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The emergence of multi-drug-resistant strains of Staphylococcus epidermidis emphasizes the need to develop new antibiotics. The unique and essential role of the peptide deformylase (PDF) in catalysing the removal of the N-terminal formyl group from newly synthesized polypeptides in eubacteria makes it an attractive antibacterial drug target. In the present study, both deformylase homologues from S. epidermidis (SePDF-1 and SePDF-2) were cloned and expressed, and their enzymic activities were characterized. [Co.sup.2+]-substituted SePDF-1 exhibited much higher enzymic activity ([k.sub.cat]/[K.sub.m] 6.3 x [10.sup.4] [M.sup.-1] [s.sup.-1]) than those of [Ni.sup.2+]-and [Zn.sup.2+]- substituted SePDF-1, and SePDF-1 showed much weaker binding ability towards [Ni.sup.2+] than towards [Co.sup.2+] and [Zn.sup.2+], which is different from PDF in Staphylococcus aureus (SaPDF), although they share 80% amino-acid sequence identity. The determined crystal structure of SePDF-1 was similar to that of (SaPDF), except for differences in the metal-binding sites. The other deformylase homologue, SePDF-2, was shown to have no peptide deformylase activity; the function of SePDF-2 needs to be further investigated. DOI 10.1099/mic.0.038174-0

Biofilms are surface-associated communities of microbes encompassed by an extracellular matrix. It is estimated that 80% of all bacterial infections involve biofilm formation, but the structure and regulation of biofilms are incompletely understood. Extracellular DNA (eDNA) is a major structural component in many biofilms of the pathogenic bacterium Staphylococcus aureus, but its role is enigmatic. Here, we demonstrate that beta toxin, a neutral sphingomyelinase and a virulence factor of S. aureus, forms covalent cross-links to itself in the presence of DNA (we refer to this as biofilm ligase activity, independent of sphingomyelinase activity) producing an insoluble nucleoprotein matrix in vitro. Furthermore, we show that beta toxin strongly stimulates biofilm formation in vivo as demonstrated by a role in causation of infectious endocarditis in a rabbit model. Together, these results suggest that beta toxin cross-linking in the presence of eDNA assists in forming the skeletal framework upon which staphylococcal biofilms are established. Staphyloccus aureus | virulence | exotoxins doi/ 10.1073/pnas.0911032107

The sensor kinase NreB from Staphylococcus carnosus contains an [O.sub.2]- sensitive [[4Fe-4S].sup.2+] cluster which is converted by [O.sub.2] to a [[2Fe-2S].sup.2+] cluster, followed by complete degradation and formation of Fe-S-less apo-NreB. NreB x [[2Fe-2S].sup.2+] and apoNreB are devoid of kinase activity. NreB contains four Cys residues which ligate the Fe-S clusters. The accessibility of the Cys residues to alkylating agents was tested and used to differentiate Fe-S-containing and Fe-S-less NreB. In a two-step labeling procedure, accessible Cys residues in the native protein were first labeled by iodoaeetate. In the second step, Cys residues not labeled in the first step were aikylated with the fluorescent munobromobimane (mBBr) after denaturing of the protein. In purified (aerobic) apoNreB, most (96%) of the Cys residues were alkylated in the first step, but in anaerobic (Fe-Scontaining) NreB only a small portion (23%) were alkylated. In anaerobic bacteria, a very small portion of the Cys residues of NreB (9%) were accessible to alkylation in the native state, whereas most (89%) of the Cys residues from aerobic bacteria were accessible. The change in accessibility allowed determination of the half-time (6 min) for the conversion of NreB x [[4Fe-4S].sup.2+] to apoNreB after the addition of air in vitro. Overall, in anaerobic bacteria most of the NreB exists as NreB x [[4Fe-4S].sup.2+], whereas in aerobic bacteria the (Fe-S- less) apoNreB is predominant and represents the physiological form. The number of accessible Cys residues was also determined by iodoacetate alkylation followed by mass spectrometry of Cys- containing peptides. The pattern of mass increases confirmed the results from the two-step labeling experiments. doi: 10.1128/JB.01248-09

In Staphylococcus, the twin-arginine translocation (Tat) pathway is present only in some species and is composed of Tara and TatC. The tatAC operon is associated with the fepABC operon, which encodes homologs to an iron-binding lipoprotein, an iron-dependent peroxidase (FepB), and a high-affinity iron permease. The FepB protein has a typical twin-arginine (RR) signal peptide. The tat and fep operons constitute an entity that is not present in all staphylococcal species. Our analysis was focused on Staphylococcus aureus and S. carnosus strains. Tat deletion mutants ([DELTA]tatAC) were unable to export active FepB, indicating that this enzyme is a Tat substrate. When the RR signal sequence from FepB was fused to prolipase and protein A, their export became Tat dependent. Since no other protein with a Tat signal could be detected, the fepABC-tatAC genes comprise not only a genetic but also a functional unit. We demonstrated that FepABC drives iron import, and in a mouse kidney abscess model, the bacterial loads of [DELTA]tatAC and [DELTA]tat-fep mutants were decreased. For the first time, we show that the Tat pathway in S. aureus is functional and serves to translocate the iron-dependent peroxidase FepB. doi: 10.1128/JB.00642-09

We isolated the methicillin-resistant Macrococcus caseolyticus strain JCSC5402 from animal meat in a supermarket and determined its whole-genome nucleotide sequence. This is the first report on the genome analysis of a macrococcal species that is evolutionarily closely related to the human pathogens Staphylococcus aureus and Bacillus anthracis. The essential biological pathways of M. caseolyticus are similar to those of staphylococci. However, the species has a small chromosome (2.1 MB) and lacks many sugar and amino acid metabolism pathways and a plethora of virulence genes that are present in S. aureus. On the other hand, M. caseolyticus possesses a series of oxidative phosphorylation machineries that are closely related to those in the family Bacillaceae. We also discovered a probable primordial form of a Macrococcus methicillin resistance gene complex, [mecIRA.sub.m] on one of the eight plasmids harbored by the M. caseolyticus strain. This is the first finding of a plasmid-encoding methicillin resistance gene. Macrococcus is considered to reflect the genome of ancestral bacteria before the speciation of staphylococcal species and may be closely associated with the origin of the methicillin resistance gene complex of the notorious human pathogen methicillin-resistant S. aureus.

Through the agr quorum-sensing system, staphylococci secrete unique autoinducing peptides (AIPs) and detect their concentration via the AgrC transmembrane receptor, coordinating local bacterial population density with global changes in gene expression. Unique AIP and AgrC variants exist within and between species, and although autologous interactions lead to agr activation, heterologous interactions usually lead to cross-inhibition, resulting in natural quorum-sensing interference. To gain insight into the mechanisms responsible for these phenomena at the level of the receptor, we used random mutagenesis to isolate variants of Staphylococcus aureus AgrC-I with constitutive activity. Constitutive mutations in the sensor domain of the receptor were localized to the last transmembrane helix, whereas those in the histidine kinase domain were mostly clustered to a region near the phosphorylation site histidine. Analysis of these mutants with a range of noncognate AIPs revealed that inhibition is manifested by inverse agonism in certain heterologous pairings and by neutral antagonism in others. In addition, we isolated and characterized an AgrC sensor domain mutant with dramatically broadened activation specificity and reduced sensitivity to inhibition, identifying a single amino acid as a critical determinant of ligand-mediated inhibition. These results suggest that certain noncognate AIPs stabilize an inhibitory receptor conformation that may be a critical feature of the ligand-receptor interaction not initially appreciated in previous analyses of agr inhibition. constitute mutant | inverse agonism | staphylococci | quorum sensing

Hospital-acquired bacterial infections are an increasingly important cause of morbidity and mortality worldwide. Staphylococcal species are responsible for the majority of hospital-acquired infections, which are often complicated by the ability of staphylococci to grow as biofilms. Biofilm formation by Staphylococcus epidermidis and Staphylococcus aureus requires cell-surface proteins (Aap and SasG) containing sequence repeats known as G5 domains; however, the precise role of these proteins in biofilm formation is unclear. We show here, using analytical ultracentrifugation (AUC) and circular dichroism (CD), that G5 domains from Aap are zinc ([Zn.sup.2+])-dependent adhesion modules analogous to mammalian cadherin domains. The G5 domain dimerizes in the presence of [Zn.sup.2+], incorporating 2-3 [Zn.sup.2+] ions in the dimer interface. Tandem G5 domains associate in a modular fashion, suggesting a 'zinc zipper' mechanism for G5 domain-based intercellular adhesion in staphylococcal biofilms. We demonstrate, using a biofilm plate assay, that [Zn.sup.2+] chelation specifically prevents biofilm formation by S. epidermidis and methicillin-resistant S. aureus (MRSA). Furthermore, individual soluble G5 domains inhibit biofilm formation in a dose-dependent manner. Thus, the complex three-dimensional architecture of staphylococcal biofilms results from the self-association of a single type of protein domain. Surface proteins with tandem G5 domains are also found in other bacterial species, suggesting that this mechanism for intercellular adhesion in biofilms may be conserved among staphylococci and other Gram-positive bacteria. [Zn.sup.2+] chelation represents a potential therapeutic approach for combating biofilm growth in a wide range of bacterial biofilm-related infections. bacterial pathogenesis | G5 domain | Aap | chelation | Staphylococcus

Staphylococcus epidermidis is a major nosocomial pathogen primarily infecting immunocompromised individuals or those with implanted biomaterials (e.g., catheters). Biomaterial-associated infections often involve the formation of a biofilm on the surface of the medical device. In S. epidermidis, polysaccharide intercellular adhesin (PIA) is an important mediator of biofilm formation and pathogenesis. Synthesis of PIA is regulated by at least three DNA binding proteins (IcaR, SarA, and [sigma]B) and several environmental and nutritional conditions. Previously, we observed the environmental conditions that increased PIA synthesis decreased tricarboxylic acid (TCA) cycle activity. In this study, S. epidermidis TCA cycle mutants were constructed, and the function of central metabolism in PIA biosynthesis was examined. TCA cycle inactivation altered the metabolic status of S. epidermidis, resulting in a massive derepression of PIA biosynthetic genes and a redirection of carbon from growth into PIA biosynthesis. These data demonstrate that the bacterial metabolic status is a critical regulatory determinant of PIA synthesis. In addition, these data lead us to propose that the TCA cycle acts as a signal transduction pathway to translate external environmental cues into intracellular metabolic signals that modulate the activity of transcriptional regulators.

Cyclic dimeric GMP (c-di-GMP) is an important biofilm regulator that allosterically activates enzymes of exopolysaccharide biosynthesis. Proteobacterial genomes usually encode multiple GGDEF domain-containing diguanylate cyclases responsible for c-di-GMP synthesis. In contrast, only one conserved GGDEF domain protein, GdpS (for GGDEF domain protein from Staphylococcus), and a second protein with a highly modified GGDEF domain, GdpP, are present in the sequenced staphylococcal genomes. Here, we investigated the role of GdpS in biofilm formation in Staphylococcus epidermidis. Inactivation of gdpS impaired biofilm formation in medium supplemented with NaCI under static and flow-cell conditions, whereas gdpS overexpression complemented the mutation and enhanced wild-type biofilm development. GdpS increased production of the icaADBC-encoded exopolysaccharide, poly-N-acetyl-glucosamine, by elevating icaADBC mRNA levels. Unexpectedly, c-di-GMP synthesis was found to be irrelevant for the ability of GdpS to elevate icaADBC expression. Mutagenesis of the GGEEF motif essential for diguanylate cyclase activity did not impair GdpS, and the N-terminal fragment of GdpS lacking the GGDEF domain partially complemented the gdpS mutation. Furthermore, heterologous diguanylate cyclases expressed in traus failed to complement the gdpS mutation, and the purified GGDEF domain from GdpS possessed no diguanylate cyclase activity in vitro. The gdpS gene from Staphylococcus aureus exhibited similar characteristics to its S. epidermidis orthoiog, suggesting that the GdpS-mediated signal transduction is conserved in staphylococci. Therefore, GdpS affects biofilm formation through a novel c-di-GMP-independent mechanism involving increased icaADBC mRNA levels and exopolysaccharide biosynthesis. Our data raise the possibility that staphylococci cannot synthesize c-di-GMP and have only remnants of a c-di-GMP signaling pathway.

The observation of heterogeneous protein folding kinetics has been widely interpreted in terms of multiple independent unrelated pathways (IUP model), both experimentally and in theoretical calculations. However, direct structural information on folding intermediates and their properties now indicates that all of a protein population folds through essentially the same stepwise pathway, determined by cooperative native-like foldon units and the way that the foldons fit together in the native protein. It is essential to decide between these fundamentally different folding mechanisms. This article shows, contrary to previous supposition, that the heterogeneous folding kinetics observed for the staphylococcal nuclease protein (SNase) does not require alternative parallel pathways. SNase folding kinetics can be fit equally well by a single predetermined pathway that allows for optional misfolding errors, which are known to occur ubiquitously in protein folding. Structural, kinetic, and thermodynamic information for the folding intermediates and pathways of many proteins is consistent with the predetermined pathway-optional error (PPOE) model but contrary to the properties implied in IUP models. foldons | PPOE model | staphylococcal nuclease

Tryptophan residues can possess a multitude of functions within a multidrug transport protein, e.g., mediating interactions with substrates or distal parts of the protein, or fulfilling a structural requirement, such as guiding the depth of membrane insertion. In this study, the nine tryptophan residues of the staphylococcal QacA muitidrug efflux protein were individually mutated to alanine and phenylalanine, and the functional consequences of these changes were determined. Phenylalanine substitutions for each tryptophan residue were functionally tolerated. However, alanine modifications revealed an important functional role for three tryptophan residues, W58, W149, and W173, each of which is well conserved among QacA-related transport proteins in the major facilitator superfamily. The most functionally compromising mutation, an alanine substitution for W58, likely to be located at the extracellular interface of transmembrane segment 2, abolished all detectable QacA-mediated resistance and transport function. Second-site suppressor analyses identified several mutations that rescued the function of the W58A QacA mutant. Remarkably, all of these suppressor mutations were shown to be located in cytoplasmic loops between transmembrane helices 2 and 3 or 12 and 13, demonstrating novel functional associations between amino acid positions on opposite sides of the membrane and in distal N-and C-terminal regions of the QacA protein.

This paper describes an investigation of the complex internal regulatory circuitry of the staphylococcal sae locus and the impact of modifying this circuitry on the expression of external genes in the sae regulon. The sae locus contains four genes, the saeR and S two-component signalling module (TCS), and saeP and Q, two upstream genes of hitherto unknown function. It is expressed from two promoters, [P.sub.A]sae, which transcribes only the TCS, and [P.sub.C]sae, which transcribes the entire locus. A bursa aurealis (bursa) transposon insertion in saeP in a derivative of Staphylococcus aureus NCTC 8325 has a profound effect on sae function. It modifies the activity of the TCS, changing the expression of many genes in the sae regulon, even though transcription of the TCS (from [P.sub.A]sae) is not interrupted. Moreover, these effects are not due to disruption of saeP since an in-frame deletion in saeP has essentially no phenotype. The phenotype of S. aureus strain Newman is remarkably similar to that of the saeP::bursa and this similarity is explained by an amino acid substitution in the Newman saeS gene that is predicted to modify profoundly the signalling function of the protein. This concurrence suggests that the saeP::bursa insertion affects the signalling function of saeS, a suggestion that is supported by the ability of an saeQR clone, but not an saeR clone, to complement the effects of the saeP::bursa insertion.

The DNA sequence of the genome of Staphylococcus haemolyticus JCSC1435 revealed a putative capsule operon composed of 13 genes in tandem. The first seven genes (capABCDEFGsh) showed [greater than or equal to] 57% similarity with the Staphylococcus aureus cap5 or cap8 locus. However, the capHIJKLMsh genes are unique to S. haemolyticus and include genes encoding a putative flippase, an aminotransferase, two glycosyltransferases, and a transcriptional regulator. Capsule-like material was readily apparent by immunoelectron microscopy on bacteria harvested in the postexponential phase of growth. Electron micrographs of a JCSC1435 mutant with a deleted cap region lacked the capsule-like material. Both strains produced small amounts of surface-associated material that reacted with antibodies to polyglutamic acid. S. haemolyticus cap genes were amplified from four of seven clinical isolates of S. haemolyticus from humans, and three of these strains produced a serologically cross-reactive capsular polysaccharide. In vitro assays demonstrated that the acapsular mutant strain showed greater biofilm formation but was more susceptible to complement-mediated opsonophagocytic killing than the parent strain. Structural characterization of capsule purified from S. haemolyticus strain JCSC1435 showed a trisaccharide repeating unit: --3-[alpha]-LFucNAc-3-(2-NAc-4-N-Asp-2,4, 6-trideoxy-[beta]-D-Glc)-4-[alpha]-D-GicNAc-. This structure is unique among staphylococcal polysaccharides in that its composition includes a trideoxy sugar residue with aspartic acid as an N-acyl substituent.

A close homologue of the acquired Staphylococcus aureus mecA gene is present as a native gene in Staphylococcus sciuri. We determined the patterns of penicillin-binding proteins (PBPs) and the peptidoglycan compositions of several S. sciuri strains to explore the functions of this mecA homologue, named pbpD, in its native S. sciuri environment. The protein product of pbpD was identified as PBP4 with a molecular mass of 84 kDa, one of the six PBPs present in representatives of each of three subspecies of S. sciuri examined. PBP4 had a low affinity for nafcillin, reacted with a monoclonal antibody raised against S. aureus PBP2A, and was greatly overproduced in oxacillin-resistant clinical isolate S. sciuri SS37 and to a lesser extent in resistant laboratory mutant K1M200. An additional PBP inducible by oxacillin and corresponding to S. aureus PBP2A was identified in another oxacillin-resistant clinical isolate, S. sciuri K3, which harbors an S. aureus copy of mecA. Oxacillin resistance depended on the overtranscribed S. sciuri pbpD gene in strains SS37 and KIM200, while the resistance of strain K3 depended on the S. aureus copy of mecA. Our data provide evidence that both S. aureus mecA and S. sciuri pbpD can function as resistance determinants in either an S. aureus or an S. sciuri background and that the protein products of these genes, S. aureus PBP2A and S. sciuri PBP4, can participate in the biosynthesis of peptidoglycan, the muropeptide composition of which depends on the bacterium 'hosting' the resistance gene.

Nukacin ISK-1 is a lantibiotic produced by Staphylococcus warneri ISK-1. Previous studies have reported that the self-protection system of the nukacin ISK-1 producer involves the cooperative function of the ABC transporter NukFEG and the lantibiotic-binding immunity protein NukH. In this study, the cooperative mechanism between NukFEG and NukH was characterized by using fluorescein-4-isothiocyanate (FITC)labeled nukacin ISK-1 (FITC-nuk) to clarify the localization of nukacin ISK-1 in the immunity process. Lactococcus lactis recombinants expressing nukFEGH, nukFEG, or nukH showed immunity against FITC-nuk, suggesting that FITC-nuk was recognized by the self-protection system against nukacin ISK-1. Analysis of the interaction between FITC-nuk and energy-deprived cells of the L. lactis recombinants showed that FITC-nuk specifically bound to cells expressing nukH. The interaction between FITC-nuk and nukH-expressing cells was inhibited by the addition of unlabeled nukacin ISK-1 and its derivatives with deletions of the N-terminal tail region, but not by the addition of a synthesized N-terminal tail region. This suggests that the NukH protein recognizes the C-terminal ring region of nukacin ISK-1. The addition of glucose to nukFEGH-expressing cells treated with FITC-nuk resulted in a time-dependent decrease in fluorescence intensity, indicating that FITC-nuk was transported from the cell membrane by the NukFEG protein. These results revealed that after being captured by NukH in an energy-independent manner, nukacin ISK-1 was transported to the extracellular space by NukFEG in an energy-dependent manner.

The changes in the physiology of CoNS triggered by biofilm formation in the presence of a low concentration of dicloxacillin, a major antibiotic used to treat staphylococcal infections in Portugal, is evaluated. The oxygen contents were decreased in Staphylococcus epidermidis, whereas these parameters were increased in Staphylococcus haemolyticus and also the increase in resistance to several antibiotics were observed for the cells within biofilms formed in the presence of dicloxacillin

The isolation of plasmid-protein relaxation complexes from bacteria is indicative of the plasmid nicking-closing equilibrium in vivo that serves to ready the plasmids for conjugal transfer. In pC221 and pC223, the components required for in vivo site- and strand-specific nicking at oriT are MobC and MobA. In order to investigate the minimal requirements for nicking in the absence of host-encoded factors, the reactions were reconstituted in vitro. Purified MobA and MobC, in the presence of [Mg.sup.2+] or [Mn.sup.2+], were found to nick at oriT with a concomitant phosphorylation-resistant modification at the 5' end of nic. The position ofnic is consistent with that determined in vivo. MobA, MobC, and [Mg.sup.2+] or [Mn.sup.2+] therefore represent the minimal requirements for nicking activity. Cross-complementation analyses showed that the MobC proteins possess binding specificity for oriT DNA of either plasmid and are able to complement each other in the nicking reaction. Conversely, nicking by the MobA proteins is plasmid specific. This suggests the MobA proteins may encode the nicking specificity determinant.

Staphylococcus aureus binds to human desquamated nasal epithelial cells, a phenomenon likely to be important in nasal colonization. ClfB was identified previously as one staphylococcal adhesin that promoted binding to nasal epithelia. In this study, it is shown that the S. aureus surface protein SasG, identified previously by in silico analysis of genome sequences, and two homologous proteins, Pls of S. aureus and AAP of Staphylococcus epidermidis, also promote bacterial adherence to nasal epithelial cells. Conditions for in vitro expression of SasG by S. aureus were not found. Adherence assays were therefore performed with S. aureus and Lactococcus lactis expressing SasG from an expression plasmid. These studies showed that SasG did not bind several ligands typically bound by S. aureus. Significantly, SasG and Pls did promote bacterial adherence to nasal epithelial cells. Furthermore, pre-incubation of epithelial ceils with purified recombinant proteins revealed that the N-terminal A regions of SasG, Pls and AAP, but not the B repeats of SasG, inhibited adherence of L. lactis expressing SasG in a dose-dependent fashion. These results suggest that SasG, Pls and AAP bind to the same as-yet-unidentified receptor on the surface of nasal epithelial cells, In addition, expression of SasG, like Pls, reduced adherence of S. aureus to fibronectin and fibrinogen.

Staphylococcus epidermidis biofilm formation on polymer surfaces is considered a major pathogenicity factor in foreign-body-associated infections. Previously, the 148 kDa autolysin AtlE from S. epidermidis, which is involved in the initial attachment of the cells to polymer surfaces and also binds to the extracellular matrix protein vitronectin, was characterized. Here, the characterization of a novel autolysin/adhesin (Aae) in S. epidermidis is described. Aae was identified as a 35 kDa surface-associated protein that has bacteriolytic activity and binds vitronectin. Its N-terminal amino acid sequence was determined and the respective gene, aae, was cloned. DNA-sequence analysis revealed that aae encodes a deduced protein of 324 amino acids with a predicted molecular mass of 35 kDa. Aae contains three repetitive sequences in its N-terminal portion. These repeats comprise features of a putative peptidoglycan binding domain (LysM domain) found in a number of enzymes involved in cell-wall metabolism and also in some adhesins. Expression of aae by Escherichia coli and subsequent analysis revealed that Aae possesses bacteriolytic activity and adhesive properties. The interaction of Aae with fibrinogen, fibronectin and vitronectin was found to be dose-dependent and saturable and to occur with high affinity, by using the real-time Biomolecular Interaction Analysis (BIA). Aae binds to the A[alpha]-and B[beta]Fchains of fibrinogen and to the 29 kDa N-terminal fragment of fibronectin. In conclusion, Aae is a surface-associated protein with bacteriolytic and adhesive properties representing a new member of the staphylococcal autolysin/adhesins potentially involved in colonization.

A method is presented for the rapid detection and characterization of trace amounts of peptides secreted from microorganisms, including pheromones, virulence factors, and quorum-sensing peptides. The procedure, based on targeted multistage MS, uses a novel matrix-assisted laser desorption/ionization-ion trap mass spectrometer to overcome limitations of current MS methods (limited dynamic range, signal suppression effects, and chemical noise) that impair observation of low abundance peptides from complex biological matrixes. Here, secreted peptides that are hypothesized to be present in the supernatant, but that may not be sufficiently abundant to be observed in single-stage mass spectra, are subjected to multistage MS. Highly specific fragmentation signatures enable unambiguous identification of the peptides of interest and differentiation of the signals from the background. As examples, we demonstrate the rapid (

Research has been conducted on Staphylococcus aureus C (sub)30 carotene synthase CrtM and Erwinia uredovora C (sub)40 carotene cynthase CrtB. These synthases have been swapped into their C (sub)40 and C (sub)30 biosynthetic pathways expressed in Escherichia coli and their function has been evaluated and discussed.

Research has been conducted on two-component regulatory system NreBC where NreB is a histidine sensor kinase and NreC is a response regulator. Results suggest that NreC binds to GC-rich palidromic sequences at the promoters of operons nir and narGHJI and of narT gene which encodes putative nitrate transporter, and that oxygen is NreB effector molecule.

Research has been conducted on Staphylococcus aureus strain COL. The strains' mutants resistant to household pine oil cleaner have been isolated on laboratoty media containing pine oil cleaner-resistant S. aureus, and the relationships between oxacillin, pine oil cleaner, vancomycin resistance and SigB have been investigated and discussed.

Research has been conducted on the staphylococcal gamma-hemolysin transmembrane pore complexes from the human erythrocyte membranes. The isolation of these complexes and the study of the pore complex stoichiometry have been carried out and the details are reported.

An algorithm is applied here to compute folding pathways of staphylococcal protein A, fragment B. Emphasis is on studies of the complete process, starting from an ensemble of fully denatured conformations and ending at the folded state. The stochastic difference equation algorithm is based on optimization of an action that makes it possible to use a large integration step. Motions with typical displacements that change rapidly on the size scale of the step are filtered out, providing numerically stable and approximate solutions. The present approach is unique in maintaining an atomically detailed picture while providing a systematic, controlled approximation to the classical equations of motion. Analysis of 130 trajectories suggests the following folding mechanism for protein A: At an early precollapse phase of the process, a few native hydrogen bonds form near the C terminus of the protein. The hydrogen bonds are formed mostly within the third helix. The next step is chain collapse that occurs in parallel to additional growth of secondary structure seeds. Therefore, the present study does not support a pure hydrophobic collapse, or substantial early formation of secondary structure. At the last step, native tertiary contacts are formed at the same time as the completion of the secondary structure elements. To a large extent, the process is parallel and not sequential. The early formation of the third helix of protein A, fragment B (in the calculation), is consistent with experimental data.

Virulent Staphylococcus aureus strains typically produce and secrete large quantities of many extracellular proteins involved in pathogenesis. Such strains cause the classical staphylococcal lesion--local tissue destruction and aggressive inflammation accompanied by the massive influx of polymorphonuclear leukocytes, leading to the formation of pus. Most strains causing toxic shock syndrome, however, produce and secrete very small quantities of most exoproteins although they elaborate high levels of toxic shock syndrome toxin-1 (TSST-1). These strains cause local infections that are remarkably apurulent although potentially fatal owing to the superantigen. We have analyzed this disparity and have found that TSST-1 itself is a negative global regulator of exoprotein gene transcription. TSST-1 not only represses most exoprotein genes but determines its own high expression level by autorepression. We report also that a second superantigen, enterotoxin B, has similar regulatory properties.

Research demonstrates that fibrinogen-binding proteins Fbe and SdrG from Staphylococcus epidermidis HB and K28 strains, respectively, are analogous and together constitute Fbe. Gene mutation in the fbe gene suggests that Fbe proteins promote bacterial adherence to fibrinogen.

Research has been conducted on the lactic acid bacteria producing heterologous proteins of therapeutical interest. The use of the staphylococcal nuclease in developing the heterologous protein secretion model in Lactococcus lactis is described.

Research has been conducted on the facultative anaerobic bacterium Staphylococcus xylosus. The analysis of the antioxidant capacities of this organism has been carried out via characterization of the superoxide dismutase, and the results are discussed.

Results demonstrate that the cell surface of liquid grown Staphylococcus epidermidis is soft but solid agar grown cells exhibit even softer cell surfaces. The fixed charge distribution on the outer cell surface show less significant variation between the cells grown on liquid versus solid media.

Results reveal that HPr kinase mediates the activation of the catabolite control protein A in Staphylococcus xylosus. Data indicate that two additional proteins, the glucose uptake protein and glucose kinase are also involved in this activation in a cooperative way with HPr kinase.

The immune system protects the body by responding to invading organisms. But how is an attack on useful resident microbes prevented? A pathway has now been identified that allows immune cells to sense and respond to beneficial bacteria. The immune system protects the body by responding to invading organisms. But how is an attack on useful resident microbes prevented? A pathway has now been identified that allows immune cells to sense and respond to beneficial bacteria., Author(s): Paul Klenerman, Graham Ogg Author Affiliations: Killer T cells show their kinder side The immune system performs a difficult balancing act. It must respond rapidly to dangerous microorganisms that [...]

Rat tongues sections in a microbial growth media were analyzed to map or identify the nitrite-producing microorganisms on the tongue surface and to determine nitrite reduction velocities by nitrite-producing bacteria. Analysis of tongue sections in nutrient agar and blood agar growth media indicated the presence of similar microbial populations composed mainly of Streptococcus and Staphylococcus species. Nitrite production in the tongue sections was also affected by changes in nitrite dietary intake.

The Staphylococcus epidermidis adhesin exists in the form of fimbria-like appendages protruding from the cell surface of the organism. Of the two staphylococcal surface proteins (SSP), it is SSP-1 which was found to be the bacterium's primary biomaterial adhesin. When the amount of SSP-2 exceeds that of SSP1, the adhesive function was lost, suggesting that that the two SSPs are antigenically related.

A study was conducted on the role of the Staphylococcus epidermidis enzyme EpiP in the biosynthesis of epidermin. Epidermin is first synthesized as EpiA, a prepeptide which would subsequently be modified and processed to become a mature antibiotic. Results revealed that the EpiA precursor peptide was cleaved only to leader peptide and proepidermin when EpiP was present, indicating that EpiP catalyzes the processing of the prepeptide.

A unique linear glucosaminoglycan purified from a polysaccharide antigen of Staphylococcus epidermidis has been found to play a key role in intercellular adhesion during biofilm accumulation. The specific antigen consisted of a major polysaccharide, characterized as a linear homoglycan and a moderately anionic minor polysaccharide. Based on its unique structure and function, the polysaccharide was named polysaccharide intercellular adhesin.

Staphylococcus epidermidis biofilms affected extracellular virulence factor production of S. epidermidis, associated with iron chelator, exopolysaccharide and protease production, which were studied as a function of specific growth rate. Perfused biofilms enhanced protease and iron chelator production with increasing growth rate.

Various species of staphylococci are associated with the initial and chronic colonization of mucus gel in the airway. An investigation was conducted to determine the role of calcium in the adhesion of staphylococci to immobilized mucin using a modified radioassay procedure. The results showed that calcium enhances the adhesion of staphylococci to mucin by binding to the sialic acid and sulfate residues of mucin. Furthermore, adhesion to mucin could also be mediated by mucin-binding surface proteins unrelated to calcium.

A study was done on the distinct binding sites on HLA-DR for invariant chain and staphylococcal enterotoxins. It was shown that staphylococcal enterotoxins A to E and exfoliative toxin bind to cells expressing the alphabetaIi complex at levels similar to cells expressing only alphabeta chains at the cell surface. Ii inhibits the binding of toxic shock syndrome toxin and the subsequent stimulation of T cells.

A study was conducted to show the binding of the soluble T-cell antigen receptor beta-chain molecule to the staphylococcal enterotoxin A (SEA) and major histocompatibility complex on the cell surface. The peptide corresponding to amino acids 57-77 of Vbeta3 was also shown to inhibit binding of the soluble molecule. These data suggest that the Vbeta3 region displays the appropriate sequenc and conformation for binding of the SEA molecule and blocking of the resultant interaction with the T-cell antigen receptor.

gamma-Lysin, a staphylococcal hemolysin, was purified from Staphylococcus aureus strains Smith 5R and PG23. Characterization studies showed that gamma-lysin is composed of two components, termed gamma-1 and gamma-2. Assays for hemolytic activity on rabbit and sheep erythrocytes showed that the individual components are only weakly hemolytic. However, they acted synergistically to produce a more efficient hemolysis. Similar synergistic effects using papain and trypsin were observed for gamma-1, but not gamma-2. These results suggest that gamma-1 is a protease.

The mobile element IS256 causes phase variation of biofilm formation in Staphylococcus epidermidis by insertion and precise excision from the icaADBC operon. Precise excision, i.e., removal of the target site duplications (TSDs) and restoration of the original DNA sequence, occurs rarely but independently of functional transposase. Instead, the integrity of the TSDs is crucial for precise excision. Excision increased significantly when the TSDs were brought into closer spatial proximity, suggesting that excision is a hostdriven process that might involve most likely illegitimate recombination.

Antibody phage display technology was used to immortalize genes from a hybridoma clone encoding monoclonal antibody against staphylococcal enterotoxin B (SEB) which is the most potent toxin listed as biological warfare (BW) agent. The results demonstrated the application of the constructed recombinant antibody via immortalizing the antibody genes from a hybridoma clone for immunodetection of SEB.

Resistance to lysostaphin, a staphylolytic glycylglycine endopeptidase, is because of a FemABX-like immunity protein that has inserted serines in place of some glycines in peptidoglycan cross bridges. The modifications have inhibited both binding of the recombinant cell wall targeting domain and catalysis by the recombinant catalytic domain of lysostaphin.