Louisiana State University baton rouge, Louisiana, United States
George Nwokocha (Louisiana State University)| Anne Grove (Louisiana State University)
Bacterial plant pathogens have devised means of surviving in a hostile environment created by their hosts during the pathogenic phase of their life cycle. Critical to this survival mechanism are a family of transcriptional regulators known as Multiple antibiotic resistance Regulators (MarR), known to regulate the expression of genes involved in virulence, stress response, multidrug resistance etc. Recent studies have associated PecS, a member of the MarR family, as a master regulator of virulence gene expressions in the Enterobacterium Dickeya dadantii, a soft rot-causing phytopathogen of a range of plant species. D. dadantii PecS controls both the expression of pectinase genes and biosynthesis of a blue pigment known as indigoidine (an antioxidant). PecS has also been characterized in other plant pathogens such as, Pectobacterium atrosepticum, and it has been identified in the human pathogens, Klebsiella pneumoniae and Vibrio vulnificus. However, the role of PecS in the crown gall-causing Agrobacterium fabrum remains largely unknown. To understand the role of A. fabrum PecS in the physiology of the bacterium, plant association, and promotion of survival in response to host defenses, we created a pecS knockout and determined growth, motility, biofilm and stress response. Our result shows a higher growth rate in pecS knockout than the Wild Type over a 14 hour period, while the Wild Type was more motile after 48 hours of incubation in a 0.3% (wt/vol) agar. Biofilm formation was measured at 24, 48 and 72 hours, using crystal violet staining, and the data shows that Wild Type forms more biofilm than the knockout at all the time points. Stress response assays show the Wild Type was more sensitive to 5 mM of both cumene hydroperoxide and hydrogen peroxide, 10 mM tert-butyl hydroperoxide and 25 ug ampicillin compared to the knockout strain, while the knockout was more sensitive to 25 ug and 200 ug trimethoprim and streptomycin respectively. The study expands our knowledge about the master regulatory role of A. fabrum PecS and proves that A. fabrum PecS is implicated in bacterial physiology, plant association and survival.