Using the voltage-multiplying circuits of chemolitho-autotrophic Fe-oxidizing bacteria (Mariprofundus ferrooxydans), we describe an integrated bioelectrochemical system that affords simultaneous CO2 reduction and H2O oxidation at an external voltage of less than 1.24 V.

Respiration consumes a large portion of annual gross primary productivity in forest ecosystems and is dominated by belowground metabolism. Here, we present evidence of a previously unaccounted for internal CO(2) flux of large magnitude from tree roots through stems. If this pattern is shown to persist over time and in other forests, it suggests that belowground respiration has been grossly unde...

Imbalances in phylogenetic diversity could be the result of variable diversification rates, differing limits on diversity, or a combination of the two. We propose an approach to distinguish between rates and limits as the primary cause of phylogenetic imbalance, using parasitic plants as a model. With sister-taxon comparisons, we show that parasitic plant lineages are typically much less divers...

In the facultative autotrophic organism Chloroflexus aurantiacus, a phototrophic green nonsulfur bacterium, the Calvin cycle does not appear to be operative in autotrophic carbon assimilation. An alternative cyclic pathway, the 3-hydroxypropionate cycle, has been proposed. In this pathway, acetyl coenzyme A (acetyl-CoA) is assumed to be converted to malate, and two CO(2) molecules are thereby f...

In wastewater treatment plants with anaerobic sludge digestion, 15–20% of the nitrogen load is recirculated to the main stream with the return liquors from dewatering. Separate treatment of this ammonium-rich digester supernatant significantly reduces the nitrogen load of the activated sludge system. Two biological applications are considered for nitrogen elimination: (i) classical autotrophic ...

Autotrophic members of the Sulfolobales (Crenarchaeota) contain acetyl-coenzyme A (CoA)/propionyl-CoA carboxylase as the CO2 fixation enzyme and use a modified 3-hydroxypropionate cycle to assimilate CO2 into cell material. In this central metabolic pathway malonyl-CoA, the product of acetyl-CoA carboxylation, is further reduced to 3-hydroxypropionate. Extracts of Metallosphaera sedula containe...

Marine Crenarchaeota represent an abundant component of oceanic microbiota with potential to significantly influence biogeochemical cycling in marine ecosystems. Prior studies using specific archaeal lipid biomarkers and isotopic analyses indicated that planktonic Crenarchaeota have the capacity for autotrophic growth, and more recent cultivation studies support an ammonia-based chemolithoautot...

The expression of the cbb and gap-pgk operons of Xanthobacter flavus encoding enzymes of the Calvin cycle is regulated by the transcriptional regulator CbbR. In order to identify other genes involved in the regulation of these operons, a mutant was isolated with a lowered activity of a fusion between the promoter of the cbb operon and the reporter gene lacZ. This mutant was unable to grow autot...

Rose and Caron (2007) have compiled a comprehensive data set of individual growth rates of planktonic protists in an attempt to answer a fundamental question in marine ecology: ‘‘Why are blooms of phytoplankton such common events in the ocean?’’. They reach the interesting conclusion that, because the temperature dependence of the growth rate of heterotrophic protists is much stronger than that...