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

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.

Download Full-text

Archaeal biofilms: widespread and complex

Biochemical Society Transactions ◽

10.1042/bst20120304 ◽

2013 ◽

Vol 41 (1) ◽

pp. 393-398 ◽

Cited By ~ 52

Author(s):

Sabrina Fröls

Keyword(s):

Biofilm Formation ◽

Extracellular Polymeric Substances ◽

Bacterial Species ◽

Surface Adhesion ◽

Form Complex ◽

Abiotic Surfaces ◽

Archaeal Species ◽

Physical And Chemical ◽

Insight Into ◽

Mixed Communities

Biofilms or multicellular structures become accepted as the dominant microbial lifestyle in Nature, but in the past they were only studied extensively in bacteria. Investigations on archaeal monospecies cultures have shown that many archaeal species are able to adhere on biotic and abiotic surfaces and form complex biofilm structures. Biofilm-forming archaea were identified in a broad range of extreme and moderate environments. Natural biofilms observed are mostly mixed communities composed of archaeal and bacterial species of various abundances. The physiological functions of the archaea identified in such mixed communities suggest a significant impact on the biochemical cycles maintaining the flow and recycling of the nutrients on earth. Therefore it is of high interest to investigate the characteristics and mechanisms underlying the archaeal biofilm formation. In the present review, I summarize and discuss the present investigations of biofilm-forming archaeal species, i.e. their diverse biofilm architectures in monospecies or mixed communities, the identified EPSs (extracellular polymeric substances), archaeal structures mediating surface adhesion or cell–cell connections, and the response to physical and chemical stressors implying that archaeal biofilm formation is an adaptive reaction to changing environmental conditions. A first insight into the molecular differentiation of cells within archaeal biofilms is given.

Download Full-text

Cell Autoaggregation, Biofilm Formation, and Plant Attachment in a Sinorhizobium meliloti lpsB Mutant

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-01-18-0004-r ◽

2018 ◽

Vol 31 (10) ◽

pp. 1075-1082 ◽

Cited By ~ 5

Author(s):

Fernando Sorroche ◽

Pablo Bogino ◽

Daniela M. Russo ◽

Angeles Zorreguieta ◽

Fiorela Nievas ◽

...

Keyword(s):

Biofilm Formation ◽

Sinorhizobium Meliloti ◽

Planktonic Cell ◽

Confocal Laser ◽

Bacterial Surface ◽

Abiotic Surfaces ◽

Defective Mutant ◽

Mutant Strains ◽

Adhesive Interactions ◽

Biofilm Development

Bacterial surface molecules are crucial for the establishment of a successful rhizobia-legume symbiosis, and, in most bacteria, are also critical for adherence properties, surface colonization, and as a barrier for defense. Rhizobial mutants defective in the production of exopolysaccharides (EPSs), lipopolysaccharides (LPSs), or capsular polysaccharides are usually affected in symbiosis with their plant hosts. In the present study, we evaluated the role of the combined effects of LPS and EPS II in cell-to-cell and cell-to-surface interactions in Sinorhizobium meliloti by studying planktonic cell autoaggregation, biofilm formation, and symbiosis with the host plant Medicago sativa. The lpsB mutant, which has a defective core portion of LPS, exhibited a reduction in biofilm formation on abiotic surfaces as well as altered biofilm architecture compared with the wild-type Rm8530 strain. Atomic force microscopy and confocal laser microscopy revealed an increase in polar cell-to-cell interactions in the lpsB mutant, which might account for the biofilm deficiency. However, a certain level of biofilm development was observed in the lpsB strain compared with the EPS II-defective mutant strains. Autoaggregation experiments carried out with LPS and EPS mutant strains showed that both polysaccharides have an impact on the cell-to-cell adhesive interactions of planktonic bacteria. Although the lpsB mutation and the loss of EPS II production strongly stimulated early attachment to alfalfa roots, the number of nodules induced in M. sativa was not increased. Taken together, this work demonstrates that S. meliloti interactions with biotic and abiotic surfaces depend on the interplay between LPS and EPS II.

Download Full-text

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

Infection and Immunity ◽

10.1128/iai.00661-10 ◽

2010 ◽

Vol 78 (11) ◽

pp. 4870-4881 ◽

Cited By ~ 36

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.

Download Full-text

Motility control through an anti-activation mechanism in Agrobacterium tumefaciens

10.1101/2021.06.24.449765 ◽

2021 ◽

Author(s):

Melene A Alakavuklar ◽

Brynn C Heckel ◽

Ari M Stoner ◽

Joseph A Stembel ◽

Clay Fuqua

Keyword(s):

Agrobacterium Tumefaciens ◽

Gene Activation ◽

Activation Mechanism ◽

Flagellar Motility ◽

Class Iii ◽

Two Component System ◽

Gene Encoding ◽

Acid Protein ◽

Motility Regulation ◽

Flagellar Biogenesis

Many bacteria can migrate from a free-living, planktonic state to an attached, biofilm existence. One factor regulating this transition in the facultative plant pathogen Agrobacterium tumefaciens is the ExoR-ChvG-ChvI system. Periplasmic ExoR regulates activity of the ChvG-ChvI two-component system in response to environmental stress, most notably low pH. ChvI impacts hundreds of genes, including those required for type VI secretion, virulence, biofilm formation, and flagellar motility. Previous studies revealed that activated ChvG-ChvI represses expression of most of class II and class III flagellar biogenesis genes, but not the master motility regulators visN, visR, and rem. In this study, we characterized the integration of the ExoR-ChvG-ChvI and VisNR-Rem pathways. We isolated motile suppressors of the non-motile ΔexoR mutant and thereby identified the previously unannotated mirA gene encoding a 76 amino acid protein. We report that the MirA protein interacts directly with the Rem DNA-binding domain, sequestering Rem and preventing motility gene activation. The ChvG-ChvI pathway activates mirA expression and elevated mirA is sufficient to block motility. This study reveals how the ExoR-ChvG-ChvI pathway prevents flagellar motility in A. tumefaciens. MirA is also conserved among other members of the Rhizobiales suggesting similar mechanisms of motility regulation.

Download Full-text

Flagellar Motility Is Critical for Listeria monocytogenes Biofilm Formation

Journal of Bacteriology ◽

10.1128/jb.01967-06 ◽

2007 ◽

Vol 189 (12) ◽

pp. 4418-4424 ◽

Cited By ~ 231

Author(s):

Katherine P. Lemon ◽

Darren E. Higgins ◽

Roberto Kolter

Keyword(s):

Listeria Monocytogenes ◽

Biofilm Formation ◽

Molecular Mechanisms ◽

Early Stage ◽

Food Contamination ◽

Initial Surface ◽

Flagellar Motility ◽

Surface Attachment ◽

Abiotic Surfaces ◽

Biofilm Development

ABSTRACT The food-borne pathogen Listeria monocytogenes attaches to environmental surfaces and forms biofilms that can be a source of food contamination, yet little is known about the molecular mechanisms of its biofilm development. We observed that nonmotile mutants were defective in biofilm formation. To investigate how flagella might function during biofilm formation, we compared the wild type with flagellum-minus and paralyzed-flagellum mutants. Both nonmotile mutants were defective in biofilm development, presumably at an early stage, as they were also defective in attachment to glass during the first few hours of surface exposure. This attachment defect could be significantly overcome by providing exogenous movement toward the surface via centrifugation. However, this centrifugation did not restore mature biofilm formation. Our results indicate that it is flagellum-mediated motility that is critical for both initial surface attachment and subsequent biofilm formation. Also, any role for L. monocytogenes flagella as adhesins on abiotic surfaces appears to be either minimal or motility dependent under the conditions we examined.

Download Full-text

The Enterococcus faecalis fsr Two-Component System Controls Biofilm Development through Production of Gelatinase

Journal of Bacteriology ◽

10.1128/jb.186.17.5629-5639.2004 ◽

2004 ◽

Vol 186 (17) ◽

pp. 5629-5639 ◽

Cited By ~ 173

Author(s):

Lynn E. Hancock ◽

Marta Perego

Keyword(s):

Enterococcus Faecalis ◽

Bacterial Growth ◽

Biofilm Formation ◽

Heart Valves ◽

Bacterial Resistance ◽

Two Component System ◽

Component System ◽

Abiotic Surfaces ◽

Two Component ◽

Biofilm Development

ABSTRACT Bacterial growth as a biofilm on solid surfaces is strongly associated with the development of human infections. Biofilms on native heart valves (infective endocarditis) is a life-threatening disease as a consequence of bacterial resistance to antimicrobials in such a state. Enterococci have emerged as a cause of endocarditis and nosocomial infections despite being normal commensals of the gastrointestinal and female genital tracts. We examined the role of two-component signal transduction systems in biofilm formation by the Enterococcus faecalis V583 clinical isolate and identified the fsr regulatory locus as the sole two-component system affecting this unique mode of bacterial growth. Insertion mutations in the fsr operon affected biofilm formation on two distinct abiotic surfaces. Inactivation of the fsr-controlled gene gelE encoding the zinc-metalloprotease gelatinase was found to prevent biofilm formation, suggesting that this enzyme may present a unique target for therapeutic intervention in enterococcal endocarditis.

Download Full-text

Integration of Transcriptome and Metabolome Reveals the Genes and Metabolites Involved in Bifidobacterium bifidum Biofilm Formation

International Journal of Molecular Sciences ◽

10.3390/ijms22147596 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7596

Author(s):

Zongmin Liu ◽

Lingzhi Li ◽

Zhifeng Fang ◽

Yuankun Lee ◽

Jianxin Zhao ◽

...

Keyword(s):

Quorum Sensing ◽

Biofilm Formation ◽

Bifidobacterium Bifidum ◽

Differentially Expressed ◽

Glutathione Metabolism ◽

Two Component System ◽

Metabolomics Data ◽

Component System ◽

Abiotic Surfaces ◽

Two Component

Bifidobacterium bifidum strains, an important component of probiotic foods, can form biofilms on abiotic surfaces, leading to increased self-resistance. However, little is known about the molecular mechanism of B. bifidum biofilm formation. A time series transcriptome sequencing and untargeted metabolomics analysis of both B. bifidum biofilm and planktonic cells was performed to identify key genes and metabolites involved in biofilm formation. Two hundred thirty-five nonredundant differentially expressed genes (DEGs) (including vanY, pstS, degP, groS, infC, groL, yajC, tadB and sigA) and 219 nonredundant differentially expressed metabolites (including L-threonine, L-cystine, L-tyrosine, ascorbic acid, niacinamide, butyric acid and sphinganine) were identified. Thirteen pathways were identified during the integration of both transcriptomics and metabolomics data, including ABC transporters; quorum sensing; two-component system; oxidative phosphorylation; cysteine and methionine metabolism; glutathione metabolism; glycine, serine and threonine metabolism; and valine, leucine and isoleucine biosynthesis. The DEGs that relate to the integration pathways included asd, atpB, degP, folC, ilvE, metC, pheA, pstS, pyrE, serB, ulaE, yajC and zwf. The differentially accumulated metabolites included L-cystine, L-serine, L-threonine, L-tyrosine, methylmalonate, monodehydroascorbate, nicotinamide, orthophosphate, spermine and tocopherol. These results indicate that quorum sensing, two-component system and amino acid metabolism are essential during B. bifidum biofilm formation.

Download Full-text

Methods for eradication of the biofilms formed by opportunistic pathogens using novel techniques – A review

Folia Biologica et Oecologica ◽

10.1515/fobio-2016-0003 ◽

2016 ◽

Vol 12 ◽

pp. 26-37 ◽

Cited By ~ 1

Author(s):

Julia Zabielska ◽

Agnieszka Tyfa ◽

Alina Kunicka-Styczyńska

Keyword(s):

Medical Devices ◽

Biofilm Formation ◽

Cold Plasma ◽

Plant Tissues ◽

Opportunistic Pathogens ◽

Microbial Biofilms ◽

Synthetic Chemicals ◽

Abiotic Surfaces ◽

Severe Infections ◽

Microbial Adherence

The inconvenient environmental conditions force microorganisms to colonize either abiotic surfaces or animal and plant tissues and, therefore, form more resistant structures – biofilms. The phenomenon of microbial adherence, opportunistic pathogens in particular, is of a great concern. Colonization of medical devices and biofilm formation on their surface, may lead to severe infections mainly in humans with impaired immune system. Although, current research consider various methods for prevention of microbial biofilms formation, still, once a biofilm is formed, its elimination is almost impossible. This study focuses on the overview of novel methods applied for eradication of mature opportunistic pathogens' biofilms. Among various techniques the following: cold plasma, electric field, ultrasounds, ozonated water treatment, phagotherapy, matrix targeting enzymes, bacteriocins, synthetic chemicals and natural origin compounds used for biofilm matrix disruption were briefly described.

Download Full-text

Antibiotics Application Strategies to Control Biofilm Formation in Pathogenic Bacteria

Current Pharmaceutical Biotechnology ◽

10.2174/1389201020666191112155905 ◽

2020 ◽

Vol 21 (4) ◽

pp. 270-286 ◽

Cited By ~ 2

Author(s):

Fazlurrahman Khan ◽

Dung T.N. Pham ◽

Sandra F. Oloketuyi ◽

Young-Mog Kim

Keyword(s):

Biofilm Formation ◽

Pathogenic Bacteria ◽

Extracellular Polymeric Substances ◽

Quorum Quenching ◽

Resistance Mechanisms ◽

Bacterial Biofilm ◽

Bacterial Cells ◽

High Concentration ◽

Biofilm Inhibition ◽

Abiotic Surfaces

Background: The establishment of a biofilm by most pathogenic bacteria has been known as one of the resistance mechanisms against antibiotics. A biofilm is a structural component where the bacterial community adheres to the biotic or abiotic surfaces by the help of Extracellular Polymeric Substances (EPS) produced by bacterial cells. The biofilm matrix possesses the ability to resist several adverse environmental factors, including the effect of antibiotics. Therefore, the resistance of bacterial biofilm-forming cells could be increased up to 1000 times than the planktonic cells, hence requiring a significantly high concentration of antibiotics for treatment. Methods: Up to the present, several methodologies employing antibiotics as an anti-biofilm, antivirulence or quorum quenching agent have been developed for biofilm inhibition and eradication of a pre-formed mature biofilm. Results: Among the anti-biofilm strategies being tested, the sub-minimal inhibitory concentration of several antibiotics either alone or in combination has been shown to inhibit biofilm formation and down-regulate the production of virulence factors. The combinatorial strategies include (1) combination of multiple antibiotics, (2) combination of antibiotics with non-antibiotic agents and (3) loading of antibiotics onto a carrier. Conclusion: The present review paper describes the role of several antibiotics as biofilm inhibitors and also the alternative strategies adopted for applications in eradicating and inhibiting the formation of biofilm by pathogenic bacteria.

Download Full-text