Analysis of the effects of osmoprotectants on the high osmolality-dependent induction of increased thermotolerance inSalmonella typhimurium

Abstract Challenge of Salmonella typhimurium with high osmolality enhances its thermotolerance, manifested as faster growth rate at non-lethal high temperatures and enhanced resistance to killing at lethal high temperatures. Previously, it has been shown that the potent osmoprotectant glycine betaine blocks the latter response. In this work, we tested the effects of ten other osmoprotectants on the induction of thermotolerance by high osmolality. The high osmolality-dependent growth stimulation at 45°C was decreased partially by γ -aminobutyrate betaine, 3,4-dehydroproline betaine, and blocked completely by pipecolate betaine and homarine. Osmotic enhancement of survival at 53°C was greatly impaired by dehydroproline betaine, pipecolate betaine, and proline betaine. Our observations point to the need for further research to discover additional betaine analogs, which might act as even more potent antagonists of the induction of thermotolerance, for possible use in food products to enhance the susceptibility of Salmonella to thermal injury or killing.