Influence of increasing dissolved inorganic carbon concentrations and decreasing pH on chemolithoautrophic bacteria from oxic-sulfidic interfaces

Increases in the dissolved inorganic carbon (DIC) concentration are  expected to cause a decrease in the pH of ocean waters, a process  known as ocean acidification. In oxygen-deficient zones this will  add to already increased DIC and decreased pH values. It is not  known how this might affect microbial communities and microbially  mediated processes. In this study, the potential effects of ocean  acidification on chemolithoautotrophic prokaryotes of marine  oxic-anoxic transition zones were investigated, using the  chemoautotrophic denitrifying ε-proteobacterium  “Sulfurimonas gotlandica” strain GD1 as a model  organism. This and related taxa use reduced sulfur compounds, e.g.  sulfide and thiosulfate, as electron donors and were previously  shown to be responsible for nitrate removal and sulfide  detoxification in redox zones of the Baltic Sea water column but  occur also in other oxygen-deficient marine systems. Bacterial cell  growth within a broad range of DIC concentrations and pH values was  monitored and substrate utilization was determined. The results  showed that the DIC saturation concentration for growth was already  reached at 800 μM, which is well below in situ DIC  levels. The pH optimum was between 6.6 and 8.0. Within a pH range of  6.6–7.1 there was no significant difference in substrate  utilization; however, at lower pH values cell growth decreased  sharply and cell-specific substrate consumption increased. These  findings suggest that a direct effect of ocean acidification, with  the predicted changes in pH and DIC, on chemolithoautotrophic  bacteria such as “S. gotlandica” str. GD1 is generally  not very probable.

Mammitzsch K., Jost G. & Jürgens K., 2012. Influence of increasing dissolved inorganic carbon concentrations and decreasing pH on chemolithoautrophic bacteria from oxic-sulfidic interfaces. Biogeosciences Discussions 9: 18371-18395. Article.


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