title: Effect of salt stress on morphology and membrane composition of Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum, and their adhesion to human intestinal epithelial-like Caco-2 cells.
abstract: The effects of NaCl reduction (10.0, 7.5, 5.0, 2.5, and 0% NaCl) and its substitution with KCl (50% substitution at each given concentration) on morphology of Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium longum was investigated using transmission electron microscopy. Changes in membrane composition, including fatty acids and phospholipids, were investigated using gas chromatography and thin layer chromatography. Adhesion ability of these bacteria to human intestinal epithelial-like Caco-2 cells, as affected by NaCl and its substitution with KCl, was also evaluated. Bacteria appeared elongated and the intracellular content appeared contracted when subjected to salt stress, as observed by transmission electron microscopy. Fatty acid content was altered with an increase in the ratio of unsaturated to saturated fatty acid content on increasing the NaCl-induced stress. Among the phospholipids, phosphatidylglycerol was reduced, whereas phosphatidylinositol and cardioplipin were increased when the bacteria were subjected to salt stress. There was a significant reduction in adhesion ability of the bacteria to Caco-2 cells when cultured in media supplemented with NaCl; however, the adhesion ability was improved on substitution with KCl at a given total salt concentration. The findings provide insights into bacterial membrane damage caused by NaCl.
authors.affiliation: Food and Nutritional Science, School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong.
authors.forename: Akanksha
authors.initials: A
authors.lastname: Gandhi
authors.affiliation: Food and Nutritional Science, School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong. Electronic address: npshah@hku.hk.
authors.forename: Nagendra P
authors.initials: NP
authors.lastname: Shah
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000187:drug effects*; D001644:Bifidobacterium / Q000187:drug effects; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000737:chemistry* / Q000187:drug effects*; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D007779:Lactobacillus acidophilus / Q000187:drug effects; D007780:Lacticaseibacillus casei / Q000187:drug effects; D019936:Probiotics; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D012965:Sodium Chloride
keywords: CaCO-2; phospholipids; potassium chloride substitution; transmission electron microscopy