CO metabolism of Desulfovibrio vulgaris strain Madison: physiological function in the absence or presence of exogeneous substrates

Abstract Trace amounts of carbon monoxide were produced and subsequently consumed during the growth of Desulfovibrio vulgaris on organic electron donors. D. vulgaris also utilized carbon monoxide as the sole electron donor for growth and sulfate reduction. Growth of D. vulgaris on CO, H₂ or organic electron donors was inhibited at ≥4.5% CO in the culture headspace. At lower CO concentrations, hydrogen was produced as a consequence of CO consumption and consumed when the CO partial pressure was decreased. The rate of CO consumption was ten-fold higher in D. vulgaris grown on either CO, lactate or pyruvate than when cells were grown on H₂ as electron donor. The physiological function of CO metabolism and a CO-dependent hydrogen cycle in D. vulgaris is discussed.     

Sodium dependent acetate formation from CO2 in Peptostreptococcus productus (strain Marburg)

Abstract Washed cells of Peptostreptococcus productus (strain Marburg), which were incubated in the presence of CO/CO₂/N₂ (50%/ 17%/ 33%; 200 kPa) catalyzed the synthesis of acetate from carbon monoxide. The rate of acetate formation from CO was stimulated more than threefold by the addition of sodium (10 mM); potassium did not effect acetate synthesis. The degree of stimulation was dependent on the sodium concentration; the dependence followed simple Michaelis-Menten kinetics. The apparent K _m for sodium was determined to be about 2 mmol/1. Sodium also stimulated acetate synthesis from H₂ plus CO₂. In the absence of added sodium the formation of formate as an intermediate in methyl group synthesis was stimulated. It is suggested that the sodium dependent reaction(s) is one (or more) of the reactions involved in methyl group synthesis from CO₂.     

Aerobic and anaerobic microbial consumption of hydrogen in geothermal spring water

Abstract Hydrogen consumption was measured in hot geothermal water from two ponds of the San Federigo solfatara, Tuscany, Italy, where emanation gases contained approx. 4% H₂. H₂ consumption was completely inhibited by NaOH and partially by HgCl₂ indicating microbial utilization. Aerobic and anaerobic H₂ consumption activities coexisted in the same water with aerobic activity being higher in one pond and anaerobic activity in the other. The kinetics of H₂ consumption were consistent with those of 'Knallgas', methanogenic or sulfidogenic bacteria.     

Temporal change of gas metabolism by hydrogen-syntrophic methanogenic bacterial associations in anoxic paddy soil

Abstract Interspecies H₂ transfer within methanogenic bacterial associations (MBA) accounted for 95–97% of the conversion of ¹⁴CO₂ to ¹⁴CH₄ in anoxic paddy soil. Only 3–5% of the ¹⁴CH₄ were produced from the turnover of dissolved H₂. The H₂-syntrophic MBA developed within 5 days after the paddy soil had been submerged and placed under anoxic atmosphere. Afterwards, both the contribution of MBA to H₂-dependent methanogenesis and the turnover of dissolved H₂ did not change significantly for up to 7 months of incubation. However, while the rates of H₂-dependent methanogenesis stayed relatively constant, the rates of total methanogenesis decreased. The contribution of MBA to H₂-dependent methanogenesis was further enhanced to 99% when the temperature was shifted from 30°C to 17°C, or when the soil had been planted with rice. This enhancement was partially due to an increased utilization of dissolved H₂ by chloroform-insensitive non-methanogenic bacteria, most probably homoacetogens, so that CH₄ production was almost completely restricted to H₂-syntrophic MBA. The activity of MBA, as measured by the conversion of ¹⁴CO₂ to ¹⁴CH₄, was stimulated by glucose, lactate, and ethanol to a similar or greater extent than by exogenous H₂. Propionate and acetate had no effect.     

Combined effects of varying water content and CO2 concentration on photosynthesis in Spagnum fuscum

The photosynthesis of Spagnum fuscum (Schimp.) Klinggr. at different water contents and CO₂ concentrations was measured in the laboratory. The optimal water content for photosynthesis near the current atmospheric CO₂ concentration is 600–800% (percentage of dry weight). The decrease in photosynthesis is very steep towards lower water contents and less steep towards higher water contents. The optimal water content range moves higher and becomes wider with increasing CO₂ concentration. At 3000 ppm there is no longer any decrease in photosynthesis with increasing water content. The water content of S. fuscum has a considerable effect on the response of photosynthesis to CO₂ concentration. In a moss saturated with water, photosynthesis increases gradually until 8000 ppm CO₂, but this saturation concentration becomes lower with decreasing water content, being c. 1500 ppm at a water content of 700–800%. An increase in CO₂ concentration over 300 ppm will raise photosynthesis very little in dry moss with a water content of only 300–400%.     

Response of Mediterranean coralline algae to ocean acidification and elevated temperature

The effects of elevated partial pressure of CO₂ ( p CO₂) and temperature, alone and in combination, on survival, calcification and dissolution were investigated in the crustose coralline alga Lithophyllum cabiochae . Algae were maintained in aquaria during 1 year at near-ambient conditions of irradiance, at ambient or elevated temperature (+3 °C) and at ambient [ca. 400 parts per million (ppm)] or elevated p CO₂ (ca. 700 ppm). Algal necroses appeared at the end of summer under elevated temperature first at 700 ppm (60% of the thallus surface) and then at 400 ppm (30%). The death of algae was observed only under elevated temperature and was two- to threefold higher under elevated p CO₂. During the first month of the experiment, net calcification was significantly reduced under elevated p CO₂. At the end of the summer period, net calcification decreased by 50% when both temperature and p CO₂ were elevated while no effect was found under elevated temperature and elevated p CO₂ alone. In autumn and winter, net calcification in healthy algae increased with increasing temperature, independently of the p CO₂ level, while necroses and death in the algal population caused a net dissolution at elevated temperature and p CO₂. The dissolution of dead algal thalli was affected by elevated p CO₂, being two- to fourfold higher than under ambient p CO₂. These results suggest that net dissolution is likely to exceed net calcification in L. cabiochae by the end of this century. This could have major consequences in terms of biodiversity and biogeochemistry in coralligenous communities dominated by these algae.     

The Effect of Elevated [CO2] on Uptake and Allocation of 13C and 15N in Beech (Fagus sylvatica L.) during Leafing

Abstract: A continuous dual ¹³CO₂ and ¹⁵NH₄¹⁵NO₃ labelling experiment was undertaken to determine the effects of ambient (350μmol mol^-1) or elevated (700μmol mol^-1) atmospheric CO₂ concentrations on C and N uptake and allocation within 3-year-old beech ( Fagus sylvatica L.) during leafing. After six weeks of growth, total carbon uptake was increased by 63 % (calculated on total C content) under elevated CO₂ but the carbon partitioning was not altered. 56 % of the new carbon was found in the leaves. On a dry weight basis was the content of structural biomass in leaves 10 % lower and the lignin content remained unaffected under elevated as compared to ambient [CO₂]. Under ambient [CO₂] 37 %, and under elevated [CO₂] 51 %, of the lignin C of the leaves derived from new assimilates. For both treatments, internal N pools provided more than 90 % of the nitrogen used for leaf-growth and the partitioning of nitrogen was not altered under elevated [CO₂]. The C/N ratio was unaffected by elevated [CO₂] at the whole plant level, but the C/N ratio of the new C and N uptake was increased by 32 % under elevated [CO₂].     

Cloning and DNA homology of 3-isopropylmalate dehydrogenase genes from thermophilic bacilli

Abstract Clostridium thermoaceticum was cultivated heterotrophically under CO₂, carbon monoxide (CO), and H₂ gas phases. Formate dehydrogenase (FDH) levels increased 4-fold in CO cultures; formyltetrahydrofolate synthetase (FTS) levels were not influenced by the cultivation gas phases tested. While CO dehydrogenase (CODH) was slightly stimulated in CO cultures, CO-dependent acetyl phosphate-synthesizing system (APSS) activity increased sharply in both CO and H₂ cultures. Y _glucose values increased, whereas doubling times and acetate to biomass ratios decreased significantly in CO cultures, suggesting that CO cultures were energetically dissimilar to non-CO cultures. This finding, together with the absence of CO-dependent ATP-independent synthesis of formyltetrahydrofolate (formyl-THF), supports the hypothesis that conservation of CO-derived energy involves electron transport phosphorylation.     

Transformation of tetrachloroethylene to trichloroethylene by homoacetogenic bacteria

Abstract Eight homoacetogenic strains of the genera Acetobacterium, Clostridium and Sporomusa were tested for their ability to dechlorinate tetrachloroethylene (perchloroethene, PCE). Of the organisms tested only Sporomusa ovata was able to reductively dechlorinate PCE with methanol as an electron donor. Resting cells of S. ovata reductively dechlorinated PCE at a rate of 9.8 nmol h⁻¹ (mg protein)⁻¹ to trichloroethylene (TCE) as the sole product. The dechlorination activity depended on concomitant acetogenesis from methanol and CO₂. Cell-free extracts of S. ovata, Clostridium formicoaceticum, Acetobacterium woodii , and the methanogenic bacterium Methanolobus tindarius transformed PCE to TCE with Ti(III) or carbon monoxide as electron donors. Corrinoids were shown in S. ovata to be involved in the dechlorination reaction of PCE to TCE as evident from the reversible inhibition with propyl iodide. Rates of dechlorination followed a pseudo-first-order kinetic.     

Influence of leaf chemistry of Lotus corniculatus (Fabaceae) on larval development of Polyommatus icarus (Lepidoptera, Lycaenidae): effects of elevated CO2 and plant genotype

1. Four Lotus corniculatus genotypes differing in cyanoglycoside and condensed tannin concentrations were grown in either low (350 ppm) or high (700 ppm) atmospheric CO₂ environments. Larval performance, consumption and conversion efficiency of Polyommatus icarus feeding on this plant material were measured.
2. Plants grown under elevated CO₂ contained less cyanoglycosides, more condensed tannins and more starch than control plants. However, water concentration, nitrogen and protein as well as nitrogen concentration in relation to carbon concentration did not differ between CO₂ treatments.
3. The four genotypes differed significantly in condensed tannins, cyanoglucoside, leaf water and leaf nitrogen but no genotype–CO₂ interaction was detected, except for total phenolics and condensed tannins in which two plant genotypes showed stronger increases under elevated CO₂ than the other two.
4. Larvae of P . icarus consumed more plant material and used and converted it more efficiently from plants grown at high atmospheric CO₂.
5. Larvae developed significantly faster and were significantly heavier when fed plant material grown under elevated CO₂. The observed difference in mass disappeared in the pupal and adult stages. However, lipid concentration of adults from the elevated CO₂ treatment was marginally significantly higher than of controls.
6. It is concluded that the higher carbohydrate concentration of L . corniculatus plants grown at elevated CO₂ renders leaves more suitable and better digestible to P . icarus . Furthermore, differences in allelochemicals might influence the palatability of L . corniculatus leaves for this specialist on Fabaceae.     

Combined effect of organic acids and supercritical carbon dioxide treatments against nonpathogenic Escherichia coli, Listeria monocytogenes, Salmonella typhimurium and E. coli O157:H7 in fresh pork

Aims:  To evaluate the effectiveness of organic acids and supercritical carbon dioxide (SC-CO₂) treatments as well as their combined effect for the reduction of nonpathogenic Escherichia coli and three pathogenic bacteria in fresh pork.
Methods and Results:  The different treatment conditions were as follows: (i) treatment with acetic (1%, 2% or 3%) or lactic acid (1%, 2% or 3%) only, (ii) treatment with SC-CO₂ at 12 MPa and 35°C for 30 min only and (iii) treatment with 3% acetic or lactic acid followed by treatment with SC-CO₂. Within the same organic acid concentration, the lactic and acetic acid treatments had similar reductions. For the combined treatment of lactic acid and SC-CO₂, micro-organism levels were maximally reduced, ranging from 2·10 to 2·60 log CFU cm⁻² ( E. coli , 2·58 log CFU cm⁻²; Listeria monocytogenes , 2·60 log CFU cm⁻²; Salmonella typhimurium , 2·33 log CFU cm⁻²; E. coli O157:H7, 2·10 log CFU cm⁻²).
Conclusions:  The results of this study indicate that the combined treatments of SC-CO₂ and organic acids were more effective at destroying foodborne pathogens than the treatments of SC-CO₂ or organic acids alone.
Significance and Impact of the Study:  The combination treatment of SC-CO₂ and organic acids may be useful in the meat industry to help increase microbial safety.     

PCR amplification of the 3'' external transcribed and intergenic spacers of the ribosomal DNA repeat unit in three species of Saccharomyces

Abstract Desulfotomaculum thermobenzoicum TSB converted 4 mol pyruvate to 5 mol acetate in the absence of sulfate. The cells grown on pyruvate without sulfate showed both carbon monoxide dehydrogenase (CODH) and methylmalonyl-CoA: pyruvate transcarboxylase activities. However, considering the fermentation products, the acetogenesis from pyruvate might be conducted by CODH pathway rather than methylmalonyl-CoA pathway. Contrary to this finding, Desulfobulbus propionicus MUD fermented 3 mol pyruvate to 2 mol acetate and 1 mol propionate stoichiometrically via methylmalonyl-CoA pathway. Desulfovibrio vulgaris Marburg, which has neither the CODH pathway nor the methylmalonyl-CoA pathway, converted pyruvate to acetate, H₂ and CO₂ as the main products. These results indicate that the fermentation pattern of pyruvate depends on the metabolic characteristics of each sulfate-reducing bacterium.     

Rice production in a changing climate: a meta-analysis of responses to elevated carbon dioxide and elevated ozone concentration

Rice is arguably the most important food source on the planet and is consumed by over half of the world's population. Considerable increases in yield are required over this century to continue feeding the world's growing population. This meta-analysis synthesizes the research to date on rice responses to two elements of global change, rising atmospheric carbon dioxide concentration ([CO₂]) and rising tropospheric ozone concentration ([O₃]). On an average, elevated [CO₂] (627 ppm) increased rice yields by 23%. Modest increases in grain mass and larger increases in panicle and grain number contributed to this response. The response of rice to elevated [CO₂] varied with fumigation technique. The more closely the fumigation conditions mimicked field conditions, the smaller was the stimulation of yield by elevated [CO₂]. Free air concentration enrichment (FACE) experiments showed only a 12% increase in rice yield. The rise in atmospheric [CO₂] will be accompanied by increases in tropospheric O₃ and temperature. When compared with rice grown in charcoal-filtered air, rice exposed to 62 ppb O₃ showed a 14% decrease in yield. Many determinants of yield, including photosynthesis, biomass, leaf area index, grain number and grain mass, were reduced by elevated [O₃]. While there have been too few studies of the interaction of CO₂ and O₃ for meta-analysis, the interaction of temperature and CO₂ has been studied more widely. Elevated temperature treatments negated any enhancement in rice yield at elevated [CO₂], which suggests that identifying high temperature tolerant germplasm will be key to realizing yield benefits in the future.     

Inheritance of resistance and cross resistance pattern in indoxacarb-resistant diamondback moth Plutella xylostella L.

Leaf-dip assay of Plutella xylostella against indoxacarb showed that the concentration that produced 50% mortality (LC₅₀) of indoxacarb ranged from 20.1 to 11.9 ppm, with highest in Nasik and lowest levels in Coimbatore strains. In selection studies, the LC₅₀ of indoxacarb was 18.5 ppm at generation 1 (G1), which increased to 31.3-fold (167.8 ppm) resistance after ten exposed generations (G10) as compared to unexposed. The LC₅₀ of quinalphos was 74.4 ppm, which increased to 10.0-fold (631.5 ppm) resistance after G10. The LC₅₀ of cypermethrin resistant strain resulted in an 11.5-fold increase in resistance after G10. In P. xylostella , heritability (h²) after ten generations of selection was estimated at 0.4. The number of generations required for tenfold increase in LC₅₀ (1/R) were 6.7. The response to indoxacarb selection in P. xylostella was 0.2 and the selection differential was estimated as 0.4. The phenotypic standard deviation was 0.2. Reciprocal crosses between indoxacarb-resistant and susceptible strains showed that the inheritance of indoxacarb resistance was autosomal. The degree of heritability (D_LC) (0.4, 0.4) indicated incomplete recessive inheritance of indoxacarb resistance.     

The Eocene Arctic Azolla bloom: environmental conditions, productivity and carbon drawdown

Enormous quantities of the free-floating freshwater fern Azolla grew and reproduced in situ in the Arctic Ocean during the middle Eocene, as was demonstrated by microscopic analysis of microlaminated sediments recovered from the Lomonosov Ridge during Integrated Ocean Drilling Program (IODP) Expedition 302. The timing of the Azolla phase (~48.5 Ma) coincides with the earliest signs of onset of the transition from a greenhouse towards the modern icehouse Earth. The sustained growth of Azolla , currently ranking among the fastest growing plants on Earth, in a major anoxic oceanic basin may have contributed to decreasing atmospheric p CO₂ levels via burial of Azolla -derived organic matter. The consequences of these enormous Azolla blooms for regional and global nutrient and carbon cycles are still largely unknown. Cultivation experiments have been set up to investigate the influence of elevated p CO₂ on Azolla growth, showing a marked increase in Azolla productivity under elevated (760 and 1910 ppm) p CO₂ conditions. The combined results of organic carbon, sulphur, nitrogen content and ¹⁵N and ¹³C measurements of sediments from the Azolla interval illustrate the potential contribution of nitrogen fixation in a euxinic stratified Eocene Arctic. Flux calculations were used to quantitatively reconstruct the potential storage of carbon (0.9–3.5 10¹⁸ gC) in the Arctic during the Azolla interval. It is estimated that storing 0.9 10¹⁸ to 3.5 10¹⁸ g carbon would result in a 55 to 470 ppm drawdown of p CO₂ under Eocene conditions, indicating that the Arctic Azolla blooms may have had a significant effect on global atmospheric p CO₂ levels through enhanced burial of organic matter.     

A relationship between carbon dioxide, photosynthetic efficiency and shade tolerance

Net photosynthesis and transpiration of seedlings from shade tolerant, moderately tolerant and intolerant tree species were measured in ambient carbon dioxide (CO₂) concentrations ranging from 312 to 734 ppm. The species used, Fagus grandifolia Ehrh. (tolerant), Quercus alba L., Q. rubra L., Liriodendron tulipifera L. (moderately tolerant), Liquidambar styraciflua L. and Pinus taeda L. (intolerant), are found co-occurring in the mixed pine-hardwood forests of the Piedmont region of the southeastern United States. When seedlings were grown in shaded conditions, photosynthetic CO₂ efficiency was significantly different in all species with the highest efficiency in the most shade tolerant species, Fagus grandifolia , and progressively lower efficiencies in moderately tolerant and intolerant species. Photosynthetic CO₂ efficiency was defined as the rate of increase in net photosynthesis with increase in ambient CO₂ concentration. When plants which had grown in a high light environment were tested, the moderately tolerant and intolerant deciduous species had the highest photosynthetic CO₂ efficiencies but this capacity was reduced when these species grew in low light. The lowest CO₂ efficiency and apparent quantum yield occurred in Pinus taeda in all cases. Water use efficiency was higher for all species in enriched CO₂ environments but transpiration rate and leaf conductance were not affected by CO₂ concentration. High photosynthetic CO₂ efficiency may be advantageous for maintaining a positive carbon balance in the low light environment under a forest canopy.     

Flooding, gas exchange and hydraulic root conductivity of highbush blueberry

Highbush blueberry plants ( Vaccinium corymbosum L. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO₂ and O₂ concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO₂ levels on carbon assimilation less for flooded than unflooded plants after short-(i-2 days), intermediate-(10–14 days) and long-term (35–40 days) flooding. A reduction in O₂ levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO₂ fixed (mol CO₂)⁻¹. Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O₂, averaging 0.005 mol CO₂ fixed (mol CO₂)⁻¹. Apparent quantum yield decreased from 2.2 × 10⁻¹ mol of CO₂ fixed (mol light)⁻¹ for unflooded plants to 2.0 × 10⁻³ and 9.0 × 10⁻⁴ for intermediate- and long-term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf.     

Are legume‐feeding herbivores buffered against direct effects of elevated carbon dioxide on host plants? A test with the sulfur butterfly,Colias philodice

When grown under elevated atmospheric carbon dioxide (CO₂), leaf nitrogen content decreases less for legumes than for nonlegume C₃ plants. Given that elevated CO₂ adversely affects insect herbivores primarily through dilution of plant nitrogen, it is reasonable to expect that legume-feeding herbivores will be relatively buffered against CO₂-induced reduction in performance. However, despite their ecological and economic importance, very few studies have addressed the effects of elevated CO₂ on legume-feeding herbivores. Unlike the responses of the vast majority of nonlegume C₃ plants, when the legumes Trifolium pratense and Melilotus alba were grown under elevated (742 ppm) CO₂, leaf nitrogen and carbon contents and C : N ratios did not change. For Colias philodice larvae fed T. pratense , elevated CO₂ had little or no effect on consumption, digestion, or conversion of whole food or nitrogen and, consequently, no effect on growth rate, instar duration, or pupal weight. For larvae fed M. alba , elevated CO₂ had little or no effect on consumption of whole food or nitrogen, increased digestion but decreased conversion of both and, consequently, had no effect on growth rate, instar duration or pupal weight. These results suggest that, relative to herbivores of nonlegume C₃ plants, legume-feeding herbivores will be less affected as atmospheric CO₂ continues to rise.     

Evidence for cytochrome P-450 and P-450-mediated benzo(a) pyrene hydroxylation in the white rot fungus Phanerochaete chrysosporium

Abstract The presence of cytochrome P-450 and P-450-mediated benzo(a)pyrene hydroxylase activity in both microsomal and soluble fractions of the white rot fungus Phanerochaete chrysosporium was shown. The reduced carbon monoxide difference spectrum showed maxima at 448–450 and 452–454 nm for microsomal and cytosolic fractions, respectively. Both P-450 fractions produced a Type I substrate binding spectrum on addition of benzo(a)pyrene. Activity for benzo(a)pyrene hydroxylation was NADPH-dependent and inhibited by carbon monoxide. K _m values for activity showed a difference between the cellular fractions with a K _m of 89 μM for microsomal P-450 and 400 μM for cytosolic P-450. The V _max values observed were 0.83 nmol min⁻ (nmol microsomal P-450) ⁻¹ and 0.4 nmol min⁻¹ (nmol cytosolic P-450)⁻¹. The results indicate that P-450-mediated benzo(a)pyrene hydroxylase activity could play a role in xenobiotic transformation by this fungus beside the known ligninolytic exocellular enzymes.     

The glands of Tamarix aphylla: a system for salt recretion or for carbon concentration?

During periods of high atmospheric humidity, twigs of Tamarix aphylla (L.) Karst. become covered by an alkaline solution. The pH of that solution fluctuates between 8.0 – 8.5 in the dark and 10.5 during the light hours. Such a solution, produced by the glands, constitutes an efficient trap for atmospheric CO₂. Upon the periodic drop in pH, much of the preabsorbed carbon may gradually be released from the solution. This enriches the immediate surroundings of the twigs with CO₂ for prolonged periods of time. The expected concentrations of CO₂, at the boundary layer between the atmosphere and the surfaces of the twigs, are over 1 000 ppm. As net photosynthesis of T. aphylla reaches maximal rates only at CO₂ concentrations of above 500 ppm, the plants may benefit from this extra source of carbon and may exploit it for maximal assimilation during the early morning hours. Thus, the "salt glands'of Tamarix , which are liable for the production of the alkaline recretum, may serve a triple purpose: (a) removal of excess salts out of the twigs, (b) provision of a cover of hygroscopic solutes that moistens the twigs and shortens the duration of transpiration, and (c) providing the plants with an environment enriched in CO₂.