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H F Jenkinson

Publications and source records attributed to H F Jenkinson.

68 records · Page 4Linked to original sources
PubMed1990

Glucosyltransferase production by Streptococcus sanguis Challis and comparison with other oral streptococci.

Glucosyltransferase (GTF) activity in batch cultures of Streptococcus sanguis strain Challis in defined medium was maximum at peak growth and declined rapidly on further incubation into stationary phase. Activity was present in spent culture medium and was associated with 2 polypeptides of approximate Mrs 170 kDa (90% of activity) and 155 kDa (about 10% of activity). Other S. sanguis strains produced similar antigenically-related polypeptides but with varying activities, and antibodies to the S. sanguis enzyme did not react with enzymes produced by other species of oral streptococci. Increasing the [Na+] reduced GTF production by S. sanguis strains Challis and NCTC 7865, and by Streptococcus sobrinus, but not by Streptococcus salivarius. Addition of Tween 80 to cultures caused a rapid inhibition of GTF synthesis by strain Challis, but not by strain NCTC 7865. Benzyl alcohol had a slower and less inhibitory effect on GTF production by strain Challis. Tween 80 generally inhibited to varying degrees GTF production by other oral streptococci through in S. sobrinus it was stimulated. The results suggest controls operating on GTF synthesis and secretion by different strains of oral streptococci appear to be diverse.

Animals↗
PubMed1990

Insertional inactivation of the gene encoding a 76-kilodalton cell surface polypeptide in Streptococcus gordonii Challis has a pleiotropic effect on cell surface composition and properties.

A library of Streptococcus gordonii DL1-Challis DNA was constructed in lambda gt11. Phage plaques were screened for production of antigens that reacted with antiserum to S. gordonii cell surface proteins. A recombinant phage denoted lambda gt11-cp2 was isolated that carried 1.85 kb of S. gordonii DNA and that expressed an antigen with a molecular mass of 29 kDa in Escherichia coli. Antibodies that reacted with the expression product were affinity purified and were shown to react with a single polypeptide antigen with a molecular mass of 76 kDa in S. gordonii DL1-Challis. A segment (0.85 kb) of the cloned DNA within the transcription unit was ligated into a nonreplicative plasmid carrying an erythromycin resistance determinant and transformed into S. gordonii DL1-Challis. The plasmid integrated onto the chromosome, and expression of the 76-kDa polypeptide antigen was abolished. The gene inactivation had no obvious effect on bacterial growth or on a number of phenotypic properties, including hydrophobicity and adherence. However, it abolished serum-induced cell aggregation, mutant cells had reduced aggregation titers in saliva and in colostrum immunoglobulin A, and it also reduced coaggregation with some Actinomyces species. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of cell envelope proteins from wild-type and mutant strains showed that as well as lacking the surface-exposed 76-kDa polypeptide, mutant cell envelopes were deficient in several other polypeptides, including those that bound to immunoglobulin A. Expression of the gene encoding the 76-kDa polypeptide in S. gordonii appeared to be critical for functional conformation of the cell surface.

Animals↗
PubMed1990

Coaggregation of Streptococcus sanguis and other streptococci with Candida albicans.

Thirteen strains of viridans group streptococci and two strains of other streptococci were tested for coaggregation with Candida albicans. Streptococcus sanguis strains generally exhibited low levels of adherence to 28 degrees C-grown exponential-phase yeast cells, but starvation of yeast cells for glucose at 37 degrees C (or at 28 degrees C) increased their coaggregating activity with these streptococci by at least tenfold. This was a property common to four C. albicans strains tested, two of which were able to form mycelia (6406 and MEN) and two of which were not (MM2002 and CA2). The expression of the coaggregation adhesin during yeast cell starvation was inhibited by addition of trichodermin or amphotericin B. The strains of S. sanguis, Streptococcus gordonii, and Streptococcus oralis tested for coaggregating activity encompassed a diverse range of physiological and morphological types, yet all exhibited saturable coaggregation with starved C. albicans cells. There was no correlation of cell surface hydrophobicity, of either yeast or streptococcal cells, with their abilities to coaggregate. Strains of Streptococcus anginosus also coaggregated with starved yeast cells; Streptococcus salivarius and Streptococcus pyogenes coaggregated to a lesser degree with C. albicans, and the coaggregation with S. pyogenes was not promoted by yeast cell starvation; Streptococcus mutans and Enterococcus faecalis did not coaggregate with yeast. The coaggregation reactions of S. sanguis and S. gordonii with C. albicans were inhibited by EDTA and by heat or protease treatment of the yeast cells and were not reversible by the addition of lactose or other simple sugars. These observations extend the range of intergeneric coaggregations that are known to occur between oral microbes and suggest that coaggregations of C. albicans with viridans group streptococci may be important for colonization of oral surfaces by the yeast.

Amphotericin B↗
PubMed1989

Properties of a phosphocarrier protein (HPr) extracted from intact cells of Streptococcus sanguis.

Cells of Streptococcus sanguis strain Challis were incubated with sodium lauroylsarcosinate to extract surface proteins. A polypeptide of apparent molecular mass 16 kDa comprising about 12% of the extract was purified using anion-exchange chromatography. The polypeptide was shown to be a phosphocarrier protein (HPr) that could also be found in the soluble (cytoplasmic) fraction from cells broken by homogenization with glass beads. In vivo labelling of S. sanguis cells with 32Pi showed that the polypeptide carried a heat- and acid-stable phosphorylation and that during sucrose starvation the HPr became dephosphorylated. Antiserum raised to the S. sanguis HPr reacted on Western blots with HPrs from all oral streptococci tested, together with strains of S. pyogenes and S. salivarius, but not with HPrs from S. faecalis or S. bovis, nor with proteins from Staphylococcus aureus, Bacillus subtilis, Actinomyces viscosus and various lactobacilli. The S. sanguis HPr had a high content of alanine (17.2%) and was similar in overall amino acid composition to the HPrs from S. mutans an S. salivarius. The N-terminal residues (to 37) of the S. sanguis HPr showed strong sequence identity (82%) with the N-terminal sequence of S. faecalis HPr. It is suggested that HPr in S. sanguis is associated closely with the cytoplasmic membrane. Non-disruptive methods of removing cell-surface proteins from streptococci effect release of HPr and possibly other cytoplasmic components.

Amino Acid Sequence↗
PubMed1987

Novobiocin-resistant mutants of Streptococcus sanguis with reduced cell hydrophobicity and defective in coaggregation.

Mutants of Streptococcus sanguis resistant to novobiocin (NovR-mutants) were isolated after mutagenesis of strain Challis with ethyl methanesulphonate. The resistance phenotype was transferred by DNA-mediated transformation back into the parent strain at high frequency suggesting resistance was due to mutation(s) in a single gene or in closely-linked genes. Cells of NovR-mutants had normal morphology and secreted similar proteins to the wild-type strain. However, mutant cultures had slower growth rates, the mutant cells had reduced hydrophobicity, and they showed a reduced degree of coaggregation with Actinomyces viscosus and Actinomyces naeslundii. Cell envelopes prepared from NovR-mutants differed from wild-type cell envelopes in that they (a) were impaired in ability to coaggregate with A. viscosus cells, and (b) had altered protein composition as detected by SDS-PAGE. The results suggest that hydrophobic proteins in the cell envelope of S. sanguis may be necessary for coaggregation of this bacterium with actinomycetes.

Bacterial Adhesion↗
PubMed1987

A mutant of Candida albicans deficient in beta-N-acetylglucosaminidase (chitobiase).

A mutant of Candida albicans ATCC 10261 was isolated that was defective in the production of beta-N-acetylglucosaminidase (chitobiase). The mutant grew normally in minimal medium supplemented with either glucose or N-acetyl-D-glucosamine (GlcNAc) as carbon and energy source, and the cells formed germ-tubes at 37 degrees C when induced to do so with GlcNAc. However, unlike the wild-type parent strain, the mutant strain did not utilize N,N'-diacetylchitobiose for growth. The mutant and parent strains had similar growth rates on glucose or GlcNAc, similar rates of uptake of these sugars and similar rates of 14C-labelled amino acid incorporation. The chitobiase mutant did, however, contain 53-85% more chitin than the wild-type strain. No reversion of the mutant phenotype was observed following induction of mitotic recombination with UV light, suggesting that the mutant allele (chi) was carried homozygously in the chitobiase-deficient mutant. Although the chitobiase-deficient mutant was pathogenic, it was not as virulent as the wild-type strain.

Acetylglucosamine↗
PubMed1986

Cell-surface proteins of Streptococcus sanguis associated with cell hydrophobicity and coaggregation properties.

Incubating cells of Streptococcus sanguis with sodium lauroyl sarcosinate, under conditions that did not cause lysis, solubilized material comprising 5-8% of the cell dry weight. The treatment reduced cell hydrophobicity, and reduced the ability of the cells to coaggregate with Actinomyces spp. The extract contained about 20 polypeptides and these were identified as being cell-surface components on the basis of one or more of the following criteria: being degraded when cells were incubated with protease; being labelled when cells were iodinated using a lactoperoxidase-catalysed reaction; reacting with antibodies raised to fixed whole cells. Eight of the polypeptides accounted for more than 70% of the total protein extracted, and one component (molecular mass 16 kDa) was hydrophobic. The cell-surface proteins described are implicated in cell hydrophobicity and coaggregation.

Antigens, Bacterial↗
PubMed1986

Adherence of Streptococcus sanguis.

The presence of adhesins on the cell surface of S. sanguis enables the organism to grow and survive in the oral cavity. Many workers are now actively involved in attempting to characterise these adhesins and the molecular basis for adherence of various streptococci. The complexity of the adhesion processes is underlined by the many varied opinions as to the nature of the molecular components and biochemical interactions that are involved. Understanding the molecular mechanisms involved in bacterial adherence and in dental plaque formation will have significant impact on the prevention and treatment of oral diseases.

Adhesins, Bacterial↗
PubMed1984

Construction and characterization of recombinant phage phi 105 d(Cmrmet) for cloning in Bacillus subtilis.

A 1.6 kb fragment of DNA of plasmid pBD64, obtained after partial digestion with HpaII, carrying a chloramphenicol-resistance determinant and a single site for the enzyme Bg/II, was inserted into the genome of defective phage phi 105 d/ys. Two types of phage were subsequently isolated and both transduced cells of Bacillus subtilis to chloramphenicol resistance. One type contained 26 kb and the other 32 kb of DNA. Bacillus subtilis chromosomal DNA fragments generated by cleavage with Bg/II were ligated into the unique Bg/II site within the smaller phage genome. A specialized transducing phage was isolated which carried the metC gene on a 6 kb Bg/II fragment. This phage, denoted phi 105 d(Cmrmet), transduced B. subtilis strain MB79 pheA12 metC3 to Met+ and to chloramphenicol resistance, and the metC3 mutation was complemented in transductants.

Bacillus subtilis↗
PubMed1983

Altered arrangement of proteins in the spore coat of a germination mutant of Bacillus subtilis.

Spores produced by a mutant of Bacillus subtilis were slow to develop their resistance properties during sporulation, and were slower to germinate than were wild-type spores. The coat protein composition of the mutant spores, as analysed by SDS-PAGE, was similar to that of the wild-type spores. However, one of the proteins (mol. wt 12000) which is normally present in the outer-most layers of mature wild-type spores and which is surface-exposed, was assembled abnormally into the coat of the mutant spores and not surface-exposed. The mutation responsible for this phenotype (spo-520) has been mapped between pheA and leuB on the B. subtilis chromosome, and was 47% cotransformable with leuB16. This mutation, and three others closely linked to it, define a new sporulation locus, spoVIB, which is involved in spore coat assembly. The phenotype of the mutant(s) supports the contention that spore germination and resistance properties may be determined by the assembly of the coat.

Bacillus subtilis↗
PubMed1983

Cloning of the Bacillus subtilis lys and spoIIIB genes in phage phi 105.

The lys gene of Bacillus subtilis was inserted into prophage phi 105. The recombinant phage (phi 105dlys) contained DNA which was about 2 MDal smaller than the wild-type phage DNA, and the phage particles had no tails. The phage did not plaque but, when provided with tails in vitro, it transduced both lys-1 and lys-3 strains of B. subtilis to Lys$. The lys$ gene was located on a 2.5 MDal EcoRI restriction fragment. Subsequently this phage was phi 105 105dspoIIIB, was also defective, i.e. without tails. The DNA was 1.5 MDal smaller than the wild-type phage DNA and the spoIIIB2$ gene was located on a 3 MDal EcoRI fragment. When provided with tails in vitro, phage phi 105dspoIIIB transduced cells of a spoIIIB2 recipient to Spo$. In these transductants the spoIIIB2 mutation was complemented, and the cells sporulated normally.

Bacillus subtilis↗
PubMed1980

Temporal dissociation of late events in Bacillus subtilis sporulation from expression of genes that determine them.

During sporulation in replacement medium, resistance to toluene to heating at 65 degrees C, to lysozyme, and to heating at 80 degrees C appeared in sequence between 4 and 8 h after the induction of sporulation (i.e., between t4 and t8). The addition of sufficient chloramphenicol at t4.5 to prevent protein synthesis nevertheless allowed the emergence of all of these types of resistance except lysozyme resistance. The numbers of spores with these types of resistance (lysozyme resistance again excepted) increased about fourfold when phenylmethylsulfonyl fluoride (an inhibitor of serine protease activity) was also present. Thus, the observed increases in resistance in the 2 h after the addition of chloramphenicol resulted from the utilization of preformed protein elements. Dipicolinate did not seem to be a determining factor in the development of any of these forms of resistance. Electron micrographs showed that inhibition of protein synthesis did not prevent deposition of the outer layers of the spores. Lysozyme resistance developed differently; synthesis of the relevant proteins began later (t5), and continued synthesis was necessary up to t8. Some processing of proteins made earlier was a prerequisite for lysozyme resistance. Therefore, it appears that from the viewpoint of regulation, the expression of the genes and the production of the proteins for resistance to toluene, heating at 65 degrees C, and heating at 80 degrees C are all stage IV sporulation events, although the resistance properties themselves appear only during stages V and VI. Lysozyme resistance is the only real late event among those examined. The germination characteristics of the spores, which are also late events, are discussed in this context, as they too are dependent on proteins that are synthesized much earlier.

Bacillus subtilis↗