scholarly journals Capsular Polysaccharide of Erysipelothrix rhusiopathiae, the Causative Agent of Swine Erysipelas, and Its Modification with Phosphorylcholine

2012 ◽  
Vol 80 (11) ◽  
pp. 3993-4003 ◽  
Author(s):  
Fang Shi ◽  
Tomoyuki Harada ◽  
Yohsuke Ogawa ◽  
Hiroshi Ono ◽  
Mayumi Ohnishi-Kameyama ◽  
...  
Keyword(s):  
Cell Surface ◽  
Capsular Polysaccharide ◽  
Genetic Locus ◽  
Hot Water ◽  
Mycoplasma Species ◽  
Phylogenetic Position ◽  
Close Relative ◽  
Immunogold Electron Microscopy ◽  
Erysipelothrix Rhusiopathiae ◽  
Content Type

ABSTRACTThe capsule has been implicated in the virulence of the swine pathogenErysipelothrix rhusiopathiae, a rod-shaped, intracellular Gram-positive bacterium that has a unique phylogenetic position in the phylumFirmicutesand is a close relative ofMollicutes(mycoplasma species). In this study, we analyzed the genetic locus and composition of the capsular polysaccharide (CPS) of the Fujisawa strain ofE. rhusiopathiae. Genome analysis of the Fujisawa strain revealed that the genetic locus for capsular polysaccharide synthesis (cps) is located next to anlicoperon, which is involved in the incorporation and expression of phosphorylcholine (PCho). Reverse transcription-PCR analysis showed thatcpsandlicare transcribed as a single mRNA, indicating that the loci form an operon. Using the cell surface antigen-specific monoclonal antibody (MAb) ER21 as a probe, the capsular materials were isolated from the Fujisawa strain by hot water extraction and treatment with DNase, RNase, pronase, andN-acetylmuramidase SG, followed by anion-exchange and gel filtration chromatography. The materials were then analyzed by high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. The CPS ofE. rhusiopathiaeis heterogeneous and consists of the major monosaccharides galacturonic acid, galactose, mannose, glucose, arabinose, xylose, andN-acetylglucosamine and some minor monosaccharides containing ribose, rhamnose, andN-acetylgalactosamine. In addition, the capsule is modified by PCho, which comigrates with the capsular materials, as determined by Western immunoblotting, and colocalizes on the cell surface, as determined by immunogold electron microscopy. Virulence testing of PCho-defective mutants in mice demonstrated that PCho is critical for the virulence of this organism.

scholarly journals Nontypeable Pneumococci Can Be Divided into Multiple cps Types, Including One Type Expressing the Novel Gene pspK

mBio ◽  
2012 ◽  
Vol 3 (3) ◽  
Author(s):  
In Ho Park ◽  
Kyung-Hyo Kim ◽  
Ana Lucia Andrade ◽  
David E. Briles ◽  
Larry S. McDaniel ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Capsular Polysaccharide ◽  
Genetic Locus ◽  
The Novel ◽  
Content Type ◽  
Capsule Production ◽  
Polysaccharide Synthesis ◽  
Definition Of ◽  
Survival Mechanisms ◽  
Helical Region

ABSTRACTAlthough virulence ofStreptococcus pneumoniaeis associated with its capsule, some pathogenicS. pneumoniaeisolates lack capsules and are serologically nontypeable (NT). We obtained 64 isolates that were identified as NT “pneumococci” (i.e., bacteria satisfying the conventional definition but without the multilocus sequence typing [MLST]-based definition ofS. pneumoniae) by the traditional criteria. All 64 were optochin sensitive and hadlytA, and 63 hadply. Twelve isolates hadcpsA, suggesting the presence of a conventional but defective capsular polysaccharide synthesis (cps) locus. The 52cpsA-negative isolates could be divided into three null capsule clades (NCC) based onaliC(aliB-like ORF1),aliD(aliB-like ORF2), and our newly discovered gene,pspK, in theircpsloci.pspKencodes a protein with a long alpha-helical region containing an LPxTG motif and a YPT motif known to bind human pIgR. There were nine isolates in NCC1 (pspK+but negative foraliCandaliD), 32 isolates in NCC2 (aliC+aliD+but negative forpspK), and 11 in NCC3 (aliD+but negative foraliCandpspK). Among 52cpsA-negative isolates, 41 were identified asS. pneumoniaeby MLST analysis. All NCC1 and most NCC2 isolates wereS. pneumoniae, whereas all nine NCC3 and two NCC2 isolates were notS. pneumoniae. Several NCC1 and NCC2 isolates from multiple individuals had identical MLST andcpsregions, showing that unencapsulatedS. pneumoniaecan be infectious among humans. Furthermore, NCC1 and NCC2S. pneumoniaeisolates could colonize mice as well as encapsulatedS. pneumoniae, althoughS. pneumoniaewith an artificially disruptedcpslocus did not. Moreover, an NCC1 isolate withpspKdeletion did not colonize mice, suggesting thatpspKis critical for colonization. Thus, PspK may provide pneumococci a means of surviving in the nasopharynx without capsule.IMPORTANCEThe presence of a capsule is critical for many pathogenic bacteria, including pneumococci. Reflecting the pathogenic importance of the pneumococcal capsule, pneumococcal vaccines are designed to elicit anticapsule antibodies. Additional evidence for the pathogenic importance of the pneumococcal capsule is the fact that in pneumococci all the genes necessary for capsule production are together in one genetic locus, which is called thecpslocus. However, there are occasional pathogenic pneumococci without capsules, and how they survive in the host without the capsule is unknown. Here, we show that in these acapsular pneumococci, thecpsloci have been replaced with various novel genes and they can colonize mouse nasopharynges as well as capsulated pneumococci. Since the genes that replace thecpsloci are likely to be important in host survival, they may show new and/or alternative capsule-independent survival mechanisms used by pneumococci.

scholarly journals SssP1, aStreptococcus suisFimbria-Like Protein Transported by the SecY2/A2 System, Contributes to Bacterial Virulence

2018 ◽  
Vol 84 (18) ◽  
Author(s):  
Yue Zhang ◽  
Pengpeng Lu ◽  
Zihao Pan ◽  
Yinchu Zhu ◽  
Jiale Ma ◽  
...  
Keyword(s):  
Cell Surface ◽  
Streptococcus Suis ◽  
Secretory Protein ◽  
Genomic Islands ◽  
Host Cells ◽  
Genome Comparison ◽  
Immunogold Electron Microscopy ◽  
Infection Model ◽  
Content Type ◽  
Zoonotic Pathogen

ABSTRACTStreptococcus suisis an important Gram-positive pathogen in the swine industry and is an emerging zoonotic pathogen for humans. In our previous work, we found a virulentS. suisstrain, CZ130302, belonging to a novel serotype, Chz, to be associated with acute meningitis in piglets. However, its underlying mechanisms of pathogenesis remain poorly understood. In this study, we sequenced and analyzed the complete genomes of three Chz serotype strains, including strain CZ130302 and two avirulent strains, HN136 and AH681. By genome comparison, we found two putative genomic islands (GIs) uniquely encoded in strain CZ130302 and designated them 50K GI and 58K GI. In mouse infection model, the deletion of 50K and 58K GIs caused 270-fold and 3-fold attenuation of virulence, respectively. Notably, we identified a complete SecY2/A2 system, coupled with its secretory protein SssP1 encoded in the 50K GI, which contributed to the pathogenicity of strain CZ130302. Immunogold electron microscopy and immunofluorescence analyses indicated that SssP1 could form fimbria-like structures that extend outward from the bacterial cell surface. ThesssP1mutation also attenuated bacterial adherence in human laryngeal epithelial (HEp-2) cells and human brain microvessel endothelial cells (HBMECs) compared with the wild type. Furthermore, we showed that two analogous Ig-like subdomains of SssP1 have sialic acid binding capacities. In conclusion, our results revealed that the 50K GI and the inside SecY2/A2 system gene cluster are related to the virulence of strain CZ130302, and we clarified a newS. suispathogenesis mechanism mediated by the secretion protein SssP1.IMPORTANCEStreptococcus suisis an important zoonotic pathogen. Here, we managed to identify key factors to clarify the virulence ofS. suisstrain CZ130302 from a novel serotype, Chz. Notably, it was shown that a fimbria-like structure was significantly connected to the pathogenicity of the CZ130302 strain by comparative genomics analysis and animal infection assays. The mechanisms of how the CZ130302 strain constructs these fimbria-like structures in the cell surface by genes encoding and production transport were subsequently elucidated. Biosynthesis of the fimbria-like structure was achieved by the production of SssP1 glycoproteins, and its construction was dependent on the SecA2/Y2 secretion system. This study identified a visible fimbria-like protein, SssP1, participating in adhesion to host cells and contributing to the virulence inS. suis. These findings will promote a better understanding of the pathogenesis ofS. suis.

scholarly journals Inactivation of Transcriptional Regulator FabT Influences Colony Phase Variation of Streptococcus pneumoniae

mBio ◽  
2021 ◽  
Author(s):  
Jinghui Zhang ◽  
Weijie Ye ◽  
Kaifeng Wu ◽  
Shengnan Xiao ◽  
Yuqiang Zheng ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Cell Surface ◽  
Virulence Factors ◽  
Capsular Polysaccharide ◽  
Phase Variation ◽  
Transcriptional Regulator ◽  
Human Pathogen ◽  
Content Type ◽  
Reversible Phase

Streptococcus pneumoniae is a major human pathogen, and its virulence factors and especially the capsular polysaccharide have been extensively studied. In addition to virulence components that are present on its cell surface that directly interact with the host, S. pneumoniae undergoes a spontaneous and reversible phase variation that allows survival in different host environments.

scholarly journals Identification of the Chromosomal Region Essential for Serovar-Specific Antigen and Virulence of Serovar 1 and 2 Strains ofErysipelothrix rhusiopathiae

2018 ◽  
Vol 86 (9) ◽  
Author(s):  
Yohsuke Ogawa ◽  
Kazumasa Shiraiwa ◽  
Sayaka Nishikawa ◽  
Masahiro Eguchi ◽  
Yoshihiro Shimoji
Keyword(s):  
Capsular Polysaccharide ◽  
Chromosomal Region ◽  
Specific Antigen ◽  
Gene Organization ◽  
Rabbit Serum ◽  
Erysipelothrix Rhusiopathiae ◽  
Functional Connection ◽  
Content Type ◽  
Antigenic Reactivity ◽  
Specific Rabbit

ABSTRACTErysipelothrix rhusiopathiaecauses swine erysipelas, an infection characterized by acute septicemia or chronic endocarditis and polyarthritis. Among 17E. rhusiopathiaeserovars, determined based on heat-stable peptidoglycan antigens, serovars 1 and 2 are most commonly associated with the disease; however, the molecular basis for the association between these serovars and virulence is unknown. To search for the genetic region defining serovar 1a (Fujisawa) strain antigenicity, we examined the 15-kb chromosomal region encompassing a putative pathway for polysaccharide biosynthesis, which was previously identified in theE. rhusiopathiaeFujisawa strain. Six transposon mutants of Fujisawa strain possessing a mutation in this region lost antigenic reactivity with serovar 1a-specific rabbit serum. Sequence analysis of this region in wild-type strains of serovars 1a, 1b, and 2 and serovar N, which lacks serovar-specific antigens, revealed that gene organization was similar among the strains and that serovar 2 strains showed variation. Serovar N strains displayed the same gene organization as the serovar 1a, 1b, or 2 strain and possessed certain mutations in this region. In two of the analyzed serovar N strains, restoration of the mutations via complementation with sequences derived from serovar 1a and 2 strains recovered antigenic reactivity with 1a- and 2-specific rabbit serum, respectively. Several gene mutations in this region resulted in altered capsule expression and attenuation of virulence in mice. These results indicate a functional connection between the biosynthetic pathways for the capsular polysaccharide and peptidoglycan antigens used for serotyping, which may explain variation in virulence among strains of different serovars.

scholarly journals Characterization and Identification of a Novel Candidate Vaccine Protein through Systematic Analysis of Extracellular Proteins of Erysipelothrix rhusiopathiae

2013 ◽  
Vol 81 (12) ◽  
pp. 4333-4340 ◽  
Author(s):  
Fang Shi ◽  
Yohsuke Ogawa ◽  
Akiyuki Sano ◽  
Tomoyuki Harada ◽  
Jiro Hirota ◽  
...  
Keyword(s):  
Metabolic Enzymes ◽  
Extracellular Proteins ◽  
Vaccine Antigen ◽  
Immunogold Electron Microscopy ◽  
Major Protein ◽  
Erysipelothrix Rhusiopathiae ◽  
Lethal Challenge ◽  
Systematic Analysis ◽  
Content Type

ABSTRACTErysipelothrix rhusiopathiae, the causative agent of swine erysipelas, is a facultative intracellular Gram-positive bacterium. It has been shown that animals immunized with a filtrate fromE. rhusiopathiaecultures are protected against lethal challenge. In this study, we identified and characterized the extracellular proteins ofE. rhusiopathiaeto search for novel vaccine antigens. A concentrated culture supernatant from theE. rhusiopathiaeFujisawa strain, which has been found to induce protection in mice, was analyzed using two-dimensional electrophoresis. From more than 40 confirmed protein spots, 16 major protein spots were selected and subjected to N-terminal amino acid sequence determination, and 14 protein spots were successfully identified. The identified proteins included housekeeping proteins and other metabolic enzymes. We searched for surface-localized proteins by analyzing the genomes of twoE. rhusiopathiaestrains: Fujisawa and ATCC 19414. Genome analysis revealed that the ATCC 19414 strain has three putative surface-exposedcholine-bindingproteins (CBPs): CbpA, CbpB, and CbpC. Each CBP contains a putative choline-binding domain. The CbpC gene is mutated in Fujisawa, becoming a nonfunctional pseudogene. Immunogold electron microscopy confirmed that CbpA and CbpB, as well as the majority of the metabolic enzymes examined, are associated with the cell surface ofE. rhusiopathiaeFujisawa. Immunization with recombinant CbpB, but not with other recombinant CBPs or metabolic enzymes, protected mice against lethal challenge. A phagocytosis assay revealed that antiserum against CbpB promoted opsonin-mediated phagocytosis by murine macrophagesin vitro. The protective capabilities of CbpB were confirmed in pigs, suggesting that CbpB could be used as a vaccine antigen.

scholarly journals Antibodies to Streptococcus pneumoniae Capsular Polysaccharide Enhance Pneumococcal Quorum Sensing

mBio ◽  
2011 ◽  
Vol 2 (5) ◽  
Author(s):  
Masahide Yano ◽  
Shruti Gohil ◽  
J. Robert Coleman ◽  
Catherine Manix ◽  
Liise-anne Pirofski
Keyword(s):  
Monoclonal Antibodies ◽  
Streptococcus Pneumoniae ◽  
Quorum Sensing ◽  
Direct Effect ◽  
Pneumococcal Disease ◽  
Effector Cell ◽  
Capsular Polysaccharide ◽  
Genetic Exchange ◽  
Content Type ◽  
Specific Antibodies

ABSTRACTThe use of pneumococcal capsular polysaccharide (PPS)-based vaccines has resulted in a substantial reduction in invasive pneumococcal disease. However, much remains to be learned about vaccine-mediated immunity, as seven-valent PPS-protein conjugate vaccine use in children has been associated with nonvaccine serotype replacement and 23-valent vaccine use in adults has not prevented pneumococcal pneumonia. In this report, we demonstrate that certain PPS-specific monoclonal antibodies (MAbs) enhance the transformation frequency of two differentStreptococcus pneumoniaeserotypes. This phenomenon was mediated by PPS-specific MAbs that agglutinate but do not promote opsonic effector cell killing of the homologous serotypeinvitro. Compared to the autoinducer, competence-stimulating peptide (CSP) alone, transcriptional profiling of pneumococcal gene expression after incubation with CSP and one such MAb to the PPS of serotype 3 revealed changes in the expression of competence (com)-related and bacteriocin-like peptide (blp) genes involved in pneumococcal quorum sensing. This MAb was also found to induce a nearly 2-fold increase in CSP2-mediated bacterial killing or fratricide. These observations reveal a novel, direct effect of PPS-binding MAbs on pneumococcal biology that has important implications for antibody immunity to pneumococcus in the pneumococcal vaccine era. Taken together, our data suggest heretofore unsuspected mechanisms by which PPS-specific antibodies could affect genetic exchange and bacterial viability in the absence of host cells.IMPORTANCECurrent thought holds that pneumococcal capsular polysaccharide (PPS)-binding antibodies protect against pneumococcus by inducing effector cell opsonic killing of the homologous serotype. While such antibodies are an important part of how pneumococcal vaccines protect against pneumococcal disease, PPS-specific antibodies that do not exhibit this activity but are highly protective against pneumococcus in mice have been identified. This article examines the effect of nonopsonic PPS-specific monoclonal antibodies (MAbs) on the biology ofStreptococcus pneumoniae. The results showed that in the presence of a competence-stimulating peptide (CSP), such MAbs increase the frequency of pneumococcal transformation. Further studies with one such MAb showed that it altered the expression of genes involved in quorum sensing and increased competence-induced killing or fratricide. These findings reveal a novel, previously unsuspected mechanism by which certain PPS-specific antibodies exert a direct effect on pneumococcal biology that has broad implications for bacterial clearance, genetic exchange, and antibody immunity to pneumococcus.

scholarly journals The Carboxy-Terminal Region ofFlavobacterium johnsoniaeSprB Facilitates Its Secretion by the Type IX Secretion System and Propulsion by the Gliding Motility Machinery

2019 ◽  
Vol 201 (19) ◽  
Author(s):  
Surashree S. Kulkarni ◽  
Joseph J. Johnston ◽  
Yongtao Zhu ◽  
Zachary T. Hying ◽  
Mark J. McBride
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cell Surface ◽  
Type A ◽  
Secretion System ◽  
Gliding Motility ◽  
Foreign Protein ◽  
Type B ◽  
Content Type ◽  
Type Ix Secretion System

ABSTRACTFlavobacterium johnsoniaeSprB moves rapidly along the cell surface, resulting in gliding motility. SprB secretion requires the type IX secretion system (T9SS). Proteins secreted by the T9SS typically have conserved C-terminal domains (CTDs) belonging to the type A CTD or type B CTD family. Attachment of 70- to 100-amino-acid type A CTDs to a foreign protein allows its secretion. Type B CTDs are common but have received little attention. Secretion of the foreign protein superfolder green fluorescent protein (sfGFP) fused to regions spanning the SprB type B CTD (sfGFP-CTDSprB) was analyzed. CTDs of 218 amino acids or longer resulted in secretion of sfGFP, whereas a 149-amino-acid region did not. Some sfGFP was secreted in soluble form, whereas the rest was attached on the cell surface. Surface-attached sfGFP was rapidly propelled along the cell, suggesting productive interaction with the motility machinery. This did not result in rapid cell movement, which apparently requires additional regions of SprB. Secretion of sfGFP-CTDSprBrequired coexpression withsprF, which lies downstream ofsprB. SprF is similar in sequence toPorphyromonas gingivalisPorP. MostF. johnsoniaegenes encoding proteins with type B CTDs lie immediately upstream ofporP/sprF-like genes. sfGFP was fused to the type B CTD from one such protein (Fjoh_3952). This resulted in secretion of sfGFP only when it was coexpressed with its cognate PorP/SprF-like protein. These results highlight the need for extended regions of type B CTDs and for coexpression with the appropriate PorP/SprF-like protein for efficient secretion and cell surface localization of cargo proteins.IMPORTANCETheF. johnsoniaegliding motility adhesin SprB is delivered to the cell surface by the type IX secretion system (T9SS) and is rapidly propelled along the cell by the motility machinery. How this 6,497-amino-acid protein interacts with the secretion and motility machines is not known. Fusion of the C-terminal 218 amino acids of SprB to a foreign cargo protein resulted in its secretion, attachment to the cell surface, and rapid movement by the motility machinery. Efficient secretion of SprB required coexpression with the outer membrane protein SprF. Secreted proteins that have sequence similarity to SprB in their C-terminal regions are common in the phylumBacteroidetesand may have roles in adhesion, motility, and virulence.

scholarly journals Neutrophil Extracellular Traps Exhibit Antibacterial Activity against Burkholderia pseudomallei and Are Influenced by Bacterial and Host Factors

2012 ◽  
Vol 80 (11) ◽  
pp. 3921-3929 ◽  
Author(s):  
Donporn Riyapa ◽  
Surachat Buddhisa ◽  
Sunee Korbsrisate ◽  
Jon Cuccui ◽  
Brendan W. Wren ◽  
...  
Keyword(s):  
Burkholderia Pseudomallei ◽  
Capsular Polysaccharide ◽  
Neutrophil Extracellular Traps ◽  
Polymorphonuclear Neutrophils ◽  
Dependent Manner ◽  
Predisposing Factor ◽  
Bacterial Killing ◽  
Content Type ◽  
Extracellular Traps ◽  
Type Iii Protein Secretion

ABSTRACTBurkholderia pseudomalleiis the causative pathogen of melioidosis, of which a major predisposing factor is diabetes mellitus. Polymorphonuclear neutrophils (PMNs) kill microbes extracellularly by the release of neutrophil extracellular traps (NETs). PMNs play a key role in the control of melioidosis, but the involvement of NETs in killing ofB. pseudomalleiremains obscure. Here, we showed that bactericidal NETs were released from human PMNs in response toB. pseudomalleiin a dose- and time-dependent manner.B. pseudomallei-induced NET formation required NADPH oxidase activation but not phosphatidylinositol-3 kinase, mitogen-activated protein kinases, or Src family kinase signaling pathways.B. pseudomalleimutants defective in the virulence-associated Bsa type III protein secretion system (T3SS) or capsular polysaccharide I (CPS-I) induced elevated levels of NETs. NET induction by such mutants was associated with increased bacterial killing, phagocytosis, and oxidative burst by PMNs. Taken together the data imply that T3SS and the capsule may play a role in evading the induction of NETs. Importantly, PMNs from diabetic subjects released NETs at a lower level than PMNs from healthy subjects. Modulation of NET formation may therefore be associated with the pathogenesis and control of melioidosis.

scholarly journals Key Role of Capsular Polysaccharide in the Induction of Systemic Infection and Abortion by Hypervirulent Campylobacter jejuni

2017 ◽  
Vol 85 (6) ◽  
Author(s):  
Orhan Sahin ◽  
Samantha A. Terhorst ◽  
Eric R. Burrough ◽  
Zhangqi Shen ◽  
Zuowei Wu ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Campylobacter Jejuni ◽  
Capsular Polysaccharide ◽  
Systemic Infection ◽  
The United States ◽  
Content Type ◽  
Model Following ◽  
Capsule Production ◽  
Guinea Pig Model

ABSTRACT Campylobacter jejuni is a zoonotic pathogen, and a hypervirulent clone, named clone SA, has recently emerged as the predominant cause of ovine abortion in the United States. To induce abortion, orally ingested Campylobacter must translocate across the intestinal epithelium, spread systemically in the circulation, and reach the fetoplacental tissue. Bacterial factors involved in these steps are not well understood. C. jejuni is known to produce capsular polysaccharide (CPS), but the specific role that CPS plays in systemic infection and particularly abortion in animals remains to be determined. In this study, we evaluated the role of CPS in bacteremia using a mouse model and in abortion using a pregnant guinea pig model following oral challenge. Compared with C. jejuni NCTC 11168 and 81-176, a clone SA isolate (IA3902) resulted in significantly higher bacterial counts and a significantly longer duration of bacteremia in mice. The loss of capsule production via gene-specific mutagenesis in IA3902 led to the complete abolishment of bacteremia in mice and abortion in pregnant guinea pigs, while complementation of capsule expression almost fully restored these phenotypes. The capsule mutant strain was also impaired for survival in guinea pig sera and sheep blood. Sequence-based analyses revealed that clone SA possesses a unique CPS locus with a mosaic structure, which has been stably maintained in all clone SA isolates derived from various hosts and times. These findings establish CPS as a key virulence factor for the induction of systemic infection and abortion in pregnant animals and provide a viable candidate for the development of vaccines against hypervirulent C. jejuni.

scholarly journals Sibling Rivalry in Myxococcus xanthus Is Mediated by Kin Recognition and a Polyploid Prophage

2016 ◽  
Vol 198 (6) ◽  
pp. 994-1004 ◽  
Author(s):  
Arup Dey ◽  
Christopher N. Vassallo ◽  
Austin C. Conklin ◽  
Darshankumar T. Pathak ◽  
Vera Troselj ◽  
...  
Keyword(s):  
Cell Surface ◽  
Kin Recognition ◽  
Myxococcus Xanthus ◽  
Laboratory Strain ◽  
Cell Surface Receptor ◽  
Form Complex ◽  
Content Type ◽  
Recognition Specificity ◽  
Surface Receptor ◽  
Evolutionary Event

ABSTRACTMyxobacteria form complex social communities that elicit multicellular behaviors. One such behavior is kin recognition, in which cells identify siblings via their polymorphic TraA cell surface receptor, to transiently fuse outer membranes and exchange their contents. In addition, outer membrane exchange (OME) regulates behaviors, such as inhibition of wild-typeMyxococcus xanthus(DK1622) from swarming. Here we monitored the fate of motile cells and surprisingly found they were killed by nonmotile siblings. The kill phenotype required OME (i.e., was TraA dependent). The genetic basis of killing was traced to ancestral strains used to construct DK1622. Specifically, the kill phenotype mapped to a large “polyploid prophage,” Mx alpha. Sensitive strains contained a 200-kb deletion that removed two of three Mx alpha units. To explain these results, we suggest that Mx alpha expresses a toxin-antitoxin cassette that uses the OME machinery ofM. xanthusto transfer a toxin that makes the population “addicted” to Mx alpha. Thus, siblings that lost Mx alpha units (no immunity) are killed by cells that harbor the element. To test this, an Mx alpha-harboring laboratory strain was engineered (bytraAallele swap) to recognize a closely related species,Myxococcus fulvus. As a result,M. fulvus, which lacks Mx alpha, was killed. These TraA-mediated antagonisms provide an explanation for how kin recognition specificity might have evolved in myxobacteria. That is, recognition specificity is determined by polymorphisms intraA, which we hypothesize were selected for because OME with non-kin leads to lethal outcomes.IMPORTANCEThe transition from single cell to multicellular life is considered a major evolutionary event. Myxobacteria have successfully made this transition. For example, in response to starvation, individual cells aggregate into multicellular fruiting bodies wherein cells differentiate into spores. To build fruits, cells need to recognize their siblings, and in part, this is mediated by the TraA cell surface receptor. Surprisingly, we report that TraA recognition can also involve sibling killing. We show that killing originates from a prophage-like element that has apparently hijacked the TraA system to deliver a toxin to kin. We hypothesize that this killing system has imposed selective pressures on kin recognition, which in turn has resulted in TraA polymorphisms and hence many different recognition groups.

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