The relationship between glycosyltransferase production and membrane fatty acid composition of Streptococcus sanguis NCTC 7865 grown in the presence of protonmotive force inhibitors

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.