Osmoregulated periplasmic glucans synthesis gene family of Shigella flexneri
Osmoregulated periplasmic glucans (OPGs) of food- and water-borne enteropathogen Shigella flexneri were characterized. OPGs were composed of 100% 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 seven 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 hypo-osmotic 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 hypo-osmotic media. Longer lag times to initiate growth in hypo-osmotic media were also observed for opgC and opgD mutants but not for opgB mutant. All opg mutants were able to infect HeLa cells, and abolition of OPGs synthesis did not affect actin polymerization or plaque formation. Ability to synthesize OPGs was beneficial to bacteria in order to initiate growth under low osmolarity conditions, in vitro mammalian cell invasion assays, however, could not discriminate whether OPGs were required for basic aspect of Shigella virulence.
KeywordsPeriplasmic glucans Low osmolarity Food- and water-borne Shigellosis
The study was supported in part by the China Scholarship Council, Ministry of Education, China (LL). We would like to thank Malabi Venkatesan for support of this project. The content of this publication does not necessarily reflect the views or policies of the US Department of the Army, US Department of Agriculture or the US Department of Defense nor does the mention of trade names, commercial products, or organizations imply endorsement by the US Government.
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