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

Abstract

11Biosurfactants are amphipathic molecules produced by many microorganisms, usually bacteria, 12 fungi and yeasts. They possess the property of reducing the tension of the membrane interfaces. 13 No studies have been conducted on Shigella species showing their involvement of biosurfactant 14 like molecules (BLM) in pathogenicity. This study aims to show that environmental and clinical 15 strains of Shigella are able to produce BLM by emulsifying gasoline and diesel fuels. Our study 16 has shown that BLM are secreted in the extracellular medium with EI24 ranging from 80 to 17 100%. The secretion is depending on the type III secretion system (T3SS). We did show that S. 18 flexneri, S. boydii and S. sonnei are able to interact with hydrophobic areas with respectively 19 17.64%, 21.42% and 22.22% of hydrophobicity. 100 mM Benzoic and 1.5mg/mL Salycilic 20 acids have been inhibited T3SS and this totally stops the BLM secretion. Pseudomonas 21 aeruginosa which has T3SS is able to produce 100% of BLM in the presence or in the absence 22 of both T3SS inhibitors. The secreted BLM is extractable with an organic solvent such as 23 chloroform and could entirely be considered like lipopeptide or polypeptidic compound. By 24 secreting BLM, Shigella is able to perform multicellular phenomena like "swarming" allowing 25 to invade and disseminate inside epithelial cells. 26 Introduction 28 The ingestion of pathogenic and virulent microorganisms generally affecting peoples in both 29 developed and developing countries [1]. Shigella is one of the Gram-negative bacterium 30 belonging to Enterobacteriaceae family and is causative agent of bacillary dysentery or 31 shigellosis [2]. The genus Shigella was the major pathogen bacteria associated with dysentery 32with attributable fraction to 63,8%, but also the second most common pathogen associated with 33 watery diarrhoea with attributable fraction to 12,9% in sub-Saharan Africa and south Asia. 34 Children under 5 years are the most affected. More and more shigellosis is a pathology that 35 both towards neglected diseases but 164300 of death per years have been notified all over the 36 world in 2010. Most deaths occur in sub-Saharan Africa and in south Asia [3-6]. This is include 37 Republic of Congo and surprisingly no epidemiological studies have been conducted in this 38 field. The genus Shigella includes four species (S. flexneri, S. sonnei, S. dysenteriae and S. 39 boydii) [7]. 10 bacteria of S. dysenteriae type 1 and 100 to 180 bacteria of S. flexneri or S. 40 sonnei are enough to produce symptomatic infection [8].41Shigella's pathogenicity is based on a virulence plasmid pWR100 in which the mxi-spa locus 42 encodes the type three secretion system(T3SS) involved in effector production like IpaB, C and 43 D (Translocator and Tip) to invade host cell [9][10][11][12]. A previous study in our laboratory that 44 showed that Shigella sp. isolated from Brazzaville wastewater were able to emulsify 45 hydrocarbon from gasoline and/or diesel fuel [13]. Sachin et al. found the same pr...