Introduction, mechanisms of action and genomic description in plant probiotic ‎bacterium Bacillus velezensis

Bacillus velezensis is one of the plant probiotic bacteria that has been recently considered as one of the most powerful biocontrol agents. The purpose of this study is to introduce and investigate some of the characteristics of B. velezensis bacterium, which has been isolated from tomato rhizosphere in Kermanshah Province. In this study, B. velezensis increased shoot length, root length and dry weight of tomato plants by 78.86%, 56.68%, and 45.83%, respectively in comparison to uninoculated control; it also promoted seed germination percentage and seed vigor index under in vitro condition. Furthermore, some of the biocontrol properties of this strain such as the production of siderophore, HCN, and indole-3-acetic acid and solubilization of phosphate were evaluated. Biocontrol bioassay of this strain against Fusarium oxysporum f.sp. lycopersici under in vitro condition revealed that this strain can inhibit the mycelial growth in both dual culture and volatile compounds methods about 83% and 58%, respectively. The pot experiment results showed that B. velezensis caused a reduction in disease symptoms up to 87%. Finally, the whole genome sequence of this strain was identified using Illumina HiSeq2500 technology. Then genomic locations and coding sequences were identified in RAST database. In addition, the sequencing data were compared with existing sequences in the NCBI database. Results showed that this isolate has high similarity to (%100) B. velezensis. The genome of this isolate contains 4132868bp and 4329 CDs. The results suggest that B. velezensis has a good potential to be introduced as a plant probiotic bacterium.