Different Partial Pressures Of CO2 Research Articles

The absolute requirement for carbon dioxide for aerobic methane oxidation by a methanotrophic-heterotrophic soil community of bacteria

An aerobic methanotrophic-heterotrophic soil community has been characterised when growing with different partial pressures of CO2. The methanotrophic population using methane as carbon source reached 3 × 107 cfu ml−1 with one of the major methanotrophs being of type II which uses the serine pathway for C assimilation. Optimal methanotrophic activity required the addition of CO2, and in the absence of CO2 no methane oxidisers grew. Partial pressures of CO2 from 1.6 to 11.6 kPa gave optimal cell growth and production of soluble organic compounds. Biomass yield, soluble organics and CO2 production were 0.36, 0.15, and 0.48 mg mg−1 methane uptake, respectively, with CO2 at 11.6 kPa. The results presented here may have important implications for the use of methane-oxidising bacteria in bioremedial applications.

The effect of partial pressure of carbon dioxide on anorthite dissolution.

The dissolution experiment of anorthite was carried out under different partial pressures of CO2 (PCO2) to understand the role of weathering of Ca and Mg silicates in the removal of CO2 from the atmosphere in the Precambrian. A newly-developed apparatus can control PCO2 in a mineral-water reaction vessel and vary PCO2 and temperatures from 10−3.5 (the present atmospheric level, PAL) to 5.0 atm and from 40 to 150°C, respectively. The experiments were carried out at 150°C and pH 4.56, varying PCO2 from 10−3.5 to 1.2 atm. The dissolution rate of anorthite under high PCO2 (=1.2 atm) is faster than that under PAL by about 4 times. Calcium and Si dissolve congruently from anorthite under PAL, whereas a Ca/Si ratio in solution is lower under high PCO2. Our results suggest that the weathering rates and processes in the Archean are different from the present ones, and that the amount of Ca flux into the Archean ocean is less than that predicted assuming congruent dissolution of anorthite.

In vivo substitution of zinc by cobalt in carbonic anhydrase of a marine diatom

We examined the mechanism by which Co additions partially alleviate the growth limitation of marine diatoms in cultures with low Zn concentrations. Cultures of the coastal diatom Thalassiosira weissflogii were grown under low‐Zn conditions and provided with low and high levels of Co. Enzyme assays and autoradiographs of electrophoresis gels of cellular proteins revealed that a large fraction of the Co is found in the main isoform of the enzyme carbonic anhydrase (CA), where most of the Zn is located. The affinity of CA for Co is lower than for Zn, and the Co‐substituted enzyme is less active than the native Zn form. Comparisons of growth under different partial pressures of CO2 show that Co can ameliorate the growth of carbon‐limited cultures. We conclude that Co alleviates Zn limitation via direct substitution in CA, which is important for carbon acquisition.

Influence of air drying and soil gas‐phase carbon dioxide on DTPA‐extractable iron in calcareous soils

Abstract The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO2) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO2 level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO2, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO2 partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO2 partial pressure during incubation of the originally fiel...