Model organisms for genetics in the domain Archaea: methanogens, halophiles,ThermococcalesandSulfolobales

Abstract

The tree of life is split into three main branches: eukaryotes, bacteria, and archaea. Our knowledge of eukaryotic and bacteria cell biology has been built on a foundation of studies in model organisms, using the complementary approaches of genetics and biochemistry. Archaea have led to some exciting discoveries in the field of biochemistry, but archaeal genetics has been slow to get off the ground, not least because these organisms inhabit some of the more inhospitable places on earth and are therefore believed to be difficult to culture. In fact, many species can be cultivated with relative ease and there has been tremendous progress in the development of genetic tools for both major archaeal phyla, the Euryarchaeota and the Crenarchaeota. There are several model organisms available for methanogens, halophiles, and thermophiles; in the latter group, there are genetic systems for Sulfolobales and Thermococcales. In this review, we present the advantages and disadvantages of working with each archaeal group, give an overview of their different genetic systems, and direct the neophyte archaeologist to the most appropriate model organism.

Essential anaplerotic role for the energy-converting hydrogenase Eha in hydrogenotrophic methanogenesis

“…Our initial question was whether H 2 is a necessary substrate or intermediate for growth of hydrogenotrophic methanogens. Methanococcus maripaludis was an ideal species for addressing this question because it can substitute formate for H 2 and mutations are easily generated (10). In the conventional view, during growth on formate, H 2 generated from formate serves as the electron donor.…”

Anaerobic Metabolism in Haloferax Genus

“…As mentioned before, haloarchaea are oxygen-respiring heterotrophs that derive from methanogens-strictly anaerobic, hydrogen-dependent autotrophs (Leigh et al, 2011;NelsonSathi et al, 2012). Haloarchaeal genomes are known to have acquired, via lateral gene transfer (LGT), several genes from eubacteria.…”

“…In fact, it has been proposed that haloarchaea descended from methanogens that acquire the genes for aerobic respiration from Bacteria (Leigh et al, 2011).…”

“…This feature increases the stability of the genome within a cytoplasm with high ionic strength. Another possible advantage would be that a G+C rich genome decreases the possible targets of insertion sequences (IS) elements, which recognise A + T rich regions (Leigh et al, 2011). IS sequences were studied in Hfx.…”

Filogenia molecular e cultivo de Archaea de solos de Cerrado sensu strictoc

“…A amostra ambiental era colocada entre as membranas e a câmara de difusão era então submersa em um aquário contendo sedimentos e água provenientes do mesmo local da amostra. Tal técnica permitiu o cultivo de vários microrganismos não cultivados anteriormente e enfatizou a importância das condições naturais no estabelecimento bem sucedido de culturas laboratoriais.Em relação às archaeas especificamente, as dificuldades envolvendo seu cultivo vêm sendo reportadas na literatura com frequência (Schleper et al, 2005;Vartoukian et al, 2010;Leigh et al, 2011). Um artigo recente relata que, até 2010, apenas cerca de 60 espécies de archaeas haviam sido cultivadas em meios artificiais (Auguet et al, 2010).…”