Virulence and Stress Responses of Shigella flexneri Regulated by PhoP/PhoQ

Abstract

The two-component signal transduction system PhoP/PhoQ is an important regulator for stress responses and virulence in most Gram-negative bacteria, but characterization of PhoP/PhoQ in Shigella has not been thoroughly investigated. In the present study, we found that deletion of phoPQ (ΔphoPQ) from Shigella flexneri 2a 301 (Sf301) resulted in a significant decline (reduced by more than 15-fold) in invasion of HeLa cells and Caco-2 cells, and less inflammation (− or +) compared to Sf301 (+++) in the guinea pig Sereny test. In low Mg 2+ (10 μM) medium or pH 5 medium, the ΔphoPQ strain exhibited a growth deficiency compared to Sf301. The ΔphoPQ strain was more sensitive than Sf301 to polymyxin B, an important antimicrobial agent for treating multi-resistant Gram-negative infections. By comparing the transcriptional profiles of ΔphoPQ and Sf301 using DNA microarrays, 117 differentially expressed genes (DEGs) were identified, which were involved in Mg 2+ transport, lipopolysaccharide modification, acid resistance, bacterial virulence, respiratory, and energy metabolism. Based on the reported PhoP box motif [(T/G) GTTTA-5nt-(T/G) GTTTA], we screened 38 suspected PhoP target operons in S. flexneri, and 11 of them (phoPQ, mgtA, slyB, yoaE, yrbL, icsA, yhiWX, rstA, hdeAB, pagP, were demonstrated to be PhoP-regulated genes based on electrophoretic mobility shift assays and β-galactosidase assays. One of these PhoP-regulated genes, icsA, is a well-known virulence factor in S. flexneri. In conclusion, our data suggest that the PhoP/PhoQ system modulates S. flexneri virulence (in an icsA-dependent manner) and stress responses of Mg 2+ , pH and antibacterial peptides.

In vitro Activity and Heteroresistance of Omadacycline Against Clinical Staphylococcus aureus Isolates From China Reveal the Impact of Omadacycline Susceptibility by Branched-Chain Amino Acid Transport System II Carrier Protein, Na/Pi Cotransporter Family Protein, and Fibronectin-Binding Protein

“…Wild-type strain CHS221 (S221) and its heteroresistance-derived S. aureus isolate CHS221-O (S221-O1) were grown and prepared for total RNA extraction with TRIzol reagent (Invitrogen, Carlsbad, CA, United States) as described previously (Zheng et al, 2018). RNA-Seq of the aforementioned parental and heteroresistance-derived isolates was performed as reported previously (Lin et al, 2017). Raw data (raw reads) of fastq format were firstly processed through in-house perl scripts.…”

Identifying virulence determinants of multidrug-resistant Klebsiella pneumoniae in Galleria mellonella

“…2015) and other virulence-associated genes in many enteric pathogens (Groisman 2001; Bijlsma and Groisman 2005; Alteri et al . 2011; Lin et al . 2018).…”

“…PhoP-PhoQ is a twocomponent system, comprising the inner membrane sensor PhoQ and the cytoplasmic regulator PhoP. This system regulates lipid A remodelling in K. pneumoniae in vivo and in vitro (Llobet et al 2015) and other virulence-associated genes in many enteric pathogens (Groisman 2001;Bijlsma and Groisman 2005;Alteri et al 2011;Lin et al 2018). Salmonella Typhimurium knockout strains of phoP and phoQ are highly attenuated for virulence in macrophages and a mouse infection (Miller, Kukral and Mekalanos 1989) and this twocomponent system also makes a small contribution to K. pneumoniae virulence during G. mellonella infections (Insua et al 2013).…”

Inactivation of the sfgtr4 Gene of Shigella flexneri Induces Biofilm Formation and Affects Bacterial Pathogenicity

“…It is well known that planktonic cells produce EPS in response to a variety of environmental signals such as magnesium deficit and subsequently facilitating bacterial attachment [ 9 ]. Optimal expression of the SfpgdA-orf186-virK-msbB2 locus is associated with low Mg 2+ -containing media and is regulated by the PhoP/PhoQ two-regulatory component system [ 10 , 11 ]. In a previous study, we reported that Shigella strains lacking either PhoP or SfPgdA are highly susceptible to lysozyme degradation and are less resistant to killing by polymorphonuclear neutrophils (PMNs) [ 12 ].…”