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Title: Osmoregulated periplasmic glucans synthesis gene family of Shigella flexneri

item LIU, LIU - Northwest Agricultural & Forestry University
item DHARNE, MAHESH - University Of Poona
item KANNAN, PORTEEN - Indian Veterinary Research Institute
item Smith, Allen
item MENG, JIANCHONG - University Of Maryland
item FAN, MINGTAO - Northwest Agricultural & Forestry University
item BOREN, TARA - Walter Reed Army Institute
item RANALLO, RYAN - Walter Reed Army Institute
item Bhagwat, Arvind

Submitted to: Archives of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2009
Publication Date: 1/9/2010
Citation: Liu, L., Dharne, M., Kannan, P., Smith, A.D., Meng, J., Fan, M., Boren, T., Ranallo, R., Bhagwat, A.A. 2010. Osmoregulated periplasmic glucans synthesis gene family of Shigella flexneri. Archives Of Microbiology. 192(3):167-174.

Interpretive Summary: The ability to survive under low nutrient conditions in the environment enables Shigella spp. to successfully enter the food chain. Vegetable wash waters and irrigation waters have been implicated in recent outbreaks of infections caused by Shigella spp. In this study we show that the ability to make specific glucose-polymer offers growth advantage to Shigella strains under nutritionally challenging conditions. Understanding how pathogens overcome various stress conditions such as low nutrient environments 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 American food supply.

Technical Abstract: Osmoregulated periplasmic glucans (OPGs) of foodborne enteropathogen Shigella flexneri were characterized. OPGs were composed of 100 percent glucose with 2-linked glucose as the most abundant residue with terminal glucose, 2-linked and 2,6-linked glucose also present in high quantities. Most dominant backbone polymer chain length was 7 glucose residues. Individual genes from the Opg gene family comprising of a bicistronic operon opgGH, opgB, opgC and opgD were mutagenized to study their effect on OPGs synthesis, growth in hypoosmotic media and ability to invade HeLa cells. Mutation in opgG and opgH abolished OPGs biosynthesis and mutants experienced longer lag-time to initiate growth in hypoosmotic media. Mutations in opgB and opgC rendered OPGs to be less anionic. Mutation in opgC (but not in opgB) resulted in longer lag-time to initiate growth in hypoosmotic media. Mutation in opgD generated OPGs with heterogeneous and stronger anionic characteristics. All opg mutants were able to infect HeLa cells and were successful in polymerizing actin filament tails as well as formed plaques at comparable efficiency. Ability to synthesize OPGs was beneficial to bacteria in order to have optimal growth under low osmolarity conditions, in vitro invasion studies, however, could not discriminate if OPGs of S. flexneri are required for optimal virulence.