Serratia transcriptomics

Rhizobacteria with biocontrol ability exploit a range of mechanisms to compete successfully with other micro-organisms and to ensure their growth and survival in the rhizosphere, ultimately promoting plant growth. Two rhizosphere-inhabiting bacteria Serratia plymuthica AS13 and S. proteamaculans S4 are able to promote oilseed rape growth and increase the survival of seedlings in the presence of oilseed rape pathogen, Rhizoctonia solani AG 2-1. Genome-wide expression profiles of these bacteria were examined in the presence or absence of the phytopathogen R. solani to elucidate the possible mechanisms underlying antagonism. The differential gene expression profiles revealed that each isolate responded to the fungus differently. We observed significantly increased expression of genes related to antibiosis such as pyrrolnitrin biosynthesis, proteases production and secretion systems in S. plymuthica AS13. In S. proteamaculans S4, we found elevated expression of genes involved in virulence factors, utilisation of various nutrients including fungal derived compounds and defence mechanisms. In the presence of R. solani both bacterial isolates showed elevated levels of gene expression related to broad range of primary metabolic and physiological processes. The results presented here provide evidence that closely related bacterial isolates utilise isolate-specific modes of action during microbial interac-tions.