Characterization of non-rhizobial endophytic bacteria in algerian cowpea root nodules: unveiling potential for nitrogen fixation

Abstract

The study aimed to characterize the culturable endophytic bacteria present in cowpea nodules (Vigna unguiculata L. (Walp)). Five endophytic non-rhizobial isolates (SVU1, SVU3, SVU9, SUV15, and SUV18) were isolated from the root nodules of cowpea. Phylogenetic analysis of 16S rRNA gene sequences revealed that the isolates belonged to the genus Paenibacillus, Serratia, Microbacterium, Bacillus and Lysinibacillus. Unlike rhizobia, all five isolates absorbed Congo Red contained in the Yeast Mannitol Extract medium. The nitrate reductase test was positive for all strains except SVU18and all strains utilized, mannitol, inositol and sucrose as substrates. The oxidase reductase test was negative. The results indicated that the root nodules of the legume could host a diverse endophytic community associated with cowpea, representing the first report of endophytic bacteria from Algerian cowpea nodules. These findings shed light on a part of the diversity of non-rhizobial within the cowpea nodules. The findings about the nifH gene showed that these bacteria open avenues for further exploration of the potential applications of endophytic bacteria in promoting nitrogen fixation and enhancing plant growth. Future studies will explore the potential application of these strains in nitrogen fixation and growth promotion for sustainable agriculture.