Role of ClpX and ClpP in Streptococcus suis serotype 2 stress tolerance and virulence

Mechanisms Underlying the Effects of Secretory Protein G22 on Biological Characteristics and Virulence of Streptococcus suis

Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen that seriously harms the swine industry and human health. However, its pathogenic mechanisms are largely unknown, and the few virulence factors reported so far are insufficient to systematically explain its infectious and pathogenic mechanisms. In preliminary research, we identified a gene named G22 encoding a hypothetical secreted protein that may be closely associated with the high-level pathogenicity of S. suis. In this study, we constructed deletion and complementation strains of the G22 gene through homologous recombination and explored its roles in the pathogenicity and susceptibility of S. suis to environmental stresses through in vitro and in vivo experiments. The deletion of G22 clearly influenced the typical capsular structure of SS2 and impaired the bacterium's growth in a medium containing hydrogen peroxide (showing a growth reduction of 32.98% ± 5.23% compared to the wild-type strain SC19, p < 0.001) or with a low pH (with a growth inhibition of 17.44% ± 1.9% relative to the wild-type strain SC19, p < 0.01). ΔG22 also showed reduced survival in whole blood and in RAW 264.7 macrophages (with a survival reduction of 16.44% ± 2.29% compared to the wild-type, p < 0.001). The deletion of G22 also sharply attenuated the virulence of SS2 in a mouse infection model (reducing the mortality rate by 50% ± 0.04%, p < 0.05). We also demonstrated that G22 is required for the adhesion and invasion of SS2 in host cells. An RNA sequencing analysis revealed that 50 genes were differentially expressed in the ΔG22 and wild-type strains: 23 upregulated and 37 downregulated. Many of the genes are involved in carbohydrate metabolism and the synthesis of virulence-associated factors. Several genes associated with the phosphotransferase system were significantly upregulated in strain ΔG22. In summary, G22 plays a role in the morphological development and pathogenesis of the highly virulent SS2 strain SC19.

Characterization Studies on the sugC Gene of Streptococcus suis Serotype 2 in Adhesion, Invasion, and Virulence in Mice

The sugC gene of Streptococcus suis (S. suis) is a coding gene for the ATP-binding transporter-associated protein with strong pathogenicity. In order to reveal the effect of the sugC gene on the virulence of S. suis serotype 2, a wild-type strain of TJS75, isolated from fattening pigs' brain tissue samples, was used as a parent strain, and a knockout sugC gene (ΔsugC) and complementary strain (CΔsugC) were successfully constructed via homologous recombination technology. The biological characteristics of TJS75, ΔsugC and CΔsugC were compared and analyzed through growth curves, biochemical characteristics, hemolysis characteristics, cell infection tests and pathogenicity tests on BALB/c mice. The results of the growth characteristic experiments in vitro showed that the plateau stage growth period of ΔsugC was delayed compared to the TJS75 strain, but there was no difference in the total number of bacteria. The biochemical characteristics and hemolysis ability of ΔsugC in sheep blood had no difference compared with TJS75, but its adhesion and invasion abilities in PK-15 cells were decreased. Knockout of the sugC gene had no impact on the expression levels of adhesion-related genes in TJS75 in real-time PCR analysis. In addition, the LD50 of ΔsugC in BALB/c mice was 1.47 × 108 CFU, seven times higher than that of TJS75 (LD50 = 2.15 × 107 CFU). These results illustrate that the deletion of sugC reduced the virulence of TJS75 to BALB/c mice, but its role in the adhesion and invasion of PK-15 cells in this strain needs to be further explored. In summary, this study provides evidence that the sugC gene is a virulence-related gene in the S. suis serotype 2 strain and plays a crucial role in the adhesion and invasion of S. suis. This study lays a foundation for the further exploration of the potential virulence factors and pathogenesis of S. suis.

Streptococcus suis Deploys Multiple ATP-Dependent Proteases for Heat Stress Adaptation

Streptococcus suis is an important zoonotic pathogen, causing cytokine storms of Streptococcal toxic shock-like syndrome amongst humans after a wound infection into the bloodstream. To overcome the challenges of fever and leukocyte recruitment, invasive S. suis must deploy multiple stress responses forming a network and utilize proteases to degrade short-lived regulatory and misfolded proteins induced by adverse stresses, thereby adapting and evading host immune responses. In this study, we found that S. suis encodes multiple ATP-dependent proteases, including single-chain FtsH and double-subunit Clp protease complexes ClpAP, ClpBP, ClpCP, and ClpXP, which were activated as the fever of infected mice in vivo. The expression of genes ftsH, clpA/B/C, and clpP, but not clpX, were significantly upregulated in S. suis in response to heat stress, while were not changed notably under the treatments with several other stresses, including oxidative, acidic, and cold stimulation. FtsH and ClpP were required for S. suis survival within host blood under heat stress in vitro and in vivo. Deletion of ftsH or clpP attenuated the tolerance of S. suis to heat, oxidative and acidic stresses, and significantly impaired the bacterial survival within macrophages. Further analysis identified that repressor CtsR directly binds and controls the clpA/B/C and clpP operons and is relieved by heat stress. In summary, the deployments of multiple ATP-dependent proteases form a flexible heat stress response network that appears to allow S. suis to fine-tune the degradation or refolding of the misfolded proteins to maintain cellular homeostasis and optimal survival during infection.

The Food Additive Benzaldehyde Confers a Broad Antibiotic Tolerance by Modulating Bacterial Metabolism and Inhibiting the Formation of Bacterial Flagella

The rise of antibiotic tolerance in bacteria harboring genetic elements conferring resistance to antibiotics poses an increasing threat to public health. However, the primary factors responsible for the emergence of antibiotic tolerance and the fundamental molecular mechanisms involved remain poorly comprehended. Here, we demonstrate that the commonly utilized food additive Benzaldehyde (BZH) possesses the capacity to induce a significant level of fluoroquinolone tolerance in vitro among resistant Escherichia coli. Our findings from animal models reveal that the pre-administration of BZH results in an ineffective eradication of bacteria through ciprofloxacin treatment, leading to similar survival rates and bacterial loads as observed in the control group. These results strongly indicate that BZH elicits in vivo tolerance. Mechanistic investigations reveal several key factors: BZH inhibits the formation of bacterial flagella and releases proton motive force (PMF), which aids in expelling antibiotics from within cells to reducing their accumulation inside. In addition, BZH suppresses bacterial respiration and inhibits the production of reactive oxygen species (ROS). Moreover, exogenous pyruvate successfully reverses BZH-induced tolerance and restores the effectiveness of antibiotics, highlighting how crucial the pyruvate cycle is in combating antibiotic tolerance. The present findings elucidate the underlying mechanisms of BZH-induced tolerance and highlight potential hazards associated with the utilization of BZH.

EvfG is a multi-function protein located in the Type VI secretion system for ExPEC

The Type VI secretion system (T6SS) functions as a protein transport nanoweapon in several stages of bacterial life. Even though bacterial competition is the primary function of T6SS, different bacteria exhibit significant variations. Particularly in Extraintestinal pathogenic Escherichia coli (ExPEC), research into T6SS remains relatively limited. This study identified the uncharacterized gene evfG within the T6SS cluster of ExPEC RS218. Through our experiments, we showed that evfG is involved in T6SS expression in ExPEC RS218. We also found evfG can modulate T6SS activity by competitively binding to c-di-GMP, leading to a reduction in the inhibitory effect. Furthermore, we found that evfG can recruit sodA to alleviate oxidative stress. The research shown evfG controls an array of traits, both directly and indirectly, through transcriptome and additional tests. These traits include cell adhesion, invasion, motility, drug resistance, and pathogenicity of microorganisms. Overall, we contend that evfG serves as a multi-functional regulator for the T6SS and several crucial activities. This forms the basis for the advancement of T6SS function research, as well as new opportunities for vaccine and medication development.

Identification of ClpB, a molecular chaperone involved in the stress tolerance and virulence of Streptococcus agalactiae

Bacterial ClpB is an ATP-dependent disaggregate that belongs to the Hsp100/Clp family and facilitates bacterial survival under hostile environmental conditions. Streptococcus agalactiae, which is regarded as the major bacterial pathogen of farmed Nile tilapia (Oreochromis niloticus), is known to cause high mortality and large economic losses. Here, we report a ClpB homologue of S. agalactiae and explore its functionality. S. agalactiae with a clpB deletion mutant (∆clpB) exhibited defective tolerance against heat and acidic stress, without affecting growth or morphology under optimal conditions. Moreover, the ΔclpB mutant exhibited reduced intracellular survival in RAW264.7 cells, diminished adherence to the brain cells of tilapia, increased sensitivity to leukocytes from the head kidney of tilapia and whole blood killing, and reduced mortality and bacterial loads in a tilapia infection assay. Furthermore, the reduced virulence of the ∆clpB mutant was investigated by transcriptome analysis, which revealed that deletion of clpB altered the expression levels of multiple genes that contribute to the stress response as well as certain metabolic pathways. Collectively, our findings demonstrated that ClpB, a molecular chaperone, plays critical roles in heat and acid stress resistance and virulence in S. agalactiae. This finding provides an enhanced understanding of the functionality of this ClpB homologue in gram-positive bacteria and the survival strategy of S. agalactiae against immune clearance during infection.

Colonization of vancomycin-resistant Enterococcus faecium in human-derived colonic epithelium: unraveling the transcriptional dynamics of host-enterococcal interactions

Enterococcus faecium is an opportunistic pathogen able to colonize the intestines of hospitalized patients. This initial colonization is an important step in the downstream pathogenesis, which includes outgrowth of the intestinal microbiota and potential infection of the host. The impact of intestinal overgrowth on host-enterococcal interactions is not well understood. We therefore applied a RNAseq approach in order to unravel the transcriptional dynamics of E. faecium upon co-culturing with human derived colonic epithelium. Co-cultures of colonic epithelium with a hospital-associated vancomycin resistant (vanA-type) E. faecium (VRE) showed that VRE resided on top of the colonic epithelium when analyzed by microscopy. RNAseq revealed that exposure to the colonic epithelium resulted in upregulation of 238 VRE genes compared to the control condition, including genes implicated in pili expression, conjugation (plasmid_2), genes related to sugar uptake, and biofilm formation (chromosome). In total, 260 were downregulated, including the vanA operon located on plasmid_3. Pathway analysis revealed an overall switch in metabolism to amino acid scavenging and reduction. In summary, our study demonstrates that co-culturing of VRE with human colonic epithelium promotes an elaborate gene response in VRE, enhancing our insight in host-E. faecium interactions, which might facilitate the design of novel anti-infectivity strategies.

Effectors of the Type VI Secretion System Have the Potential to Be Modified into Antimicrobial Peptides

The use of antibiotics has led to the emergence of multidrug-resistant (MDR) bacteria, and there is an urgent need to find alternative treatments to alleviate this pressure. The type VI secretion system (T6SS) is a protein delivery system present in bacterial cells that secretes effectors that participate in bacterial virulence. Given the potential for the transformation of these effectors into antimicrobial peptides (AMPs), we designed T6SS effectors into AMPs that have a membrane-disrupting effect. These effectors kill bacteria by altering the membrane potential and increasing the intracellular reactive oxygen species (ROS) content. Moreover, AMPs also have a significant therapeutic effect both in vivo and in vitro. This finding suggests that it is possible to modify bacterial components of bacteria themselves to create compounds that fight bacteria. IMPORTANCE This study first identified and modified the T6SS effector into positively charged alpha-helical peptides. These peptides have good antibacterial and bactericidal effects on G+ bacteria and G- bacteria. This study broadens the source of AMPs and makes T6SS effectors more useful.

Revealing the role of microalgae-bacteria niche for boosting wastewater treatment and energy reclamation in response to temperature

Conventional biological treatment usually cannot achieve the same high water quality as advanced treatment when conducted under varied temperatures. Here, satisfactory wastewater treatment efficiency was observed in a microalgae-bacteria consortia (MBC) over a wide temperature range because of the predominance of microalgae. Microalgae contributed more toward wastewater treatment at low temperature because of the unsatisfactory performance of the accompanying bacteria, which experienced cold stress (e.g., bacterial abundance below 3000 sequences) and executed defensive strategies (e.g., enrichment of cold-shock proteins). A low abundance of amoA-C and hao indicated that conventional nitrogen removal was replaced through the involvement of microalgae. Diverse heterotrophic bacteria for nitrogen removal were identified at medium and high temperatures, implying this microbial niche treatment contained diverse flexible consortia with temperature variation. Additionally, pathogenic bacteria were eliminated through microalgal photosynthesis. After fitting the neutral community model and calculating the ecological niche, microalgae achieved a maximum niche breadth of 5.21 and the lowest niche overlap of 0.38, while the accompanying bacterial community in the consortia were shaped through deterministic processes. Finally, the maximum energy yield of 87.4 kJ L^-1 and lipid production of 1.9 g L^-1 were achieved at medium temperature. Altogether, this study demonstrates that advanced treatment and energy reclamation can be achieved through microalgae-bacteria niche strategies.

Establishment of Streptococcus suis Biofilm Infection Model In Vivo and Comparative Analysis of Gene Expression Profiles between In Vivo and In Vitro Biofilms

Streptococcus suis is a zoonotic pathogen that continuously threatens animal husbandry and public health worldwide. Studies have shown that S. suis can cause persistent infection by forming biofilms. In this study, a model of S. suis biofilm-related infection was successfully constructed for the first time by simulating the natural infection of S. suis, and biofilm of S. suis in vivo was successfully observed in the lung tissue of infected pigs by a variety of detection methods. Subsequently, selective capture of transcribed sequences (SCOTS) was used to identify genes expressed by S. suis in vivo biofilms. Sixty-nine genes were captured in in vivo biofilms formed by S. suis for the first time by SCOTS; they were mainly involved in metabolism, cell replication, and division, transport, signal transduction, cell wall, etc. Genes related to S. suis in vitro biofilm formation were also identified by SCOTS and RNA sequencing. Approximately half of the genes captured by SCOTS in the in vivo and in vitro biofilms were found to be different. In summary, our study provides powerful clues for future exploration of the mechanisms of S. suis biofilm formation. IMPORTANCE Streptococcus suis is considered an important zoonotic pathogen, and persistent infection caused by biofilm is currently considered to be the reason why S. suis is difficult to control in swine. However, to date, a model of the biofilm of S. suis in vivo has not been successfully constructed. Here, we successfully detected biofilms of S. suis in vivo in lung tissues of piglets infected with S. suis. Selective capture of transcribed sequences and the transcriptome were used to obtain gene profiles of S. suis in vivo and in vitro biofilms, and the results showed large differences between them. Such data are of importance for future experimental studies exploring the mechanism of biofilm formation by S. suis in vivo.

Proteomic analysis of the regulatory networks of ClpX in a model cyanobacterium Synechocystis sp. PCC 6803

Protein homeostasis is tightly regulated by protein quality control systems such as chaperones and proteases. In cyanobacteria, the ClpXP proteolytic complex is regarded as a representative proteolytic system and consists of a hexameric ATPase ClpX and a tetradecameric peptidase ClpP. However, the functions and molecular mechanisms of ClpX in cyanobacteria remain unclear. This study aimed to decipher the unique contributions and regulatory networks of ClpX in the model cyanobacterium Synechocystis sp. PCC 6803 (hereafter Synechocystis). We showed that the interruption of clpX led to slower growth, decreased high light tolerance, and impaired photosynthetic cyclic electron transfer. A quantitative proteomic strategy was employed to globally identify ClpX-regulated proteins in Synechocystis cells. In total, we identified 172 differentially expressed proteins (DEPs) upon the interruption of clpX. Functional analysis revealed that these DEPs are involved in diverse biological processes, including glycolysis, nitrogen assimilation, photosynthetic electron transport, ATP-binding cassette (ABC) transporters, and two-component signal transduction. The expression of 24 DEPs was confirmed by parallel reaction monitoring (PRM) analysis. In particular, many hypothetical or unknown proteins were found to be regulated by ClpX, providing new candidates for future functional studies on ClpX. Together, our study provides a comprehensive ClpX-regulated protein network, and the results serve as an important resource for understanding protein quality control systems in cyanobacteria.

An insight into the mechanisms of homeostasis in extremophiles

The homeostasis of extremophiles is one that is a diamond hidden in the rough. The way extremophiles adapt to their extreme environments gives a clue into the true extent of what is possible when it comes to life. The discovery of new extremophiles is ever-expanding and an explosion of knowledge surrounding their successful existence in extreme environments is obviously perceived in scientific literature. The present review paper aims to provide a comprehensive view on the different mechanisms governing the extreme adaptations of extremophiles, along with insights and discussions on what the limits of life can possibly be. The membrane adaptations that are vital for survival are discussed in detail. It was found that there are many alterations in the genetic makeup of such extremophiles when compared to their mesophilic counterparts. Apart from the several proteins involved, the significance of chaperones, efflux systems, DNA repair proteins and a host of other enzymes that adapt to maintain functionality, are enlisted, and explained. A deeper understanding of the underlying mechanisms could have a plethora of applications in the industry. There are cases when certain microbes can withstand extreme doses of antibiotics. Such microbes accumulate numerous genetic elements (or plasmids) that possess genes for multiple drug resistance (MDR). A deeper understanding of such mechanisms helps in the development of potential approaches and therapeutic schemes for treating pathogen-mediated outbreaks. An in-depth analysis of the parameters - radiation, pressure, temperature, pH value and metal resistance - are discussed in this review, and the key to survival in these precarious niches is described.

A broadly applicable, stress-mediated bacterial death pathway regulated by the phosphotransferase system (PTS) and the cAMP-Crp cascade

Recent work indicates that killing of bacteria by diverse antimicrobial classes can involve reactive oxygen species (ROS), as if a common, self-destructive response to antibiotics occurs. However, the ROS-bacterial death theory has been challenged. To better understand stress-mediated bacterial death, we enriched spontaneous antideath mutants of Escherichia coli that survive treatment by diverse bactericidal agents that include antibiotics, disinfectants, and environmental stressors, without a priori consideration of ROS. The mutants retained bacteriostatic susceptibility, thereby ruling out resistance. Surprisingly, pan-tolerance arose from carbohydrate metabolism deficiencies in ptsI (phosphotransferase) and cyaA (adenyl cyclase); these genes displayed the activity of upstream regulators of a widely shared, stress-mediated death pathway. The antideath effect was reversed by genetic complementation, exogenous cAMP, or a Crp variant that bypasses cAMP binding for activation. Downstream events comprised a metabolic shift from the TCA cycle to glycolysis and to the pentose phosphate pathway, suppression of stress-mediated ATP surges, and reduced accumulation of ROS. These observations reveal how upstream signals from diverse stress-mediated lesions stimulate shared, late-stage, ROS-mediated events. Cultures of these stable, pan-tolerant mutants grew normally and were therefore distinct from tolerance derived from growth defects described previously. Pan-tolerance raises the potential for unrestricted disinfectant use to contribute to antibiotic tolerance and resistance. It also weakens host defenses, because three agents (hypochlorite, hydrogen peroxide, and low pH) affected by pan-tolerance are used by the immune system to fight infections. Understanding and manipulating the PtsI-CyaA-Crp–mediated death process can help better control pathogens and maintain beneficial microbiota during antimicrobial treatment.

Frequencies and characteristics of genome-wide recombination in Streptococcus agalactiae, Streptococcus pyogenes, and Streptococcus suis

Streptococcus consists of ecologically diverse species, some of which are important pathogens of humans and animals. We sought to quantify and compare the frequencies and characteristics of within-species recombination in the pan-genomes of Streptococcus agalactiae, Streptococcus pyogenes and Streptococcus suis. We used 1081, 1813 and 1204 publicly available genome sequences of each species, respectively. Based on their core genomes, S. agalactiae had the highest relative rate of recombination to mutation (11.5743) compared to S. pyogenes (1.03) and S. suis (0.57). The proportion of the species pan-genome that have had a history of recombination was 12.85%, 24.18% and 20.50% of the pan-genomes of each species, respectively. The composition of recombining genes varied among the three species, and some of the most frequently recombining genes are implicated in adhesion, colonization, oxidative stress response and biofilm formation. For each species, a total of 22.75%, 29.28% and 18.75% of the recombining genes were associated with prophages. The cargo genes of integrative conjugative elements and integrative and mobilizable elements contained genes associated with antimicrobial resistance and virulence. Homologous recombination and mobilizable pan-genomes enable the creation of novel combinations of genes and sequence variants, and the potential for high-risk clones to emerge.

Comparative Genomic Analysis of Streptococcus dysgalactiae subspecies dysgalactiae Isolated From Bovine Mastitis in China

Streptococcus dysgalactiae subsp. dysgalactiae (SDSD) is one of the most prevalent pathogens causing bovine mastitis worldwide. However, there is a lack of comprehensive information regarding genetic diversity, complete profiles of virulence factors (VFs), and antimicrobial resistance (AMR) genes for SDSD associated with bovine mastitis in China. In this study, a total of 674 milk samples, including samples from 509 clinical and 165 subclinical mastitis cases, were collected from 17 herds in 7 provinces in China from November 2016 to June 2019. All SDSD isolates were included in phylogenetic analysis based on 16S rRNA and multi-locus sequence typing (MLST). In addition, whole genome sequencing was performed on 12 representative SDSD isolates to screen for VFs and AMR genes and to define pan-, core and accessory genomes. The prevalence of SDSD from mastitis milk samples was 7.57% (51/674). According to phylogenetic analysis based on 16S rRNA, 51 SDSD isolates were divided into 4 clusters, whereas based on MLST, 51 SDSD isolates were identified as 11 sequence types, including 6 registered STs and 5 novel STs (ST521, ST523, ST526, ST527, ST529) that belonged to 2 distinct clonal complexes (CCs) and 4 singletons. Based on WGS information, 108 VFs genes in 12 isolates were determined in 11 categories. In addition, 23 AMR genes were identified in 11 categories. Pan-, core and accessory genomes were composed of 2,663, 1,633 and 699 genes, respectively. These results provided a comprehensive profiles of SDSD virulence and resistance genes as well as phylogenetic relationships among mastitis associated SDSD in North China.

ATP-Dependent Protease ClpP and Its Subunits ClpA, ClpB, and ClpX Involved in the Field Bismerthiazol Resistance in Xanthomonas oryzae pv. oryzae

Resistance of Xanthomonas oryzae pv. oryzae, which causes rice bacterial leaf blight, to bismerthiazol has been detected in China since the 1990s. The strains resistant to bismerthiazol on rice plants were more sensitive to bismerthiazol than wild-type (WT) strains in vitro. Here, quantitative PCR was applied to detect the fold expression of adenosine triphosphate-dependent proteases, ClpP and its subunits, which withstand stresses including bactericides in bismerthiazol-resistant strains and their parental susceptible WT strain (ZJ173). Results showed that the expression of ClpP and its subunits was higher in bismerthiazol-resistant strains than in ZJ173. They were upregulated during the early growth phase and downregulated during the middle growth phase in ZJ173 treated with bismerthiazol but did not change in the resistant strains. ClpP and its subunits were overexpressed in X. oryzae pv. oryzae in this study; the higher expression of these genes increased sensitivity in vitro and increased resistance in vivo to bismerthiazol. Bismerthiazol inhibition of exopolysaccharide (EPS) production, biofilm production, and motility was also lower in ClpP and its subunits' overexpression mutants of X. oryzae pv. oryzae. The deletion mutants of ClpP and its subunits in ZJ173 decreased pathogenicity, biofilm production, swimming ability, EPS production, and growth in low-nutrient environments. Moreover, ClpP and its subunits may act downstream of the histidine utilization pathway, which could be inhibited by bismerthiazol in X. oryzae pv. oryzae. Taken together, our results indicated that ClpP and its subunits of X. oryzae pv. oryzae influenced resistance to bismerthiazol.

Genetic analysis and pathogenicity of different sequence types of Streptococcus suis isolated from pigs in southern China

In this study, 52 Streptococcus suis isolates from pigs in southern China were divided into four known sequence types (STs) and six new STs, using multilocus sequence typing. Ten representative isolates were selected from 10 STs for the analysis of whole genome sequences. Virulence was assessed in 10 isolates, which were classified into three pathogenic groups. The prevalence of virulence-associated factors in the moderately pathogenic group was higher than that in the highly pathogenic group. The isolates from ST1 complex and serotype 2 were allocated to the moderately pathogenic group, while the isolates from the highly pathogenic group belonged to the non-ST1 complex and non-serotype 2. Three clusters were obtained based on multilocus sequence typing sequences: cluster III isolates from the nasal cavity of healthy pigs were classified into the highly pathogenic group and showed many peculiarities compared with cluster I and II isolates in virulence genotypes, genetic typing and pathogenesis, indicating a potential independent evolutionary line. Our results suggest that S. suis infections in China are becoming more complicated with constantly mutating isolates, which makes it difficult to distinguish their virulence by recognized typing methods. Thus, increased investigation and monitoring of these infections should be a priority for the swine industry in China.

Comparative Proteomic Analyses Between Biofilm-Forming and Non-biofilm-Forming Strains of Corynebacterium pseudotuberculosis Isolated From Goats

Caseous lymphadenitis (CLA) is a chronic disease that affects small ruminants and causes economic losses in the associated breeding system. The causative agent of CLA is Corynebacterium pseudotuberculosis, a Gram-positive bacterium that exhibits tropism for external and internal lymph nodes and induces abscess formation in the host. Bacterial communities often produce a biofilm matrix that serves various functions, including protection against hostile environmental conditions, antibiotics, and the host immune response. Although biofilm formation has been reported for C. pseudotuberculosis, not all strains demonstrate this property in culture. In this work, we report the first comparative proteomic analysis of one biofilm-forming (CAPJ4) and one biofilm-non-forming strain (CAP3W) of C. pseudotuberculosis isolated from goats. Bacterial whole cell protein extracts were obtained for mass spectrometry analyses. Using LC-MS/MS, our studies reveal three and four proteins exclusively found in the CAPJ4 and CAP3W proteome, respectively. In addition, label-free quantitative analysis identified 40 proteins showing at-least 2-fold higher values in CAPJ4 compared CAP3W proteome Notably, CAPJ4 differentially synthesized the penicillin-binding protein, which participates in the formation of peptidoglycans. CAPJ4 also exhibited upregulation of N-acetylmuramoyl-L-alanine amidase and galactose-1-phosphate uridylyltransferase, which are involved in biofilm formation and exopolysaccharide biosynthesis. Here, we demonstrate that biofilm formation in C. pseudotuberculosis is likely associated with specific proteins, some of which were previously shown to be associated with virulence and biofilm formation in other organisms. Our findings may drive studies related to the bacterial mechanisms involved in the biofilm formation, in addition to providing targets for the treatment of CLA.

Streptococcus suis pathogenesis-A diverse array of virulence factors for a zoonotic lifestyle

Streptococcus suis is a major cause of respiratory tract and invasive infections in pigs and is responsible for a substantial disease burden in the pig industry. S. suis is also a significant cause of bacterial meningitis in humans, particularly in South East Asia. S. suis expresses a wide array of virulence factors, and although many are described as being required for disease, no single factor has been demonstrated to be absolutely required. The lack of uniform distribution of known virulence factors among individual strains and lack of evidence that any particular virulence factor is essential for disease makes the development of vaccines and treatments challenging. Here we review the current understanding of S. suis virulence factors and their role in the pathogenesis of this important zoonotic pathogen.

Functional Characterization and Transcriptional Analysis of clpP of Xanthomonas campestris pv. campestris

The caseinolytic protease (Clp) system is essential for survival under stress conditions and for virulence in several pathogenic bacteria. Xanthomonas campestris pv. campestris (Xcc) is a plant pathogen which causes black rot disease in crucifers. In this study, the Xcc clpP gene which is annotated to encode the proteolytic core of Clp was characterized. Mutation of clpP resulted in susceptibility to high temperature and puromycin stresses. Site-directed mutagenesis revealed that S105, H130, and D179 are critical amino acid residues for ClpP function in puromycin tolerance. Inactivation of clpP also revealed an attenuation of virulence on the host plant and a reduction in the production of extracellular cellulase, mannanase, pectinase, and protease. The affected phenotypes of the clpP mutant could be complemented to wild-type levels by the intact clpP gene. Transcriptional analysis revealed that expression of clpP is induced under heat shock condition.

Role of the ClpX from Corynebacterium crenatum involved in stress responses and energy metabolism

ClpX and ClpP are involved in many important functions, including stress responses and energy metabolism, in microorganisms. However, the ClpX and ClpP of microbes used in industrial scale have rarely been studied. Industrial bacterial fermentation experiences a variety of stresses, and energy metabolism is extremely important for industrial bacteria. Thus, the role played by the ClpX and ClpP of industrial bacteria in fermentation should be investigated. Most microorganisms have a single clpP gene, while Corynebacterium crenatum AS 1.542 possesses two clpPs. Herein, the clpX, clpP1, and clpP2 of C. crenatum were cloned, and its fusion protein was expressed and characterized. We also constructed clpX deletion mutant and complementation strain. Results indicate that ClpX serves an important function in thermal, pH, and ethanol stresses. It is also involved in NADPH synthesis and glucose consumption during fermentation.