Study of Microbial Methane Oxidation Using 14C
221
uation of the localization of active processes of turnover and of the specific
microfiora in the water basin, and (3) its chemical and biological mechanisms.
Correspondingly, the techniques used for these purposes differs. In the first
case, it is most important to perform short-term incubations with minimal
possible changes of the native environmental conditions in the experimental
vessels, like concentration of substrak, temperature, redox potential, and
oxygen content. For the second case, the conditions of incubation should be
adjusted to the optimum demand of the specific microbial population which
participates in the turnover of a given element. For example, to expose the
localization of active populations of thiobacilli on the vertical profile, an excess
of energy substrate (thiosulfate) and electron acceptors (02 or N03) is added
to the samples. Then the rate of the lithotrophic 14C02 assimilation is measured in the samples, which in this case will refer only to the variations in the
activity of specific microbial populations present in these samples, thus exposing localization of their potential activity in the water column. Very often the
in situ rates of the specific microbial processes related to the turnover of elements are noncongruous with their potential rates describing the localization
of the active microbial populations responsible for this turnover. For example,
the most active population of lithotrophic thiobacilli in the Black Sea exists
in the upper layer of bottom sediments and in the near-bottom water layer,
where its in situ activity measured as chemosynthesis rate was near zero
(Sorokin 1972b). Finally, the techniques of using radioisotopes to study the
mechanisms of in situ processes are based upon the addition of portions of a
specific labeled substrate negligible in its absolute amounts (for example,
Na~5S) into the natural samples. After incubation under in situ conditions for
some minutes or hours, large amounts (1O-30mgl-l) of nonlabeled substrate
and of probable products of its microbial or chemical transformations are
added to the samples. In the case of NaisS they are Na2S, Na2S203, Na2S04,
and So. Then the chemical separation of these carriers is carried out. Their
radio assay reveals the relationships between the end products formed while
the original substrate was metabolized (or chemically decomposed) under the
in situ conditions during the experiment.
Below the most practically useful radioisotopic methods for the study of
biogeochemical dynamics of elements are described.
5.2 Study of Microbial Methane Oxidation Using 14C
S.2.1 General Remarks
The oxidation of methane is among the most widespread biogeochemical
processes, proceeding in water bodies starting from small bogs and ponds, and
ending with the deep oceanic domains. This gas, being the minor hydrocarbon,
contains a high stock of energy. It is oxidized in aquatic environments by a
221
uation of the localization of active processes of turnover and of the specific
microfiora in the water basin, and (3) its chemical and biological mechanisms.
Correspondingly, the techniques used for these purposes differs. In the first
case, it is most important to perform short-term incubations with minimal
possible changes of the native environmental conditions in the experimental
vessels, like concentration of substrak, temperature, redox potential, and
oxygen content. For the second case, the conditions of incubation should be
adjusted to the optimum demand of the specific microbial population which
participates in the turnover of a given element. For example, to expose the
localization of active populations of thiobacilli on the vertical profile, an excess
of energy substrate (thiosulfate) and electron acceptors (02 or N03) is added
to the samples. Then the rate of the lithotrophic 14C02 assimilation is measured in the samples, which in this case will refer only to the variations in the
activity of specific microbial populations present in these samples, thus exposing localization of their potential activity in the water column. Very often the
in situ rates of the specific microbial processes related to the turnover of elements are noncongruous with their potential rates describing the localization
of the active microbial populations responsible for this turnover. For example,
the most active population of lithotrophic thiobacilli in the Black Sea exists
in the upper layer of bottom sediments and in the near-bottom water layer,
where its in situ activity measured as chemosynthesis rate was near zero
(Sorokin 1972b). Finally, the techniques of using radioisotopes to study the
mechanisms of in situ processes are based upon the addition of portions of a
specific labeled substrate negligible in its absolute amounts (for example,
Na~5S) into the natural samples. After incubation under in situ conditions for
some minutes or hours, large amounts (1O-30mgl-l) of nonlabeled substrate
and of probable products of its microbial or chemical transformations are
added to the samples. In the case of NaisS they are Na2S, Na2S203, Na2S04,
and So. Then the chemical separation of these carriers is carried out. Their
radio assay reveals the relationships between the end products formed while
the original substrate was metabolized (or chemically decomposed) under the
in situ conditions during the experiment.
Below the most practically useful radioisotopic methods for the study of
biogeochemical dynamics of elements are described.
5.2 Study of Microbial Methane Oxidation Using 14C
S.2.1 General Remarks
The oxidation of methane is among the most widespread biogeochemical
processes, proceeding in water bodies starting from small bogs and ponds, and
ending with the deep oceanic domains. This gas, being the minor hydrocarbon,
contains a high stock of energy. It is oxidized in aquatic environments by a