Large–scale genetic analysis and biological traits of two SigB factors in Listeria monocytogenes: lineage correlations and differential functions

INTRODUCTION: Listeria monocytogenes is a globally distributed bacterium that exhibits genetic diversity and trait heterogeneity. The alternative sigma factor SigB serves as a crucial transcriptional regulator essential for responding to environmental stress conditions and facilitating host infection. METHOD: We employed a comprehensive genetic analysis of sigB in a dataset comprising 46,921 L. monocytogenes genomes. The functional attributes of SigB were evaluated by phenotypic experiments. RESULTS: Our study revealed the presence of two predominant SigB factors (SigB(T1) and SigB(T2)) in L. monocytogenes, with a robust correlation between SigB(T1) and lineages I and III, as well as SigB(T2) and lineage II. Furthermore, SigB(T1) exhibits superior performance in promoting cellular invasion, cytotoxicity and enhancing biofilm formation and cold tolerance abilities under minimally defined media conditions compared to SigB(T2). DISCUSSION: The functional characteristics of SigB(T1) suggest a potential association with the epidemiology of lineages I and III strains in both human hosts and the natural environment. Our findings highlight the important role of distinct SigB factors in influencing the biological traits of L. monocytogenes of different lineages, thus highlighting its distinct pathogenic and adaptive attributes.