Soil salinization, a major challenge caused by climate change over the past century, critically affects cultivated land and consequently reduces agricultural production worldwide. Recently, plant growth-promoting rhizobacteria have been collected and utilized to enhance plant growth and mitigate the effects of salt stress in different plant species including rice. In our current study, the Serratia marcescens strain VIRS2 with remarkable salt tolerance was successfully isolated from the saline soil in the Mekong River Delta of Vietnam. This isolate exhibited diverse plant growth-promoting properties, especially the production of a high indole acetic acid level. Treatments under both in vitro and greenhouse conditions indicated that VIRS2 could enhance growth and salt tolerance in rice. The VIRS2-inoculated rice plants exhibited biochemical profile alterations including proline, malondialdehyde, and relative water contents. In addition, the expression of genes involved in the plant stress response pathways was upregulated in the VIRS2-inoculated rice under salt treatments. Importantly, the whole genome sequencing data of VIRS2 also showed the presence of different genes associated with plant growth-promotion and stress-tolerance mechanisms. These results indicated the potential of the VIRS2 isolate for enhancing growth and salt tolerance in rice as well as other important crops.

Plant growth-promoting rhizobacteria (PGPR) have been collected and used to promote plant growth and enhance disease tolerance of various crops. In the current work, Pseudomonas aeruginosa CAKS2, an endophytic strain isolated from the rhizosphere of sweet orange, exhibited both growth promotion and antimicrobial activities. Under the in vitro condition, the CAKS2 showed multiple plant growth-promoting properties such as phosphate, potassium, and calcium solubilization, nitrogen fixation as well as production of siderophores, IAA, ammonia, exopolysaccharides, hydrogen cyanide, and biofilm formation. This P. aeruginosa strain inhibited the growth of different tested fungal and bacterial pathogens. Under the in vivo condition, the CAKS2 enhanced sweet orange plant growth, indicated by increases in the root and shoot lengths, the leaf number, and the total biomass. The biochemical components and the transcription levels of genes related to plant hormone biosynthesis were altered in the CAKS2-inoculated sweet orange. Under the in vivo infection of C. gloeosporioides, the CAKS2 reduced the diameter of lesions on orange leaves and harvested fruits and decreased disease severity and incidence at the whole plant level. The whole genome sequence of CAKS2 showed the presence of candidate genes involved in different molecular pathways contributing to plant-promoting and biocontrol properties. Importantly, certain changes in the expression of gene response for plant growth promotion and biocontrol were observed when the CAKS2 was exposed to sweet orange root exudates. This study highlights P. aeruginosa CAKS2 as a potential PGPR strain for enhancing plant growth and C. gloeosporioides tolerance in sweet orange and other citrus plants.

Lactiplantibacillus pentosus is a lactic acid bacterium frequently detected in various fermented foods; however, the genomic traits related to its biotechnological potential have been underexplored. In this study, 34 catalase-negative isolates were obtained from pickled mustard greens, among which strain P7 exhibited the highest exopolysaccharide (EPS) yield (781.9 ± 14.7 mg/L) and was capable of growing in a chemically defined medium lacking riboflavin. Whole-genome sequencing revealed a 3,749,478 bp circular chromosome with 46.5% G + C content and 3389 protein-coding genes. A phylogenomic analysis identified P7 as L. pentosus. Functionally, 1 mg/mL EPS extracted from P7 demonstrated strong antioxidant activity, with DPPH and hydroxyl radical scavenging capacities of 89.8 ± 4.6% and 76.5 ± 9.5%, respectively. The use of 0.2 mg/mL EPS also protected Saccharomyces cerevisiae cells from oxidative stress. A comparative genomic analysis indicated the presence of nearly complete biosynthetic pathways for riboflavin, folate, and pyridoxine. High-performance liquid chromatography (HPLC) confirmed the production of 23.8 ± 0.4 µg/mL riboflavin, 36.6 ± 0.6 µg/mL folic acid, and 0.42 ± 0.02 µg/mL pyridoxine in the culture supernatant, which have not been previously reported. Additionally, strain P7 produced 91.2 ± 12.3 g/L of lactic acid after 24 h of incubation. These results support the potential of L. pentosus P7 as a candidate for industrial applications in the production of EPS, B-group vitamins, and lactic acid.