Growth of Wolinella succinogenes with elemental sulfur in the absence of polysulfide
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© Springer-Verlag 1996
S H O RT C O M M U N I C AT I O N
Michael Ringel · Roland Gross · Torsten Krafft · Achim Kröger · Rolf Schauder
Growth of Wolinella succinogenes with elemental sulfur in the absence of polysulfide
Received: 8 June 1995 / Accepted: 12 September 1995
Abstract Wolinella succinogenes grows by anaerobic respiration with formate and polysulfide. Polysulfide forms spontaneously from sulfur and sulfide. Here we report that this eubacterium also grows with formate and elemental sulfur under conditions that do not allow polysulfide formation. With the appropriate amount of Fe2+ added to the medium, the concentration of polysulfide was calculated to be 0.4 nM, which is 1/400th of the concentration that of dissolved elemental sulfur. At commensurable growth rates, the growth yield with sulfur was one quarter of that with polysulfide as electron acceptor. The same low growth yield either with sulfur or with polysulfide as electron acceptor was measured for a ∆psr mutant that lacks the genes encoding polysulfide reductase (Psr). Key words Sulfur reduction · Polysulfide · Wolinella succinogenes
The mechanism of polysulfide reduction is best understood for Wolinella succinogenes, which grows with formate and polysulfide (reaction 2) (Klimmek et al. 1991). HCOO– + Sn2– → CO2 + HS– + Sn – 12–
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The electron transport chain catalyzing reaction 2 consists of only two membrane-integrated enzymes: formate dehydrogenase and polysulfide reductase (Psr) (Schauder and Kröger 1993). Recently, it was discovered that W. succinogenes induces a second polysulfide-reducing enzyme in a mutant (∆psr) that lacks the genes encoding polysulfide reductase enzyme (Krafft et al. 1995). Here we report that W. succinogenes wild-type and the ∆psr mutant also grow with elemental sulfur under conditions that do not allow polysulfide formation. Such conditions are typical for archaebacteria that thrive at pH values as low as pH 2. Elucidation of the mechanism of sulfur reduction in W. succinogenes will probably help to understand this process in the acidophilic archaebacteria.
Introduction During the last two decades, many bacteria that grow by sulfur respiration have been described. Because of the poor solubility of sulfur (S8) in water (5 µg/l at room temperature; Boulègue 1978), S8 is considered an unlikely substrate for sulfur respiration. Rather, it is believed that inorganic polysulfide (Sn2–, n = 4–5 at neutral pH values) is the actual substrate for bacteria that grow at near neutral pH values where polysulfide forms spontaneously from sulfur and sulfide (reaction 1), the product of sulfur respiration (Schauder and Kröger 1993). n/ 8
S8 + HS– → Sn + 12– + H+
M. Ringel · R. Gross · T. Krafft · A. Kröger · R. Schauder (Y) Institut für Mikrobiologie, Johann Wolfgang Goethe Universität Frankfurt am Main, Marie-Curie-Strasse 9, D-60439 Frankfurt, Germany Tel. +49-69-79829509; Fax +49-69-79829527 e-mail: [email protected]
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Materials and methods Organisms and growth conditions The growth medium for Wolinella su
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