Cell Surface Attachment Structures Contribute to Biofilm Formation and Xylem Colonization by Erwinia amylovora

ABSTRACTBiofilm formation plays a critical role in the pathogenesis ofErwinia amylovoraand the systemic invasion of plant hosts. The functional role of the exopolysaccharides amylovoran and levan in pathogenesis and biofilm formation has been evaluated. However, the role of biofilm formation, independent of exopolysaccharide production, in pathogenesis and movement within plants has not been studied previously. Evaluation of the role of attachment inE. amylovorabiofilm formation and virulence was examined through the analysis of deletion mutants lacking genes encoding structures postulated to function in attachment to surfaces or in cellular aggregation. The genes and gene clusters studied were selected based onin silicoanalyses. Microscopic analyses and quantitative assays demonstrated that attachment structures such as fimbriae and pili are involved in the attachment ofE. amylovorato surfaces and are necessary for the production of mature biofilms. A time course assay indicated that type I fimbriae function earlier in attachment, while type IV pilus structures appear to function later in attachment. Our results indicate that multiple attachment structures are needed for mature biofilm formation and full virulence and that biofilm formation facilitates entry and is necessary for the buildup of large populations ofE. amylovoracells in xylem tissue.

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Biofilm Formation by Psychrobacter arcticus and the Role of a Large Adhesin in Attachment to Surfaces

Applied and Environmental Microbiology ◽

10.1128/aem.00867-13 ◽

2013 ◽

Vol 79 (13) ◽

pp. 3967-3973 ◽

Cited By ~ 10

Author(s):

Shannon M. Hinsa-Leasure ◽

Cassandra Koid ◽

James M. Tiedje ◽

Janna N. Schultzhaus

Keyword(s):

Biofilm Formation ◽

Time Course ◽

Microtiter Plate ◽

Bacterial Attachment ◽

Wild Type ◽

Microtiter Plate Assay ◽

Content Type ◽

Reading Frame ◽

Transposon Mutants

ABSTRACTPsychrobacter arcticusstrain 273-4, an isolate from a Siberian permafrost core, is capable of forming biofilms when grown in minimal medium under laboratory conditions. Biofilms form at 4 to 22°C when acetate is supplied as the lone carbon source and with 1 to 7% sea salt.P. arcticusis also capable of colonizing quartz sand. Transposon mutagenesis identified a gene important for biofilm formation byP. arcticus. Four transposon mutants were mapped to a 20.1-kbp gene, which is predicted to encode a protein of 6,715 amino acids (Psyc_1601). We refer to this open reading frame ascat1, for cold attachment gene 1. Thecat1mutants are unable to form biofilms at levels equivalent to that of the wild type, and there is no impact on the planktonic growth characteristics of the strains, indicating a specific role in biofilm formation. Through time course studies of the static microtiter plate assay, we determined thatcat1mutants are unable to form biofilms equivalent to that of the wild type under all conditions tested. In flow cell experiments,cat1mutants initially are unable to attach to the surface. Over time, however, they form microcolonies, an architecture very different from that produced by wild-type biofilms. Our results demonstrate that Cat1 is involved in the initial stages of bacterial attachment to surfaces.

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Calcium Increases Xylella fastidiosa Surface Attachment, Biofilm Formation, and Twitching Motility

Applied and Environmental Microbiology ◽

10.1128/aem.06501-11 ◽

2011 ◽

Vol 78 (5) ◽

pp. 1321-1331 ◽

Cited By ~ 89

Author(s):

Luisa F. Cruz ◽

Paul A. Cobine ◽

Leonardo De La Fuente

Keyword(s):

Biofilm Formation ◽

Cell Attachment ◽

Xylella Fastidiosa ◽

Xylem Sap ◽

Type I ◽

Initial Surface ◽

Twitching Motility ◽

Acetoxymethyl Ester ◽

Content Type ◽

Type Iv

ABSTRACTXylella fastidiosais a plant-pathogenic bacterium that forms biofilms inside xylem vessels, a process thought to be influenced by the chemical composition of xylem sap. In this work, the effect of calcium on the production ofX. fastidiosabiofilm and movement was analyzed underin vitroconditions. After a dose-response study with 96-well plates using eight metals, the strongest increase of biofilm formation was observed when medium was supplemented with at least 1.0 mM CaCl2. The removal of Ca by extracellular (EGTA, 1.5 mM) and intracellular [1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester (BAPTA/AM), 75 μM] chelators reduced biofilm formation without compromising planktonic growth. The concentration of Ca influenced the force of adhesion to the substrate, biofilm thickness, cell-to-cell aggregation, and twitching motility, as shown by assays with microfluidic chambers and other assays. The effect of Ca on attachment was lost when cells were treated with tetracycline, suggesting that Ca has a metabolic or regulatory role in cell adhesion. A double mutant (fimA pilO) lacking type I and type IV pili did not improve biofilm formation or attachment when Ca was added to the medium, while single mutants of type I (fimA) or type IV (pilB) pili formed more biofilm under conditions of higher Ca concentrations. The concentration of Ca in the medium did not significantly influence the levels of exopolysaccharide produced. Our findings indicate that the role of Ca in biofilm formation may be related to the initial surface and cell-to-cell attachment and colonization stages of biofilm establishment, which rely on critical functions by fimbrial structures.

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Bundle-Forming Pilus Locus of Aeromonas veronii bv. Sobria

Infection and Immunity ◽

10.1128/iai.06304-11 ◽

2012 ◽

Vol 80 (4) ◽

pp. 1351-1360 ◽

Cited By ~ 16

Author(s):

Nahal Hadi ◽

Qin Yang ◽

Timothy C. Barnett ◽

S. Mohammed B. Tabei ◽

Sylvia M. Kirov ◽

...

Keyword(s):

Biofilm Formation ◽

Content Type ◽

Aeromonas Veronii ◽

Colonization Factor ◽

Type Iv ◽

Transcriptional Units ◽

Pilin Gene ◽

A Minor ◽

Pilin Protein

ABSTRACTLittle is known about the colonization mechanisms ofAeromonasspp. Previous work has suggested that the type IV bundle-forming pilus (Bfp) is an aeromonad intestinal colonization factor. This study provides the first genetic characterization of this structure. To define the role of Bfp inAeromonas veroniibv. Sobria adherence, a 22-kb locus encoding the bundle-forming pilus was isolated; this contained 17 pilus-related genes similar to the mannose-sensitive hemagglutinin (MSHA) ofVibrio cholerae. Reverse transcriptase PCR (RT-PCR) demonstrated that the locus had two major transcriptional units,mshItomshFandmshBtomshQ. Transcriptional fusion experiments demonstrated the presence of two strong promoters upstream ofmshIandmshB. The locus encoded four putative prepilin proteins, one of which (MshA) corresponded to the N-terminal sequence of the previously isolated major pilin protein. All the pilin genes were inactivated, mutation of each minor or major pilin gene greatly reduced the bacterium's ability to adhere and form biofilms, and complementation of each mutant intransrescued this phenotype. Mutation of the major pilin MshA and MshB, a minor pilin, resulted in their loss. The position of themshHgene is conserved within a number of bacteria, and we have shown it is not transcriptionally linked to the othermshgenes; moreover, its mutation did not have a dramatic effect on either adhesion or biofilm formation. We conclude that the bundle-forming pilus is required forA. veroniibv. Sobria adherence and biofilm formation; furthermore, both the major and minor pilin proteins are essential for this process.

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Essential role of IPS-1 in innate immune responses against RNA viruses

Journal of Experimental Medicine ◽

10.1084/jem.20060792 ◽

2006 ◽

Vol 203 (7) ◽

pp. 1795-1803 ◽

Cited By ~ 345

Author(s):

Himanshu Kumar ◽

Taro Kawai ◽

Hiroki Kato ◽

Shintaro Sato ◽

Ken Takahashi ◽

...

Keyword(s):

Rna Viruses ◽

Rna Virus ◽

Critical Role ◽

Nuclear Factor Κb ◽

Type I ◽

Innate Immune Responses ◽

Antiviral Responses ◽

Deficient Mice

IFN-β promoter stimulator (IPS)-1 was recently identified as an adapter for retinoic acid–inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (Mda5), which recognize distinct RNA viruses. Here we show the critical role of IPS-1 in antiviral responses in vivo. IPS-1–deficient mice showed severe defects in both RIG-I– and Mda5-mediated induction of type I interferon and inflammatory cytokines and were susceptible to RNA virus infection. RNA virus–induced interferon regulatory factor-3 and nuclear factor κB activation was also impaired in IPS-1–deficient cells. IPS-1, however, was not essential for the responses to either DNA virus or double-stranded B-DNA. Thus, IPS-1 is the sole adapter in both RIG-I and Mda5 signaling that mediates effective responses against a variety of RNA viruses.

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Polysaccharides and virulence of Burkholderia pseudomallei

Journal of Medical Microbiology ◽

10.1099/jmm.0.47043-0 ◽

2007 ◽

Vol 56 (8) ◽

pp. 1005-1010 ◽

Cited By ~ 35

Author(s):

M. Sarkar-Tyson ◽

J. E. Thwaite ◽

S. V. Harding ◽

S. J. Smither ◽

P. C. F. Oyston ◽

...

Keyword(s):

Burkholderia Pseudomallei ◽

Capsular Polysaccharide ◽

Gene Clusters ◽

Type I ◽

Wild Type ◽

Time To Death ◽

Type Iii ◽

Type Iv ◽

Mutant Strains ◽

Delayed Time

Burkholderia pseudomallei is the causative agent of melioidosis, an infectious disease of humans and animals. Gene clusters which encode capsular polysaccharide (type I O-PS) and LPS (type II O-PS), both of which play roles in virulence, have previously been identified. Here, the identification of two further putative clusters, type III O-PS and type IV O-PS, is reported. Mice challenged with type III O-PS or type IV O-PS mutants showed increased mean times to death (7.8 and 11.6 days) compared to those challenged with wild-type B. pseudomallei (3 days). To investigate the possible roles of polysaccharides in protection, mice were immunized with killed cells of wild-type B. pseudomallei or killed cells of B. pseudomallei with mutations in the O antigen, capsular polysaccharide, type III O-PS or type IV O-PS gene clusters. Immunization with all polysaccharide mutant strains resulted in delayed time to death compared to the naïve controls, following challenge with wild-type B. pseudomallei strain K96243. However, immunization with killed polysaccharide mutant strains conferred different degrees of protection, demonstrating the immunological importance of the polysaccharide clusters on the surface of B. pseudomallei.

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Understanding destination evangelism: a social media viewpoint

Marketing Intelligence & Planning ◽

10.1108/mip-04-2021-0128 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Purvendu Sharma

Keyword(s):

Social Media ◽

Information Seeking ◽

Structural Equation ◽

Structural Equation Models ◽

Critical Role ◽

Content Type ◽

Mediating Role ◽

Information Seeking Behaviors ◽

Role Of Information

PurposeThe present research aims to introduce and understand the promising nature of destination evangelism in the context of social media-based tourism communities (SMTCs). Further, factors that influence evangelism and information-seeking behaviors on SMTCs are examined.Design/methodology/approachA conceptual model is developed that features an interplay of destination distinctiveness, destination evangelism, travel commitment and information-seeking engagement. Data were collected from 215 active users of SMTCs and analyzed using structural equation models.FindingsThe research findings indicate that destination distinctiveness and information-seeking positively lead to destination evangelism. Information-seeking is found to mediate the relationship between (1) destination evangelism and travel commitment and (2) destination evangelism and distinctiveness.Research limitations/implicationsThe research offers meaningful insights into exploring constituents of destination evangelism. The research also understands and highlights the critical role of information-seeking engagement about distinct destinations.Practical implicationsThis research highlights key areas to build, improve and inspire destination evangelism on SMTCs.Originality/valueThis study offers a fresh contribution to tourism literature by investigating destination evangelism and its drivers. This is explained by closely uniting vital research streams of evangelism, tourism and engagement. It further highlights the dual mediating role of information seeking, suggesting that these engagements are critical to evangelizing destinations.

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Role of the chaperone protein 14-3-3ε in the regulation of influenza A virus-activated beta interferon

Journal of Virology ◽

10.1128/jvi.00231-21 ◽

2021 ◽

Author(s):

Ee-Hong Tam ◽

Yen-Chin Liu ◽

Chian-Huey Woung ◽

Helene Minyi Liu ◽

Guan-Hong Wu ◽

...

Keyword(s):

Virus Infection ◽

Influenza A Virus ◽

Influenza A ◽

Critical Role ◽

Type I ◽

Type I Ifn ◽

Ns1 Protein ◽

Chaperone Protein ◽

Influenza A Virus Infection

The NS1 protein of the influenza A virus plays a critical role in regulating several biological processes in cells, including the type I interferon (IFN) response. We previously profiled the cellular factors that interact with the NS1 protein of influenza A virus and found that the NS1 protein interacts with proteins involved in RNA splicing/processing, cell cycle regulation, and protein targeting processes, including 14-3-3ε. Since 14-3-3ε plays an important role in RIG-I translocation to MAVS to activate type I IFN expression, the interaction of the NS1 and 14-3-3ε proteins may prevent the RIG-I-mediated IFN response. In this study, we confirmed that the 14-3-3ε protein interacts with the N-terminal domain of the NS1 protein and that the NS1 protein inhibits RIG-I-mediated IFN-β promoter activation in 14-3-3ε-overexpressing cells. In addition, our results showed that knocking down 14-3-3ε can reduce IFN-β expression elicited by influenza A virus and enhance viral replication. Furthermore, we found that threonine in the 49 th amino acid position of the NS1 protein plays a role in the interaction with 14-3-3ε. Influenza A virus expressing C-terminus-truncated NS1 with T49A mutation dramatically increases IFN-β mRNA in infected cells and causes slower replication than that of virus without the T-to-A mutation. Collectively, this study demonstrates that 14-3-3ε is involved in influenza A virus-initiated IFN-β expression and that the interaction of the NS1 protein and 14-3-3ε may be one of the mechanisms for inhibiting type I IFN activation during influenza A virus infection. IMPORTANCE Influenza A virus is an important human pathogen causing severe respiratory disease. The virus has evolved several strategies to dysregulate the innate immune response and facilitate its replication. We demonstrate that the NS1 protein of influenza A virus interacts with the cellular chaperone protein 14-3-3ε, which plays a critical role in RIG-I translocation that induces type I IFN expression, and that NS1 protein prevents RIG-I translocation to mitochondrial membrane. The interaction site for 14-3-3ε is the RNA-binding domain (RBD) of the NS1 protein. Therefore, this research elucidates a novel mechanism by which the NS1 RBD mediates IFN-β suppression to facilitate influenza A viral replication. Additionally, the findings reveal the antiviral role of 14-3-3ε during influenza A virus infection.

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Cyclic Diguanylate Regulates Virulence Factor Genes via Multiple Riboswitches inClostridium difficile

mSphere ◽

10.1128/msphere.00423-18 ◽

2018 ◽

Vol 3 (5) ◽

Cited By ~ 11

Author(s):

Robert W. McKee ◽

Carissa K. Harvest ◽

Rita Tamayo

Keyword(s):

Gene Expression ◽

Clostridium Difficile ◽

Biofilm Formation ◽

Toxin Production ◽

Intestinal Colonization ◽

Cyclic Diguanylate ◽

Signaling Molecule ◽

Content Type ◽

Surface Motility

ABSTRACTThe intracellular signaling molecule cyclic diguanylate (c-di-GMP) regulates many processes in bacteria, with a central role in controlling the switch between motile and nonmotile lifestyles. Recent work has shown that inClostridium difficile(also calledClostridioides difficile), c-di-GMP regulates swimming and surface motility, biofilm formation, toxin production, and intestinal colonization. In this study, we determined the transcriptional regulon of c-di-GMP inC. difficile,employing overexpression of a diguanylate cyclase gene to artificially manipulate intracellular c-di-GMP. Consistent with prior work, c-di-GMP regulated the expression of genes involved in swimming and surface motility. c-di-GMP also affected the expression of multiple genes encoding cell envelope proteins, several of which affected biofilm formationin vitro. A substantial proportion of the c-di-GMP regulon appears to be controlled either directly or indirectly via riboswitches. We confirmed the functionality of 11 c-di-GMP riboswitches, demonstrating their effects on downstream gene expression independent of the upstream promoters. The class I riboswitches uniformly functioned as “off” switches in response to c-di-GMP, while class II riboswitches acted as “on” switches. Transcriptional analyses of genes 3′ of c-di-GMP riboswitches over a broad range of c-di-GMP levels showed that relatively modest changes in c-di-GMP levels are capable of altering gene transcription, with concomitant effects on microbial behavior. This work expands the known c-di-GMP signaling network inC. difficileand emphasizes the role of the riboswitches in controlling known and putative virulence factors inC. difficile.IMPORTANCEInClostridium difficile, the signaling molecule c-di-GMP regulates multiple processes affecting its ability to cause disease, including swimming and surface motility, biofilm formation, toxin production, and intestinal colonization. In this study, we used RNA-seq to define the transcriptional regulon of c-di-GMP inC. difficile. Many new targets of c-di-GMP regulation were identified, including multiple putative colonization factors. Transcriptional analyses revealed a prominent role for riboswitches in c-di-GMP signaling. Only a subset of the 16 previously predicted c-di-GMP riboswitches were functionalin vivoand displayed potential variability in their response kinetics to c-di-GMP. This work underscores the importance of studying c-di-GMP riboswitches in a relevant biological context and highlights the role of the riboswitches in controlling gene expression inC. difficile.

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Cyclic Di-GMP Regulates Multiple Cellular Functions in the Symbiotic Alphaproteobacterium Sinorhizobium meliloti

Journal of Bacteriology ◽

10.1128/jb.00795-15 ◽

2015 ◽

Vol 198 (3) ◽

pp. 521-535 ◽

Cited By ~ 28

Author(s):

Simon Schäper ◽

Elizaveta Krol ◽

Dorota Skotnicka ◽

Volkhard Kaever ◽

Rolf Hilker ◽

...

Keyword(s):

Biofilm Formation ◽

Sinorhizobium Meliloti ◽

Acid Stress ◽

Second Messenger ◽

Lifestyle Changes ◽

Single Domain ◽

Receptor Protein ◽

Leguminous Plant ◽

Content Type

ABSTRACTSinorhizobium melilotiundergoes major lifestyle changes between planktonic states, biofilm formation, and symbiosis with leguminous plant hosts. In many bacteria, the second messenger 3′,5′-cyclic di-GMP (c-di-GMP, or cdG) promotes a sessile lifestyle by regulating a plethora of processes involved in biofilm formation, including motility and biosynthesis of exopolysaccharides (EPS). Here, we systematically investigated the role of cdG inS. melilotiRm2011 encoding 22 proteins putatively associated with cdG synthesis, degradation, or binding. Single mutations in 21 of these genes did not cause evident changes in biofilm formation, motility, or EPS biosynthesis. In contrast, manipulation of cdG levels by overproducing endogenous or heterologous diguanylate cyclases (DGCs) or phosphodiesterases (PDEs) affected these processes and accumulation ofN-Acyl-homoserine lactones in the culture supernatant. Specifically, individual overexpression of theS. melilotigenespleD,SMb20523,SMb20447,SMc01464, andSMc03178encoding putative DGCs and ofSMb21517encoding a single-domain PDE protein had an impact and resulted in increased levels of cdG. Compared to the wild type, anS. melilotistrain that did not produce detectable levels of cdG (cdG0) was more sensitive to acid stress. However, it was symbiotically potent, unaffected in motility, and only slightly reduced in biofilm formation. TheSMc01790-SMc01796locus, homologous to theAgrobacterium tumefaciensuppABCDEFcluster governing biosynthesis of a unipolarly localized polysaccharide, was found to be required for cdG-stimulated biofilm formation, while the single-domain PilZ protein McrA was identified as a cdG receptor protein involved in regulation of motility.IMPORTANCEWe present the first systematic genome-wide investigation of the role of 3′,5′-cyclic di-GMP (c-di-GMP, or cdG) in regulation of motility, biosynthesis of exopolysaccharides, biofilm formation, quorum sensing, and symbiosis in a symbiotic alpha-rhizobial species. Phenotypes of anS. melilotistrain unable to produce cdG (cdG0) demonstrated that this second messenger is not essential for root nodule symbiosis but may contribute to acid tolerance. Our data further suggest that enhanced levels of cdG promote sessility ofS. melilotiand uncovered a single-domain PilZ protein as regulator of motility.

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Institutional effect on born global firms in China: the role of Sun Tzu’s The Art of War strategies

Journal of Asia Business Studies ◽

10.1108/jabs-11-2014-0084 ◽

2016 ◽

Vol 10 (1) ◽

pp. 1-19 ◽

Cited By ~ 4

Author(s):

Man Zhang ◽

Qian Gao ◽

Jane V. Wheeler ◽

Jungsook Kwon

Keyword(s):

Emerging Markets ◽

Institutional Environment ◽

Critical Role ◽

Born Global ◽

Internationalization Process ◽

Content Type ◽

International Performance ◽

The Relationship ◽

Born Global Firms

Purpose – This paper aims to investigate the role of Sun Tzu’s significant strategies on the relationship between the institutional environment and international performance of Chinese born global firms, a type of small- and medium-sized enterprise (SME) characterized by the company’s limited resources and its early efforts to internationalize. Design/methodology/approach – The methodology is based on a multi-case analysis of interviews conducted with four chosen born global firms, coupled with public database and Web site searches. Through the use of qualitative methods, propositions were developed. Findings – This paper provides insights regarding how the institutional environment, both formal and informal, has a strong positive relationship with born global firm’s international performance. Moreover, Sun Tzu’s significant strategies play a critical role in the internationalization process of born global firms in emerging markets. Originality/value – Although existing studies discuss the application of Eastern philosophical strategies adopted by firms in emerging markets, to the best of our knowledge, this is one of the earliest studies which evaluates the moderation effect of Sun Tzu’s significant strategies on the relationship between institutional environment and business performance. The paper contributes to scholarly discourse on the influencing factors of born global firm’s internationalization process. It also has practical relevance to international entrepreneurs and SMEs from emerging markets.

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