EFFECT OF LOW-NUTRIENT SEAWATER ON MORPHOLOGY, CHEMICAL-COMPOSITION, AND VIRULENCE OF SALMONELLA-TYPHIMURIUM

The response of Salmonella typhimurium to low nutrient levels was dete rmined by measuring the concentrations of lipids, carbohydrates, DNA, RNA, and proteins over a 32-day starvation period. Ultrastructural int egrity was observed by transmission electron microscopy. Lipid and car bohydrate content of bacterial cells rapidly declined within the first 16 days, while DNA and proteins exhibited a more gradual decline over the 32 days of starvation. In contrast, RNA content did not decrease appreciably upon nutrient starvation. Structural damage occurred espec ially after 16 days of starvation. After 32 days of nutrient deprivati on, we recorded degenerative cellular forms, a coccoidal cell shape, a decrease in cellular volume, and the loss of the three-layered outer membrane. The morphological and structural alterations correlated with virulence in infected animals. We observed a decrease in virulence of S. typhimurium after 9, 16, and 32 days of starvation, reaching a max imal decrease after 32 days of nutrient deprivation. The decrease in v irulence correlated to surface hydrophobicity alterations, adherence t o eukaryotic cells, and phagocytosis.