Involvement of the Rcs regulon in the persistence of SalmonellaTyphimurium in tomatoes

Abstract

It is becoming clear that human enteric pathogens, like Salmonella, can efficiently colonize vegetative and reproductive organs of plants. Even though the bacterium's ability to proliferate within plant tissues has been linked to outbreaks of salmonellosis, little is known about regulatory and physiological adaptations of Salmonella, or other human pathogens, to their persistence in plants. A screen of Salmonella deletion mutants in tomatoes identified rcsA and rcsB genes as those under positive selection. In tomato fruits, populations of Salmonella rcsB mutants were as much as 100-fold lower than those of the wild type. In the follow-up experiments, competitive fitness of rcsA and rcsB mutants was strongly reduced in tomatoes. Bioinformatics predictions identified a putative Salmonella RcsAB binding box (TTMGGAWWAABCTYA) and revealed an extensive putative RcsAB regulon, of which many members were differentially fit within tomatoes.

Stress response, amino acid biosynthesis and pathogenesis genes expressed in Salmonella enterica colonizing tomato shoot and root surfaces

“…The gene of unknown function yjbE also exhibited markedly higher transcriptional levels in both Se T-shoots (3.0-fold increase; q = 0.003) and -roots (5.9-fold increase; q = 0.003). This gene was reported to facilitate growth inside red tomatoes ( Marvasi et al., 2016 ). Together with ycfJ , a putative outer membrane lipoprotein, these two genes are responsive to acetyl phosphate and regulated by RscC, and possibly RscB which represses flagellar synthesis ( Wolfe, 2005 ).…”

Salmonella Persistence in Tomatoes Requires a Distinct Set of Metabolic Functions Identified by Transposon Insertion Sequencing

“…Consequentially, bacterial growth appeared constrained, potentially imposing a limit on the possible changes in frequency of transposon insertions with differential fitness. We tested whether screening the mutant library under this condition would allow us to detect selection, using the rcsA::kan mutant strain, whose fitness is known to be modestly reduced in tomatoes (36). Because following the screen, recovered mutants were briefly grown out in LB to increase DNA output, we also confirmed in preliminary experiments with the rcsA::kan mutant that this outgrowth does not affect the recovery ratio of the mutant or its DNA (data not shown).…”