The influence of Na+ and K+ on the synthesis and secretion of extracellular glucosyltransferase (GTF; EC 2.4.1.5) and fructosyltransferase (FTF; EC 2.4.1.10) by Streptococcus sanguis NCTC 7865 and Streptococcus sanguis Challis NCTC 7868 has been determined. No FTF and little or no mutansucrase (GTF-I) activities were detectable during growth on glucose or sucrose unless the Na+/K+ ratio of the cultures was kept low. Increasing K+ concentrations stimulated the production of FTF and dextransucrase (GTF-S), but all glycosyltransferase activities decreased in high K+ media when the growth pH was maintained with NaOH instead of KOH, indicating that the Na+/K+ ratio effect was due principally to Na+ inhibition. Significant GTF and FTF activities were detected in a putative GTF- mutant of strain Challis grown in high K+ medium but not in high Na+ medium, suggesting that the mutant might be defective in a regulatory gene.

Hippurate hydrolysis can also be positive with beta-haemolytic streptoccoci groups C and L. The CAMP test which demonstrates the synergistic haemolysis between staphylococcal B-toxin and streptococcal CAMP factor on sheep or ox red blood cells is only positive in about 84% of strains.' Pigment production by group B streptoccoci (GBS), which is orange in colour and has characteristics of a carotenoid,2 was first noted by Lancefield in 1934 in nine of 29 strains grown anaerobically.3 Modifications of media by Fallon,4 Merritt,5 and Islam6 have improved the sensitivity to about 97%.We describe further investigations into this test and modifications to the media described by Islam, and a useful application of one of the modifications. Material and methodsIn the first phase, tests of sensitivity and specificity of the media were done by performing Lancefield

SUMMARYThe concentrations of adenosine 5′-mono-, -di-, and -triphosphate (AMP, ADP and ATP) in sheep digesta were measured by a new bioluminescence method. ATP in rumen digesta varied with time after feeding and diet, and most markedly according to the size of the population of ciliate protozoa: the ATP content of rumen digesta from ciliate-free sheep was less than a quarter of that of faunated animals receiving the same diet. The adenylate energy charge (EC) (ATP + ADP/[ATP + ADP + AMP]), an indicator of metabolic activity, was high (0·77–0·94) in all rumen samples, but did not appear to be as useful a measurement of activity as ATP alone. As digesta passed along the alimentary tract, the ATP content decreased progressively, from 0·9–2·2 μmol/g dry matter in the rumen to 0·5–1·0μmol/g in the abomasum and duodenum, 07middot;03–0·08 μmol/g in ileal digesta and 0·01–0·02 μmol/g in faeces. EC also tended to decrease, further emphasizing the large decrease in microbial activity which occurs in the hindgut.

The fatty acid composition of Streptococcus sanguis NCTC 7865 was not altered by changing the cation composition (Na+/K+) of the growth medium; glucosyltransferase (GTF; EC 2.4.1.5) also remained constant. In contrast, fructosyltransferase (FTF-S; EC 2.4.1.10) production was reduced by at least 50% in medium with a high Na+ concentration. Growth in the presence of ionophores (gramicidin, nigericin or valinomycin) resulted in an increased proportion of saturated fatty acids, principally octadecanoic acid (C18:0), while the proportion of unsaturated fatty acids, predominantly octadecenoic (C18:1) and hexadecenoic (C16:1) acids, decreased. GTF-S production was reduced in the presence of ionophores whereas FTF-S production was completely abolished. Tween 80 significantly increased both GTF-S production and the proportion of unsaturated fatty acids in the cytoplasmic membrane; FTF-S production was unaltered by Tween 80. The production of GTF-S was inversely proportional to the C18:0:C18:1 fatty acid ratio of the cytoplasmic membrane. It was concluded that FTF-S production is directly influenced by protonmotive force (pmf), whereas GTF-S production is affected more by the physical properties of the cytoplasmic membrane, in particular its fatty acid composition. However, as perturbations in pmf generation can lead to variations in membrane fatty acid composition it can be argued that pmf indirectly influences GTF production by changing the saturated:unsaturated or C18:0:C18:1 fatty acid ratio of the cytoplasmic membrane.

No abstract