Effect of environmental stress on cell surface and membrane fatty acids of Lactobacillus plantarum (original) (raw)

2017, Archives of Microbiology

AI-generated Abstract

Adhesion has been regarded as one of the basic features of probiotics. We undertake this study in the aim to give new insight about the change in cellular physiological state under heat and acid treatments of Lactobacillus plantarum. Different cell properties have been investigated such as adhesive ability to abiotic surfaces, the cell surface hydrophobicity and the fatty acids profiles. The results of cell surface properties and Gas chromatography analysis demonstrated a modification in term adhesive ability and fatty acid (FA) composition of the tested strain under stressful conditions. In fact, after the exposure of the strain to heat and acid treatments, an increase in the hydrophobicity level and the adhesion capacity on HeLa cells was shown. Our findings revealed that high temperature and low pH change the fatty acids profiles of the treated cells, especially the proportions of unsaturated and saturated fatty acid. In this context, our data revealed that the unsaturated FA-to-saturated FA ratio was increased significantly (P < 0.05) for stressed strains compared with control cells. The results of the present finding suggest that the tested strain have suffered changes like the modifications on bacterial membrane as a cellular response to survive the hard environmental conditions, allowing them to withstand harsh conditions and sudden environmental changes to survive under. The presence of linoleic and linolenic acids in a minimal growth medium reduced the acid and heat tolerance of Lactobacillus johnsonii NCC533 by 6-and 20-fold, respectively. However, the regulation of the biosynthetic routes of fatty acids in the majority of microorganisms has been poorly studied. In particular, the way in which the fatty acid composition of membrane lipids is altered in response to growth temperature appears to depend on the mechanism of unsaturated fatty acid synthesis utilized. Therefore, to overcome stressful conditions, bacterial strains activate stress responses systems that involve metabolic and molecular regulation. Generally, bacteria have a natural tendency to adhere to surfaces as a survival mechanism. In the phenomenon of bacterial adhesion to biotic and abiotic surfaces, the physicochemical properties of the cell like the hydrophobicity, charges, substrates or surface topography are playing an important role. Bacterial colonization of solid surfaces has been described as a basic and natural bacterial stratagem in a wide variety of environments. In this respect, the hydrophobicity of the bacterial cell surface has been proposed to be one of the most important factors that govern the mechanism of bacterial adhesion to biological surfaces. In fact, proper fluidity of the membrane is essential for the mobility and functionality of embedded proteins and lipids, diffusion of proteins and other molecules across the membrane and the appropriate separation of membranes during cell division. It has been reported that bacterial membrane composition changes during acid shock, osmolarity fluctuations, freeze-drying, and exposure to suboptimal growth temperatures.