INDUCTION OF AGGREGATION IN PLANT GROWTH PROMOTING RHIZOBACTERIA

G. SAMATHA¹, K. KUMUTHA²*, R. ANANDHAM³, E. KOKILA DEVI⁴, R. KRISHNAMOORTHY⁵, N. SAI APARNA^6
1Department of Agricultural Microbiology, Agricultural College and Research Institute, Madurai, 625 104, Tamil Nadu Agricultural University, Coimbatore, 641003, India
²Department of Agricultural Microbiology, Agricultural College and Research Institute, Madurai, 625 104, Tamil Nadu Agricultural University, Coimbatore, 641003, India
³Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore, 641003, India
⁴Department of Biotechnology, Tamil Nadu Agricultural University, Coimbatore, 641003, India
⁵Department of Crop Management, Vanavarayar Institute of Agriculture, Pollachi, 642 103, Tamil Nadu Agricultural University, Coimbatore, 641003, India
⁶Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore, 641003, India
* Corresponding Author : kkumuthatnau@gmail.com

Received : 30-06-2019     Accepted : 26-07-2019     Published : 30-07-2019
Volume : 11     Issue : 7       Pages : 1645 - 1650
Int J Microbiol Res 11.7 (2019):1645-1650

Keywords : Methylobacterium, Fructose, Ammonium chloride, Aggregated cells, Plant growth promoting traits
Conflict of Interest : None declared
Acknowledgements/Funding : Authors are thankful to Agricultural College and Research Institute, Madurai, 625 104, Tamil Nadu Agricultural University, Coimbatore, 641003, Tamil Nadu, India
Author Contribution : All authors equally contributed

Bio-inoculants have to overcome several biotic and abiotic stresses for their successful colonization on the rhizosphere region. Such adverse conditions drive the researchers to exploit the abilities of the aggregated bacterial cells in enhancing their survivability in rhizosphere. The main objective of this study is to develop aggregated cells by preparing aggregation inducing medium using fructose and ammonium chloride as carbon and nitrogen sources respectively which resulted in aggregation in high C:N medium visible to the naked eye after 24 hours of inoculation. Methylobacterium, Azospirillum, Pseudomonas and Pantoea formed aggregated cells whereas no aggregation was noticed in Bacillus cultures. Poly-β-hydroxybutyrate granules or inclusion bodies were observed higher in aggregated cells than the non-aggregated cells. Microbial load of the aggregated cells was relatively higher than non aggregated cells which was 4×1011 CFU ml-1 with more biomass. Microbial adhesion was also observed more in aggregated Methylobacterium cells. Plant growth promoting traits such as IAA, ACC deaminase, phosphate, zinc and silica solubilization were observed more in the aggregated cells than the non aggregated cells. The results revealed the effectiveness of aggregated cells than non aggregated cells on PGP traits.

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