The Relationship between Glycosyltransferase Production and Membrane Fatty Acid Composition of Streptococcus sanguis NCTC 7865 Grown in the Presence of Protonmotive Force Inhibitors

Abstract

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.

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

“…While we found that increasing the [Na+] of the tnedium did decrease GTF production by strain Challis in a similar manner to that reported by Keevil et al (18) for strain NCTC 7865, we found Tween 80 to be inhibitory to GTF production by strain Challis. Furthermore, in our experiments GTF secretion by strain NCTC 7865 was not stimulated by addition of Tween 80 to the growth medium as it was previously reported to be (35). The growth conditions and the method we used to assay GTF activity were both different to those used by West et al (35).…”

“…Secretion of the GTF enzyme by strain NCTC 7865 is influenced by the [Na + ]/[K+] ratio in the growth medium (18) and its secretion was shown previously to be stitnulated by Tween 80 (35). Tween 80 has also been shown to stimulate GTF production by S. mutans OMZ176 (34) and by S. salivarius ATCC 25975 (36).…”

“…Tween detergents have beeti showti to stimulate GTF production in certain strains of several species of oral streptococci (15,(34)(35)(36). When Tween 80 (filter-sterilized) was added to the growth tnedium to a final concentration of 0.01% (v/v) we found it reduced GTF activity secreted by strain Challis by about 50%.…”

“…Most of the comparisons of GTF production by strain Challis were made with strain NCTC 7865 frorn which the enzyme has been purified (13) and in which the effects of incorporating Tween 80 into the growth medium (18) or increasing the [Na^ ] have been investigated (35). In cultures of S. sanguis OBll (Challis) the GTF exists as 2 forms, 90% of it as a protein approx.…”

Shifts in membrane fatty acid profiles associated with acid adaptation of Streptococcus mutans

“…Adaptation is known to involve enhanced F 1 F 0 -ATPase (H -ATPase) activity [1,2,9,13], as well as enhanced production of an Exo-III-like, DNA-repair enzyme [8]. The responses of oral streptococci to a variety of environmental stresses such as temperature shifts [11,14], alcohols [16] or ionophores [22] involve changes in membrane fatty acid composition. This sort of response is very common among bacteria [5].…”