Abstract
Uptake of 35S-labelled sulfate was studied with two sulfate-reducing bacteria, the freshwater species Desulfobulbus propionicus and the marine species Desulfococcus multivorans. Both bacteria were able to highly accumulate micromolar additions (2.5 μM) of sulfate, if the reduction of sulfate to H2S was prevented by low temperature (0° C) or oxygen. Sulfate accumulation was highest (accumulation factors 103 to 104) after growth under sulfate-limiting conditions, while cells grown with excess sulfate revealed accumulation factors below 300. With increasing sulfate concentrations added (up to 25 mM), the accumulation factors decreased down to 1.4. Sulfate accumulation in both strains was sensitive to carbonyl cyanide m-chlorophenylhydrazone (CCCP) and thiocyanate, but not directly correlated to the ATP content of the cells. Pasteurized cells did not accumulate sulfate. Sulfate transport was reversible. Accumulated 35S-labelled sulfate was quickly released after addition of non-labelled sulfate or structural sulfate analogues (thiosulfate, selenate, chromate, less effect by molybdate, tungstate, sulfite, selenite). In D. propionicus, sulfate accumulation was independent of the presence or absence of Na+, K+, Li+, Mg2+, Cl- and Br-. Sulfate accumulation was reversibly enhanced at pH 5 and diminished at pH 9. In the marine bacterium D. multivorans, sulfate accumulation depended on the presence of Na+ ions. Na+ could partially be replaced by Li+. Sulfate accumulation in D. multivorans was sensitive to the Na+/H+ antiporter monensin and the Na+/H+ antiport inhibitor amiloride. It is concluded that in D. propionicus sulfate is accumulated electrogenically in symport with at least three protons, whereas for D. multivorans electrogenic symport with sodium ions is proposed. In both species, more than one sulfate transport system must be present. High affinity transport systems appear to be derepressed under sulfate limitation only. The high affinity transport system must be regulated to avoid energy-spoiling accumulation at high sulfate concentrations.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
