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Assessment of the stoichiometry and efficiency of CO2 fixation coupled to reduced sulfur oxidation.

Klatt JM, Polerecky L - Front Microbiol (2015)

Bottom Line: We describe a generic theoretical framework for linking the stoichiometry and energy conservation efficiency of autotrophic sulfur oxidation while accounting for the partitioning of the reduced sulfur pool between the energy generating and energy conserving steps as well as between the main possible products (sulfate vs. zero-valent sulfur).Aerobic SOB equipped with reverse dissimilatory sulfite reductase tend to have higher efficiency than those relying on the complete Sox pathway, whereas for anaerobic SOB the presence of membrane-bound, as opposed to periplasmic, nitrate reductase systems appears to be linked to higher efficiency.Finally, we discuss how the framework can help researchers gain new insights into the activity of SOB and their niches.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Marine Microbiology Bremen, Germany.

ABSTRACT
Chemolithoautotrophic sulfur oxidizing bacteria (SOB) couple the oxidation of reduced sulfur compounds to the production of biomass. Their role in the cycling of carbon, sulfur, oxygen, and nitrogen is, however, difficult to quantify due to the complexity of sulfur oxidation pathways. We describe a generic theoretical framework for linking the stoichiometry and energy conservation efficiency of autotrophic sulfur oxidation while accounting for the partitioning of the reduced sulfur pool between the energy generating and energy conserving steps as well as between the main possible products (sulfate vs. zero-valent sulfur). Using this framework, we show that the energy conservation efficiency varies widely among SOB with no apparent relationship to their phylogeny. Aerobic SOB equipped with reverse dissimilatory sulfite reductase tend to have higher efficiency than those relying on the complete Sox pathway, whereas for anaerobic SOB the presence of membrane-bound, as opposed to periplasmic, nitrate reductase systems appears to be linked to higher efficiency. We employ the framework to also show how limited rate measurements can be used to estimate the primary productivity of SOB without the knowledge of the sulfate-to-zero-valent-sulfur production ratio. Finally, we discuss how the framework can help researchers gain new insights into the activity of SOB and their niches.

No MeSH data available.


CO2:TEA ratios in selected SOB calculated over the complete range of S0:SO2−4 production ratios (represented by 0<x<1). Calculations were done for two aerobic (A,C) and two anaerobic (B,D) SOB at standard biochemical conditions (solid lines) and with all reactant concentrations equal to 1 mM and pH = 7 (dashed lines), assuming that the energy conservation efficiency εII is constant (A,B) or linearly decreasing from the maximum reached at x = 0 toward zero reached at x = 1 (C,D).
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Figure 3: CO2:TEA ratios in selected SOB calculated over the complete range of S0:SO2−4 production ratios (represented by 0<x<1). Calculations were done for two aerobic (A,C) and two anaerobic (B,D) SOB at standard biochemical conditions (solid lines) and with all reactant concentrations equal to 1 mM and pH = 7 (dashed lines), assuming that the energy conservation efficiency εII is constant (A,B) or linearly decreasing from the maximum reached at x = 0 toward zero reached at x = 1 (C,D).

Mentions: We see that the efficiency-based and CO2:TEA-based approach give a very similar stoichiometry of the overall sulfide oxidation reaction, suggesting that they are almost equivalent. To verify this, we performed the same calculations over all possible values of x as well as for different aerobic and anaerobic SOB. If the two approaches were equivalent, the calculated CO2:TEA consumption ratios would not change with x. As shown in Figures 3A,B, this is approximately the case, since the calculated CO2:TEA ratios vary by less than ~20% over the complete interval of x. Additionally, this variability is decreased if the reactant concentrations are decreased from values at standard biochemical conditions to a more environmentally relevant range (compare solid and dashed lines in Figures 3A,B). This means that the possible error made when determining the stoichiometric coefficients (for an arbitrary value of x) based on the CO2:TEA-based approach or the efficiency-based approach will be relatively small (<20%).


Assessment of the stoichiometry and efficiency of CO2 fixation coupled to reduced sulfur oxidation.

Klatt JM, Polerecky L - Front Microbiol (2015)

CO2:TEA ratios in selected SOB calculated over the complete range of S0:SO2−4 production ratios (represented by 0<x<1). Calculations were done for two aerobic (A,C) and two anaerobic (B,D) SOB at standard biochemical conditions (solid lines) and with all reactant concentrations equal to 1 mM and pH = 7 (dashed lines), assuming that the energy conservation efficiency εII is constant (A,B) or linearly decreasing from the maximum reached at x = 0 toward zero reached at x = 1 (C,D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440400&req=5

Figure 3: CO2:TEA ratios in selected SOB calculated over the complete range of S0:SO2−4 production ratios (represented by 0<x<1). Calculations were done for two aerobic (A,C) and two anaerobic (B,D) SOB at standard biochemical conditions (solid lines) and with all reactant concentrations equal to 1 mM and pH = 7 (dashed lines), assuming that the energy conservation efficiency εII is constant (A,B) or linearly decreasing from the maximum reached at x = 0 toward zero reached at x = 1 (C,D).
Mentions: We see that the efficiency-based and CO2:TEA-based approach give a very similar stoichiometry of the overall sulfide oxidation reaction, suggesting that they are almost equivalent. To verify this, we performed the same calculations over all possible values of x as well as for different aerobic and anaerobic SOB. If the two approaches were equivalent, the calculated CO2:TEA consumption ratios would not change with x. As shown in Figures 3A,B, this is approximately the case, since the calculated CO2:TEA ratios vary by less than ~20% over the complete interval of x. Additionally, this variability is decreased if the reactant concentrations are decreased from values at standard biochemical conditions to a more environmentally relevant range (compare solid and dashed lines in Figures 3A,B). This means that the possible error made when determining the stoichiometric coefficients (for an arbitrary value of x) based on the CO2:TEA-based approach or the efficiency-based approach will be relatively small (<20%).

Bottom Line: We describe a generic theoretical framework for linking the stoichiometry and energy conservation efficiency of autotrophic sulfur oxidation while accounting for the partitioning of the reduced sulfur pool between the energy generating and energy conserving steps as well as between the main possible products (sulfate vs. zero-valent sulfur).Aerobic SOB equipped with reverse dissimilatory sulfite reductase tend to have higher efficiency than those relying on the complete Sox pathway, whereas for anaerobic SOB the presence of membrane-bound, as opposed to periplasmic, nitrate reductase systems appears to be linked to higher efficiency.Finally, we discuss how the framework can help researchers gain new insights into the activity of SOB and their niches.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Marine Microbiology Bremen, Germany.

ABSTRACT
Chemolithoautotrophic sulfur oxidizing bacteria (SOB) couple the oxidation of reduced sulfur compounds to the production of biomass. Their role in the cycling of carbon, sulfur, oxygen, and nitrogen is, however, difficult to quantify due to the complexity of sulfur oxidation pathways. We describe a generic theoretical framework for linking the stoichiometry and energy conservation efficiency of autotrophic sulfur oxidation while accounting for the partitioning of the reduced sulfur pool between the energy generating and energy conserving steps as well as between the main possible products (sulfate vs. zero-valent sulfur). Using this framework, we show that the energy conservation efficiency varies widely among SOB with no apparent relationship to their phylogeny. Aerobic SOB equipped with reverse dissimilatory sulfite reductase tend to have higher efficiency than those relying on the complete Sox pathway, whereas for anaerobic SOB the presence of membrane-bound, as opposed to periplasmic, nitrate reductase systems appears to be linked to higher efficiency. We employ the framework to also show how limited rate measurements can be used to estimate the primary productivity of SOB without the knowledge of the sulfate-to-zero-valent-sulfur production ratio. Finally, we discuss how the framework can help researchers gain new insights into the activity of SOB and their niches.

No MeSH data available.