Impaired acid stress resistance in Salmonella Typhi Ty2.

Salmonella Typhi Ty2 shows significantly impaired growth at pH 4.5 compared to Salmonella Typhimurium 14028s, due to loss of acid resistance genes.

• Why it matters: Understanding acid stress resistance is crucial because it influences Salmonella's ability to survive gastrointestinal transit and macrophage environments, impacting infection and disease progression.
• What they did: The study compared growth at various pH levels, performed transcriptomic profiling at pH 4.5 and 7.5, and used gene deletion and heterologous expression to identify and confirm key genes involved in acid resistance.
• The result: S. Typhi's compromised acid tolerance results from pseudogenization of genes encoding membrane proteins, a regulator, and stress response proteins, suggesting evolutionary gene loss impairs its ability to withstand acid stress.