scholarly journals Investigation of LuxS-mediated quorum sensing in Klebsiella pneumoniae

2020 ◽  
Vol 69 (3) ◽  
pp. 402-413 ◽  
Author(s):  
Lijiang Chen ◽  
Jonathan J. Wilksch ◽  
Haiyang Liu ◽  
Xiaoxiao Zhang ◽  
Von V. L. Torres ◽  
...  
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Klebsiella Pneumoniae ◽  
Biofilm Formation ◽  
Type Species ◽  
Microtiter Plate ◽  
Resistant Isolate ◽  
Wild Type ◽  
Content Type ◽  
Link Type

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.

Two regulatory factors of Vibrio cholerae activating the mannose-sensitive haemagglutinin pilus expression is important for biofilm formation and colonization in mice

Microbiology ◽  
2021 ◽  
Vol 167 (10) ◽  
Author(s):  
Mengting Shi ◽  
Yue Zheng ◽  
Xianghong Wang ◽  
Zhengjia Wang ◽  
Menghua Yang
Keyword(s):  
Mouse Model ◽  
Vibrio Cholerae ◽  
Biofilm Formation ◽  
Type Species ◽  
Wild Type ◽  
Expression Library ◽  
Content Type ◽  
Genomic Expression ◽  
Infant Mouse ◽  
Link Type

Vibrio cholerae the causative agent of cholera, uses a large number of coordinated transcriptional regulatory events to transition from its environmental reservoir to the host intestine, which is its preferred colonization site. Transcription of the mannose-sensitive haemagglutinin pilus (MSHA), which aids the persistence of V. cholerae in aquatic environments, but causes its clearance by host immune defenses, was found to be regulated by a yet unknown mechanism during the infection cycle of V. cholerae . In this study, genomic expression library screening revealed that two regulators, VC1371 and VcRfaH, are able to positively activate the transcription of MSHA operon. VC1371 is localized and active in the cell membrane. Deletion of vc1371 or VcrfaH genes in V. cholerae resulted in less MshA protein production and less efficiency of biofilm formation compared to that in the wild-type strain. An adult mouse model showed that the mutants with vc1371 or VcrfaH deletion colonized less efficiently than the wild-type; the VcrfaH deletion mutant showed less colonization efficiency in the infant mouse model. The findings strongly suggested that the two regulators, namely VC1371 and VcRfaH, which are involved in the regulation of MSHA expression, play an important role in V. cholerae biofilm formation and colonization in mice.

scholarly journals Study of quorum-sensing LasR and RhlR genes and their dependent virulence factors in Pseudomonas aeruginosa isolates from infected burn wounds

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Aya Ahmad Elnegery ◽  
Wafaa Kamel Mowafy ◽  
Tarek Ahmed Zahra ◽  
Noha Tharwat Abou El-Khier
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Proteolytic Activity ◽  
Virulence Factors ◽  
Biofilm Formation ◽  
Type Species ◽  
Assay Method ◽  
Content Type ◽  
Burn Wounds ◽  
Link Type

Background. Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen responsible for burn-wound infection. High incidence, infection severity and increasing resistance characterize P. aeruginosa -induced burn infection. Purpose. To estimate quorum-sensing (QS)-dependent virulence factors of P. aeruginosa isolates from burn wounds and correlate it to the presence of QS genes. Methods. A cross-sectional descriptive study included 50 P . aeruginosa isolates from burn patients in Mansoura University Plastic and Burn Hospital, Egypt. Antibiotic sensitivity tests were done. All isolates were tested for their ability to produce biofilm using a micro-titration assay method. Protease, pyocyanin and rhamnolipid virulence factors were determined using skimmed milk agar, King’s A medium and CTAB agar test, respectively. The identity of QS lasR and rhlR genes was confirmed using PCR. Results. In total, 86 % of isolates had proteolytic activity. Production of pyocyanin pigment was manifested in 66 % of isolates. Altogether, 76 % of isolates were rhamnolipid producers. Biofilm formation was detected in 96 % of isolates. QS lasR and rhlR genes were harboured by nearly all isolates except three isolates were negative for both lasR and rhlR genes and two isolates were positive for lasR gene and negative for rhlR gene. Forty-nine isolates were considered as extremely QS-proficient strains as they produced QS-dependent virulence factors. In contrast, one isolate was a QS deficient strain. Conclusions. QS affects P. aeruginosa virulence-factor production and biofilm in burn wounds. Isolates containing lasR and rhlR seem to be a crucial regulator of virulence factors and biofilm formation in P. aeruginosa whereas the lasR gene positively regulates biofilm formation, proteolytic activity, pyocyanin production and rhamnolipid biosurfactant synthesis. The QS regulatory RhlR gene affects protease and rhamnolipid production positively.

scholarly journals Transcriptome profiling of Variovorax paradoxus EPS under different growth conditions reveals regulatory and structural novelty in biofilm formation

2020 ◽  
Vol 2 (6) ◽  
Author(s):  
Richard J. Fredendall ◽  
Jenny L. Stone ◽  
Michael J. Pehl ◽  
Paul M. Orwin
Keyword(s):  
Gene Expression ◽  
Stationary Phase ◽  
Exponential Growth ◽  
Biofilm Formation ◽  
Type Species ◽  
Extracellular Dna ◽  
Differentially Expressed ◽  
Content Type ◽  
Variovorax Paradoxus ◽  
Link Type

We used transcriptome analysis by paired-end strand-specific RNA-seq to evaluate the specific changes in gene expression associated with the transition to static biofilm growth in the rhizosphere plant growth-promoting bacterium Variovorax paradoxus EPS. Triplicate biological samples of exponential growth, stationary phase and static biofilm samples were examined. DESeq2 and Rockhopper were used to identify robust and widespread shifts in gene expression specific to each growth phase. We identified 1711 protein-coding genes (28%) using DESeq2 that had altered expression greater than twofold specifically in biofilms compared to exponential growth. Fewer genes were specifically differentially expressed in stationary-phase culture (757, 12%). A small set of genes (103/6020) were differentially expressed in opposing fashions in biofilm and stationary phase, indicating potentially substantial shifts in phenotype. Gene-ontology analysis showed that the only class of genes specifically upregulated in biofilms was associated with nutrient transport, highlighting the importance of nutrient uptake in the biofilm. The biofilm-specific genes did not overlap substantially with the loci identified by mutagenesis studies, although some were present in both sets. The most highly upregulated biofilm-specific gene is predicted to be a part of the RNA degradosome, which indicates that RNA stability is used to regulate the biofilm phenotype. Two small putative proteins, Varpa_0407 and Varpa_3832, are highly expressed specifically in biofilms and are predicted to be secreted DNA-binding proteins, which may stabilize extracellular DNA as a component of the biofilm matrix. An flp/tad type-IV pilus locus (Varpa_5148–60) is strongly downregulated specifically in biofilms, in contrast with results from other systems for these pili. Mutagenesis confirms that this locus is important in surface motility rather than biofilm formation. These experimental results suggest that V. paradoxus EPS biofilms have substantial regulatory and structural novelty.

scholarly journals Comparative genomics of wild-type and laboratory-evolved biofilm-overproducing Deinococcus metallilatus strains

2020 ◽  
Vol 6 (12) ◽  
Author(s):  
Chulwoo Park ◽  
Bora Shin ◽  
Wonjae Kim ◽  
Hoon Cheong ◽  
Soyoon Park ◽  
...  
Keyword(s):  
Cell Death ◽  
Biofilm Formation ◽  
Type Species ◽  
High Rate ◽  
Wild Type ◽  
Content Type ◽  
Link Type ◽  
Extracellular Matrix Components ◽  
Mutant Strains ◽  
Mutant Cells

Deinococcus metallilatus MA1002 was exposed to ultraviolet radiation to generate mutants with enhanced biofilm production. Two strains (nos 5 and 6) were then selected based on their high biofilm formation, as well as their possession of higher concentrations of extracellular matrix components (eDNA, protein and saccharides) than the wild-type (WT). Genomic sequencing revealed the presence of large genome deletions in a secondary chromosome in the mutants. Expression analyses of the WT and mutant strains indicated the upregulation of genes associated with exopolysaccharide synthesis and stress response. The mutant strains showed high mortality in glucose-supplemented (TYG) medium; however, cell death and biofilm formation were not increased in mutant cells grown under acetate- or glyoxylate-added media, suggesting that metabolic toxicity during glucose metabolism induced a high rate of cell death but improved biofilm formation in mutant strains. In damaged cells, eDNAs contributed to the enhanced biofilm formation of D. metallilatus .

scholarly journals Role of quorum sensing in UVA-induced biofilm formation in Pseudomonas aeruginosa

Microbiology ◽  
2020 ◽  
Vol 166 (8) ◽  
pp. 735-750 ◽  
Author(s):  
Magdalena Pezzoni ◽  
Ramón A. Pizarro ◽  
Cristina S. Costa
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Biofilm Formation ◽  
Type Species ◽  
Transcriptional Level ◽  
Content Type ◽  
Link Type ◽  
Opportunistic Human Pathogen ◽  
Biofilm Development

Pseudomonas aeruginosa , a versatile bacterium present in terrestrial and aquatic environments and a relevant opportunistic human pathogen, is largely known for the production of robust biofilms. The unique properties of these structures complicate biofilm eradication, because they make the biofilms very resistant to diverse antibacterial agents. Biofilm development and establishment is a complex process regulated by multiple regulatory genetic systems, among them is quorum sensing (QS), a mechanism employed by bacteria to regulate gene transcription in response to population density. In addition, environmental factors such as UVA radiation (400–315 nm) have been linked to biofilm formation. In this work, we further investigate the mechanism underlying the induction of biofilm formation by UVA, analysing the role of QS in this phenomenon. We demonstrate that UVA induces key genes of the Las and Rhl QS systems at the transcriptional level. We also report that pelA and pslA genes, which are essential for biofilm formation and whose transcription depends in part on QS, are significantly induced under UVA exposure. Finally, the results demonstrate that in a relA strain (impaired for ppGpp production), the UVA treatment does not induce biofilm formation or QS genes, suggesting that the increase of biofilm formation due to exposure to UVA in P. aeruginosa could rely on a ppGpp-dependent QS induction.

scholarly journals Transcriptomic analysis of Pseudomonas ogarae F113 reveals the antagonistic roles of AmrZ and FleQ during rhizosphere adaption

2022 ◽  
Vol 8 (1) ◽  
Author(s):  
Esther Blanco-Romero ◽  
David Durán ◽  
Daniel Garrido-Sanz ◽  
Rafael Rivilla ◽  
Marta Martín ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Biofilm Formation ◽  
Type Species ◽  
Global Changes ◽  
Secretion Systems ◽  
Content Type ◽  
Rhizosphere Colonization ◽  
Link Type ◽  
Metabolic Versatility

Rhizosphere colonization by bacteria involves molecular and cellular mechanisms, such as motility and chemotaxis, biofilm formation, metabolic versatility, or biosynthesis of secondary metabolites, among others. Nonetheless, there is limited knowledge concerning the main regulatory factors that drive the rhizosphere colonization process. Here we show the importance of the AmrZ and FleQ transcription factors for adaption in the plant growth-promoting rhizobacterium (PGPR) and rhizosphere colonization model Pseudomonas ogarae F113. RNA-Seq analyses of P. ogarae F113 grown in liquid cultures either in exponential and stationary growth phase, and rhizosphere conditions, revealed that rhizosphere is a key driver of global changes in gene expression in this bacterium. Regarding the genetic background, this work has revealed that a mutation in fleQ causes considerably more alterations in the gene expression profile of this bacterium than a mutation in amrZ under rhizosphere conditions. The functional analysis has revealed that in P. ogarae F113, the transcription factors AmrZ and FleQ regulate genes involved in diverse bacterial functions. Notably, in the rhizosphere, these transcription factors antagonistically regulate genes related to motility, biofilm formation, nitrogen, sulfur, and amino acid metabolism, transport, signalling, and secretion, especially the type VI secretion systems. These results define the regulon of two important bifunctional transcriptional regulators in pseudomonads during the process of rhizosphere colonization.

scholarly journals Cellobiose-Specific Phosphotransferase System of Klebsiella pneumoniae and Its Importance in Biofilm Formation and Virulence

2012 ◽  
Vol 80 (7) ◽  
pp. 2464-2472 ◽  
Author(s):  
Meng-Chuan Wu ◽  
Ying-Chun Chen ◽  
Tzu-Lung Lin ◽  
Pei-Fang Hsieh ◽  
Jin-Town Wang
Keyword(s):  
Klebsiella Pneumoniae ◽  
Biofilm Formation ◽  
Type Strain ◽  
Minimal Medium ◽  
Wild Type Strain ◽  
Microtiter Plate ◽  
Wild Type ◽  
Phosphotransferase System ◽  
Microtiter Plate Assay ◽  
Content Type

ABSTRACTKlebsiella pneumoniaeis a Gram-negative bacillus belonging to the familyEnterobacteriaceae. In the past 20 years,K. pneumoniaehas become the predominant pathogen causing community-acquired pyogenic liver abscess (PLA). The formation of biofilm facilitates bacterial colonization and has been implicated in reduced susceptibility to the host immune response. To investigate genes related to biofilm formation in a PLA-associatedK. pneumoniaestrain, a transposon mutant library was screened by microtiter plate assay to identify isolates impaired for biofilm formation. One of the mutants was disrupted incelB, encoding the putative cellobiose-specific subunit IIC of enzyme II (EIIC) of a carbohydrate phosphotransferase system (PTS). This transmembrane protein is responsible for recognizing and binding specific sugars and transporting them across the cell membrane into the cytoplasm. Deletion and chromosomal complementation ofcelBconfirmed, by microtiter plate and slide culture assays, thatcelBwas indeed responsible for biofilm formation. Cellobiose-specific PTS activities of deletion mutants grown in LB broth and 0.005% cellobiose minimal medium were markedly lower than that of the wild-type strain grown under the same conditions, thereby confirming the involvement ofcelBin cellobiose transport. In 0.005% cellobiose minimal medium, thecelBmutant showed a delay in growth compared to the wild-type strain. In a mouse model of intragastric infection, deletion of thecelBgene increased the survival rate from 12.5% to 87.5%, which suggests that thecelBdeletion mutant also exhibited reduced virulence. Thus, thecelBlocus ofK. pneumoniae may contribute to biofilm formation and virulence through the metabolism of cellobiose.

scholarly journals Eucalyptol inhibits biofilm formation of Streptococcus pyogenes and its mediated virulence factors

2020 ◽  
Vol 69 (11) ◽  
pp. 1308-1318
Author(s):  
Karuppiah Vijayakumar ◽  
Vajravelu Manigandan ◽  
Danaraj Jeyapragash ◽  
Veeraiyan Bharathidasan ◽  
Balaiyan Anandharaj ◽  
...  
Keyword(s):  
Gene Expression ◽  
Streptococcus Pyogenes ◽  
Biofilm Formation ◽  
Type Species ◽  
Inhibitory Concentration ◽  
Antibiofilm Activity ◽  
Dependent Manner ◽  
Biofilm Inhibition ◽  
Content Type ◽  
Link Type

Introduction. Streptococcus pyogenes is a diverse virulent synthesis pathogen responsible for invasive systemic infections. Establishment of antibiotic resistance in the pathogen has produced a need for new antibiofilm agents to control the biofilm formation and reduce biofilm-associated resistance development. Aim. The present study investigates the in vitro antibiofilm activity of eucalyptol against S. pyogenes . Methodology. The antibiofilm potential of eucalyptol was assessed using a microdilution method and their biofilm inhibition efficacy was visualized by microscopic analysis. The biochemical assays were performed to assess the influence of eucalyptol on virulence productions. Real-time PCR analysis was performed to evaluate the expression profile of the virulence genes. Results. Eucalyptol showed significant antibiofilm potential in a dose-dependent manner without affecting bacterial growth. Eucalyptol at 300 µg ml−1 (biofilm inhibitory concentration) significantly inhibited the initial stage of biofilm formation in S. pyogenes . However, eucalyptol failed to diminish the mature biofilms of S. pyogenes at biofilm inhibitory concentration and it effectively reduced the biofilm formation on stainless steel, titanium, and silicone surfaces. The biochemical assay results revealed that eucalyptol greatly affects the cell-surface hydrophobicity, auto-aggregation, extracellular protease, haemolysis and hyaluronic acid synthesis. Further, the gene-expression analysis results showed significant downregulation of virulence gene expression upon eucalyptol treatment. Conclusion. The present study suggests that eucalyptol applies its antibiofilm assets by intruding the initial biofilm formation of S. pyogenes . Supplementary studies are needed to understand the mode of action involved in biofilm inhibition.

PBP4 and PBP5 are involved in regulating exopolysaccharide synthesis during Escherichia coli biofilm formation

Microbiology ◽  
2021 ◽  
Vol 167 (3) ◽  
Author(s):  
Sathi Mallick ◽  
Shanti Kiran ◽  
Tapas Kumar Maiti ◽  
Anindya S. Ghosh
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Type Species ◽  
Pentose Phosphate ◽  
Bacterial Cells ◽  
Surface Adhesion ◽  
Content Type ◽  
Penicillin Binding Proteins ◽  
E Coli ◽  
Link Type

Escherichia coli low-molecular-mass (LMM) Penicillin-binding proteins (PBPs) help in hydrolysing the peptidoglycan fragments from their cell wall and recycling them back into the growing peptidoglycan matrix, in addition to their reported involvement in biofilm formation. Biofilms are external slime layers of extra-polymeric substances that sessile bacterial cells secrete to form a habitable niche for themselves. Here, we hypothesize the involvement of Escherichia coli LMM PBPs in regulating the nature of exopolysaccharides (EPS) prevailing in its extra-polymeric substances during biofilm formation. Therefore, this study includes the assessment of physiological characteristics of E. coli CS109 LMM PBP deletion mutants to address biofilm formation abilities, viability and surface adhesion. Finally, EPS from parent CS109 and its ΔPBP4 and ΔPBP5 mutants were purified and analysed for sugars present. Deletions of LMM PBP reduced biofilm formation, bacterial adhesion and their viability in biofilms. Deletions also diminished EPS production by ΔPBP4 and ΔPBP5 mutants, purification of which suggested an increased overall negative charge compared with their parent. Also, EPS analyses from both mutants revealed the appearance of an unusual sugar, xylose, that was absent in CS109. Accordingly, the reason for reduced biofilm formation in LMM PBP mutants may be speculated as the subsequent production of xylitol and a hindrance in the standard flow of the pentose phosphate pathway.

scholarly journals Genomic evolution and local epidemiology of Klebsiella pneumoniae from a major hospital in Beijing, China, over a 15 year period: dissemination of known and novel high-risk clones

2021 ◽  
Author(s):  
Mattia Palmieri ◽  
Kelly L. Wyres ◽  
Caroline Mirande ◽  
Zhao Qiang ◽  
Ye Liyan ◽  
...  
Keyword(s):  
High Risk ◽  
Klebsiella Pneumoniae ◽  
Type Species ◽  
Treatment Options ◽  
Multidrug Resistant ◽  
Virulence Plasmid ◽  
Content Type ◽  
Origin And Evolution ◽  
Link Type ◽  
Beijing China

Klebsiella pneumoniae is a frequent cause of nosocomial and severe community-acquired infections. Multidrug-resistant (MDR) and hypervirulent (hv) strains represent major threats, and tracking their emergence, evolution and the emerging convergence of MDR and hv traits is of major importance. We employed whole-genome sequencing (WGS) to study the evolution and epidemiology of a large longitudinal collection of clinical K. pneumoniae isolates from the H301 hospital in Beijing, China. Overall, the population was highly diverse, although some clones were predominant. Strains belonging to clonal group (CG) 258 were dominant, and represented the majority of carbapenemase-producers. While CG258 strains showed high diversity, one clone, ST11-KL47, represented the majority of isolates, and was highly associated with the KPC-2 carbapenemase and several virulence factors, including a virulence plasmid. The second dominant clone was CG23, which is the major hv clone globally. While it is usually susceptible to multiple antibiotics, we found some isolates harbouring MDR plasmids encoding for ESBLs and carbapenemases. We also reported the local emergence of a recently described high-risk clone, ST383. Conversely to strains belonging to CG258, which are usually associated to KPC-2, ST383 strains seem to readily acquire carbapenemases of different types. Moreover, we found several ST383 strains carrying the hypervirulence plasmid. Overall, we detected about 5 % of simultaneous carriage of AMR genes (ESBLs or carbapenemases) and hypervirulence genes. Tracking the emergence and evolution of such strains, causing severe infections with limited treatment options, is fundamental in order to understand their origin and evolution and to limit their spread. This article contains data hosted by Microreact.

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