Adaptation of Shigella flexneri to starvation: morphology, outer membrane proteins and lipopolysaccharide changes

Lack of nutrients is a common challenge for enteric pathogens, like Shigella, when discharged in waters and soils by infected persons. These bacteria must evolve protective mechanisms to survive nutrient changing conditions. Many studies have demonstrated that bacterial starvation can affect cell morphology and surface properties such as lipopolysaccharide content. This study focuses on the morphological and physiological alterations of Shigella flexneri, a human pathogen, under nutrient starvation during 30 days. Our results showed that S. flexneri can survive under nutrient deficiency during 4 weeks. However, starved cells revealed several morphological changes indicating decrease of the size and change of the cell shape as observed by transmission electron microscopy. Furthermore, the outer membrane proteins and lipopolysaccharide profiles of starved cells revealed the disappearance, the appearance, and changes of the protein band levels. The survival and physiological adaptation of S. flexneri under nutrient limitation during 30 days may increase the risk of human and animal infections.