Effects of tolC on tolerance to bile salts and biofilm formation in Cronobacter malonaticus

Abstract

Bile salts is one of essential components of bile secreted into the intestine to confer antibacterial protection. Cronobacter species are associated with necrotizing enterocolitis in newborns and show a strong tolerance to bile salts. However, little attempt has been made to focus on the molecular basis of the tolerance to bile salts. In this study, we investigated the roles of tolC on growth, cell morphology, motility, and biofilm formation ability in Cronobacter malonaticus under bile salt stress. The results indicated that the absence of tolC significantly affected the colony morphology and outer membrane structure in a normal situation, compared with those of the wild type strain. The deletion of tolC caused the decline in resistance to bile salt stress, inhibition of growth, and observable reduction in relative growth rate and motility. Moreover, the bacterial stress response promoted the biofilm formation ability of the mutant strain. The expression of the AcrAB-TolC system (acrA, acrB, and tolC) was effectively upregulated compared with the control sample when exposed to different bile salt concentrations. The findings provide valuable information for deeply understanding molecular mechanisms about the roles of tolC under bile salt stress and the prevention and control of C. malonaticus.

Genomic Characterization of Cronobacter spp. and Salmonella spp. Strains Isolated From Powdered Infant Formula in Chile

“…For the antibiotic resistance genes, all C. sakazakii strains and the C. malonaticus strain exhibited the same efflux, antibiotic inactivation, and antibiotic target alteration genes that confer antibiotic resistance to β-lactams, fluoroquinolones, aminoglycosides, imidazoles, and disinfectants such as triclosan. The marA gene, whose transcription function regulates multidrug efflux, modulates membrane permeability and activates the transcription of the AcrAB-TolC efflux pump that plays an important role in antibiotic resistance ( Wang X. et al, 2021 ). Several authors have detected the msbA , emrR , H-NS , emrB , marA , CRP , PBP3 , H-NS , and msrB genes that are associated with antibiotic resistance by using efflux pumps, regulatory systems, and antibiotic target protection genes ( Aly et al, 2019 ; Lepuschitz et al, 2019 ; Parra-Flores et al, 2021b ).…”

Wolf in Sheep’s Clothing: Clostridioides difficile Biofilm as a Reservoir for Recurrent Infections

“…Additionally, Acinetobater baumannii, Cronobacter malonaticus, and Bifidobacterium formed more biofilms when exposed to bile salts [118][119][120]. In Bifidobacterium breve, bile-saltinduced biofilm formation involved QS, EPS production and eDNA release, and increased its viability when exposed to porcine bile salts [118].…”

“…In A. baumannii, exposure to bile salts increased expression of virulence factors associated with surface motility, biofilm, and type VI secretion systems, and these are also associated with activation of the QS system [119]. In the case of C. malonaticus, bile salts exposure induced an upregulation of the AcrAB-TolC system, but the molecular mechanisms involved in biofilm formation remain unknown [120].…”

Uncovering phenotypic changes of luxS‐mediated acid tolerance in Cronobacter malonaticus

“…Ye et al (2016) found that Sribosylhomocysteinelyase are differentially expressed proteins between biofilm and planktonic cells by two-dimensional gel electrophoresis (2-DE) technique, evidencing that Sribosylhomocysteinelyase may regulate Cronobacter. Cronobacter escaped from the acidic environment by up-regulating flagellar genes, while luxS regulated biofilm formation, adhesion and cellular motility in Cronobacter by negatively regulating flgM, and positively regulating flagellar assembly fliC expression (Wang et al 2021). Cronobacter has strong drying resistance characteristic, allowing it to survive in low-moisture infant formula; luxS also improves the desiccation resistance of Cronobacter.…”

“…Cronobacter escaped from the acidic environment by up‐regulating flagellar genes, while luxS regulated biofilm formation, adhesion and cellular motility in Cronobacter by negatively regulating flgM , and positively regulating flagellar assembly fliC expression (Wang et al . 2021). Cronobacter has strong drying resistance characteristic, allowing it to survive in low‐moisture infant formula; luxS also improves the desiccation resistance of Cronobacter .…”