Characterisation of adsorbed anthrax vaccine by two-dimensional gel electrophoresis

The current UK anthrax vaccine is an alum precipitate prepared from static culture filtrate of the avirulent, unencapsulated Sterne strain of Bacillus anthracis. Protective antigen (PA) is regarded as the major immunogen in the vaccine and production conditions are intended to maximize the PA content. However, the precise composition of the vaccine is unknown and there are concerns that the observed side effects of vaccination may be caused by residual enzymatically active toxin components. Two-dimensional gel electrophoresis (2DGE) was used to define the protein components of the current UK anthrax vaccine. Consistency of composition was assessed by examining batches spanning 14 years of vaccine production. The reproducibility of the 2DGE technique was assessed by repeated analysis of selected vaccine batches. For two recently produced batches, between 86.7 and 88.8% of the spots could be matched. However, for one older batch, reproducibility of the spot pattern was considerably less, with a mean similarity of 53.4%. This difference may be explained by a change in production or because of decay during storage. Variation between the recently produced batches ranged from 72.9 to 84.3%, whereas the similarity between these and old batches was comparatively low at between 30 and 59%. Our results demonstrate that, as expected, the major antigen present in the vaccine is PA. The 83 and 63 kDa species are dominant but there are numerous lower molecular weight fragments resulting from proteolytic cleavage. In addition, we have established the presence of the toxin components, oedema factor and lethal factor, and S-layer proteins, EA1 and SAP. Mass spectrometry has also enabled us to identify several bacterial cell-derived proteins present in the vaccine, including PA, enolase, fructose-bisphosphate aldolase, nucleoside diphosphate kinase and a 60 kDa heat shock protein. The use of proteomics can provide useful information on the antigenic make up of this vaccine and the consistency of vaccine production.

Purification of native alpha-enolase from Streptococcus pneumoniae that binds plasminogen and is immunogenic

Many pathogenic bacteria express plasminogen receptors on their surface, which may play a role in the dissemination of organisms by binding plasminogen that, when converted to plasmin, can digest extracellular matrix proteins. A 45-kDa protein was purified from Streptococcus pneumoniae and confirmed as an alpha-enolase by its ability to catalyse the dehydration of 2-phospho-D-glycerate to phosphoenolpyruvate and by N-terminal sequencing. The activity of alpha-enolase was found in the cytoplasm and in whole cells. Activity was also demonstrated in cell wall fractions, which confirmed that alpha-enolase is a cytoplasmic antigen also expressed on the surface of S. pneumoniae. The plasminogen-binding activity of alpha-enolase was examined by Western blot, which showed that purified alpha-enolase was able to bind human plasminogen. Immunoblots of the purified 45-kDa alpha-enolase with 22 sera from patients with pneumococcal disease showed binding in 15 cases, indicating that pneumococcal enolase is immunogenic.

Detection of penicillin susceptibility in Streptococcus pneumoniae by pbp2b PCR-restriction fragment length polymorphism analysis

A PCR-restriction fragment length polymorphism strategy directed against the pbp2b gene was evaluated for identification of penicillin susceptibility. A total of 106 United Kingdom (U.K.), 30 Danish, and 11 Papua New Guinean strains were tested. Of the U.K. strains, all the susceptible and all but one of the resistant isolates were correctly assigned. By using conventional definitions of "not resistant" and "not susceptible," the sensitivities were 97. 5 and 94.4%, the specificities were 100 and 98.9%, the positive predictive values were 100 and 94.4%, and the negative predictive values were 93.1 and 98.9%, respectively. This technique may allow susceptible (MIC, <0.1 mg/liter) and resistant (MIC, >1 mg/liter) isolates to be distinguished in a single PCR.

Allelic variation in Streptococcus pneumoniae autolysin (N-acetyl muramoyl-L-alanine amidase)

The lytA gene encoding the autolysin of Streptococcus pneumoniae may be a virulence determinant. Single-strand conformational polymorphism analysis demonstrated heterogenicity throughout the gene in clinical isolates and strains from the clonal serotypes 7 and 14. Sequence analysis of part of the choline-binding domain showed that in two isolates four amino acid substitutions occurred.

Investigation of a choline phosphate synthesis pathway in Streptococcus pneumoniae: evidence for choline phosphate cytidylyltransferase activity

In this study we have demonstrated the activity of a choline phosphate cytidylyltransferase in cell free extracts of Streptococcus pneumoniae. Southern blot analysis of restricted S. pneumoniae genomic DNA probed with the gene coding for the choline phosphate cytidylyltransferase of Saccharomyces cerevisiae demonstrated that there is homology between the S. cerevisiae cct gene and genomic DNA of S. pneumoniae. We believe that this enzyme is involved in the biosynthesis of the choline containing cell wall antigens, teichoic acid and lipoteichoic acid, catalysing the activation of choline phosphate to CDP-choline which is then incorporated into the polysaccharide moiety.

Incorporation of choline into Streptococcus pneumoniae cell wall antigens: evidence for choline kinase activity

The choline-containing teichoic and lipoteichoic acids play an important part in cell wall metabolism of Streptococcus pneumoniae. We propose that a choline kinase enzyme has a role in the synthesis of these antigens. The presence of this enzyme was demonstrated in cell free extracts of S. pneumoniae by measuring the fall in ATP concentration due to phosphorylation of choline. Genomic DNA of S. pneumoniae hybridised with a probe consisting of an internal fragment of the choline kinase gene of Saccharomyces cerevisiae and one consisting of the choline binding domain of lytA.

Insertional inactivation of the Streptococcus mutans dexA (dextranase) gene results in altered adherence and dextran catabolism

Streptococcus mutans is able to synthesize extracellular glucans from sucrose which contribute to adherence of these bacteria. Extracellular dextranase can partially degrade the glucans, and may therefore affect virulence of S. mutans. In order to isolate mutants unable to produce dextranase, a DNA library was constructed by inserting random Sau3AI-digested fragments of chromosomal DNA from S. mutans into the BamHI site of the streptococcal integration vector pVA891, which is able to replicate in Escherichia coli but does not possess a streptococcal origin of replication. The resultant plasmids were introduced into S. mutans LT11, allowing insertional inactivation through homologous recombination. Two transformants were identified which did not possess dextranase activity. Integration of a single copy of the plasmid into the chromosome of these transformants was confirmed by Southern hybridization analysis. Chromosomal DNA fragments flanking the plasmid were recovered using a marker rescue technique, and sequenced. Comparison with known sequences using the BLASTX program showed 56% homology at the amino acid level between the sequenced gene fragment and dextranase from Streptococcus sobrinus, strongly suggesting that the S. mutans dextranase gene (dexA) had been inactivated. The colony morphology of the dextranase mutants when grown on Todd-Hewitt agar containing sucrose was altered compared to the parent strain, with an apparent build-up of extracellular polymer. The mutants were also more adherent to a smooth surface than LT11 but there was no apparent difference in sucrose-dependent cell-cell aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased resistance of Escherichia coli to acrylic acid and to copper ions after cold-shock

The effects of cold-shock on the resistance of plasmid-free and plasmid-carrying Escherichia coli to acrylate and copper ions have been tested. Such shock, produced by transfer from 37 to 5 degrees C, with 60 min incubation at the lower temperature, significantly enhanced the resistance of all the tested strains to both inhibitors. Such resistances may have arisen because the inhibitory agents are less able, due to porin changes, to penetrate into the organisms after cold-shock. It is more likely, however, that inhibitor penetration is unaffected but that cold-shocked organisms are better able to repair the damage caused (e.g. to membranes, DNA or cellular enzymes) by the inhibitors.

Metabolism of polysaccharides by the Streptococcus mutants dexB gene product

The Streptococcus mutans dexB gene, a member of the multiple sugar metabolism (msm) operon, encodes an intracellular glucan 1,6-alpha-glucosidase which releases glucose from the non-reducing terminus of alpha-1,6-linked isomaltosaccharides and dextran. Comparison of primary amino acid sequences showed strong homology to Bacillus oligo-1,6-glucosidases and, like these enzymes, DexB was able to release free glucose from the alpha-1,4,6-branch point in panose. This suggested a role for DexB in the metabolism of either starch or intracellular polysaccharide, which contain such branch points. However, purified intracellular polysaccharide from the wild-type S. mutans strain LT11 and a mutant deficient in dexB revealed no substantial differences in the extent of branching as demonstrated by iodine staining spectra and the degree of polymerization. Furthermore, thin layer chromatography of radiolabelled intracellular polysaccharide digested with S. mutans wild-type and mutant cell extracts showed no differences in the products obtained. The involvement of DexB in dietary starch metabolism was investigated using alpha-limit dextrins produced from the action of alpha-amylase on starch. These induced the msm operon, including dexB, and the DexB enzyme was able to act on the alpha-limit dextrins to give further fermentable substrates. The transport system encoded by the msm operon can also transport alpha-limit dextrin. DexB may therefore be important in the metabolism of extracellular starch.

A new nicotinamide-adenine dinucleotide-dependent hydroaromatic dehydrogenase of Lactobacillus plantarum and its role in formation of (minus)t-3,t-4-dihydroxycyclohexane-c-1-carboxylate

1. A new induced NAD-dependent hydroaromatic dehydrogenase was isolated from a cell-free extract of Lactobacillus plantarum 13a and purified 175-fold. 2. The enzyme catalyses the oxidation of (-)-quinate, (-)-shikimate, (-)-dihydroshikimate and (-)t-3,t-4-dihydroxycyclohexane-c-1-carboxylate with NAD(+), and the reverse action with NADH. 3. The K(m) values at the optimal pH10.0 for these substrates are 0.85, 0.75, 0.52 and 0.74mm respectively, and the corresponding values for NAD(+) are 0.45, 0.26, 0.34 and 0.36mm respectively. 4. The stereochemical requirements of the enzyme and the role it may play in the reduction of (-)-quinate to (-)t-3,t-4-dihydroxycyclohexane-c-1-carboxylate are discussed and a pathway is suggested.

The oxidation of D-quinate and related acids by Acetomonas oxydans

1. Growing cells of a small number of strains of Acetomonas oxydans oxidized d-quinate to 5-dehydroquinate. 2. d-Shikimate was oxidized to 4,5-dihydroxy-3-oxocyclohex-1-ene-1-carboxylate (3-dehydroshikimate, formerly 5-dehydroshikimate). 3. d-Dihydroshikimate was oxidized to the corresponding 5-dehydro compound, but epidihydroshikimate oxidation by growing cells was not observed. 4. Cell-free extracts oxidized d-quinate to 5-dehydroquinate with the consumption of the stoicheiometric amount of oxygen, but oxidation of shikimate and dihydroshikimate did not go to completion. 5. Oxidation of quinate was brought about by a constitutive particulate enzyme probably localized in the cytoplasmic membrane. No evidence was found for the participation of NAD, NADP or free flavine compounds in electron transport, but the system was cytochrome-linked.