Abstract
Among the diverse soil bacteria, plant growth promoting rhizobacteria (PGPR) mark an important role in enhancing plant growth through a range of beneficial functions. This is mainly achieved by effective rhizosphere colonization by PGPR. Biofilm development by PGPR is considered as a survival strategy over the planktonic mode of growth under stress and natural conditions. Since the performance of microbial inoculants under field conditions is not always consistent due to various biotic and abiotic factors affecting survival, colonization and functions. Therefore, the rhizobacteria with efficient colonization ability and exhibiting multiple PGP traits are expected to perform better. We hypothesized that the biofilm forming ability of PGPR on plant root will be an added advantage to rhizosphere colonization. Therefore, we have selected a promising isolate of PGPR through random screening programme from rhizoplane of wheat (Triticum aestivum). The selection was based on biofilm development ability, multifarious PGP activities (production of indole acetic acid, sidero-phore, phosphate solubilization, hydrogen cyanide, ammonia production and biocontrol activity) and tolerance to salinity and heavy metals. The selected isolate was identified by 16 s rRNA partial gene sequencing as Pseudomonas entomophila-FAP1. The strain FAP1 formed strong biofilm in microtitre plate, glass surface as well as on the roots of wheat seedlings. Biofilm forming capacity of the FAP1 was characterized by scanning electron microscopy and confocal laser scanning microscopy. FAP1 exhibited biofilm-related traits such as the production of exopolysaccharides, EPS (1501.33 ± 1.08 μg ml-1), alginate (212.81 ± 1.09 μg ml-1), swarming motility (22 ± 1.36 mm), swimming motility (31 ± 2.12 mm) and cell surface hydrophobicity (63%). Rhizosphere colonization by FAP1 was found 7.5 Log CFU g-1 of soil comparable with rhizoplane colonization (7.2 Log CFU g-1 of root). Therefore, biofilm formation on plant roots by promising PGPR may be included as an additional criterion to select a better rhizosphere colonizer. Further, study with mutant deficient in biofilm should be developed for comparative study to explore the exact contribution of biofilm in root colonization under natural soil-plant system.
Highlights
Biofilm development by rhizobacteria is considered as a common mode of lifestyle under the natural condition and provided protection to a number of biotic and abiotic stress conditions
Biofilm development by plant growth promoting rhizobacteria (PGPR) is considered as a survival strategy over the planktonic mode of growth under stress and natural conditions
Majority of the rhizobacteria are capable of forming biofilm in vitro but root-associated biofilm in situ has yet to be explored as the conditions are different in the soil-plant root system
Summary
Biofilm development by rhizobacteria is considered as a common mode of lifestyle under the natural condition and provided protection to a number of biotic and abiotic stress conditions. The interaction among various plant growth promoting rhizobacteria has been explored mainly under the planktonic mode of growth. Understanding on the behavior of PGPR in biofilm mode on the root surface and soil is still in the stage of infancy. An in-depth investigation of the biofilm development on root surface and rhizosphere colonization is needed to improve the understanding of plant-microbe interaction. Biofilm constitutes a protected growth modality allowing bacteria to survive in hostile environment. Various traits which are associated directly or indirectly to the biofilm development includes EPS production, swarming and swimming motility, cell surface hydrophobicity and alginate production in Pseudomonas sp. Various traits which are associated directly or indirectly to the biofilm development includes EPS production, swarming and swimming motility, cell surface hydrophobicity and alginate production in Pseudomonas sp. and other bacteria [1]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
