Opposing effects of acellular and whole cell pertussis vaccines on Bordetella pertussis biofilm formation, Siglec-F+ neutrophil recruitment and bacterial clearance in mouse nasal tissues

Despite global vaccination, pertussis caused by Bordetella pertussis (Bp) is resurging. Pertussis resurgence is correlated with the switch from whole cell vaccines (wPV) that elicit TH1/TH17 polarized immune responses to acellular pertussis vaccines (aPV) that elicit primarily TH2 polarized immune responses. One explanation for the increased incidence in aPV-immunized individuals is the lack of bacterial clearance from the nose. To understand the host and bacterial mechanisms that contribute to Bp persistence, we evaluated bacterial localization and the immune response in the nasal associated tissues (NT) of naïve and immunized mice following Bp challenge. Bp resided in the NT of unimmunized and aPV-immunized mice as biofilms. In contrast, Bp biofilms were not observed in wPV-immunized mice. Following infection, Siglec-F+ neutrophils, critical for eliminating Bp from the nose, were recruited to the nose at higher levels in wPV immunized mice compared to aPV immunized mice. Consistent with this observation, the neutrophil chemokine CXCL1 was only detected in the NT of wPV immunized mice. Importantly, the bacteria and immune cells were primarily localized within the NT and were not recovered by nasal lavage (NL). Together, our data suggest that the TH2 polarized immune response generated by aPV vaccination facilitates persistence in the NT by impeding the infiltration of immune effectors and the eradication of biofilms In contrast, the TH1/TH17 immune phenotype generated by wPV, recruits Siglec-F+ neutrophils that rapidly eliminate the bacterial burden and prevent biofilm establishment. Thus, our work shows that aPV and wPV have opposing effects on Bp biofilm formation in the respiratory tract and provides a mechanistic explanation for the inability of aPV vaccination to control bacterial numbers in the nose and prevent transmission.

Systemic priming and intranasal booster with a BcfA-adjuvanted acellular pertussis vaccine generates CD4+ IL-17+ nasal tissue resident T cells and reduces B. pertussis nasal colonization

Introduction

Resurgence of pertussis, caused by Bordetella pertussis, necessitates novel vaccines and vaccination strategies to combat this disease. Alum-adjuvanted acellular pertussis vaccines (aPV) delivered intramuscularly reduce bacterial numbers in the lungs of immunized animals and humans, but do not reduce nasal colonization. Thus, aPV-immunized individuals are sources of community transmission. We showed previously that modification of a commercial aPV (Boostrix) by addition of the Th1/17 polarizing adjuvant Bordetella Colonization Factor A (BcfA) attenuated Th2 responses elicited by alum and accelerated clearance of B. pertussis from mouse lungs. Here we tested whether a heterologous immunization strategy with systemic priming and mucosal booster (prime-pull) would reduce nasal colonization.

Methods

Adult male and female mice were immunized intramuscularly (i.m.) with aPV or aPV/BcfA and boosted either i.m. or intranasally (i.n.) with the same formulation. Tissue-resident memory (TRM) responses in the respiratory tract were quantified by flow cytometry, and mucosal and systemic antibodies were quantified by ELISA. Immunized and naïve mice were challenged i.n. with Bordetella pertussis and bacterial load in the nose and lungs enumerated at days 1-14 post-challenge.

Results

We show that prime-pull immunization with Boostrix plus BcfA (aPV/BcfA) generated IFNγ+ and IL-17+ CD4+ lung resident memory T cells (TRM), and CD4+IL-17+ TRM in the nose. In contrast, aPV alone delivered by the same route generated IL-5+ CD4+ resident memory T cells in the lungs and nose. Importantly, nasal colonization was only reduced in mice immunized with aPV/BcfA by the prime-pull regimen.

Conclusions

These results suggest that TH17 polarized TRM generated by aPV/BcfA may reduce nasal colonization thereby preventing pertussis transmission and subsequent resurgence.

Prime-Pull Immunization of Mice with a BcfA-Adjuvanted Vaccine Elicits Sustained Mucosal Immunity That Prevents SARS-CoV-2 Infection and Pathology

Vaccines against SARS-CoV-2 that induce mucosal immunity capable of preventing infection and disease remain urgently needed. In this study, we demonstrate the efficacy of Bordetella colonization factor A (BcfA), a novel bacteria-derived protein adjuvant, in SARS-CoV-2 spike-based prime-pull immunizations. We show that i.m. priming of mice with an aluminum hydroxide- and BcfA-adjuvanted spike subunit vaccine, followed by a BcfA-adjuvanted mucosal booster, generated Th17-polarized CD4+ tissue-resident memory T cells and neutralizing Abs. Immunization with this heterologous vaccine prevented weight loss following challenge with mouse-adapted SARS-CoV-2 (MA10) and reduced viral replication in the respiratory tract. Histopathology showed a strong leukocyte and polymorphonuclear cell infiltrate without epithelial damage in mice immunized with BcfA-containing vaccines. Importantly, neutralizing Abs and tissue-resident memory T cells were maintained until 3 mo postbooster. Viral load in the nose of mice challenged with the MA10 virus at this time point was significantly reduced compared with naive challenged mice and mice immunized with an aluminum hydroxide-adjuvanted vaccine. We show that vaccines adjuvanted with alum and BcfA, delivered through a heterologous prime-pull regimen, provide sustained protection against SARS-CoV-2 infection.

Architecture and matrix assembly determinants of Bordetella pertussis biofilms on primary human airway epithelium

Traditionally, whooping cough or pertussis caused by the obligate human pathogen Bordetella pertussis (Bp) is described as an acute disease with severe symptoms. However, many individuals who contract pertussis are either asymptomatic or show very mild symptoms and yet can serve as carriers and sources of bacterial transmission. Biofilms are an important survival mechanism for bacteria in human infections and disease. However, bacterial determinants that drive biofilm formation in humans are ill-defined. In the current study, we show that Bp infection of well-differentiated primary human bronchial epithelial cells leads to formation of bacterial aggregates, clusters, and highly structured biofilms which are colocalized with cilia. These findings mimic observations from pathological analyses of tissues from pertussis patients. Distinct arrangements (mono-, bi-, and tri-partite) of the polysaccharide Bps, extracellular DNA, and bacterial cells were visualized, suggesting complex heterogeneity in bacteria-matrix interactions. Analyses of mutant biofilms revealed positive roles in matrix production, cell cluster formation, and biofilm maturity for three critical Bp virulence factors: Bps, filamentous hemagglutinin, and adenylate cyclase toxin. Adherence assays identified Bps as a new Bp adhesin for primary human airway cells. Taken together, our results demonstrate the multi-factorial nature of the biofilm extracellular matrix and biofilm development process under conditions mimicking the human respiratory tract and highlight the importance of model systems resembling the natural host environment to investigate pathogenesis and potential therapeutic strategies.

Development of carbohydrate based next-generation anti-pertussis vaccines

Pertussis is a highly contagious respiratory disease caused by the Gram-negative bacterial pathogen, Bordetella pertussis. Despite high global vaccination rates, pertussis is resurging worldwide. Here we discuss the development of current pertussis vaccines and their limitations, which highlight the need for new vaccines that can protect against the disease and prevent development of the carrier state, thereby reducing transmission. The lipo-oligosaccharide of Bp is an attractive antigen for vaccine development as the anti-glycan antibodies could have bactericidal activities. The structure of the lipo-oligosaccharide has been determined and its immunological properties analyzed. Strategies enabling the expression, isolation, and bioconjugation have been presented. However, obtaining the saccharide on a large scale with high purity remains one of the main obstacles. Chemical synthesis provides a complementary approach to accessing the carbohydrate epitopes in a pure and structurally well-defined form. The first total synthesis of the non-reducing end pertussis pentasaccharide is discussed. The conjugate of the synthetic glycan with a powerful immunogenic carrier, bacteriophage Qβ, results in high levels and long-lasting anti-glycan IgG antibodies, paving the way for the development of a new generation of anti-pertussis vaccines with high bactericidal activities and biocompatibilities.

Chemical Synthesis and Immunological Evaluation of a Pentasaccharide Bearing Multiple Rare Sugars as a Potential Anti-pertussis Vaccine

With the infection rate of Bordetella pertussis at a 60-year high, there is an urgent need for new anti-pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis-LPS-like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti-glycan IgG responses with IgG titers reaching several million enzyme-linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qβ-glycan as a new anti-pertussis vaccine.

Structural mechanism for regulation of DNA binding of BpsR, a Bordetella regulator of biofilm formation, by 6-hydroxynicotinic acid

Bordetella bacteria are respiratory pathogens of humans, birds, and livestock. Bordetella pertussis the causative agent of whopping cough remains a significant health issue. The transcriptional regulator, BpsR, represses a number of Bordetella genes relating to virulence, cell adhesion, cell motility, and nicotinic acid metabolism. DNA binding of BpsR is allosterically regulated by interaction with 6-hydroxynicotinic acid (6HNA), the first product in the nicotinic acid degradation pathway. To understand the mechanism of this regulation, we have determined the crystal structures of BpsR and BpsR in complex with 6HNA. The structures reveal that BpsR binding of 6HNA induces a conformational change in the protein to prevent DNA binding. We have also identified homologs of BpsR in other Gram negative bacteria in which the amino acids involved in recognition of 6HNA are conserved, suggesting a similar mechanism for regulating nicotinic acid degradation.

A porcine xenograft-derived bone scaffold is a biocompatible bone graft substitute: An assessment of cytocompatibility and the alpha-Gal epitope

BACKGROUND

Xenografts are an attractive alternative to traditional bone grafts because of the large supply from donors with predictable morphology and biology as well as minimal risk of human disease transmission. Clinical series involving xenograft bone transplantation, most commonly from bovine sources, have reported poor results with frequent graft rejection and failure to integrate with host tissue. Failures have been attributed to residual alpha-Gal epitope in the xenograft which humans produce natural antibody against. To the authors' knowledge, there is currently no xenograft-derived bone graft substitute that has been adopted by orthopedic surgeons for routine clinical use.

METHODS

In the current study, a bone scaffold intended to serve as a bone graft substitute was derived from porcine cancellous bone using a tissue decellularization and chemical oxidation protocol. In vitro cytocompatibility, pathogen clearance, and alpha-Gal quantification tests were used to assess the safety of the bone scaffold intended for human use.

RESULTS

In vitro studies showed the scaffold was free of processing chemicals and biocompatible with mouse and human cell lines. When bacterial and viral pathogens were purposefully added to porcine donor tissue, processing successfully removed these pathogens to comply with sterility assurance levels established by allograft tissue providers. Critically, 98.5% of the alpha-Gal epitope was removed from donor tissue after decellularization as shown by ELISA inhibition assay and immunohistochemical staining.

CONCLUSIONS

The current investigation supports the biologic safety of bone scaffolds derived from porcine donors using a decellularization protocol that meets current sterility assurance standards. The majority of the highly immunogenic xenograft carbohydrate was removed from donor tissue, and these findings support further in vivo investigation of xenograft-derived bone tissue for orthopedic clinical application.

Evaluation of Host-Pathogen Responses and Vaccine Efficacy in Mice

Vaccines are a 20^th century medical marvel. They have dramatically reduced the morbidity and mortality caused by infectious diseases and contributed to a striking increase in life expectancy around the globe. Nonetheless, determining vaccine efficacy remains a challenge. Emerging evidence suggests that the current acellular vaccine (aPV) for Bordetella pertussis (B. pertussis) induces suboptimal immunity. Therefore, a major challenge is designing a next-generation vaccine that induces protective immunity without the adverse side effects of a whole-cell vaccine (wPV). Here we describe a protocol that we used to test the efficacy of a promising, novel adjuvant that skews immune responses to a protective Th1/Th17 phenotype and promotes a better clearance of a B. pertussis challenge from the murine respiratory tract. This article describes the protocol for mouse immunization, bacterial inoculation, tissue harvesting, and analysis of immune responses. Using this method, within our model, we have successfully elucidated crucial mechanisms elicited by a promising, next-generation acellular pertussis vaccine. This method can be applied to any infectious disease model in order to determine vaccine efficacy.

Structural Analysis of Bordetella pertussis Biofilms by Confocal Laser Scanning Microscopy

Biofilms are sessile communities of microbial cells embedded in a self-produced or host-derived exopolymeric matrix. Biofilms can both be beneficial or detrimental depending on the surface. Compared to their planktonic counterparts, biofilm cells display enhanced resistance to killing by environmental threats, chemicals, antimicrobials and host immune defenses. When in biofilms, the microbial cells interact with each other and with the surface to develop architecturally complex multi-dimensional structures. Numerous imaging techniques and tools are currently available for architectural analyses of biofilm communities. This allows examination of biofilm development through acquisition of three-dimensional images that can render structural features of the sessile community. A frequently utilized tool is Confocal Laser Scanning Microscopy. We present a detailed protocol to grow, observe and analyze biofilms of the respiratory human pathogen, Bordetella pertussis in space and time.

The Transcriptional Regulator BpsR Controls the Growth of Bordetella bronchiseptica by Repressing Genes Involved in Nicotinic Acid Degradation

Many of the pathogenic species of the genus Bordetella have an absolute requirement for nicotinic acid (NA) for laboratory growth. These Gram-negative bacteria also harbor a gene cluster homologous to the nic cluster of Pseudomonas putida which is involved in the aerobic degradation of NA and its transcriptional control. We report here that BpsR, a negative regulator of biofilm formation and Bps polysaccharide production, controls the growth of Bordetella bronchiseptica by repressing the expression of nic genes. The severe growth defect of the ΔbpsR strain in Stainer-Scholte medium was restored by supplementation with NA, which also functioned as an inducer of nic genes at low micromolar concentrations that are usually present in animals and humans. Purified BpsR protein bound to the nic promoter region, and its DNA binding activity was inhibited by 6-hydroxynicotinic acid (6-HNA), the first metabolite of the NA degradative pathway. Reporter assays with the isogenic mutant derivative of the wild-type (WT) strain harboring deletion in nicA, which encodes a putative nicotinic acid hydroxylase responsible for conversion of NA to 6-HNA, showed that 6-HNA is the actual inducer of the nic genes in the bacterial cell. Gene expression profiling further showed that BpsR dually activated and repressed the expression of genes associated with pathogenesis, transcriptional regulation, metabolism, and other cellular processes. We discuss the implications of these findings with respect to the selection of pyridines such as NA and quinolinic acid for optimum bacterial growth depending on the ecological niche.IMPORTANCE BpsR, the previously described regulator of biofilm formation and Bps polysaccharide production, controls Bordetella bronchiseptica growth by regulating the expression of genes involved in the degradation of nicotinic acid (NA). 6-Hydroxynicotinic acid (6-HNA), the first metabolite of the NA degradation pathway prevented BpsR from binding to DNA and was the actual in vivo inducer. We hypothesize that BpsR enables Bordetella bacteria to efficiently and selectively utilize NA for their survival depending on the environment in which they reside. The results reported herein lay the foundation for future investigations of how BpsR and the alteration of its activity by NA orchestrate the control of Bordetella growth, metabolism, biofilm formation, and pathogenesis.

Intranasal immunization with an acellular pertussis vaccine containing a Th1/17 skewing adjuvant, BcfA, improves B. pertussis clearance from the mouse respiratory tract

Bordetella pertussis is the causative agent of whooping cough, a resurging vaccine-preventable disease. This highly contagious disease is most severe in infants and young children. Current alum-adjuvanted acellular pertussis vaccines (aPV) prevent severe disease but do not prevent nasal carriage and subsequent person-to-person pathogen transmission. The Th1/2 skewed immune response induced by aPV is one potential explanation for this failure. We are testing the hypothesis that modification of current aPV by the addition of an adjuvant, BcfA, that skews immune responses towards the more protective Th1/17 phenotype will improve protection. We also hypothesize that changing the delivery route from intramuscular (i.m) to intranasal (i.n) administration will generate mucosal immunity and further improve protection. In the established mouse model of B. pertussis infection, we found that i.m. immunization of mice with an experimental aPV containing BcfA and alum as the adjuvants significantly reduced bacterial numbers in the lungs compared to an alum-adjuvanted vaccine alone. Further, i.n administration of the BcfA+alum containing vaccine provided better protection against colonization of the trachea and lungs than i.m. immunization. Alum-induced Th2 cytokine responses were reduced by addition of BcfA, and were further reduced by i.n. vaccine delivery. Thus, a revised aPV that includes BcfA, administered i.n, may improve protection against B. pertussis infection compared with current formulations and delivery method.

PgaB orthologues contain a glycoside hydrolase domain that cleaves deacetylated poly-β(1,6)-N-acetylglucosamine and can disrupt bacterial biofilms

Poly-β(1,6)-N-acetyl-D-glucosamine (PNAG) is a major biofilm component of many pathogenic bacteria. The production, modification, and export of PNAG in Escherichia coli and Bordetella species require the protein products encoded by the pgaABCD operon. PgaB is a two-domain periplasmic protein that contains an N-terminal deacetylase domain and a C-terminal PNAG binding domain that is critical for export. However, the exact function of the PgaB C-terminal domain remains unclear. Herein, we show that the C-terminal domains of Bordetella bronchiseptica PgaB (PgaB_Bb) and E. coli PgaB (PgaB_Ec) function as glycoside hydrolases. These enzymes hydrolyze purified deacetylated PNAG (dPNAG) from Staphylococcus aureus, disrupt PNAG-dependent biofilms formed by Bordetella pertussis, Staphylococcus carnosus, Staphylococcus epidermidis, and E. coli, and potentiate bacterial killing by gentamicin. Furthermore, we found that PgaB_Bb was only able to hydrolyze PNAG produced in situ by the E. coli PgaCD synthase complex when an active deacetylase domain was present. Mass spectrometry analysis of the PgaB-hydrolyzed dPNAG substrate showed a GlcN-GlcNAc-GlcNAc motif at the new reducing end of detected fragments. Our 1.76 Å structure of the C-terminal domain of PgaB_Bb reveals a central cavity within an elongated surface groove that appears ideally suited to recognize the GlcN-GlcNAc-GlcNAc motif. The structure, in conjunction with molecular modeling and site directed mutagenesis led to the identification of the dPNAG binding subsites and D474 as the probable catalytic acid. This work expands the role of PgaB within the PNAG biosynthesis machinery, defines a new glycoside hydrolase family GH153, and identifies PgaB as a possible therapeutic agent for treating PNAG-dependent biofilm infections.

From plaque on teeth to infections in the lungs of cystic fibrosis patients, biofilms are a serious health concern and difficult to eradicate. One of the key building blocks involved in biofilm formation are polymeric sugar compounds that are secreted by the bacteria. Our work focuses on the biopolymer poly-β(1,6)-N-acetyl-D-glucosamine (PNAG), which is produced by numerous pathogenic organisms. Deacetylation of PNAG by the N-terminal domain of PgaB is a critical step in polymer maturation and is required for the formation of robust biofilms. Herein, we show that the C-terminal domain of PgaB is a glycoside hydrolase active on partially deacetylated PNAG, and that the enzyme disrupts PNAG-dependent biofilms and potentiates killing by antibiotics. Only deacetylated PNAG could be cleaved, suggesting that PgaB deacetylates and hydrolyses the polymer in sequential order. Analyzing the chemical structure of the cleaved dPNAG fragments revealed a distinct motif of sugar units. Structural and functional studies identify key amino acids positioned in an elongated polymer-binding groove that potentially recognize the sugar motif during cleavage. Our study provides further insight into the mechanism of periplasmic PNAG modification, and suggests PgaB could be utilized as a therapeutic agent to eliminate biofilms.

Bordetella Pertussis virulence factors in the continuing evolution of whooping cough vaccines for improved performance

Despite high vaccine coverage, whooping cough caused by Bordetella pertussis remains one of the most common vaccine-preventable diseases worldwide. Introduction of whole-cell pertussis (wP) vaccines in the 1940s and acellular pertussis (aP) vaccines in 1990s reduced the mortality due to pertussis. Despite induction of both antibody and cell-mediated immune (CMI) responses by aP and wP vaccines, there has been resurgence of pertussis in many countries in recent years. Possible reasons hypothesised for resurgence have ranged from incompliance with the recommended vaccination programmes with the currently used aP vaccine to infection with a resurged clinical isolates characterised by mutations in the virulence factors, resulting in antigenic divergence with vaccine strain, and increased production of pertussis toxin, resulting in dampening of immune responses. While use of these vaccines provide varying degrees of protection against whooping cough, protection against infection and transmission appears to be less effective, warranting continuation of efforts in the development of an improved pertussis vaccine formulations capable of achieving this objective. Major approaches currently under evaluation for the development of an improved pertussis vaccine include identification of novel biofilm-associated antigens for incorporation in current aP vaccine formulations, development of live attenuated vaccines and discovery of novel non-toxic adjuvants capable of inducing both antibody and CMI. In this review, the potential roles of different accredited virulence factors, including novel biofilm-associated antigens, of B. pertussis in the evolution, formulation and delivery of improved pertussis vaccines, with potential to block the transmission of whooping cough in the community, are discussed.

Bordetella biofilms: a lifestyle leading to persistent infections

Bordetella bronchiseptica and B. pertussis are Gram-negative bacteria that cause respiratory diseases in animals and humans. The current incidence of whooping cough or pertussis caused by B. pertussis has reached levels not observed since the 1950s. Although pertussis is traditionally known as an acute childhood disease, it has recently resurged in vaccinated adolescents and adults. These individuals often become silent carriers, facilitating bacterial circulation and transmission. Similarly, vaccinated and non-vaccinated animals continue to be carriers of B. bronchiseptica and shed bacteria resulting in disease outbreaks. The persistence mechanisms of these bacteria remain poorly characterized. It has been proposed that adoption of a biofilm lifestyle allows persistent colonization of the mammalian respiratory tract. The history of Bordetella biofilm research is only a decade long and there is no single review article that has exclusively focused on this area. We systematically discuss the role of Bordetella factors in biofilm development in vitro and in the mouse respiratory tract. We further outline the implications of biofilms to bacterial persistence and transmission in humans and for the design of new acellular pertussis vaccines.

The protein BpsB is a poly-β-1,6-N-acetyl-D-glucosamine deacetylase required for biofilm formation in Bordetella bronchiseptica

Bordetella pertussis and Bordetella bronchiseptica are the causative agents of whooping cough in humans and a variety of respiratory diseases in animals, respectively. Bordetella species produce an exopolysaccharide, known as the Bordetella polysaccharide (Bps), which is encoded by the bpsABCD operon. Bps is required for Bordetella biofilm formation, colonization of the respiratory tract, and confers protection from complement-mediated killing. In this report, we have investigated the role of BpsB in the biosynthesis of Bps and biofilm formation by B. bronchiseptica. BpsB is a two-domain protein that localizes to the periplasm and outer membrane. BpsB displays metal- and length-dependent deacetylation on poly-β-1,6-N-acetyl-d-glucosamine (PNAG) oligomers, supporting previous immunogenic data that suggests Bps is a PNAG polymer. BpsB can use a variety of divalent metal cations for deacetylase activity and showed highest activity in the presence of Ni(2+) and Co(2+). The structure of the BpsB deacetylase domain is similar to the PNAG deacetylases PgaB and IcaB and contains the same circularly permuted family four carbohydrate esterase motifs. Unlike PgaB from Escherichia coli, BpsB is not required for polymer export and has unique structural differences that allow the N-terminal deacetylase domain to be active when purified in isolation from the C-terminal domain. Our enzymatic characterizations highlight the importance of conserved active site residues in PNAG deacetylation and demonstrate that the C-terminal domain is required for maximal deacetylation of longer PNAG oligomers. Furthermore, we show that BpsB is critical for the formation and complex architecture of B. bronchiseptica biofilms.

The Bordetella pertussis Bps polysaccharide enhances lung colonization by conferring protection from complement-mediated killing

Bordetella pertussis is a human-restricted Gram-negative bacterial pathogen that causes whooping cough or pertussis. Pertussis is the leading vaccine preventable disease that is resurging in the USA and other parts of the developed world. There is an incomplete understanding of the mechanisms by which B. pertussis evades killing and clearance by the complement system, a first line of host innate immune defence. The present study examined the role of the Bps polysaccharide to resist complement activity in vitro and in the mouse respiratory tract. The isogenic bps mutant strain containing a large non-polar in-frame deletion of the bpsA-D locus was more sensitive to serum and complement mediated killing than the WT strain. As determined by Western blotting, flow cytometry and electron microscopic studies, the heightened sensitivity of the mutant strain was due to enhanced deposition of complement proteins and the formation of membrane attack complex, the end-product of complement activation. Bps was sufficient to confer complement resistance as evidenced by a Bps-expressing Escherichia coli being protected by serum killing. Additionally, Western blotting and flow cytometry assays revealed that Bps inhibited the deposition of complement proteins independent of other B. pertussis factors. The bps mutant strain colonized the lungs of complement-deficient mice at higher levels than that observed in C57Bl/6 mice. These results reveal a previously unknown interaction between Bps and the complement system in controlling B. pertussis colonization of the respiratory tract. These findings also make Bps a potential target for the prevention and therapy of whooping cough.

The genetic composition of Oxalobacter formigenes and its relationship to colonization and calcium oxalate stone disease

Oxalobacter formigenes is a unique intestinal organism that relies on oxalate degradation to meet most of its energy and carbon needs. A lack of colonization is a risk factor for calcium oxalate stone disease. Protection against calcium oxalate stone disease appears to be due to the oxalate degradation that occurs in the gut on low calcium diets with a possible further contribution from intestinal oxalate secretion. Much remains to be learned about how the organism establishes and maintains gut colonization and the precise mechanisms by which it modifies stone risk. The sequencing and annotation of the genomes of a Group 1 and a Group 2 strain of O. formigenes should provide the informatic tools required for the identification of the genes and pathways associated with colonization and survival. In this review we have identified genes that may be involved and where appropriate suggested how they may be important in calcium oxalate stone disease. Elaborating the functional roles of these genes should accelerate our understanding of the organism and clarify its role in preventing stone formation.

Transcriptome profiling reveals stage-specific production and requirement of flagella during biofilm development in Bordetella bronchiseptica

We have used microarray analysis to study the transcriptome of the bacterial pathogen Bordetella bronchiseptica over the course of five time points representing distinct stages of biofilm development. The results suggest that B. bronchiseptica undergoes a coordinately regulated gene expression program similar to a bacterial developmental process. Expression and subsequent production of the genes encoding flagella, a classical Bvg⁻ phase phenotype, occurs and is under tight regulatory control during B. bronchiseptica biofilm development. Using mutational analysis, we demonstrate that flagella production at the appropriate stage of biofilm development, i.e. production early subsequently followed by repression, is required for robust biofilm formation and maturation. We also demonstrate that flagella are necessary and enhance the initial cell-surface interactions, thereby providing mechanistic information on the initial stages of biofilm development for B. bronchiseptica. Biofilm formation by B. bronchiseptica involves the production of both Bvg-activated and Bvg-repressed factors followed by the repression of factors that inhibit formation of mature biofilms.

Bordetella bronchiseptica in a paediatric cystic fibrosis patient: possible transmission from a household cat

Bordetella bronchiseptica is a zoonotic respiratory pathogen commonly found in domesticated farm and companion animals, including dogs and cats. Here, we report isolation of B. bronchiseptica from a sputum sample of a cystic fibrosis patient recently exposed to a kitten with an acute respiratory illness. Genetic characterization of the isolate and comparison with other isolates of human or feline origin strongly suggest that the kitten was the source of infection.

FHA-mediated cell-substrate and cell-cell adhesions are critical for Bordetella pertussis biofilm formation on abiotic surfaces and in the mouse nose and the trachea

Bordetella spp. form biofilms in the mouse nasopharynx, thereby providing a potential mechanism for establishing chronic infections in humans and animals. Filamentous hemagglutinin (FHA) is a major virulence factor of B. pertussis, the causative agent of the highly transmissible and infectious disease, pertussis. In this study, we dissected the role of FHA in the distinct biofilm developmental stages of B. pertussis on abiotic substrates and in the respiratory tract by employing a murine model of respiratory biofilms. Our results show that the lack of FHA reduced attachment and decreased accumulation of biofilm biomass on artificial surfaces. FHA contributes to biofilm development by promoting the formation of microcolonies. Absence of FHA from B. pertussis or antibody-mediated blockade of surface-associated FHA impaired the attachment of bacteria to the biofilm community. Exogenous addition of FHA resulted in a dose-dependent inhibitory effect on bacterial association with the biofilms. Furthermore, we show that FHA is important for the structural integrity of biofilms formed on the mouse nose and trachea. Together, these results strongly support the hypothesis that FHA promotes the formation and maintenance of biofilms by mediating cell-substrate and inter-bacterial adhesions. These discoveries highlight FHA as a key factor in establishing structured biofilm communities in the respiratory tract.

The Bps polysaccharide of Bordetella pertussis promotes colonization and biofilm formation in the nose by functioning as an adhesin

Many respiratory pathogens establish persistent infection or a carrier state in the human nasopharynx without overt disease symptoms but the presence of these in the lungs usually results in disease. Although the anatomy and microenvironments between nasopharynx and lungs are different, a virulence factor with an organ-specific function in the colonization of the nasopharynx is unknown. In contrast to the severity of pertussis and mortality in non-vaccinated young children, Bordetella pertussis results in milder and prolonged cough in vaccinated adolescents and adults. Individuals harbouring bacteria in the nasopharynx serve as reservoirs for intrafamilial and nosocomial transmission. We show that the Bps polysaccharide of B. pertussis is critical for initial colonization of the mouse nose and the trachea but not of the lungs. Our data reveal a biofilm lifestyle for B. pertussis in the nose and the requirement of Bps in this developmental process. Bps functions as an adhesin by promoting adherence of B. pertussis and Escherichia coli to human nasal but not to human lung epithelia. Patient serum specifically recognized Bps suggesting its expression during natural human infections. We describe the first bacterial factor that exhibits a differential role in colonization and adherence between the nasopharynx and the lungs.

Polysaccharides cellulose, poly-beta-1,6-n-acetyl-D-glucosamine, and colanic acid are required for optimal binding of Escherichia coli O157:H7 strains to alfalfa sprouts and K-12 strains to plastic but not for binding to epithelial cells

When Escherichia coli O157:H7 bacteria are added to alfalfa sprouts growing in water, the bacteria bind tightly to the sprouts. In contrast, laboratory K-12 strains of E. coli do not bind to sprouts under similar conditions. The roles of E. coli O157:H7 lipopolysaccharide (LPS), capsular polysaccharide, and exopolysaccharides in binding to sprouts were examined. An LPS mutant had no effect on the binding of the pathogenic strain. Cellulose synthase mutants showed a significant reduction in binding; colanic acid mutants were more severely reduced, and binding by poly-beta-1,6-N-acetylglucosamine (PGA) mutants was barely detectable. The addition of a plasmid carrying a cellulose synthase gene to K-12 strains allowed them to bind to sprouts. A plasmid carrying the Bps biosynthesis genes had only a marginal effect on the binding of K-12 bacteria. However, the introduction of the same plasmid allowed Sinorhizobium meliloti and a nonbinding mutant of Agrobacterium tumefaciens to bind to tomato root segments. These results suggest that although multiple redundant protein adhesins are involved in the binding of E. coli O157:H7 to sprouts, the polysaccharides required for binding are not redundant and each polysaccharide may play a distinct role. PGA, colanic acid, and cellulose were also required for biofilm formation by a K-12 strain on plastic, but not for the binding of E. coli O157:H7 to mammalian cells.

The Bordetella Bps polysaccharide is critical for biofilm development in the mouse respiratory tract

Bordetellae are respiratory pathogens that infect both humans and animals. Bordetella bronchiseptica establishes asymptomatic and long-term to life-long infections of animal nasopharynges. While the human pathogen Bordetella pertussis is the etiological agent of the acute disease whooping cough in infants and young children, it is now being increasingly isolated from the nasopharynges of vaccinated adolescents and adults who sometimes show milder symptoms, such as prolonged cough illness. Although it has been shown that Bordetella can form biofilms in vitro, nothing is known about its biofilm mode of existence in mammalian hosts. Using indirect immunofluorescence and scanning electron microscopy, we examined nasal tissues from mice infected with B. bronchiseptica. Our results demonstrate that a wild-type strain formed robust biofilms that were adherent to the nasal epithelium and displayed architectural attributes characteristic of a number of bacterial biofilms formed on inert surfaces. We have previously shown that the Bordetella Bps polysaccharide encoded by the bpsABCD locus is critical for the stability and maintenance of three-dimensional structures of biofilms. We show here that Bps is essential for the formation of efficient nasal biofilms and is required for the colonization of the nose. Our results document a biofilm lifestyle for Bordetella in mammalian respiratory tracts and highlight the essential role of the Bps polysaccharide in this process and in persistence of the nares.

Differential Bvg phase-dependent regulation and combinatorial role in pathogenesis of two Bordetella paralogs, BipA and BcfA

To successfully colonize their mammalian hosts, many bacteria produce multiple virulence factors that play essential roles in disease processes and pathogenesis. Some of these molecules are adhesins that allow efficient attachment to host cells, a prerequisite for successful host colonization. Bordetella spp. express a number of proteins which either play a direct role in attachment to the respiratory epithelia or exhibit similarity to known bacterial adhesins. One such recently identified protein is BipA. Despite the similarity of BipA to intimins and invasins, deletion of this protein from B. bronchiseptica did not result in any significant defect in respiratory tract colonization. In this study, we identified an open reading frame in B. bronchiseptica, designated bcfA (encoding BcfA [bordetella colonization factor A]), that is similar to bipA. In contrast to the maximal expression of bipA in the Bvg intermediate (Bvg(i)) phase, bcfA is expressed at high levels in both the Bvg(+) and Bvg(i) phases. We show here that BvgA and phosphorylated BvgA bind differentially to the bcfA promoter region. Utilizing immunoblot assays, we found that BcfA is localized to the outer membrane and that it is expressed during animal infection. While deletion of either bipA or bcfA did not significantly affect respiratory tract colonization, concomitant deletion of both genes resulted in a defect in colonization of the rat trachea. Our results indicate that the two paralogous proteins have a combinatorial role in mediating efficient respiratory tract colonization.

Role of a putative polysaccharide locus in Bordetella biofilm development

Bordetellae are gram-negative bacteria that colonize the respiratory tracts of animals and humans. We and others have recently shown that these bacteria are capable of living as sessile communities known as biofilms on a number of abiotic surfaces. During the biofilm mode of existence, bacteria produce one or more extracellular polymeric substances that function, in part, to hold the cells together and to a surface. There is little information on either the constituents of the biofilm matrix or the genetic basis of biofilm development by Bordetella spp. By utilizing immunoblot assays and by enzymatic hydrolysis using dispersin B (DspB), a glycosyl hydrolase that specifically cleaves the polysaccharide poly-beta-1,6-N-acetyl-D-glucosamine (poly-beta-1,6-GlcNAc), we provide evidence for the production of poly-beta-1,6-GlcNAc by various Bordetella species (Bordetella bronchiseptica, B. pertussis, and B. parapertussis) and its role in their biofilm development. We have investigated the role of a Bordetella locus, here designated bpsABCD, in biofilm formation. The bps (Bordetella polysaccharide) locus is homologous to several bacterial loci that are required for the production of poly-beta-1,6-GlcNAc and have been implicated in bacterial biofilm formation. By utilizing multiple microscopic techniques to analyze biofilm formation under both static and hydrodynamic conditions, we demonstrate that the bps locus, although not essential at the initial stages of biofilm formation, contributes to the stability and the maintenance of the complex architecture of Bordetella biofilms.

Bordetella bronchiseptica flagellin is a proinflammatory determinant for airway epithelial cells

Motility is an important virulence phenotype for many bacteria, and flagellin, the monomeric component of flagella, is a potent proinflammatory factor. Of the three Bordetella species, Bordetella pertussis and Bordetella parapertussis are nonmotile human pathogens, while Bordetella bronchiseptica expresses flagellin and causes disease in animals and immunocompromised human hosts. The BvgAS two-component signal transduction system regulates phenotypic-phase transition (Bvg+, Bvg-, and Bvg(i)) in bordetellae. The Bvg- phase of B. bronchiseptica is characterized by the expression of flagellin and the repression of adhesins and toxins necessary for the colonization of the respiratory tract. B. bronchiseptica naturally infects a variety of animal hosts and constitutes an excellent model to study Bordetella pathogenesis. Using in vitro coculture models of bacteria and human lung epithelial cells, we studied the effects of B. bronchiseptica flagellin on host defense responses. Our results show that B. bronchiseptica flagellin is a potent proinflammatory factor that induces chemokine, cytokine, and host defense gene expression. Furthermore, we investigated receptor specificity in the response to B. bronchiseptica flagellin. Our results show that B. bronchiseptica flagellin is able to signal effectively through both human and mouse Toll-like receptor 5.

Mode of action of the Bordetella BvgA protein: transcriptional activation and repression of the Bordetella bronchiseptica bipA promoter

The Bordetella BvgAS signal transduction system controls the transition among at least three known phenotypic phases (Bvg+, Bvg(i), and Bvg-) and the expression of a number of genes which have distinct phase-specific expression profiles. This complex regulation of gene expression along the Bvg signaling continuum is best exemplified by the gene bipA, which is expressed at a low level in the Bvg+ phase, at a maximal level in the Bvg(i) phase, and at undetectable levels in the Bvg- phase. The bipA promoter has multiple BvgA binding sites which play distinct regulatory roles. We had previously speculated that the expression profile of bipA is a consequence of the differential occupancy of the various BvgA binding sites as a result of variation in the levels of phosphorylated BvgA (BvgA-P) inside the cell. In this report, we provide in vitro evidence for this model and show that bipA expression is activated at low concentrations of BvgA-P and is repressed at high concentrations. By using independent DNA binding assays, we demonstrate that under activating conditions there is a synergistic effect on the binding of BvgA and RNA polymerase (RNAP), leading to the formation of open complexes at the promoter. We further show that, under in vitro conditions, when bipA transcription is minimal, there is competition between the binding of RNAP and BvgA-P to the bipA promoter. Our results show that the BvgA binding site IR2 plays a central role in mediating this repression.

The BvgAS signal transduction system regulates biofilm development in Bordetella

The majority of Bordetella sp. virulence determinants are regulated by the BvgAS signal transduction system. BvgAS mediates the control of multiple phenotypic phases and a spectrum of gene expression profiles specific to each phase in response to incremental changes in the concentrations of environmental signals. Studies highlighting the critical role of this signaling circuitry in the Bordetella infectious cycle have focused on planktonically growing bacterial cells. It is becoming increasingly clear that the major mode of bacterial existence in the environment and within the body is a surface-attached state known as a biofilm. Biofilms are defined as consortia of sessile microorganisms that are embedded in a matrix. During routine growth of Bordetella under agitating conditions, we noticed the formation of a bacterial ring at the air-liquid interface of the culture tubes. We show here that this surface adherence property reflects the ability of these organisms to form biofilms. Our data demonstrate that the BvgAS locus regulates biofilm development in Bordetella. The results reported in this study suggest that the Bvg-mediated control in biofilm development is exerted at later time points after the initial attachment of bacteria to the different surfaces. Additionally, we show that these biofilms are highly tolerant of a number of antimicrobials, including the ones that are currently recommended for treatment of veterinary and human infections caused by Bordetella spp. Finally, we discuss the significance of the biofilm lifestyle mode as a potential contributor to persistent infections.

Tropism switching in Bordetella bacteriophage defines a family of diversity-generating retroelements

Bordetella bacteriophages generate diversity in a gene that specifies host tropism. This microevolutionary adaptation is produced by a genetic element that combines the basic retroelement life cycle of transcription, reverse transcription and integration with site-directed, adenine-specific mutagenesis. Central to this process is a reverse transcriptase-mediated exchange between two repeats; one serving as a donor template (TR) and the other as a recipient of variable sequence information (VR). Here we describe the genetic basis for diversity generation. The directionality of information transfer is determined by a 21-base-pair sequence present at the 3' end of VR. On the basis of patterns of marker transfer in response to variant selective pressures, we propose that a TR reverse transcript is mutagenized, integrated into VR as a single non-coding strand, and then partially converted to the parental VR sequence. This allows the diversity-generating system to minimize variability to the subset of bases under selection. Using the Bordetella phage cassette as a signature, we have identified numerous related elements in diverse bacteria. These elements constitute a new family of retroelements with the potential to confer selective advantages to their host genomes.

A phosphorylation site in Bruton's tyrosine kinase selectively regulates B cell calcium signaling efficiency by altering phospholipase C-gamma activation

Loss of function of Bruton's tyrosine kinase (Btk) causes X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency in mice (xid). By using MS analysis and phosphopeptide-specific antibodies, we identified a tyrosine phosphorylation site (Y617) near the carboxyl terminus of the Btk domain from Btk expressed in 293T as well as DT-40 cells. Y617 is conserved in all Tec family kinases except murine Tec. Replacement of Y617 with a negatively charged glutamic acid (E) suppressed Btk-mediated phospholipase Cgamma2 activation and calcium response in DT-40 cells, whereas Akt activation was not affected. The Btk Y617E mutant could partially restore conventional B cell development and proliferation in Btk(-)/Tec(-) mice but failed to rescue CD5(+) B-1 cell development and the TI-II immune response to 2,4,6,-trinitrophenyl-Ficoll. These data suggest that Y617 phosphorylation or a negative charge at this site may down-regulate the function of Btk by selectively suppressing the B cell calcium signaling pathway.

Differential regulation of the Bordetella bipA gene: distinct roles for different BvgA binding sites

The BvgAS signal transduction system of Bordetella controls an entire spectrum of gene expression states in response to differences in environmental conditions. In particular, the Bordetella Bvg-intermediate-phase gene bipA displays a complex regulatory pattern in response to various concentrations of modulators. Expression of bipA is low in the absence of modulating signals, maximal at intermediate concentrations of modulators, and near background levels at high concentrations of modulators. bipA is regulated at the transcriptional level, and the bipA promoter contains multiple BvgA binding sites present both upstream and downstream of the transcriptional initiation site. In vivo transcriptional analyses, utilizing several mutant promoter fusions to the reporter enzyme beta-galactosidase, suggest that the upstream binding site IR1 is essential for expression and that the downstream binding sites IR2 and IR3 are involved in transcriptional repression. Mutations of IR2 or IR3 convert the expression profile of bipA from that of a Bvg-intermediate-specific-phase gene to that of a Bvg(+)-phase gene. To gain insight into the mechanism responsible for differential bipA regulation, DNase I protection studies were conducted with various mutant promoters. These analyses suggest that IR1 and IR2 function as core binding sites and are the primary determinants for the phosphorylation-induced oligomerization of BvgA to the adjacent regions.

Reverse transcriptase-mediated tropism switching in Bordetella bacteriophage

Host-pathogen interactions are often driven by mechanisms that promote genetic variability. We have identified a group of temperate bacteriophages that generate diversity in a gene, designated mtd (major tropism determinant), which specifies tropism for receptor molecules on host Bordetella species. Tropism switching is the result of a template-dependent, reverse transcriptase-mediated process that introduces nucleotide substitutions at defined locations within mtd. This cassette-based mechanism is capable of providing a vast repertoire of potential ligand-receptor interactions.

Diversity in the Bordetella virulence regulon: transcriptional control of a Bvg-intermediate phase gene

The BvgAS signal transduction system controls the expression of at least three distinct phenotypic phases that lie along a continuum of gene expression states. The Bvg+ phase is characterized by the expression of adhesins and toxins, whereas the Bvg- phase is characterized by motility in Bordetella bronchiseptica and the expression of vrg loci in Bordetella pertussis. The Bvg-intermediate (Bvgi) phase is characterized by the absence of Bvg-repressed phenotypes, the expression of some, but not all, Bvg-activated virulence factors and the presence of a recently discovered set of antigens and phenotypes that are unique to this phase. We report here the transcriptional regulation of bipA, the first-identified Bvgi phase gene. We have mapped the bipA promoter and identified numerous BvgA binding sites in the transcriptional control region. Based on these data, we present a model in which phase-dependent expression of bipA results from the spatial distribution and relative affinities of multiple BvgA binding sites relative to the start site of transcription.

ZntR is an autoregulatory protein and negatively regulates the chromosomal zinc resistance operon znt of Staphylococcus aureus

A chromosomally encoded znt operon of Staphylococcus aureus consists of two consecutive putative genes designated zntR and zntA. The zntA gene encodes a transmembrane protein that facilitates extrusion of Zn2+ and Co2+, whereas the zntR gene encodes a putative regulatory protein that controls the expression of the znt operon. The zntR gene was amplified using the polymerase chain reaction, cloned into Escherichia coli for overexpression as His-tagged ZntR and purified by Ni2+-affinity column. His-tag-free ZntR was purified to near homogeneity after digestion with enterokinase. Electrophoretic mobility shift assays (EMSAs) indicated that the ZntR bound to a fragment of DNA corresponding to the chromosomal znt promoter region with an affinity of about 8.0 x 10-12 M. The addition of 25 microM Zn2+ or Co2+ in the binding reaction completely or significantly inhibited association of ZntR with the znt promoter. DNase I footprinting assays identified a ZntR binding site encompassing 49 nucleotides in the znt promoter region that contained repeated TGAA sequences. These sequences have been proposed to be the binding sites for SmtB, a metallorepressor protein from the cyanobacterium Synechococcus, to its corresponding operator/promoter. In vitro transcription assays, using S. aureus RNA polymerase, revealed that ZntR represses transcription from the znt promoter in a concentration-dependent fashion. The EMSAs, DNase I footprinting and in vitro transcription assays indicate that ZntR is a trans-acting repressor protein that binds to the znt promoter region and regulates its own transcription together with that of zntA.

Alternative transcription factor sigmaSB of Staphylococcus aureus: characterization and role in transcription of the global regulatory locus sar

A homolog of the multiple-stress-responsive transcription factor sigmaB of Bacillus subtilis was predicted from the DNA sequence analysis of a region of the Staphylococcus aureus chromosome. A hybrid between the coding sequence of the first 11 amino acids of the gene 10 leader peptide of phage T7 (T7.Tag) and the putative sigB gene of S. aureus was constructed and cloned into Escherichia coli BL21(DE3)pLysS for overexpression from a T7 promoter. A homogeneous preparation of the overproduced protein was obtained by affinity chromatography with a T7.Tag monoclonal antibody coupled to agarose. The amino-terminal amino acid sequence of the first 22 residues of the purified protein matched that deduced from the nucleotide sequence. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified protein, designated sigmaSB, indicated that it migrated as an approximately 39-kDa polypeptide. Promoter-specific transcription from the B. subtilis sigmaB-dependent PB promoter of the sigB operon was stimulated by sigmaSB in a concentration-dependent fashion when reconstituted with the S. aureus core RNA polymerase (RNAP). Specific transcript from the predicted sigmaB-dependent PB promoter of the sigB operon of S. aureus was obtained by the reconstituted RNAP in a runoff transcription reaction. The sar operon of S. aureus contains three promoter elements (P1, P2, and P3) and is known to partly control the synthesis of a number of extracellular toxins and several cell wall proteins. Our in vitro studies revealed that transcription from the P1 promoter is dependent on the primary sigma factor sigmaSA, while that of the P3 promoter is dependent on sigmaSB. As determined by primer extension studies, the 5' end of the sigmaSB-initiated mRNA synthesized in vitro from the sar P3 promoter is in agreement with the 5' end of the cellular RNA.

Characterization of the primary sigma factor of Staphylococcus aureus

RNA polymerase (RNAP) isolated from Staphylococcus aureus is deficient in sigma factor and is poorly active in transcription assays. Based on amino acid sequence homology of the Bacillus subtilis vegetative sigma factor sigmaA and the predicted product of the chromosomally located plaC gene of S. aureus, it was hypothesized that plaC could encode the vegetative sigma factor. We cloned plaC under a T7 promoter and overexpressed it in Escherichia coli strain BL21(DE3)pLysE. The overproduced protein, present in inclusion bodies, was solubilized with guanidine hydrochloride, renatured, and purified by DEAE-Sephacel and Sephadex G-75 chromatography. The purified protein, designated sigmaSA, cross-reacted with the B. subtilis anti-sigmaA antibody. E. coli core RNAP, reconstituted with sigmaSA, initiated promoter-specific transcription from the S. aureus promoters hla, sea, and sec and from the E. coli promoters rpoH P1, rpoH P4, and ColE1 RNA-1, which are recognized by the E. coli sigma70. sigmaSA, when added to the purified RNAP from S. aureus, stimulated transcriptional activity of the RNAP up to 72-fold. As determined by primer extension studies, the 5'-ends of the sigmaSA-initiated mRNAs synthesized in vitro from the agr P2 and sea promoters are in general agreement with the 5'-ends of the cellular RNAs. Disruption of the plaC gene on the S. aureus chromosome was lethal. We conclude that plaC encodes the primary sigma factor in S. aureus.

Purification and characterization of DNA dependent RNA polymerase from Staphylococcus aureus

DNA dependent RNA polymerase from exponentially growing Staphylococcus aureus cells was purified. An SDS-polyacrylamide gel analysis of the most purified preparation revealed that it consists of beta, beta', alpha, and sigma with apparent molecular masses of 151, 147, 42, and 55 kDa, respectively. The sigma subunit cross reacted with a polyclonal antibody against Bacillus subtilis sigma 43. The cross reacting peptide co-migrated with the B. subtilis sigma 43 subunit. The implications of these results are discussed. Promoter specific in vitro run-off transcripts were obtained using the purified enzyme preparation. Specific conditions for the polymerization reaction are defined.