Beyond a Pathogen: Chromobacterium violaceum, a Rhizobacterium with Plant Growth-Promoting Potential

Current global climate change and its challenges have led to a search for green approaches to ensuring sustainable agriculture. Microbe-based fertilizers have been reported as potent eco-friendly alternatives to chemical fertilizers owing to their plant growth-promoting potential. This research identified an often scientifically reported pathogen as a rhizobacterium with plant growth-promoting potential. The rhizobacterium was isolated from the rhizosphere of Leersia oryzoides (L.) Sw. growing in waterlogged soil and screened for plant growth-promoting traits: indole-3-acetic acid (IAA) production and phosphate solubilization. It was further tested for plant growth-promoting activity via a maize seed germination bioassay for five days. The rhizobacterium was identified phenotypically and via biochemical tests. The rhizobacterium was negative for IAA production and phosphate solubilization. After five days of incubation during the seed germination bioassay, the radicle and hypocotyl length of the maize seeds inoculated with the rhizobacterium (RS PUR) were 6.6 cm and 0.7 cm, respectively, while those of the control (maize seeds + sterile distilled water only) were 5.7 cm and 0.3 cm, respectively. Student’s t-test statistical analysis showed P<0.05, indicating that there was a significant difference between the rhizobacterium-treated seeds and the control. The rhizobacterium was tentatively identified as Chromobacterium violaceum. This research thus shows the significance of bioprospecting studies and the plant growth potential of this unidentified strain of Chromobacterium violaceum beyond it being a pathogenic strain. Screening for more plant growth-promoting traits and the strain-level identification (16s rDNA sequencing) of this rhizobacterium are therefore recommended.