Genomics assisted functional characterization of Paenibacillus polymyxa HK4 as a biocontrol and plant growth promoting bacterium.

The diseases caused by phytopathogens account for huge economic losses in the agricultural sector. Paenibacillus polymyxa is one of the agriculturally important biocontrol agents and plant growth promoting bacterium. This study describes the antifungal potential of P. polymyxa HK4 against an array of fungal phytopathogens and its ability to stimulate seed germination of cumin and groundnut under in vitro conditions. The cumin and groundnut seeds bacterized with HK4 exhibited enhanced germination efficiency in comparison to controls. The use of HK4 as a soil inoculant significantly promoted the shoot length and fresh weight of groundnut plants in pot studies. The draft genome analysis of HK4 revealed the genetic attributes for motility, root colonization, antagonism, phosphate solubilization, siderophore production and production of volatile organic compounds. The bacterium HK4 harnessed several hydrolytic enzymes that may assist its competence in the rhizosphere. The PCR amplification and sequence analysis of the conserved region of the fusA gene amplicon revealed the ability of HK4 to produce fusaricidin. Furthermore, the LC-ESI-MS/MS of crude cell pellet extract of HK4 confirmed the presence of fusaricidin as a major antifungal metabolite. This study demonstrated the potential of HK4 as a biocontrol agent and a plant growth promoter.

Decoding social behaviors in a glycerol dependent bacterial consortium during Reactive Blue 28 degradation.

Biodegradation of reactive azo dyes has been an arduous problem for decades. Several efficient biosystems have been proposed for dye degradation, but most of them are dependent on the availability of costly co-substrates such as peptone, yeast extract, and/or glucose. The present study describes the azo dye degradation by a bacterial consortium using glycerol as a sole co-substrate. The consortium was developed from a mixed bacterial culture obtained upon enrichment of soil sediment for Reactive Blue 28 (RB28) decolorization in the presence of glycerol (0.1%; v/v). The consortium with three bacterial species, i.e., Stenotrophomonas acidaminiphila APG1, Cellulomonas sp. APG4, and Pseudomonas stutzeri APG2, designated as "SCP," decolorized 92% of 100 ppm dye in 96 h. The intricacies of the interactions existing within the members of the consortium were resolved by a simple and unique analysis called "BSocial." Among all the members, Cellulomonas sp. APG4 exerted a net-positive impact for decolorization (%) on the consortium. The net fitness of the community increased when all the three species were present, and thus, all of them were selected for further analysis. Moreover, APG4 seemed to be central in the reductive decolorization as it possessed the highest reductase activity. The dye degradation by the consortium was demonstrated by UV-Visible spectroscopy, HPTLC, and FTIR spectroscopy of control and decolorized cell-free supernatant. The LC-ESI-MS analysis of metabolites extracted from decolorized cell-free medium led to the identification of degradation products, thus leading us to propose the plausible pathway for degradation of RB28 by bacterial consortium.