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1.
The ADP-ribosylating toxin, AexT, from Aeromonas salmonicida subsp. salmonicida is translocated via a type III secretion pathway
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AexT is an extracellular ADP ribosyltransferase produced by the fish pathogen Aeromonas salmonicida subsp. salmonicida. The protein is secreted by the bacterium via a recently identified type III secretion system. In this study, we have identified a further 12 open reading frames that possess high homology to genes encoding both structural and regulatory components of the Yersinia type III secretion apparatus. Using marker replacement mutagenesis of aopB, the A. salmonicida subsp. salmonicida homologue of yopB in Yersinia, we demonstrate that the bacterium translocates the AexT toxin directly into the cytosol of cultured fish cells via this type III secretion pathway. An acrV mutant of A. salmonicida subsp. salmonicida displays a calcium-blind phenotype, expressing and secreting significant amounts of AexT even in the presence of CaCl2 concentrations as high as 10 mM. This acrV mutant is also unable to translocate AexT into the cytosol of fish cells, indicating AcrV is involved in the translocation process. Inactivation of either the aopB or acrV gene in A. salmonicida subsp. salmonicida (resulting in an inability to translocate AexT) is accompanied by a loss of cytotoxicity that can be restored by trans complementation. Finally, we present data indicating that preincubation of the wild-type bacteria with antibodies directed against recombinant AcrV-His protein provides fish cells protection against the toxic effects of the bacterium. 相似文献
2.
Aeromonas salmonicida subsp. salmonicida possesses a number of potential virulence factors, including a recently identified plasmid-encoded Type III secretion system. A number of field isolates of A. salmonicida subsp. salmonicida were examined for the presence of Type III secretion genes. Using in vitro experiments, it was found that field isolates containing such genes are cytotoxic to fish cell lines, whereas those that lack these genes are not. Using a rainbow trout in vivo model, the virulence of a wild type A. salmonicida subsp. salmonicida strain (Strain JF2267), which possesses Type III secretion genes, was compared to that of a laboratory derivative of the same strain that has lost these genes. While Strain JF2267 was virulent towards rainbow trout, its derivative was not. The A. salmonicida subsp. salmonicida Type Strain ATCC 33658T, which also lacks Type III secretion genes, was also found to be avirulent by this challenge model. The findings from both the in vitro and in vivo experiments suggest that the presence of Type III secretion genes is associated with the virulence of this important fish pathogen. 相似文献
3.
Characterization of an ADP-ribosyltransferase toxin (AexT) from Aeromonas salmonicida subsp. salmonicida
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Braun M Stuber K Schlatter Y Wahli T Kuhnert P Frey J 《Journal of bacteriology》2002,184(7):1851-1858
An ADP-ribosylating toxin named Aeromonas salmonicida exoenzyme T (AexT) in A. salmonicida subsp. salmonicida, the etiological agent of furunculosis in fish, was characterized. Gene aexT, encoding toxin AexT, was cloned and characterized by sequence analysis. AexT shows significant sequence similarity to the ExoS and ExoT exotoxins of Pseudomonas aeruginosa and to the YopE cytotoxin of different Yersinia species. The aexT gene was detected in all of the 12 A. salmonicida subsp. salmonicida strains tested but was absent from all other Aeromonas species. Recombinant AexT produced in Escherichia coli possesses enzymatic ADP-ribosyltransferase activity. Monospecific polyclonal antibodies directed against purified recombinant AexT detected the toxin produced by A. salmonicida subsp. salmonicida and cross-reacted with ExoS and ExoT of P. aeruginosa. AexT toxin could be detected in a wild type (wt) strain of A. salmonicida subsp. salmonicida freshly isolated from a fish with furunculosis; however, its expression required contact with RTG-2 rainbow trout gonad cells. Under these conditions, the AexT protein was found to be intracellular or tightly cell associated. No AexT was found when A. salmonicida subsp. salmonicida was incubated in cell culture medium in the absence of RTG-2 cells. Upon infection with wt A. salmonicida subsp. salmonicida, the fish gonad RTG-2 cells rapidly underwent significant morphological changes. These changes were demonstrated to constitute cell rounding, which accompanied induction of production of AexT and which led to cell lysis after extended incubation. An aexT mutant which was constructed from the wt strain with an insertionally inactivated aexT gene by allelic exchange had no toxic effect on RTG-2 cells and was devoid of AexT production. Hence AexT is directly involved in the toxicity of A. salmonicida subsp. salmonicida for RTG-2 fish cells. 相似文献
4.
BopB is a type III secreted protein in Bordetella bronchiseptica and is required for cytotoxicity against cultured mammalian cells 总被引:1,自引:0,他引:1
The cytotoxicity of Bordetella bronchiseptica to infected cells is known to be dependent on a B. bronchiseptica type III secretion system. Although the precise mechanism of the type III secretion system is unknown, BopN, BopD and Bsp22 have been identified as type III secreted proteins. In order to identify other proteins secreted via the type III secretion machinery in Bordetella, a type III mutant was generated, and its secretion profile was compared with that of the wild-type strain. The results showed that the wild-type strain, but not the type III mutant, secreted a 40-kDa protein into the culture supernatant. This protein was identified as BopB by the analysis of its N-terminal amino acid sequence. Severe cytotoxicity such as necrosis was induced in L2 cells by infection with the wild-type B. bronchiseptica. In contrast, this effect was not observed by the BopB mutant infection. The haemolytic activity of the BopB mutant was greatly impaired compared with that of the wild-type strain. The results of a digitonin assay strongly suggested that BopB was translocated into HeLa cells infected with the wild-type strain. Taken together, our results demonstrate that Bordetella secretes BopB via a type III secretion system during infection. BopB may play a role in the formation of pores in the host plasma membrane which serve as a conduit for the translocation of effector proteins into host cells. 相似文献
5.
Vilches S Urgell C Merino S Chacón MR Soler L Castro-Escarpulli G Figueras MJ Tomás JM 《Applied and environmental microbiology》2004,70(11):6914-6919
We have investigated the existence and genetic organization of a functional type III secretion system (TTSS) in a mesophilic Aeromonas strain by initially using the Aeromonas hydrophila strain AH-3. We report for the first time the complete TTSS DNA sequence of an Aeromonas strain that comprises 35 genes organized in a similar disposition as that in Pseudomonas aeruginosa. Using several gene probes, we also determined the presence of a TTSS in clinical or environmental strains of different Aeromonas species: A. hydrophila, A. veronii, and A. caviae. By using one of the TTSS genes (ascV), we were able to obtain a defined insertion mutant in strain AH-3 (AH-3AscV), which showed reduced toxicity and virulence in comparison with the wild-type strain. Complementation of the mutant strain with a plasmid vector carrying ascV was fully able to restore the wild-type toxicity and virulence. 相似文献
6.
Virulence factors for Aeromonas salmonicida subsp. salmonicida (ASS) strains isolated from cultured turbot Psetta maxima L. are unknown with regard to this host. The presence of virulence genes associated with different stages of ASS infection in salmonids (vapA, tapA, fla, ascV, ascC, aexT, satA and aspA) was analysed using a polymerase chain reaction (PCR) technique in ASS strains isolated from turbot. Other ASS strains isolated from salmonids and environmental A. salmonicida (AS) strains were included for comparison. The presence of the genes was evaluated with respect to ASS virulence in turbot based on intraperitoneal and bath challenges. The genetic profile, including all of the genes studied, that was linked to virulent behaviour after intraperitoneal challenge was significantly more frequent in strains isolated from turbot than in those from salmonids or the environment. The data prove that it is not possible to predict the virulence of ASS in turbot based only on the presence of all genes tested. Moreover, the combined PCR results of vapA, aexT, ascV and ascC were useful for separating most of the ASS from environmental A. salmonicida strains. An association between virulence or genetic profile and the geographical or facility origin of the strains was not found. 相似文献
7.
Aeromonas salmonicida expresses a large number of proven and suspected virulence factors including bacterial surface proteins, extracellular degradative enzymes, and toxins. We report the isolation and characterization of a 4-gene cluster, tapABCD, from virulent A. salmonicida A450 that encodes proteins homologous to components required for type IV pilus biogenesis. One gene, tapA, encodes a protein with high homology to type IV pilus subunit proteins from many gram-negative bacterial pathogens, including Aeromonas hydrophila, Pseudomonas aeruginosa, and Vibrio vulnificus. A survey of A. salmonicida isolates from a variety of sources shows that the tapA gene is as ubiquitous in this species as it is in other members of the Aeromonads. Immunoblotting experiments demonstrate that it is expressed in vitro and is antigenically conserved among the A. salmonicida strains tested. A mutant A. salmonicida strain defective in expression of TapA was constructed by allelic exchange and found to be slightly less pathogenic for juvenile Oncorhynchus mykiss (rainbow trout) than wild type when delivered by intraperitoneal injection. In addition, fish initially challenged with a high dose of wild type were slightly more resistant to rechallenge with wild type than those initially challenged with the tapA mutant strain, suggesting that presence of TapA contributes to immunity. Two of the other three genes identified, tapB and tapC, encode proteins with homology to factors known to be required for type IV pilus assembly in P. aeruginosa, but in an as yet unidentified manner. TapB is a member of the ABC-transporter family of proteins that contain characteristic nucleotide-binding regions, and which may provide energy for type IV pilus assembly through the hydrolysis of ATP. TapC homologs are integral cytoplasmic membrane proteins that may play a role in pilus anchoring or initiation of assembly. The fourth gene, tapD, encodes a product that shares homology with a family of proteins with a known biochemical function, namely, the type IV prepilin leader peptidases. These bifunctional enzymes proteolytically cleave the leader peptide from the pilin precursor (prepilin) and then N-methylate the newly exposed N-terminal amino acid prior to assembly of the subunits into the pilus structure. We demonstrate that A. salmonicida TapD is able to restore type IV pilus assembly and type II secretion in a P. aeruginosa strain carrying a mutation in its type IV peptidase gene, suggesting that it plays the same role in A. salmonicida. 相似文献
8.
'Atypical', cytochrome oxidase-negative variants of the fish pathogen Aeromonas salmonicida , isolated from ulcerated flounder ( Platichthys flesus ), were studied using different methods. Two of the strains possessed a protein that corresponded to the A-layer protein of Aer. salmonicida . The strains reacted with antibodies against the A-layer and monoclonal antibodies against the O-antigen of typical Aer. salmonicida . These tests confirm that the isolates from flounder should be classified as Aer. salmonicida . Analysis of the fatty acids showed that the isolates were rather homogenous but the values of the guanine plus cytosine content of the DNA of the bacteria varied too much for any conclusion to be drawn on their taxonomic location. The strains examined exhibited several biochemical characters that differed from those of the type strains of Aer. salmonicida subsp. salmonicida and Aer. salmonicida , subsp. achromogenes . The results suggest that these 'atypical', cytochrome oxidase-negative variants may form a new subspecies of Aer. salmonicida . 相似文献
9.
Aeromonas salmonicida subsp. salmonicida is a Gram-negative bacterium that is the etiological agent of furunculosis, a serious infectious disease of salmonids. Aeromonas spp. are ubiquitous waterborne bacteria responsible for a wide spectrum of diseases among aquatic organisms and humans. Bacterial outer membrane proteins (OMPs) play a significant role in virulence as they comprise the outermost surface in contact with host cells and immune defense factors. To identify the major OMPs of A. salmonicida a proteomic analysis was undertaken using a carbonate OMP-enrichment protocol. The enriched OMP-extracts were separated by 2-dimensional electrophoresis (2-DE) and the spots identified using liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) via an electrospray ionization source. In total, 76 unique proteins were identified from the 125 spots observed on the 2-D gel. The surface layer (S-layer) VapA protein dominated the A. salmonicida OMP 2-D profile, accounting for 60% of the protein on the 2-D gels. Among the other outer membrane proteins identified were at least 10 porins and various receptors involved in nutrient acquisition. Also identified in the carbonate insoluble fraction were phosphoglycerate kinase, enolase and others that lacked classical export sorting signals. The putative association of these proteins with the cell surface might provide new insights concerning the biological and pathogenic roles of these molecules in A. salmonicida infection. This work represents the first systematic attempt to characterize the cell surface of A. salmonicida. 相似文献
10.
Plasmid profile analyses were performed for 113 strains of atypical Aeromonas salmonicida and the reference strain A. salmonicida subsp. salmonicida ATCC 14174. The atypical A. salmonicida strains comprised 98 strains obtained from fish originating from 54 farms and 2 lakes in Norway, 10 strains from Canada (2), Denmark (2), Finland (1), Iceland (1) and Sweden (4), the reference strains NCMB 1109 and ATCC 15711 (Haemophilus piscium) of A. salmonicida subsp. achromogenes, and the type cultures A. salmonicida subsp. achromogenes NCMB 1110, A. salmonicida subsp. masoucida ATCC 27013 and A. salmonicida subsp. smithia CCM 4103. A total of 95 strains of atypical A. salmonicida were separated into 7 groups (I to VII) based on the plasmid profiles. Eighteen strains of atypical A. salmonicida had no common plasmid profile. The type strain NCMB 1110 and the reference strain NCMB 1109 were included in group IV, and the type strain ATCC 27013 in group V, but the other reference and type strains had plasmid profiles different from all the other strains. An epidemiological link was documented between strains collected from different farms/localities in each of groups I, III, V and VII. Physiological and biochemical characterizations were performed for 93 of the strains to investigate phenotypic differences between the plasmid groups. Group VII strains and 3 strains with no common plasmid profile differed from the other groups in being catalase-negative. Differences in phenotypic characteristics were shown between the plasmid groups. However, significant variations in reactions for several phenotypic characteristics also occurred within each of the groups I to VII. The present study indicates that plasmid profiling may give useful epidemiological information during outbreaks of atypical A. salmonicida infections in fish. Additional comprehensive phenotypic characterisation is of limited value since the phenotypic characteristics in each plasmid group are not uniform. 相似文献
11.
Jeffrey E. Christensen Sophia A. Pacheco Michael E. Konkel 《Molecular microbiology》2009,73(4):650-662
The food-borne pathogen Campylobacter jejuni is dependent on a functional flagellum for motility and the export of virulence proteins that promote maximal host cell invasion. Both the flagellar and non-flagellar proteins exported via the flagellar type III secretion system contain a sequence within the amino-terminus that directs their export from the bacterial cell. Accordingly, we developed a genetic screen to identify C. jejuni genes that encode a type III secretion amino-terminal sequence that utilizes the flagellar type III secretion system of Yersinia enterocolitica and a phospholipase reporter ( yplA ). We screened a library of 321 C. jejuni genes and identified proteins with putative type III secretion amino-terminal sequences. One gene identified by the screen was Cj1242. We generated a mutation in Cj1242 , and performed growth rate, motility, secretion and INT 407 cell adherence and internalization assays. The C. jejuni Cj1242 mutant was not altered in growth rate or motility when compared with the wild-type strain, but displayed an altered secretion profile and a reduction in host cell internalization. Based on the phenotype of the C. jejuni Cj1242 mutant, we designated the protein Campylobacter invasion antigen C (CiaC). Collectively, our findings indicate that CiaC is a potentially important virulence factor. 相似文献
12.
Duarté X Anderson CT Grimson M Barabote RD Strauss RE Gollahon LS San Francisco MJ 《FEMS microbiology letters》2000,190(1):81-86
The bacterium Erwinia chrysanthemi is a model plant pathogen, responsible for causing cell death in plant tissue. Cell-wall depolymerizing enzymes and avirulence proteins essential for parasitism by this bacterium utilize dedicated type II and type III secretion systems, respectively. Although E. chrysanthemi is not recognized as a mammalian pathogen, we have observed that the bacterium can adhere to, cause an oxidative stress response in and kill cultured human adenocarcinoma cells. These bacteria express a surface protein that bears immunological identity to intimin, a protein required for full virulence of enterohemorrhagic and enteropathogenic Escherichia coli. A type III secretion mutant of E. chrysanthemi was observed to have a significantly lower capability of causing death than the wild-type strain in parallel cultures of human colon adenocarcinoma cells. These observations suggest that E. chrysanthemi has the potential to parasitize mammalian hosts as well as plants. 相似文献
13.
The current taxonomy of Aeromonas salmonicida includes 4 subspecies. A. salmonicida subsp. salmonicida is associated with salmonid furunculosis, and A. salmonicida subsp. achromogenes, A. salmonicida subsp. masoucida, and A. salmonicida subsp. smithia are strains that show variation in some biochemical properties. This classification does not readily encompass isolates from a wide range of fish hosts currently described as atypical A. salmonicida. This study examined 17 typical strains, 39 atypical strains and 3 type A. salmonicida subspecies strains for genetic similarity using the random amplified polymophic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) techniques. On the basis of RAPD- and PFGE-derived profiles, similarity matrices and dendrograms were constructed. The results showed that species A. salmonicida constituted a genetically heterogeneous group of strains, encompassing within an homogeneous or clonal lineage comprised solely of typical strains and the A. salmonicida subsp. salmonicida type strain. 相似文献
14.
Molecular characterization and quantitative analysis of superoxide dismutases in virulent and avirulent strains of Aeromonas salmonicida subsp. salmonicida
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Dacanay A Johnson SC Bjornsdottir R Ebanks RO Ross NW Reith M Singh RK Hiu J Brown LL 《Journal of bacteriology》2003,185(15):4336-4344
Aeromonas salmonicida subsp. salmonicida is a facultatively intracellular gram-negative bacterium that is the etiological agent of furunculosis, a bacterial septicemia of salmonids that causes significant economic loss to the salmon farming industry. The mechanisms by which A. salmonicida evades intracellular killing may be relevant in understanding virulence and the eventual design of appropriate treatment strategies for furunculosis. We have identified two open reading frames (ORFs) and related upstream sequences that code for two putative superoxide dismutases (SODs), sodA and sodB. The sodA gene encoded a protein of 204 amino acids with a molecular mass of approximately 23.0 kDa (SodA) that had high similarity to other prokaryotic Mn-SODs. The sodB gene encoded a protein of 194 amino acids with a molecular mass of approximately 22.3 kDa that had high similarity to other prokaryotic Fe-SODs. Two enzymes with activities consistent with both these ORFs were identified by inhibition of O(2)(-)-catalyzed tetrazolium salt reduction in both gels and microtiter plate assays. The two enzymes differed in their expression patterns in in vivo- and in vitro-cultured bacteria. The regulatory sequences upstream of putative sodA were consistent with these differences. We could not identify other SOD isozymes such as sodC either functionally or through data mining. Levels of SOD were significantly higher in virulent than in avirulent strains of A. salmonicida subsp. salmonicida strain A449 when cultured in vitro and in vivo. 相似文献
15.
Campylobacter jejuni survival within human epithelial cells is enhanced by the secreted protein CiaI 总被引:1,自引:0,他引:1
Although it is known that Campylobacter jejuni invade the cells that line the human intestinal tract, the bacterial proteins that enable this pathogen to survive within Campylobacter-containing vacuoles (CCV) have not been identified. Here, we describe the identification and characterization of a protein that we termed CiaI for Campylobacter invasion antigen involved in intracellular survival. We show that CiaI harbours an amino-terminal type III secretion sequence and is secreted from C. jejuni through the flagellar type III secretion system. In addition, the ciaI mutant was impaired in intracellular survival when compared with a wild-type strain, as judged by the gentamicin-protection assay. Fluorescence microscopy examination of epithelial cells infected with the C. jejuni ciaI mutant revealed that the CCV were more frequently co-localized with Cathepsin D (a lysosomal marker) than the CCV in cells infected with a C. jejuni wild-type strain. Ectopic expression of CiaI-GFP in epithelial cells yielded a punctate phenotype not observed with the other C. jejuni genes, and this phenotype was abolished by mutation of a dileucine motif located in the carboxy-terminus of the protein. Based on the data, we conclude that CiaI contributes to the ability of C. jejuni to survive within epithelial cells. 相似文献
16.
Kim JH Son JS Choi YJ Choresca CH Shin SP Han JE Jun JW Kang DH Oh C Heo SJ Park SC 《Current microbiology》2012,64(5):418-426
To search for candidate control agents against Aeromonas salmonicida subsp. salmonicida infections in aquaculture, one bacteriophage (phage), designated as PAS-1, was isolated from the sediment samples of the rainbow trout (Oncorhynchus mykiss) culture farm in Korea. The PAS-1 was morphologically classified as Myoviridae and possessed approximately 48 kb of double-strand genomic DNA. The phage showed broad host ranges to other subspecies of A. salmonicida as well as A. salmonicida subsp. salmonicida including antibiotic-resistant strains. Its latent period and burst size were estimated to be approximately 40 min and 116.7 PFU/cell, respectively. Furthermore, genomic and structural proteomic analysis of PAS-1 revealed that the phage was closely related to other Myoviridae phages infecting enterobacteria or Aeromonas species. The bacteriolytic activity of phage PAS-1 was evaluated using three subspecies of A. salmonicida strain at different doses of multiplicity of infection, and the results proved to be efficient for the reduction of bacterial growth. Based on these results, PAS-1 could be considered as a novel Aeromonas phage and might have potentiality to reduce the impacts of A. salmonicida infections in aquaculture. 相似文献
17.
Valrie E. Paquet Antony T. Vincent Sylvain Moineau Steve J. Charette 《Molecular microbiology》2019,112(2):667-677
Aeromonas salmonicida subsp. salmonicida is a fish pathogen that causes furunculosis. Antibiotherapy used to treat furunculosis in fish has led to resistance. Virulent phages are increasingly seen as alternatives or complementary treatments against furunculosis in aquaculture environments. For phage therapy to be successful, it is essential to study the natural mechanisms of phage resistance in A. salmonicida subsp. salmonicida. Here, we generated bacteriophage‐insensitive mutants (BIMs) of A. salmonicida subsp. salmonicida, using a myophage with broad host range and characterized them. Phage plaques were different depending on whether the A‐layer surface array protein was expressed or not. The genome analysis of the BIMs helped to identify mutations in genes involved in the biogenesis of lipopolysaccharides (LPS) and on an uncharacterized gene (ASA_1998). The characterization of the LPS profile and gene complementation assays identified LPS as a phage receptor and confirmed the involvement of the uncharacterized protein ASA_1998 in phage infection. In addition, we confirmed that the presence of an A‐layer at the bacterial surface could act as protection against phages. This study brings new elements into our understanding of the phage adsorption to A. salmonicida subsp. salmonicida cells. 相似文献
18.
19.
Restriction endonuclease fingerprinting analysis of Canadian isolates of Aeromonas salmonicida 总被引:2,自引:0,他引:2
Restriction endonuclease fingerprinting (REF) analysis was used to examine total cellular DNA prepared from 56 independent field isolates of the fish pathogen, Aeromonas salmonicida. DNA was digested singly with the restriction enzymes EcoRI and HindIII, and the resulting fragments separated by polyacrylamide gel electrophoresis and visualized by silver staining. The REF patterns of typical isolates of A. salmonicida subsp. salmonicida were distinct from those of A. hydrophila, A. salmonicida subsp. achromogenes, A. salmonicida subsp. masoucida, and atypical isolates of A. salmonicida subsp. salmonicida. Differences between strains of typical A. salmonicida subsp. salmonicida could also be distinguished. Canadian isolates examined could be assigned to 1 of 12 different groups (REF groups), with the majority of the isolates belonging to REF groups 1 and 5. REF group 1 strains were isolated from British Columbia and New Brunswick while REF group 5 isolates were found in Ontario. None of the European strains examined had REF patterns identical to those of Canadian isolates. Based on REF analysis, there was little genetic heterogeneity detected among 23 isolates from two short-term studies of naturally occurring infections. Several different REF groups were seen among A. salmonicida collected over a 10-year period from coho salmon from the Credit River. Consistent with earlier biochemical and hybridization studies, the REF data suggest that A. salmonicida is a clonal pathogen. REF analysis can, however, permit the identification of subgroups, which may be useful in epidemiological studies. 相似文献
20.
The cytotoxicity of Bordetella bronchiseptica to infected cells is known to be dependent on a B. bronchiseptica type III secretion system. Although BopB, BopN, BopD, and Bsp22 have been identified as type III secreted proteins, these proteins remain to be characterized. In this study, in order to clarify the function of BopD during Bordetella infection, a BopD mutant was generated. Although secretion of BopD into the culture supernatant was completely abolished by the bopD mutation, the secretion of other type III secreted proteins was not affected by this mutation. It has been reported that severe cytotoxicity, including cell detachment from the substrata, and release of lactate dehydrogenase (LDH) into the supernatant are induced in L2 cells by wild-type B. bronchiseptica infection, and these phenotypes are dependent on the type III secretion system. In contrast, neither cell detachment nor LDH release was induced in L2 cells infected with the BopD mutant. Furthermore, the hemolytic activity of the BopD mutant was greatly impaired compared with that of the wild-type strain. On the basis of the results of coimmunoprecipitation assays with anti-BopB antibodies, we conclude that BopD has the ability to associate with BopB. Finally, we show that the BopD-BopB complex is responsible for the pore formation in the host plasma membrane that functions as the conduit for the transition of effector proteins into host cells. 相似文献