Exploring the Plant Growth-Promoting Potential of a Purple Non-Sulfur Bacterium: Cereibacter sphaeroides PW15.

Purple non-sulfur bacteria (PNSB) are phototrophic microorganisms recognized for their ability to produce compounds beneficial for plant growth, increasing their interest as plant growth-promoting bacteria. This study investigates the growth-promoting traits of Cereibacter sphaeroides PW15 under both microaerobic light and aerobic dark conditions. The findings demonstrate that the PNSB isolate PW15 exhibits notable salt tolerance, phosphate solubilization, nitrogen fixation, and the production of several plant-beneficial metabolites, including indole-3-acetic acid, ammonia, siderophores, and 5-aminolevulinic acid. The presence of the nifH gene, which is associated with Mo-Fe nitrogenase, further confirmed its nitrogen-fixing potential. Additionally, C. sphaeroides PW15 formed biofilm on abiotic surfaces and significantly enhanced root and shoot growth in Arabidopsis thaliana ecotype Col-0 upon inoculation. These results highlight the potential of C. sphaeroides PW15 as a promising candidate for use as an effective biofertilizer in sustainable agriculture.