scholarly journals RssAB-FlhDC-ShlBA as a Major Pathogenesis Pathway in Serratia marcescens

2010 ◽  
Vol 78 (11) ◽  
pp. 4870-4881 ◽  
Author(s):  
Chuan-Sheng Lin ◽  
Jim-Tong Horng ◽  
Chun-Hung Yang ◽  
Yu-Huan Tsai ◽  
Lin-Hui Su ◽  
...  
Keyword(s):  
Serratia Marcescens ◽  
Biofilm Formation ◽  
Inflammatory Responses ◽  
Systemic Infection ◽  
Opportunistic Pathogen ◽  
Positive Control ◽  
Regulatory Pathway ◽  
Two Component System ◽  
Infection Models ◽  
Animal Infection

ABSTRACT Serratia marcescens has long been recognized as an important opportunistic pathogen, but the underlying pathogenesis mechanism is not completely clear. Here, we report a key pathogenesis pathway in S. marcescens comprising the RssAB two-component system and its downstream elements, FlhDC and the dominant virulence factor hemolysin ShlBA. Expression of shlBA is under the positive control of FlhDC, which is repressed by RssAB signaling. At 37°C, functional RssAB inhibits swarming, represses hemolysin production, and promotes S. marcescens biofilm formation. In comparison, when rssBA is deleted, S. marcescens displays aberrant multicellularity favoring motile swarming with unbridled hemolysin production. Cellular and animal infection models further demonstrate that loss of rssBA transforms this opportunistic pathogen into hypervirulent phenotypes, leading to extensive inflammatory responses coupled with destructive and systemic infection. Hemolysin production is essential in this context. Collectively, a major virulence regulatory pathway is identified in S. marcescens.

scholarly journals Agrobacterium tumefaciens ExoR represses succinoglycan biosynthesis and is required for biofilm formation and motility

Microbiology ◽  
2010 ◽  
Vol 156 (9) ◽  
pp. 2670-2681 ◽  
Author(s):  
Amelia D. Tomlinson ◽  
Bronwyn Ramey-Hartung ◽  
Travis W. Day ◽  
Peter M. Merritt ◽  
Clay Fuqua
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Biofilm Formation ◽  
Sinorhizobium Meliloti ◽  
Plant Tissues ◽  
Flagellar Motility ◽  
Regulatory Pathway ◽  
Flow Conditions ◽  
Two Component System ◽  
Form Complex ◽  
Abiotic Surfaces

The ubiquitous plant pathogen Agrobacterium tumefaciens attaches efficiently to plant tissues and abiotic surfaces and can form complex biofilms. A genetic screen for mutants unable to form biofilms on PVC identified disruptions in a homologue of the exoR gene. ExoR is a predicted periplasmic protein, originally identified in Sinorhizobium meliloti, but widely conserved among alphaproteobacteria. Disruptions in the A. tumefaciens exoR gene result in severely compromised attachment to abiotic surfaces under static and flow conditions, and to plant tissues. These mutants are hypermucoid due to elevated production of the exopolysaccharide succinoglycan, via derepression of the exo genes that direct succinoglycan synthesis. In addition, exoR mutants have lost flagellar motility, do not synthesize detectable flagellin and are diminished in flagellar gene expression. The attachment deficiency is, however, complex and not solely attributable to succinoglycan overproduction or motility disruption. A. tumefaciens ExoR can function independently of the ChvG–ChvI two component system, implicated in ExoR-dependent regulation in S. meliloti. Mutations that suppress the exoR motility defect suggest a branched regulatory pathway controlling succinoglycan synthesis, motility and biofilm formation.

scholarly journals Modulation of antibiotic sensitivity and biofilm formation in Pseudomonas aeruginosa by interspecies diffusible signal factor analogues

2018 ◽  
Author(s):  
Shi-qi An ◽  
Julie Murtagh ◽  
Kate B. Twomey ◽  
Manoj K. Gupta ◽  
Timothy P. O’Sullivan ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Unsaturated Fatty Acids ◽  
Antibiotic Sensitivity ◽  
Opportunistic Pathogen ◽  
Lead Compounds ◽  
Infection Models ◽  
Diffusible Signal Factor ◽  
Input Domain

ABSTRACTThe opportunistic pathogen Pseudomonas aeruginosa can participate in inter-species communication through signaling by cis-2-unsaturated fatty acids of the diffusible signal factor (DSF) family. Sensing these signals involves the histidine kinase PA1396 and leads to altered biofilm formation and increased tolerance to various antibiotics. Here, we show that the membrane-associated sensory input domain of PA1396 has five trans-membrane helices, two of which are required for DSF sensing. DSF binding is associated with enhanced auto-phosphorylation of PA1396 incorporated into liposomes. Further, we examined the ability of synthetic DSF analogues to modulate or inhibit PA1396 activity. Several of these analogues block the ability of DSF to trigger auto-phosphorylation and gene expression, whereas others act as inverse agonists reducing biofilm formation and antibiotic tolerance, both in vitro and in murine infection models. These analogues may thus represent lead compounds for novel adjuvants to improve the efficacy of existing antibiotics.

scholarly journals Novel Two-Component System ofStreptococcus sanguinisAffecting Functions Associated with Viability in Saliva and Biofilm Formation

2018 ◽  
Vol 86 (4) ◽  
Author(s):  
Tarsila M. Camargo ◽  
Rafael N. Stipp ◽  
Lívia A. Alves ◽  
Erika N. Harth-Chu ◽  
José F. Höfling ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Ex Vivo ◽  
Opportunistic Pathogen ◽  
Dna Looping ◽  
Extracellular Dna ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Cell Counts ◽  
Two Component

ABSTRACTStreptococcus sanguinisis a pioneer species of teeth and a common opportunistic pathogen of infective endocarditis. In this study, we identified a two-component system,S. sanguinisSptRS (SptRSSs), affectingS. sanguinissurvival in saliva and biofilm formation. Isogenic mutants ofsptRSs(SKsptR) andsptSSs(SKsptS) showed reduced cell counts inex vivoassays of viability in saliva compared to those of parent strain SK36 and complemented mutants. Reduced counts of the mutants in saliva were associated with reduced growth rates in nutrient-poor medium (RPMI) and increased susceptibility to the deposition of C3b and the membrane attach complex (MAC) of the complement system, a defense component of saliva and serum. Conversely,sptRSsandsptSSsmutants showed increased biofilm formation associated with higher levels of production of H2O2and extracellular DNA. Reverse transcription-quantitative PCR (RT-qPCR) comparisons of strains indicated a global role of SptRSSsin repressing genes for H2O2production (2.5- to 15-fold upregulation ofspxB,spxR,vicR,tpk, andackAinsptRSsandsptSSsmutants), biofilm formation, and/or evasion of host immunity (2.1- to 11.4-fold upregulation ofsrtA,pcsB,cwdP,iga, andnt5e). Compatible with the homology of SptRSswith AraC-type regulators, duplicate to multiple conserved repeats were identified in 1,000-bp regulatory regions of downstream genes, suggesting that SptRSsregulates transcription by DNA looping. Significant transcriptional changes in the regulatory genesvicR,spxR,comE,comX, andmecAin thesptRSsandsptSSsmutants further indicated that SptRSSsis part of a regulatory network that coordinates cell wall homeostasis, H2O2production, and competence. This study reveals that SptRSSsis involved in the regulation of crucial functions forS. sanguinispersistence in the oral cavity.

scholarly journals Structural insights into loss of function of a pore forming toxin and its role in pneumococcal adaptation to an intracellular lifestyle

2020 ◽  
Vol 16 (11) ◽  
pp. e1009016
Author(s):  
Dilip C. Badgujar ◽  
Anjali Anil ◽  
Angharad E. Green ◽  
Manalee Vishnu Surve ◽  
Shilpa Madhavan ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Hydrophobic Interactions ◽  
Opportunistic Pathogen ◽  
Crystal Structure Analysis ◽  
Loss Of Function ◽  
Structural Rigidity ◽  
Infection Models ◽  
Serotype 1 ◽  
Domain 3

The opportunistic pathogen Streptococcus pneumoniae has dual lifestyles: one of an asymptomatic colonizer in the human nasopharynx and the other of a deadly pathogen invading sterile host compartments. The latter triggers an overwhelming inflammatory response, partly driven via pore forming activity of the cholesterol dependent cytolysin (CDC), pneumolysin. Although pneumolysin-induced inflammation drives person-to-person transmission from nasopharynx, the primary reservoir for pneumococcus, it also contributes to high mortality rates, creating a bottleneck that hampers widespread bacterial dissemination, thus acting as a double-edged sword. Serotype 1 ST306, a widespread pneumococcal clone, harbours a non-hemolytic variant of pneumolysin (Ply-NH). Performing crystal structure analysis of Ply-NH, we identified Y150H and T172I as key substitutions responsible for loss of its pore forming activity. We uncovered a novel inter-molecular cation-π interaction, governing formation of the transmembrane β-hairpins (TMH) in the pore state of Ply, which can be extended to other CDCs. H150 in Ply-NH disrupts this interaction, while I172 provides structural rigidity to domain-3, through hydrophobic interactions, inhibiting TMH formation. Loss of pore forming activity enabled improved cellular invasion and autophagy evasion, promoting an atypical intracellular lifestyle for pneumococcus, a finding that was corroborated in in vivo infection models. Attenuation of inflammatory responses and tissue damage promoted tolerance of Ply-NH-expressing pneumococcus in the lower respiratory tract. Adoption of this altered lifestyle may be necessary for ST306 due to its limited nasopharyngeal carriage, with Ply-NH, aided partly by loss of its pore forming ability, facilitating a benign association of SPN in an alternative, intracellular host niche.

scholarly journals Inverse Regulation of Biofilm Formation and Swarming Motility by Pseudomonas aeruginosa PA14

2007 ◽  
Vol 189 (9) ◽  
pp. 3603-3612 ◽  
Author(s):  
Nicky C. Caiazza ◽  
Judith H. Merritt ◽  
Kimberly M. Brothers ◽  
George A. O'Toole
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Opportunistic Pathogen ◽  
Wild Type ◽  
Regulatory Pathway ◽  
Early Step ◽  
Swarming Motility ◽  
Epistasis Analysis

ABSTRACT We previously reported that SadB, a protein of unknown function, is required for an early step in biofilm formation by the opportunistic pathogen Pseudomonas aeruginosa. Here we report that a mutation in sadB also results in increased swarming compared to the wild-type strain. Our data are consistent with a model in which SadB inversely regulates biofilm formation and swarming motility via its ability both to modulate flagellar reversals in a viscosity-dependent fashion and to influence the production of the Pel exopolysaccharide. We also show that SadB is required to properly modulate flagellar reversal rates via chemotaxis cluster IV (CheIV cluster). Mutational analyses of two components of the CheIV cluster, the methyl-accepting chemotaxis protein PilJ and the PilJ demethylase ChpB, support a model wherein this chemotaxis cluster participates in the inverse regulation of biofilm formation and swarming motility. Epistasis analysis indicates that SadB functions upstream of the CheIV cluster. We propose that P. aeruginosa utilizes a SadB-dependent, chemotaxis-like regulatory pathway to inversely regulate two key surface behaviors, biofilm formation and swarming motility.

scholarly journals A Serratia marcescens OxyR Homolog Mediates Surface Attachment and Biofilm Formation

2007 ◽  
Vol 189 (20) ◽  
pp. 7262-7272 ◽  
Author(s):  
Robert M. Q. Shanks ◽  
Nicholas A. Stella ◽  
Eric J. Kalivoda ◽  
Megan R. Doe ◽  
Dawn M. O'Dee ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Serratia Marcescens ◽  
Biofilm Formation ◽  
Bacterial Species ◽  
Opportunistic Pathogen ◽  
Type I ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
Resistance Mutations ◽  
In The Wild

ABSTRACT OxyR is a conserved bacterial transcription factor with a regulatory role in oxidative stress response. From a genetic screen for genes that modulate biofilm formation in the opportunistic pathogen Serratia marcescens, mutations in an oxyR homolog and predicted fimbria structural genes were identified. S. marcescens oxyR mutants were severely impaired in biofilm formation, in contrast to the hyperbiofilm phenotype exhibited by oxyR mutants of Escherichia coli and Burkholderia pseudomallei. Further analysis revealed that OxyR plays a role in the primary attachment of cells to a surface. Similar to what is observed in other bacterial species, S. marcescens OxyR is required for oxidative stress resistance. Mutations in oxyR and type I fimbrial genes resulted in severe defects in fimbria-associated phenotypes, revealing roles in cell-cell and cell-biotic surface interactions. Transmission electron microscopy revealed the absence of fimbria-like surface structures on an OxyR-deficient strain and an enhanced fimbrial phenotype in strains bearing oxyR on a multicopy plasmid. The hyperfimbriated phenotype conferred by the multicopy oxyR plasmid was absent in a type I fimbrial mutant background. Real-time reverse transcriptase PCR indicated an absence of transcripts from a fimbrial operon in an oxyR mutant that were present in the wild type and a complemented oxyR mutant strain. Lastly, chromosomal Plac -mediated expression of fimABCD was sufficient to restore wild-type levels of yeast agglutination and biofilm formation to an oxyR mutant. Together, these data support a model in which OxyR contributes to early stages of S. marcescens biofilm formation by influencing fimbrial gene expression.

scholarly journals High-Throughput Screens for Small-Molecule Inhibitors of Pseudomonas aeruginosa Biofilm Development

2007 ◽  
Vol 51 (10) ◽  
pp. 3582-3590 ◽  
Author(s):  
Lauren M. Junker ◽  
Jon Clardy
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Small Molecule ◽  
High Throughput ◽  
Biofilm Formation ◽  
Small Molecule Inhibitors ◽  
Opportunistic Pathogen ◽  
Positive Control ◽  
Strain Pao1 ◽  
Small Molecule Modulators ◽  
Biofilm Development

ABSTRACT Pseudomonas aeruginosa is both a model biofilm-forming organism and an opportunistic pathogen responsible for chronic lung infections in cystic fibrosis (CF) patients and infections in burn patients, among other maladies. Here we describe the development of an efficient high-throughput screen to identify small-molecule modulators of biofilm formation. This screen has been run with 66,095 compounds to identify those that prevent biofilm formation without affecting planktonic bacterial growth. The screen is a luminescence-based attachment assay that has been validated with several strains of P. aeruginosa and compared to a well-established but low-throughput crystal violet staining biofilm assay. P. aeruginosa strain PAO1 was selected for use in the screen both because it forms robust biofilms and because genetic information and tools are available for the organism. The attachment-inhibited mutant, strain PAO1 ΔfliC, was used as a screening-positive control. We have also developed and validated a complementary biofilm detachment assay that can be used as an alternative primary screen or secondary screen for the attachment screening-positive compounds. We have determined the potencies of 61 compounds against biofilm attachment and have identified 30 compounds that fall into different structural classes as biofilm attachment inhibitors with 50% effective concentrations of less than 20 μM. These small-molecule inhibitors could lead to the identification of their relevant biofilm targets or potential therapeutics for P. aeruginosa infections.

scholarly journals atpD gene sequencing, multidrug resistance traits, virulence-determinants, and antimicrobial resistance genes of emerging XDR and MDR-Proteus mirabilis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abdelazeem M. Algammal ◽  
Hany R. Hashem ◽  
Khyreyah J. Alfifi ◽  
Helal F. Hetta ◽  
Norhan S. Sheraba ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Resistance Genes ◽  
Proteus Mirabilis ◽  
Biofilm Formation ◽  
Gene Sequencing ◽  
Opportunistic Pathogen ◽  
Severe Illness ◽  
Virulence Determinants ◽  
Antimicrobial Resistance Genes ◽  
Port Said

AbstractProteus mirabilis is a common opportunistic pathogen causing severe illness in humans and animals. To determine the prevalence, antibiogram, biofilm-formation, screening of virulence, and antimicrobial resistance genes in P. mirabilis isolates from ducks; 240 samples were obtained from apparently healthy and diseased ducks from private farms in Port-Said Province, Egypt. The collected samples were examined bacteriologically, and then the recovered isolates were tested for atpD gene sequencing, antimicrobial susceptibility, biofilm-formation, PCR detection of virulence, and antimicrobial resistance genes. The prevalence of P. mirabilis in the examined samples was 14.6% (35/240). The identification of the recovered isolates was confirmed by the atpD gene sequencing, where the tested isolates shared a common ancestor. Besides, 94.3% of P. mirabilis isolates were biofilm producers. The recovered isolates were resistant to penicillins, sulfonamides, β-Lactam-β-lactamase-inhibitor-combinations, tetracyclines, cephalosporins, macrolides, and quinolones. Using PCR, the retrieved strains harbored atpD, ureC, rsbA, and zapA virulence genes with a prevalence of 100%, 100%, 94.3%, and 91.4%, respectively. Moreover, 31.4% (11/35) of the recovered strains were XDR to 8 antimicrobial classes that harbored blaTEM, blaOXA-1, blaCTX-M, tetA, and sul1 genes. Besides, 22.8% (8/35) of the tested strains were MDR to 3 antimicrobial classes and possessed blaTEM, tetA, and sul1genes. Furthermore, 17.1% (6/35) of the tested strains were MDR to 7 antimicrobial classes and harbored blaTEM, blaOXA-1, blaCTX-M, tetA, and sul1 genes. Alarmingly, three strains were carbapenem-resistant that exhibited PDR to all the tested 10 antimicrobial classes and shared blaTEM, blaOXA-1, blaCTX-M, tetA, and sul1 genes. Of them, two strains harbored the blaNDM-1 gene, and one strain carried the blaKPC gene. In brief, to the best of our knowledge, this is the first study demonstrating the emergence of XDR and MDR-P.mirabilis in ducks. Norfloxacin exhibited promising antibacterial activity against the recovered XDR and MDR-P. mirabilis. The emergence of PDR, XDR, and MDR-strains constitutes a threat alarm that indicates the complicated treatment of the infections caused by these superbugs.

Sign in / Sign up

Export Citation Format

Share Document