Studying Sulfur Cycling with the Aid of 35S
241
and sulfur bacteria (Sorokin 1970b; Jorgensen 1988). Because of their intensive biological oxidation, the absolute concentration of s2ol- and SO in the
water samples taken within the redox zone are very low, less than 0.1 mg S I-I,
while their flows in this zone can be quite high. In the anoxic zone gradual
accumulation of thiosulfate takes place. In the deep layers of the anoxic zone
of the Black Sea it attains up tu 0.3-0.4 mg S I-I, while that of the elemental
sulfur remains less than O.lmgl- 1 (Volkov 1991).
The process of biological oxidation of reduced sulfur compounds by
bacteria results in a significant autotrophic production of microbial biomass
in the redox zones of stratified water basins. The efficiency of the energy use
of thiosulfate by thiobacilli for chemosynthetic production of organic matter
approaches 20-2S% (Sorokin 1970b). Therefore it is important to know not
only the ambiental concentrations of SO and thiosulfate but also their flows as
evidenced by the rates of their in situ oxidation. The latter may be estimated
with the use of labeled thiosulfate 3SS2032- and sulfur 3SSo.
The working solution of thiosulfate is prepared from its batch to adjust its
radioactivity to 1-2 ~Ci ml- I for work in freshwater and to 3-S ~Ci ml- I for
saline waters. The content of the carrier thiosulfate in the working solution
should be 20-30 ~gS ml- I . Correspondingly, it is most convenient way to
acquire the batches of labeled thiosulfate with a total radioactivity of 0.2-0.S
mCi from the supplier. After the batch is opened, 1 ml of S% thiosulfate solution is added to it as carrier. Then the content of the batch is transferred to
the beaker with 20ml of water or of 4% NaCI solution when working in
the sea. This solution should be passed through the membrane filter covered
with a fine layer of MgC03 (see above) to eliminate the possible presence
of elemental sulfur. The real radioactivity of the sulfane sulfur of labeled
thiosulfate in this batch solution should be measured. To do this, 0.1 ml of
it is injected into 100 ml of water with 0.2 ml of the mixed carrier solution
added (see above). Then 1-2ml of this water is placed into the beaker with
20ml of water and with O.OSml of the carrier solution added; O.Sml of 10%
AgN03 solution is added to this mixture. The precipitate is filtered, dried, and
directly radioassayed. The radioactivity of sulfur in thiosulfate is calculated
taking into account that sulfane thus precipitated sulfur represents only a half
of its total sulfur. The batch solution is then diluted to the volume of 100-300
ml with the distilled water or with the NaCI solution to attain the necessary
radioactivity of thiosulfate in this working solution. The prepared solution is
distributed into 1-ml glass ampules as described in the case of labeled sulfide
(see above). The ampules are sterilized by pasteurization twice at 60°C with
a 2-day interval.
The working solution of elemental sulfur can be prepared as follows. The
batch preparation containing some O.OS-O.l mCi of 3SSo is opened and 1 ml of
benzole solution of SO carrier containing 3 mg of sulfur in S ml is added to
extract the labeled material from the batch container. This liquid is transferred
into the remaing 4ml of the above-mentioned SO-carrier solution in benzol.
The working solution of 3SSo is used for the corresponding experiments.
241
and sulfur bacteria (Sorokin 1970b; Jorgensen 1988). Because of their intensive biological oxidation, the absolute concentration of s2ol- and SO in the
water samples taken within the redox zone are very low, less than 0.1 mg S I-I,
while their flows in this zone can be quite high. In the anoxic zone gradual
accumulation of thiosulfate takes place. In the deep layers of the anoxic zone
of the Black Sea it attains up tu 0.3-0.4 mg S I-I, while that of the elemental
sulfur remains less than O.lmgl- 1 (Volkov 1991).
The process of biological oxidation of reduced sulfur compounds by
bacteria results in a significant autotrophic production of microbial biomass
in the redox zones of stratified water basins. The efficiency of the energy use
of thiosulfate by thiobacilli for chemosynthetic production of organic matter
approaches 20-2S% (Sorokin 1970b). Therefore it is important to know not
only the ambiental concentrations of SO and thiosulfate but also their flows as
evidenced by the rates of their in situ oxidation. The latter may be estimated
with the use of labeled thiosulfate 3SS2032- and sulfur 3SSo.
The working solution of thiosulfate is prepared from its batch to adjust its
radioactivity to 1-2 ~Ci ml- I for work in freshwater and to 3-S ~Ci ml- I for
saline waters. The content of the carrier thiosulfate in the working solution
should be 20-30 ~gS ml- I . Correspondingly, it is most convenient way to
acquire the batches of labeled thiosulfate with a total radioactivity of 0.2-0.S
mCi from the supplier. After the batch is opened, 1 ml of S% thiosulfate solution is added to it as carrier. Then the content of the batch is transferred to
the beaker with 20ml of water or of 4% NaCI solution when working in
the sea. This solution should be passed through the membrane filter covered
with a fine layer of MgC03 (see above) to eliminate the possible presence
of elemental sulfur. The real radioactivity of the sulfane sulfur of labeled
thiosulfate in this batch solution should be measured. To do this, 0.1 ml of
it is injected into 100 ml of water with 0.2 ml of the mixed carrier solution
added (see above). Then 1-2ml of this water is placed into the beaker with
20ml of water and with O.OSml of the carrier solution added; O.Sml of 10%
AgN03 solution is added to this mixture. The precipitate is filtered, dried, and
directly radioassayed. The radioactivity of sulfur in thiosulfate is calculated
taking into account that sulfane thus precipitated sulfur represents only a half
of its total sulfur. The batch solution is then diluted to the volume of 100-300
ml with the distilled water or with the NaCI solution to attain the necessary
radioactivity of thiosulfate in this working solution. The prepared solution is
distributed into 1-ml glass ampules as described in the case of labeled sulfide
(see above). The ampules are sterilized by pasteurization twice at 60°C with
a 2-day interval.
The working solution of elemental sulfur can be prepared as follows. The
batch preparation containing some O.OS-O.l mCi of 3SSo is opened and 1 ml of
benzole solution of SO carrier containing 3 mg of sulfur in S ml is added to
extract the labeled material from the batch container. This liquid is transferred
into the remaing 4ml of the above-mentioned SO-carrier solution in benzol.
The working solution of 3SSo is used for the corresponding experiments.