Biomedical subjects

D W Harty

Publications and source records attributed to D W Harty.

21 records · Page 2Linked to original sources

PubMed1988

Ruthenium red staining reveals surface fibrils and a layer external to the cell wall in Streptococcus salivarius HB and adhesion deficient mutants.

Ruthenium red staining revealed both the long and short classes of cell surface fibril in thin sections of Streptococcus salivarius HB, indicating that the fibrils contained polyanionic polymers, probably polysaccharides. Also visible was a 16.2 +/- 2.2 nm thick ruthenium red staining layer (RRL) outside the 16.7 +/- 2.2 nm thick cell wall. The fibrils could not be seen after conventional glutaraldehyde and osmium fixation. The RRL was protease resistant and was not involved in septum formation. Loss of the fibrils after protease treatment coincided with a decrease of 54% in cell surface hydrophobicity, indicating that cell surface hydrophobicity was due partly to fibrils and partly to the RRL. There was no correlation between the lengths of fibrils as measured on whole cells after negative staining and on thin sections of ruthenium red stained cells. The thickness of the RRL was the same in three adhesion deficient mutants--strains HB-7, HB-V5 and HB-V51--with various fibril lengths. However, a completely bald mutant, HB-B, had a significantly thicker RRL than S. salivarius HB, although it was unable to adhere to buccal epithelial cells, and it could not co-aggregate with Veillonella parvula V1. The RRL therefore did not contain adhesins.

Bacterial Adhesion↗

PubMed1988

Fermentation products, amino acid utilization, maintenance energies and growth yields for the fibrillar Streptococcus salivarius HB and a non-fibrillar mutant HB-B grown in continuous culture under glucose limitation.

The fibrillar strain Streptococcus salivarius HB and a non-fibrillar mutant, strain HB-B, were grown in a defined medium under glucose limitation in a chemostat. Fermentation balances were produced for both strains in batch culture and at growth rates between 0.1/h and 1.1/h. In batch culture both strains fermented glucose to lactate, but in continuous culture glucose was fermented to formate, acetate and ethanol with increasing amounts of lactate as the growth rate was increased. Lactate never became the major fermentation product even at the highest growth rate. Amino acid analysis showed that only lysine was more than 50% utilized, while proline and tyrosine showed net production. The non-fibrillar strain HB-B showed, in general, a reduced utilization of amino acids compared with the fibrillar strain HB. Calculated growth yields and maintenance energies for the two strains showed that there was a reduction in the true growth yield and the maintenance energy coefficient of the non-fibrillar strain HB-B when compared with the fibrillar strain HB. The increase in the maintenance energy of the fibrillar strain HB (1.382 mmol/g/h) when compared with the non-fibrillar strain HB-B (0.546 mmol/g/h) of 153% is proposed to be the energy required for the maintenance of the fibrillar surface of the cell.

Amino Acids↗

PubMed1987

A comparison of the adhesion, coaggregation and cell-surface hydrophobicity properties of fibrillar and fimbriate strains of Streptococcus salivarius.

Fibrillar and fimbriate strains of Streptococcus salivarius were compared for their ability to adhere to buccal epithelial cells and saliva-coated hydroxyapatite beads, and for their ability to coaggregate with Veillonella strains. The fibrillar Lancefield group K strains adhered statistically significantly better to both buccal epithelial cells and saliva-coated hydroxyapatite beads than the fimbriate strains, which lacked the Lancefield group K antigen. After 1 h the fibrillar strains coaggregated statistically significantly better than the fimbriate strains with V. parvula strain V1, but after 24 h, coaggregation both of fibrillar and of fimbriate strains reached approximately 90%. Freshly isolated Veillonella strains all coaggregated with the S. salivarius strains, but the percentage coaggregation varied considerably after 1 h depending on the Veillonella strain. Coaggregation was independent of the presence of Ca2+. S. salivarius strain HB-V5, a mutant of strain HB that had lost the Veillonella-binding protein, coaggregated weakly with V. parvula strain V1, but coaggregated very well with other wild-type veillonellae, suggesting the presence of an alternative mechanism for Veillonella-binding for strain HB. Fibrillar strains were, therefore, more adhesive to oral surfaces and coaggregated with veillonellae after 1 h better than the fimbriate S. salivarius strains. Both fibrillar and fimbriate strains were highly hydrophobic in the hexadecane-buffer partition assay.

Bacterial Adhesion↗