Invasion of epithelial cells are correlated with secretion of Biosurfactant via the type 3 secretion system (SST3) of Shigella flexneri

Biosurfactants are amphipathic molecules produced by many microorganisms, usually bacteria, fungi and yeasts. They possess the property of reducing the tension of the membrane interfaces. No studies have been conducted on Shigella species showing their involvement of biosurfactant like molecules (BLM) in pathogenicity. This study aims to show that environmental and clinical strains of Shigella are able to produce BLM by emulsifying gasoline and diesel fuels. Our study has shown that BLM are secreted in the extracellular medium with EI24 ranging from 80 to 100%. The secretion is depending on the type III secretion system (T3SS). We did show that S. flexneri, S. boydii and S. sonnei are able to interact with hydrophobic areas with respectively 17.64%, 21.42% and 22.22% of hydrophobicity. 100 mM Benzoic and 1.5mg/mL Salycilic acids have been inhibited T3SS and this totally stops the BLM secretion. Pseudomonas aeruginosa which has T3SS is able to produce 100% of BLM in the presence or in the absence of both T3SS inhibitors. The secreted BLM is extractable with an organic solvent such as chloroform and could entirely be considered like lipopeptide or polypeptidic compound. By secreting BLM, Shigella is able to perform multicellular phenomena like "swarming" allowing to invade and disseminate inside epithelial cells.