380
CLAUDE FROMAGEOT AND JACQUES C. SENEZ
ing the oxidation of sulfur by T. thiooxidans. These inclusions had
previously been described as lipide globules since the sulfur gave
them the same staining properties and affinity for iodine as are routinely
used for the histochemical characterization of fats. Later, Barker and
Kornberg (118) confirmed the accumulation of easily hydrolyzable
polyphosphates by cells of T. thiooxidans. Vishniac and Santer (38)
consider the role of these polymetaphosphates to be essentially that of
energy storage. The concomitant content of phosphorus and sulfur of
the vacuoles may also represent the transitory accumulation of certain
intermediates in the oxidation of sulfur.
Santer and Vishniac (119) showed that in the absence of inorganic
phosphate the oxidation of thiosulfate and tetrathionate by T. thioparus
does not go to completion as shown by the fact that under these conditions the cells consume only 70% of the 0 2 consumed in the presence of
phosphate, which is also the stoichiometric amount for the complete
oxidation to sulfate. Inorganic phosphate may be replaced by arsenate.
According to Margulies and Santer (120), the oxidation of thiosulfate or
tetrathionate in the absence of phosphate yields several other sulfur
compounds in addition to sulfate which have been separated by paper
chromatography but not identified. These findings suggest that inorganic
phosphate is involved in the oxidation of certain intermediates which in
its absence cannot be metabolized further and therefore accumulate.
Vishniac and Santer (38) separated by chromatography the products
formed by T. thioparus in the presence of both thiosulfate-S
35 and
phosphate-P
32 . One or several doubly labeled compounds were thus
obtained; these were considered to be mixed anhydrides of the type
R—S—O—P0 3
2
~
which can transfer their phosphate bond secondarily to ADP to yield
ATP. This hypothesis gained support from the demonstration of phosphorylated compounds of this type in other organisms. Robbins and
Lipmann (121) and Wilson and Bandurski (122) showed that yeast and
mammals activate sulfate by a process involving first the formation of
adenosine-5'-sulfophosphate (APS) and then that of adenosine-3'phospho-5'-sulfophosphate (PAPS):
(1)
S0 4
2 - + ATP -» APS + PP(pyrophosphate)
(2)
APS + ATP -> PAPS + ADP
The sulfo-oxidizing bacteria may be expected to carry out all or part
of this process. Quite recently, Peck (123) showed that the reduction of
sulfate to sulfite by the sulfo-reducing bacterium Desulfovibrio desulfuricans involves the first of these two reactions, i.e., the formation of APS,
CLAUDE FROMAGEOT AND JACQUES C. SENEZ
ing the oxidation of sulfur by T. thiooxidans. These inclusions had
previously been described as lipide globules since the sulfur gave
them the same staining properties and affinity for iodine as are routinely
used for the histochemical characterization of fats. Later, Barker and
Kornberg (118) confirmed the accumulation of easily hydrolyzable
polyphosphates by cells of T. thiooxidans. Vishniac and Santer (38)
consider the role of these polymetaphosphates to be essentially that of
energy storage. The concomitant content of phosphorus and sulfur of
the vacuoles may also represent the transitory accumulation of certain
intermediates in the oxidation of sulfur.
Santer and Vishniac (119) showed that in the absence of inorganic
phosphate the oxidation of thiosulfate and tetrathionate by T. thioparus
does not go to completion as shown by the fact that under these conditions the cells consume only 70% of the 0 2 consumed in the presence of
phosphate, which is also the stoichiometric amount for the complete
oxidation to sulfate. Inorganic phosphate may be replaced by arsenate.
According to Margulies and Santer (120), the oxidation of thiosulfate or
tetrathionate in the absence of phosphate yields several other sulfur
compounds in addition to sulfate which have been separated by paper
chromatography but not identified. These findings suggest that inorganic
phosphate is involved in the oxidation of certain intermediates which in
its absence cannot be metabolized further and therefore accumulate.
Vishniac and Santer (38) separated by chromatography the products
formed by T. thioparus in the presence of both thiosulfate-S
35 and
phosphate-P
32 . One or several doubly labeled compounds were thus
obtained; these were considered to be mixed anhydrides of the type
R—S—O—P0 3
2
~
which can transfer their phosphate bond secondarily to ADP to yield
ATP. This hypothesis gained support from the demonstration of phosphorylated compounds of this type in other organisms. Robbins and
Lipmann (121) and Wilson and Bandurski (122) showed that yeast and
mammals activate sulfate by a process involving first the formation of
adenosine-5'-sulfophosphate (APS) and then that of adenosine-3'phospho-5'-sulfophosphate (PAPS):
(1)
S0 4
2 - + ATP -» APS + PP(pyrophosphate)
(2)
APS + ATP -> PAPS + ADP
The sulfo-oxidizing bacteria may be expected to carry out all or part
of this process. Quite recently, Peck (123) showed that the reduction of
sulfate to sulfite by the sulfo-reducing bacterium Desulfovibrio desulfuricans involves the first of these two reactions, i.e., the formation of APS,