as evidenced by the increased vigor index and fresh weight irrespective of the level of NaCl. 

Interpretation: It was observed that halotolerant bacterial strains were able to promote plant growth in the presence of NaCl through the mechanisms of EPS production, flocculation and biofilm formations.?????? ??????????

Copyright ? 2017 Triveni Enterprises. All rights reserved. No part of the Journal can be reproduced in any form without prior permission. Responsibility regarding the authenticity of the data, and the acceptability of the conclusions enforced or derived, rest completely with the author(s).