PhoP/PhoQ System and Its Role in Serratia marcescens Pathogenesis

• Published in: Journal of Bacteriology 2012-06, Vol.194 (11), p.2949-2961
• Main Authors: Barchiesi, Julieta, Castelli, María Eugenia, Di Venanzio, Gisela, Colombo, María Isabel, García Véscovi, Eleonora
• Format: Article
• Language: English
• Subjects: Acids - metabolism; Amino Acid Sequence; Animals; bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Base Sequence; Binding sites; Biological and medical sciences; Cell Line; environmental factors; epithelial cells; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Bacterial; Genotype & phenotype; Gram-negative bacteria; homeostasis; Humans; Lysosomes - metabolism; Lysosomes - microbiology; magnesium; Magnesium - metabolism; Microbial Viability; Microbiology; Miscellaneous; Molecular Sequence Data; mutants; Pathogenesis; phenotype; Physiology; polymyxin B; Sequence Alignment; Serratia; Serratia Infections - microbiology; Serratia marcescens; Serratia marcescens - genetics; Serratia marcescens - growth & development; Serratia marcescens - metabolism; Serratia marcescens - pathogenicity; Signal transduction; vacuoles; Virulence
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/JB.06820-11

Serratia marcescens is able to invade, persist, and multiply inside nonphagocytic cells, residing in nonacidic, nondegradative, autophagosome-like vacuoles. In this work, we have examined the physiological role of the PhoP/PhoQ system and its function in the control of critical virulence phenotypes in S. marcescens. We have demonstrated the involvement of the PhoP/PhoQ system in the adaptation of this bacterium to growth on scarce environmental Mg2+, at acidic pH, and in the presence of polymyxin B. We have also shown that these environmental conditions constitute signals that activate the PhoP/PhoQ system. We have found that the two S. marcescens mgtE orthologs present a conserved PhoP-binding motif and demonstrated that mgtE1 expression is PhoP dependent, reinforcing the importance of PhoP control in magnesium homeostasis. Finally, we have demonstrated that phoP expression is activated intracellularly and that a phoP mutant strain is defective in survival inside epithelial cells. We have shown that the Serratia PhoP/PhoQ system is involved in prevention of the delivery to degradative/acidic compartments.