Nitrification is a core process in the global nitrogen cycle that is essential for the functioning of many ecosystems. The discovery of autotrophic ammonia-oxidizing archaea (AOA) within the phylum Thaumarchaeota has changed our perception of the microbiology of nitrification, in particular since their numerical dominance over ammonia-oxidizing bacteria (AOB) in many environments has been revealed. These and other data have led to a widely held assumption that all amoA-encoding members of the Thaumarchaeota (AEA) are autotrophic nitrifiers. In this study, 52 municipal and industrial wastewater treatment plants were screened for the presence of AEA and AOB. Thaumarchaeota carrying amoA were detected in high abundance only in four industrial plants. In one plant, thaumarchaeotes closely related to soil group I.1b outnumbered AOB up to 10,000-fold, and their numbers, which can only be explained by active growth in this continuous culture system, were two to three orders of magnitude higher than could be sustained by autotrophic ammonia oxidation. Consistently, 14 CO 2 fixation could only be detected in AOB but not in AEA in actively nitrifying sludge from this plant via FISH combined with microautoradiography. Furthermore, in situ transcription of archaeal amoA, and very weak in situ labeling of crenarchaeol after addition of 13 CO 2 , was independent of the addition of ammonium. These data demonstrate that some amoA-carrying group I.1b Thaumarchaeota are not obligate chemolithoautotrophs.heterotrophy | physiology | modeling | ammonia monooxygenase

While the contribution of Bacteria to bioremediation of oil-contaminated shorelines is well established, the response of Archaea to spilled oil and bioremediation treatments is unknown. The relationship between archaeal community structure and oil spill bioremediation was examined in laboratory microcosms and in a bioremediation field trial. 16S rRNA gene-based PCR and denaturing gradient gel analysis revealed that the archaeal community in oil-free laboratory microcosms was stable for 26 days. In contrast, in oil-polluted microcosms a dramatic decrease in the ability to detect Archaea was observed, and it was not possible to amplify fragments of archaeal 16S rRNA genes from samples taken from microcosms treated with oil. This was the case irrespective of whether a bioremediation treatment (addition of inorganic nutrients) was applied. Since rapid oil biodegradation occurred in nutrient-treated microcosms, we concluded that Archaea are unlikely to play a role in oil degradation in beach ecosystems. A clear-cut relationship between the presence of oil and the absence of Archaea was not apparent in the field experiment. This may have been related to continuous inoculation of beach sediments in the field with Archaea from seawater or invertebrates and shows that the reestablishment of Archaea following bioremediation cannot be used as a determinant of ecosystem recovery following bioremediation. Comparative 16S rRNA sequence analysis showed that the majority of the Archaea detected (94%) belonged to a novel, distinct cluster of group II uncultured Euryarchaeota, which exhibited less than 87% identity to previously described sequences. A minor contribution of group I uncultured Crenarchaeota was observed.

Heterotrophic activity in macroalgae has been little studied, but the red macroalga Grateloupia doryphora is known to grow in light at a higher rate in a glycerol-containing medium than in seawater. The effects of 0.1 M exogenous glycerol in seawater (SW90-gly) on the respiration rate of G. doryphova and the role played by light were investigated. The algae pretreated for 2 h in the light and in SW90-gly evolved oxygen and fixed carbon dioxide ( H~~c o , ) , but also evolved radioactive I4co2 from [L4~]glycerol. The rate of oxygen evolution was lower than that of samples in seawater, due to a high respiration rate and/or a partial inhibition of photosynthesis induced ~U L I L I~J L , LLLC t a~c ui i i i u i~a i i i c c o i v v i i i i n a i i u i i v v a~ i i i s i i c i 11non-photosynthetic patterns were operating. In darkness, after pretreatment in the light in SW90-gly, samples showed a high oxygen uptake rate just after the light was turned off. Twenty minutes of darkness were enough to decrease this high respiration rate to that of samples in seawater. The oxygen uptake observed in al1 experiments with glycerol was mitochondrial as it was inhibited by potassium a cyanide and salicylhydroxamic acid (SHAM). Pretreatment of samples in the light in SW90-gly with the photosynthetic inhibitor DCMU ! .did not inhibit ensuing dark respiration, thus providing evidence for a non-photosynthetic effect of the light. The highest dark respiration E rate was observed after the samples were pretreated in monochromatic blue light in glycerol-containing media.

No abstract

No abstract