ARS | Publication request: Role of anionic charges of periplasmic glucans of Shigella flexneri in overcoming detergent stress

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2012
Publication Date: July 5, 2012
Citation: Bhagwat, A.A., Yi Ning, L., Liu, L., Mahesh, D., Porteen, K. 2012. Role of anionic charges of periplasmic glucans of Shigella flexneri in overcoming detergent stress. Foodborne Pathogens and Disease. 9(7):632-637.

Interpretive Summary: The ability to survive detergents and sanitation agents during produce cleaning and washing steps 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 sp. In this study we show that the ability to make specific glucose-polymer offers protection to Shigella strains during produce clean-up and wash steps. Understanding how pathogens overcome various stress conditions such as presence of detergents 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: Osmoregulated periplasmic glucans (OPGs) are synthesized by the members of the family Enterobacteriaceae when grown under low osmotic growth conditions. Enteropathogens such as Shigella flexneri spend considerable time outside the host environment such as irrigation waters where low nutrient low osmolarity conditions normally may exist. We recently demonstrated that OPGs of S. flexneri are required for optimal growth under low osmolarity low nutrient conditions (Liu et al., Arch. Microbiol. 192: 167-174, 2010). OPGs of S. flexneri are anionic and based on homology of the OPG biosynthesis genes to those of Escherichia coli it is most likely to be the function of opgC and opgB genes which add succinate and phosphoglycerol residues respectively on OPGs. We constructed opgB, opgC and opgBC mutants of S. flexneri. The mutant strain defective in opgC and opgB genes synthesized neutral OPGs which although were beneficial for the organism’s growth in hypoosmotic media were ineffective in combating stress caused by anionic detergents. Cloned wild type genes opgB, opgC, and opgBC upon mobilization to respective opg mutants, simultaneously restored anionic charges to OPGs and tolerance to detergents to wild type levels. It appears that anionic charges on the OPGs contribute towards overcoming the stress by anionic detergents such as sodium dodecyl sulfate (SDS) and sodium deoxycholate.