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Title: Transcriptomic analysis of swarm motility phenotype of Salmonella enterica serovar Typhimurium mutant defective in periplasmic glucan synthesis

item Bhagwat, Arvind
item YOUNG, LYNN - National Institutes Of Health (NIH)
item Smith, Allen
item BHAGWAT, MEDHA - National Institutes Of Health (NIH)

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2017
Publication Date: 6/8/2017
Citation: Bhagwat, A.A., Young, L., Smith, A.D., Bhagwat, M. 2017. Transcriptomic analysis of swarm motility phenotype of Salmonella enterica serovar Typhimurium mutant defective in periplasmic glucan synthesis. Current Microbiology. doi:10.1007/s00284-017-1267-1.

Interpretive Summary: Controlling spread of human pathogens on fresh produce is a top priority for public health reasons. Salmonella sp. migrate on wet surfaces by a movement called swarming motility. We investigated role of periplasmic glucose polymer (glucans) of Salmonella in swarming motility. Using advanced sequencing techniques, we examined and compared synthesis of all Salmonella genes in normally swarming (wild-type) and non-swarming (mutant) cells. Our studies show that non-swarming cells lacked in optimal expression of subset of virulence related genes. Understanding how pathogens migrate over wet surfaces will advance our knowledge of how enteric human pathogens enter our food chain. The research will benefit the fresh produce industry, as well as increasing the microbial food safety of the Americans food supply.

Technical Abstract: Movement of food-borne pathogens on moist surfaces enables them to migrate towards more favorable niches and facilitate their survival for extended periods of time. Salmonella enterica serovar Typhimurium mutants defective in OPG synthesis are unable to exhibit motility on moist surfaces (swarming) however their mobility in liquid (swim motility) remains unaffected. In order to understand the role of OPG in swarm motility, transcriptomic analysis was performed using cells growing on moist agar surface. In opgGH-deletion mutant, lack of OPG significantly altered transcription of 1039 genes out of total 4712 genes (22%). Introduction of plasmid borne copy of opgGH into opgGH-deletion mutant restored normal expression of all but 30 genes, indicating wide-range influence of OPG on gene expression under swarm motility condition. Major pathways that were differentially-expressed in opgGH mutants were motility, virulence and invasion, and genes related to secondary messenger molecule, cyclic di-GMP. These observations provide insights and help explain the pleiotropic nature of OPG mutants such as sub-optimal virulence and competitive organ colonization in mice, biofilm formation, and sensitivity towards detergent stress.