Maltose aids in the growth of Salmonella Typhimurium in nitrogen-deficient conditions

Enteric pathogens, such as Salmonella, encounter uncertain nutrients in both the host and the environment. Nutrients such as carbon and nitrogen are essential for growth, and when these nutrients are limited, bacteria have developed various mechanisms to overcome stress and thrive in nutrient-rich environments. In this study, we investigated the role of the disaccharide sugar maltose in the growth and pathogenicity of Salmonella Typhimurium (STM) under nitrogen-deficient culture conditions. Throughout the study, we used Burk's medium to mimic nitrogen-deficient conditions. STM growth in Burk's medium was minimal, and maltose supplementation enhanced STM growth in both liquid and solid Burk's media. The STM grown in Burk's medium had a reduced bacterial cell length, which increased upon the addition of maltose and became comparable to that of LB-grown STM WT. Growth was dependent on the NtrBC two-component system and sigma factor RpoE. Deletion of ntrB and rpoE significantly reduced the growth in Burk's medium during the log phase. Salmonella grown in Burk's medium with maltose had reduced invasion in Caco-2 cells, phagocytosis in RAW 264.7 macrophages, and organ burden in C57BL/6 mice. Our findings revealed the role of maltose in enhancing the growth and length of Salmonella under nitrogen-deficient conditions. However, Salmonella grown in Burk's medium with maltose is defective in pathogenesis.