Abstract
Bacillus cereus is a Gram-positive pathogen that causes a wide variety of diseases in humans. It secretes into the extracellular milieu proteins that may contribute directly or indirectly to its virulence. EntD is a novel exoprotein identified by proteogenomics of B. cereus ATCC 14579. We constructed a ΔentD mutant and analyzed the impact of entD disruption on the cellular proteome and exoproteome isolated from early, late, and stationary-phase cultures. We identified 308 and 79 proteins regulated by EntD in the cellular proteome and the exoproteome, respectively. The contribution of these proteins to important virulence-associated functions, including central metabolism, cell structure, antioxidative ability, cell motility, and toxin production, are presented. The proteomic data were correlated with the growth defect, cell morphology change, reduced motility, and reduced cytotoxicity of the ΔentD mutant strain. We conclude that EntD is an important player in B. cereus virulence. The function of EntD and the putative EntD-dependent regulatory network are discussed. To our knowledge, this study is the first characterization of an Ent family protein in a species of the B. cereus group.
Highlights
Microbial pathogens are involved in a wide range of severe, and sometimes fatal, human diseases, including nosocomial infections, foodborne infections and toxic shock syndrome
The aim of this study was to evaluate the role of EntD, an exoprotein identified by proteogenomics of B. cereus ATCC 14579 (Ivanova et al, 2003), in the virulence of B. cereus ATCC 14579 by indepth characterization of an entD knockout mutant
Cereus ATCC 14579 Proteogenomic analysis of the B. cereus ATCC 14579 exoproteome identified 4 peptides that could be mapped to the BC_3716 locus (Figure 1A), which was annotated as a noncoding pseudogene (Ivanova et al, 2003)
Summary
Microbial pathogens are involved in a wide range of severe, and sometimes fatal, human diseases, including nosocomial infections, foodborne infections and toxic shock syndrome. The pathogenesis of the majority of bacterial diseases is a multifactorial process. Crucial steps may be listed: (i) resistance to environmental stresses during infection, (ii) adhesion to the host cell, (iii) invasion, (iv) damage to host tissues, and (v) subversion of the host immune response (Finlay and Falkow, 1997). Completion of each stage is dependent on orchestrated activities of specific exoproteins. Exoproteins, which play a pivotal role in the adaptability of the pathogen to the specificities of the host’s intracellular environment and promote efficient infection, are recognized as virulence factors (Wilson et al, 2002).
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