Key Laboratory of Animal Bacteriology

Nanjing, China

Key Laboratory of Animal Bacteriology

Nanjing, China
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Ma J.,Nanjing Agricultural University | Ma J.,Key Laboratory of Animal Bacteriology | Sun M.,Nanjing Agricultural University | Sun M.,Key Laboratory of Animal Bacteriology | And 8 more authors.
Environmental Microbiology | Year: 2017

The type VI secretion system (T6SS) of bacteria plays a key role in competing for specific niches by the contact-dependent killing of competitors. Recently, Rhs proteins with polymorphic C-terminal toxin-domains that inhibit or kill neighboring cells were identified. In this report, we identified a novel Rhs with an MPTase4 (Metallopeptidase-4) domain (designated as Rhs-CT1) that showed an antibacterial effect via T6SS in Escherichia coli. We managed to develop a specific strategy by matching the diagnostic domain-architecture of Rhs-CT1 (Rhs with an N-terminal PAAR-motif and a C-terminal toxin domain) for effector retrieval and discovered a series of Rhs-CTs in E. coli. Indeed, the screened Rhs-CT3 with a REase-3 (Restriction endonuclease-3) domain also mediated interbacterial antagonism. Further analysis revealed that vgrGO1 and eagR/DUF1795 (upstream of rhs-ct) were required for the delivery of Rhs-CTs, suggesting eagR as a potential T6SS chaperone. In addition to chaperoned Rhs-CTs, neighborless Rhs-CTs could be classified into a distinct family (Rhs-Nb) sharing close evolutionary relationship with T6SS2-Rhs (encoded in the T6SS2 cluster of E. coli). Notably, the Rhs-Nb-CT5 was confirmed bioinformatically and experimentally to mediate interbacterial antagonism via Hcp2B-VgrG2 module. In a further retrieval analysis, we discovered various toxin/immunity pairs in extensive bacterial species that could be systematically classified into eight referential clans, suggesting that Rhs-CTs greatly diversify the antibacterial pathways of T6SS. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd

Ma J.,Nanjing Agricultural University | Ma J.,Key Laboratory of Animal Bacteriology | Pan Z.,Nanjing Agricultural University | Pan Z.,Key Laboratory of Animal Bacteriology | And 8 more authors.
Virulence | Year: 2017

The type VI secretion system (T6SS) is a widespread molecular weapon deployed by many bacterial species to target eukaryotic host cells or rival bacteria. Using a dynamic injection mechanism, diverse effectors can be delivered by T6SS directly into recipient cells. Here, we report a new family of T6SS effectors encoded by extended Hcps carrying diverse toxin domains. Bioinformatic analyses revealed that these Hcps with C-terminal extension toxins, designated as Hcp-ET, exist widely in the Enterobacteriaceae. To verify our findings, Hcp-ET1 was tested for its antibacterial effect, and showed effective inhibition of target cell growth via the predicted HNH-DNase activity by T6SS-dependent delivery. Further studies showed that Hcp-ET2 mediated interbacterial antagonism via a Tle1 phospholipase (encoded by DUF2235 domain) activity. Notably, comprehensive analyses of protein homology and genomic neighborhoods revealed that Hcp-ET3–4 is fused with 2 toxin domains (Pyocin S3 and Colicin-DNase) C-terminally, and its encoding gene is followed 3 duplications of the cognate immunity genes. However, some bacteria encode a separated hcp-et3 and an orphan et4 (et4O1) genes caused by a termination-codon mutation in the fusion region between Pyocin S3 and Colicin-DNase encoding fragments. Our results demonstrated that both of these toxins had antibacterial effects. Further, all duplications of the cognate immunity protein contributed to neutralize the DNase toxicity of Pyocin S3 and Colicin, which has not been reported previously. In conclusion, we propose that Hcp-ET proteins are polymorphic T6SS effectors, and thus present a novel encoding pattern of T6SS effectors. © 2017 Taylor & Francis

Shao J.,Key Laboratory of Animal Bacteriology | Shao J.,OIE Reference Laboratory for Swine Streptococcosis | Zhang W.,Key Laboratory of Animal Bacteriology | Zhang W.,OIE Reference Laboratory for Swine Streptococcosis | And 4 more authors.
Current Microbiology | Year: 2014

Streptococcus suis serotype 2 (SS2) is an emerging zoonotic agent responsible for a number of infections in pigs and humans. Pili have been proposed as virulence factors in Gram-positive bacteria. However, due to the abolition of pili production, the function of the srtBCD pilus cluster, especially the truncated major pilin subunit Sbp2 (Sbp2′, Sbp2″), has not been explored. In this study, isogenic mutants (Δsbp2′, Δsbp2″) were constructed by homologous replacement in SS2 strain P1/7. Deletion of sbp2′ attenuated the virulence in a zebrafish model as shown by more than an eightfold increase in the LD50 of Δsbp2′, compared with that of the parent strain. In addition, the adhesion of Δsbp2′ to HEp-2 cell monolayers decreased significantly. Compared with the parent strain, no obvious differences in virulence and adherence efficiency were observed for Δsbp2″. Our data suggest that Sbp2′ could be involved in SS2 pathogenesis despite absence of its pilus shaft. © 2014 Springer Science+Business Media New York.

Wu Z.,Nanjing Agricultural University | Wu Z.,Key Laboratory of Animal Bacteriology | Wu Z.,OIE Reference Laboratory for Swine Streptococcosis | Wu C.,BGI Shenzhen | And 24 more authors.
RNA | Year: 2014

Streptococcus suis (SS) is an important pathogen of pigs, and it is also recognized as a zoonotic agent for humans. SS infection may result in septicemia or meningitis in the host. However, little is known about genes that contribute to the virulence process and survival within host blood or cerebrospinal fluid (CSF). Small RNAs (sRNA) have emerged as key regulators of virulence in several bacteria, but they have not been investigated in SS. Here, using a differential RNA-sequencing approach and RNAs from SS strain P1/7 grown in rich medium, pig blood, or CSF, we present the SS genome-wide map of 793 transcriptional start sites and 370 operons. In addition to identifying 29 sRNAs, we show that five sRNA deletion mutants attenuate SS virulence in a zebrafish infection model. Homology searches revealed that 10 sRNAs were predicted to be present in other pathogenic Streptococcus species. Compared with wild-type strain P1/7, sRNAs rss03, rss05, and rss06 deletion mutants were significantly more sensitive to killing by pig blood. It is possible that rss06 contributes to SS virulence by indirectly activating expression of SSU0308, a virulence gene encoding a zinc-binding lipoprotein. In blood, genes involved in the synthesis of capsular polysaccharide (CPS) and subversion of host defenses were up-regulated. In contrast, in CSF, genes for CPS synthesis were down-regulated. Our study is the first analysis of SS sRNAs involved in virulence and has both improved our understanding of SS pathogenesis and increased the number of sRNAs known to play definitive roles in bacterial virulence. © 2014 Wu et al.

Wang S.,Chinese Academy of Agricultural Sciences | Meng Q.,Chinese Academy of Agricultural Sciences | Meng Q.,Key Laboratory of Animal Bacteriology | Meng Q.,Nanjing Agricultural University | And 7 more authors.
PLoS ONE | Year: 2014

Systemic infections by avian pathogenic Escherichia coli (APEC) are economically devastating to poultry industries worldwide. E. coli strains belonging to serotypes O1, O2, O18 and O78 are preferentially associated with avian colibacillosis. The rfb gene cluster controlling O antigen synthesis is usually various among different E. coli serotypes. In present study, the rfb gene clusters of E. coli serotypes O1, O2, O18 and O78 were characterized and compared. Based on the serotype-specific genes in rfb gene cluster, an allele-specific polymerase chain reaction (PCR) assay was developed. This PCR assay was highly specific and reliable for sero-typing of APEC O1, O2, O18 and O78 strains. The sensitivity of the assay was determined as 10 pg DNA or 10 colony forming units (CFUs) bacteria for serotypes O2 and O18 strains, and 500 pg DNA or 1,000 CFUs bacteria for serotypes O1 and O78 strains. Using this PCR system, APEC isolates and the infected tissue samples were categorized successfully. Furthermore, it was able to differentiate the serotypes for the samples with multi-agglutination in the traditional serum agglutination assay. Therefore, the allele-specific PCR is more simple, rapid and accurate assay for APEC diagnosis, epidemiologic study and vaccine development. © 2014 Wang et al.

Ma J.,Nanjing Agricultural University | Ma J.,Key Laboratory of Animal Bacteriology | Bao Y.,Nanjing Agricultural University | Bao Y.,Key Laboratory of Animal Bacteriology | And 12 more authors.
Infection and Immunity | Year: 2014

Type VI secretion systems (T6SSs) are involved in the pathogenicity of several Gram-negative bacteria. The VgrG protein, a core component and effector of T6SS, has been demonstrated to perform diverse functions. The N-terminal domain of VgrG protein is a homologue of tail fiber protein gp27 of phage T4, which performs a receptor binding function and determines the host specificity. Based on sequence analysis, we found that two putative T6SS loci exist in the genome of the avian pathogenic Escherichia coli (APEC) strain TW-XM. To assess the contribution of these two T6SSs to TW-XM pathogenesis, the crucial clpV clusters of these two T6SS loci and their vgrG genes were deleted to generate a series of mutants. Consequently, T6SS1-associated mutants presented diminished adherence to and invasion of several host cell lines cultured in vitro, decreased pathogenicity in duck and mouse infection models in vivo, and decreased biofilm formation and bacterial competitive advantage. In contrast, T6SS2-associated mutants presented a significant decrease only in the adherence to and invasion of mouse brain microvascular endothelial cell (BMEC) line bEnd.3 and brain tissue of the duck infection model. These results suggested that T6SS1 was involved in the proliferation of APEC in systemic infection, whereas VgrG-T6SS2 was responsible only for cerebral infection. Further study demonstrated that VgrG-T6SS2 was able to bind to the surface of bEnd.3 cells, whereas it did not bind to DF-1 (chicken embryo fibroblast) cells, which further proved the interaction of VgrG-T6SS2 with the surface of BMECs. © 2014, American Society for Microbiology.

He S.,Nanjing Agricultural University | He S.,Key Laboratory of Animal Bacteriology | He S.,OIE Reference Laboratory for Swine Streptococcosis | Shi J.,Chinese Academy of Agricultural Sciences | And 6 more authors.
Microbes and Infection | Year: 2015

In early 2013, a Bengal tiger (Panthera tigris) in a zoo died of respiratory distress. All specimens from the tiger were positive for HPAI H5N1, which were detected by real-time PCR, including nose swab, throat swab, tracheal swab, heart, liver, spleen, lung, kidney, aquae pericardii and cerebrospinal fluid. One stain of virus, A/Tiger/JS/1/2013, was isolated from the lung sample. Pathogenicity experiments showed that the isolate was able to replicate and cause death in mice. Phylogenetic analysis indicated that HA and NA of A/Tiger/JS/1/2013 clustered with A/duck/Vietnam/OIE-2202/2012 (H5N1), which belongs to clade Interestingly, the gene segment PB2 shared 98% homology with A/wild duck/Korea/CSM-28/20/2010 (H4N6), which suggested that A/Tiger/JS/1/2013 is a novel reassortant H5N1 subtype virus. Immunohistochemical analysis also confirmed that the tiger was infected by this new reassortant HPAI H5N1 virus. Overall, our results showed that this Bengal tiger was infected by a novel reassortant H5N1, suggesting that the H5N1 virus can successfully cross species barriers from avian to mammal through reassortment. © 2014 Institut Pasteur.

Sun M.,Nanjing Agricultural University | Sun M.,Key Laboratory of Animal Bacteriology | Ma J.,Nanjing Agricultural University | Ma J.,Key Laboratory of Animal Bacteriology | And 11 more authors.
Journal of Clinical Microbiology | Year: 2015

Porcine epidemic diarrhea has become pandemic in the Asian pig-breeding industry, causing significant economic loss. In the present study, 11 complete genomes of porcine epidemic diarrhea virus (PEDV) field isolates from China were determined and analyzed. Frequently occurring mutations were observed, which suggested that full understanding of the genomic and epidemiological characteristics is critical in the fight against PEDV epidemics. Comparative analysis of 49 available genomes clustered the PEDV strains into pandemic (PX) and classical (CX) groups and identified four hypervariable regions (V1 to V4). Further study indicated key roles for the spike (S) gene and the V2 region in distinguishing between the PX and CX groups and for studying genetic evolution. Genotyping and phylogeny-based geographical dissection based on 219 S genes revealed the complexity and severity of PEDV epidemics in Asia. Many subgroups have formed, with a wide array of mutations in different countries, leading to the outbreak of PEDV in Asia. Spatiotemporal reconstruction based on the analysis suggested that the pandemic group strains originated from South Korea and then extended into Japan, Thailand, and China. However, the novel pandemic strains in South Korea that appeared after 2013 may have originated from a Chinese variant. Thus, the serious PED epidemics in China and South Korea in recent years were caused by the complex subgroups of PEDV. The data in this study have important implications for understanding the ongoing PEDV outbreaks in Asia and will guide future efforts to effectively prevent and control PEDV. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

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