Galactose transport in Streptococcus thermophilus

R. Hutkins, H. A. Morris, L. L. McKay

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Although Streptococcus thermophilus accumulated [14C]lactose in the absence of an endogenous energy source, galactose-fermenting (Gal+) cells were unable to accumulate [14C]galactose unless an additional energy source was added to the test system. Both Gal+ and galactose-nonfermenting (Gal-) strains transported galactose when preincubated with sucrose. Accumulation was inhibited 50 or 95% when 10 mM sodium fluoride or 1.0 mM iodoacetic acid, respectively, was added to sucrose-treated cells, indicating that ATP was required for galactose transport activity. Proton-conducting ionophores also inhibited galactose uptake, although N,N'-dicyclohexyl carbodiimide had no effect. The results suggest that galactose transport in S. thermophilus occurs via an ATP-dependent galactose permease and that a proton motive force is involved. The galactose permease in S. thermophilus TS2b (Gal+) had a K(m) for galactose of 0.25 mM and a V(max) of 195 μmol of galactose accumulated per min per g (dry weight) of cells. Several structurally similar sugars inhibited galactose uptake, indicating that the galactose permease had high affinities for these sugars.

Original languageEnglish (US)
Pages (from-to)772-776
Number of pages5
JournalApplied and environmental microbiology
Issue number4
StatePublished - 1985
Externally publishedYes

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

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