Anaerobic coculture of microalgae with Thermosipho globiformans and Methanocaldococcus jannaschii at 68°C enhances generation of n-alkane-rich biofuels after pyrolysis.

We tested different alga-bacterium-archaeon consortia to investigate the production of oil-like mixtures, expecting that n-alkane-rich biofuels might be synthesized after pyrolysis. Thermosipho globiformans and Methanocaldococcus jannaschii were cocultured at 68°C with microalgae for 9 days under two anaerobic conditions, followed by pyrolysis at 300°C for 4 days. Arthrospira platensis (Cyanobacteria), Dunaliella tertiolecta (Chlorophyta), Emiliania huxleyi (Haptophyta), and Euglena gracilis (Euglenophyta) served as microalgal raw materials. D. tertiolecta, E. huxleyi, and E. gracilis cocultured with the bacterium and archaeon inhibited their growth and CH(4) production. E. huxleyi had the strongest inhibitory effect. Biofuel generation was enhanced by reducing impurities containing alkanenitriles during pyrolysis. The composition and amounts of n-alkanes produced by pyrolysis were closely related to the lipid contents and composition of the microalgae. Pyrolysis of A. platensis and D. tertiolecta containing mainly phospholipids and glycolipids generated short-carbon-chain n-alkanes (n-tridecane to n-nonadecane) and considerable amounts of isoprenoids. E. gracilis also produced mainly short n-alkanes. In contrast, E. huxleyi containing long-chain (31 and 33 carbon atoms) alkenes and very long-chain (37 to 39 carbon atoms) alkenones, in addition to phospholipids and glycolipids, generated a high yield of n-alkanes of various lengths (n-tridecane to n-pentatriacontane). The gas chromatography-mass spectrometry (GC-MS) profiles of these n-alkanes were similar to those of native petroleum crude oils despite containing a considerable amount of n-hentriacontane. The ratio of phytane to n-octadecane was also similar to that of native crude oils.

Coenzyme F420-dependent sulfite reductase-enabled sulfite detoxification and use of sulfite as a sole sulfur source by Methanococcus maripaludis.

Coenzyme F(420)-dependent sulfite reductase (Fsr) of Methanocaldococcus jannaschii, a sulfite-tolerant methanogen, was expressed with activity in Methanococcus maripaludis, a sulfite-sensitive methanogen. The recombinant organism reduced sulfite to sulfide and grew with sulfite as the sole sulfur source, indicating that Fsr is a sulfite detoxification and assimilation enzyme for methanogens and that M. maripaludis synthesizes siroheme.

Phylogenetic diversity of the archaeal community in a continental high-temperature, water-flooded petroleum reservoir.

The diversity of an archaeal community was analyzed in the water from a continental high-temperature, long-term water-flooded petroleum reservoir in Huabei Oilfield in China. The archaea were characterized by their 16S rRNA genes. An archaeal 16S rDNA clone library was constructed from the DNA isolated from the formation water, and 237 randomly selected positive clones were clustered in 28 phylotypes by sequencing analyses. Phylogenetic analysis of these sequences indicated that the dominant members of the archaeal phylotypes were affiliated with the order Methanomicrobiales. Totally, the archaeal community was composed of methanogens belonging to four orders: Methanobacteriales, Methanococcales, Methanomicrobiales, and Methanosarcinales. Most of the clones clustered with sequences previously described for methanogens, but there was a difference in the relative distribution of sequences detected here as compared to that of previous studies. Some thermophilic methanogens detected had been previously isolated from a number of high-temperature petroleum reservoirs worldwide; thus, they might exhibit adaptations to the environments and be the common habitants of geothermally heated subsurface environments.

Aerobic methane oxidation and methanotroph community composition during seasonal stratification in Mono Lake, California (USA).

Patterns of aerobic methane (CH4) oxidation and associated methanotroph community composition were investigated during the development of seasonal stratification in Mono Lake, California (USA). CH4 oxidation rates were measured using a tritiated CH4 radiotracer technique. Fluorescence in situ hybridization (FISH), denaturing gradient gel electrophoresis (DGGE) and sequence analysis were used to characterize methanotroph community composition. A temporally shifting zone of elevated CH4 oxidation (59-123 nM day(-1)) was consistently associated with a suboxycline, microaerophilic zone that migrated upwards in the water column as stratification progressed. FISH analysis revealed stable numbers of type I (4.1-9.3 x 10(5) cells ml(-1)) and type II (1.4-3.4 x 10(5) cells ml(-1)) methanotrophs over depth and over time. Denaturing gradient gel electrophoresis and sequence analysis indicated slight shifts in methanotroph community composition despite stable absolute cell numbers. Variable CH4 oxidation rates in the presence of a relatively stable methanotroph population suggested that zones of high CH4 oxidation resulted from an increase in activity of a subset of the existing methanotroph population. These results challenge existing paradigms suggesting that zones of elevated CH4 oxidation activity result from the accumulation of methanotrophic biomass and illustrate that type II methanotrophs may be an important component of the methanotroph population in saline and/or alkaline pelagic environments.

Methanotorris formicicus sp. nov., a novel extremely thermophilic, methane-producing archaeon isolated from a black smoker chimney in the Central Indian Ridge.

A novel extremely thermophilic, methane-producing archaeon was isolated from a black smoker chimney at the Kairei field in the Central Indian Ridge. Cells of this isolate were irregular cocci with several flagella; motility was not observed. Growth was observed between 55 and 83 degrees C (optimum of 75 degrees C; 30 min doubling time) and between pH 6.0 and 8.5 (optimum of pH 6.7). The isolate was a strictly anaerobic, methanogenic autotroph capable of using hydrogen and carbon dioxide as sole energy and carbon sources. Formate was utilized as an alternative energy source. The G+C content of the genomic DNA was 33.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate was most closely related to Methanotorris igneus strain Kol 5T. The isolate, however, could be genetically differentiated from this species by DNA-DNA hybridization analysis and on the basis of its physiological properties. The name Methanotorris formicicus sp. nov. is proposed for this isolate; the type strain is Mc-S-70T (=JCM 11930T=ATCC BAA-687T).

Sulfide ameliorates metal toxicity for deep-sea hydrothermal vent archaea.

The chemical stress factors for microbial life at deep-sea hydrothermal vents include high concentrations of heavy metals and sulfide. Three hyperthermophilic vent archaea, the sulfur-reducing heterotrophs Thermococcus fumicolans and Pyrococcus strain GB-D and the chemolithoautotrophic methanogen Methanocaldococcus jannaschii, were tested for survival tolerance to heavy metals (Zn, Co, and Cu) and sulfide. The sulfide addition consistently ameliorated the high toxicity of free metal cations by the formation of dissolved metal-sulfide complexes as well as solid precipitates. Thus, chemical speciation of heavy metals with sulfide allows hydrothermal vent archaea to tolerate otherwise toxic metal concentrations in their natural environment.

Cold adaptation of archaeal elongation factor 2 (EF-2) proteins.

Cell growth at low temperature is dependent on the ability of cells to perform protein synthesis. Cold adapted micro-organisms (psychrophilic or psychrotolerant) have a superior ability to perform translation at low temperature. This review addresses cold adaptation of protein synthesis in Archaea by examining what is presently known about thermal adaptation of elongation factor 2 (EF-2) proteins from Archaea. Despite the knowledge that Archaea are abundant in cold environments (e.g. the ocean), few cold adapted species have been isolated and studied. As a result this review is largely confined to comparative analyses of EF-2 proteins from psychrotolerant (Methanococcoides burtonii) and thermophilic (Methanosarcina thermophila) methanogens. A key finding from these studies is that in addition to inherent properties of the EF-2 proteins, intracellular factors (e.g. ribosomes and intracellular solutes) play a central role in thermal adaptation.