Investigation of LuxS-mediated quorum sensing in Klebsiella pneumoniae

Abstract

Introduction. Autoinducer-2 (AI-2) quorum sensing is a bacterial communication system that responds to cell density. The system requires luxS activity to produce AI-2, which can regulate gene expression and processes such as biofilm formation. Aim. To investigate the role of luxS in biofilm formation and gene expression in the nosocomial pathogen Klebsiella pneumoniae . Methodology. A ΔluxS gene deletion was made in K. pneumoniae KP563, an extensively drug-resistant isolate. AI-2 production was assessed in wild-type and ΔluxS strains grown in media supplemented with different carbohydrates. Potential roles of luxS in biofilm formation were investigated using a microtiter plate biofilm assay and scanning electron microscopy. Quantitative RT-PCR evaluated the expression of lipopolysaccharide (wzm and wbbM), polysaccharide (pgaA), and type 3 fimbriae (mrkA) synthesis genes in wild-type and ΔluxS mutant biofilm extracts. Results. AI-2 production was dependent on the presence of luxS. AI-2 accumulation was highest during early stationary phase in media supplemented with glucose, sucrose or glycerol. Changes in biofilm architecture were observed in the ΔluxS mutant, with less surface coverage and reduced macrocolony formation; however, no differences in biofilm formation between the wild-type and ΔluxS mutant using a microtiter plate assay were observed. In ΔluxS mutant biofilm extracts, the expression of wzm was down-regulated, and the expression of pgaA, which encodes a porin for poly-β−1,6-N-acetyl-d-glucosamine (PNAG) polysaccharide secretion, was upregulated. Conclusion. Relationships among AI-2-mediated quorum sensing, biofilm formation and gene expression of outer-membrane components were identified in K. pneumoniae . These inter-connected processes could be important for bacterial group behaviour and persistence.

The influence of biofilm formation on carbapenem resistance in clinicalKlebsiella pneumoniaeinfections: phenotype vs genome-wide analysis

“…The genetic mechanisms known to be involved for a successful biofilm formation in K. pneumoniae include factors for adhesion (fimbriae and pili) [6] , cohesion (adhesins, polysaccharides), CPS [7] , QS [9] , and loss of mucoidal nature (colonic acid) [8] . Here, genes responsible for each of these factors were analysed for the study isolates in comparison with global clones.…”

“…QS is a well-established mechanism in the process of biofilm formation, where the population is regulated on sensing the cell-cell contact [9] . Previously a Type II QS system was identified in K. pneumoniae, which showed the role of luxS in autoinducer AI-2 synthesis [37,38] .…”

“…Previously a Type II QS system was identified in K. pneumoniae, which showed the role of luxS in autoinducer AI-2 synthesis [37,38] . It was also noted that changes in biofilm architecture were observed in the luxS mutant K. pneumoniae with less surface coverage and reduced macrocolony formation [9] . luxS was present in almost all isolates in the study irrespective of ST.…”

“…Biofilm formation mechanisms in clinical K. pneumoniae is reported to be mediated by a series of genetic factors, including allantoin (allS), aerobactin (iutA), type I (fimA and fimH) and type III fimbriae (mrkA and mrkD), polysaccharides and adhesins (pgaA, pgaB, pgaC, bcsA), capsular polysaccharide (CPS) (wzc, cpsD, treC, wcaG, wabG, rmpA/A2, magA, k2a, wzyk2), quorum sensing (QS) (luxS) and colonic acid (wcaJ) [6][7][8][9][10][11] . Though these genetic factors were individually studied, a collective approach on their analysis in a set of clinical isolates is still lacking.…”

Table_1.DOCX

“…QS is a well-established mechanism in the process of biofilm formation, where the population is regulated on sensing the cellcell contact (Chen et al, 2020). Type II QS system reported in K. pneumoniae showed the role of luxS in autoinducer AI-2 synthesis (Balestrino et al, 2005;Zhu et al, 2011).…”