CodY orchestrates the expression of virulence determinants in emetic Bacillus cereus by impacting key regulatory circuits

Abstract

SummaryBacillus cereus causes gastrointestinal diseases and local and systemic infections elicited by the depsipeptide cereulide, enterotoxins, phospholipases, cytolysins and proteases. The PlcR-PapR quorum sensing system activates the expression of several virulence factors, whereas the Spo0A-AbrB regulatory circuit partially controls the plasmid-borne cereulide synthetase (ces) operon. Here, we show that CodY, a nutrient-responsive regulator of Gram-positive bacteria, has a profound effect on both regulatory systems, which have been assumed to operate independently of each other. Deletion of codY resulted in downregulation of virulence genes belonging to the PlcR regulon and a concomitant upregulation of the ces genes. CodY was found to be a repressor of the ces operon, but did not interact with the promoter regions of PlcRdependent virulence genes in vitro, suggesting an indirect regulation of the latter. Furthermore, CodY binds to the promoter of the immune inhibitor metalloprotease InhA1, demonstrating that CodY directly links B. cereus metabolism to virulence. In vivo studies using a Galleria mellonella infection model, showed that the codY mutant was substantially attenuated, highlighting the importance of CodY as a key regulator of pathogenicity. Our results demonstrate that CodY profoundly modulates the virulence of B. cereus, possibly controlling the development of pathogenic traits in suitable host environments.

Proteomic Evidences for Rex Regulation of Metabolism in Toxin-Producing Bacillus cereus ATCC 14579

“…Our results show that many cytoplasmic proteins predicted to be involved in active growth, either directly (such as metabolic enzymes, translational and post-translational-related proteins) or indirectly by preventing inappropriate gene expression (such as AbrB and CodY under aerobiosis [62]), were less abundant in B. cereus exoproteome when Rex was absent. We assume that cell lysis cannot account for changes in the abundance level of these cytoplasmic proteins since: (i) cell viability count did not change (data not shown), (ii) EF-Tu did not accumulate in extracellular medium (Table S7, [63]), and (iii) the abundance pattern of cytoplasmic proteins was dependent on growth conditions and did not always correlate with intracellular abundance changes (Table 2 and 4).…”

Bacterial Quorum Sensing: Its Role in Virulence and Possibilities for Its Control

“…However, despite its important role in regulating virulence factor production, disruption of plcR does not fully eliminate virulence (Lereclus et al 2000;Callegan et al 2003) because several additional systems feed into the B. cereus QS circuit and virulence factor regulation. These additional sensory inputs include sporulation through SpoOA P, nutritional state through CodY, motility through FlhA, and other two-component systems (Lereclus et al 2000;Bouillaut et al 2005;Brillard et al 2008;Frenzel et al 2012).…”

Branching Out: Alterations in Bacterial Physiology and Virulence Due to Branched-Chain Amino Acid Deprivation

“…CodY regulates metabolic genes involved in amino acid synthesis, purine biosynthesis, sugar and amino acid transport, and the Krebs cycle (31, 36–39), as well as, in some species, sporulation (27, 40–42) and biofilm formation (43–45). CodY also regulates virulence gene expression in Gram-positive pathogens, including Bacillus anthracis (46–48), Bacillus cereus (43, 49–51), Clostridium difficile (40, 52, 53), Clostridium perfringens (41, 54, 55), Listeria monocytogenes (35, 39, 56, 57), Staphylococcus aureus (5, 37, 38, 58–60), S. pneumoniae (32), and Streptococcus pyogenes (45, 61–63).…”