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#archaeal species

2 public questions tagged with this topic.

Microbial Physiology

Which archaeal species contains pseudomurein in its cell wall?

Distribution of pseudomurein within Archaea is limited to certain methanogenic euryarchaeota that build rigid wall sacculus, whereas many other archaea rely solely on proteinaceous S-layers. Methanobrevibacter species, including human commensal Methanobrevibacter smithii and rumen isolate Methanobrevibacter ruminantium within order Methanobacteriales, synthesize pseudomurein composed of N-acetylglucosamine and N-acetyltalosaminuronic acid linked beta-1,3 and crosslinked with tetrapeptides containing L-amino acids. Related genera like Methanobacterium and Methanothermobacter share this trait, distinguishing them from methanococci and methanosarcinales that lack walls. Sulfolobus, a crenarchaeon, possesses S-layer and tetraether lipids but not pseudomurein. Thermococcus, also euryarchaeon but within Thermococcales, possesses only S-layer or glycoprotein sheath. Thus among choices presented, Methanobrevibacter clearly contains pseudomurein, exemplifying lineage-specific wall innovation, while statement that all listed genera possess it would be incorrect because envelope diversity across archaea is extensive and pseudomurein evolved only within methanobacteriales and related orders. Interestingly, Methanobacteriales also produce unique coenzymes such as coenzyme M and methanofuran essential for methanogenesis, linking wall chemistry with specialized metabolism, and environmental surveys detect pseudomurein-encoding genes only within this lineage, confirming narrow distribution that supports using pseudomurein as chemotaxonomic marker for this group.

Ref: Kandler, Microbiol Sci 1982, Pseudomurein Distribution; Doddema et al., Int J Syst Bacteriol 1982, Methanobrevibacter.

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Microbial Physiology

Which of the following archaeal species does NOT contain histones?

Histones were long considered exclusive to eukaryotes, organizing DNA into nucleosomes with wrapping around octameric cores. Discovery of archaeal histones revealed evolutionary connection, yet distribution is not uniform. Euryarchaeota such as Methanothermus fervidus, Methanothermus sociabilis, and halophiles like Halobacterium salinarum encode HMf and HMt family histones that form tetramers wrapping DNA into nucleosome-like particles and regulating transcription by restricting access. These histones share histone fold motif with eukaryotic H3 and H4. In contrast, most members of Crenarchaeota, particularly hyperthermophilic genera like Sulfolobus acidocaldarius, Thermoproteus, and Pyrolobus, lack sequence homologs of true histones and instead use alternative DNA packaging proteins such as Alba, Sul7d, and Cren7 that coat DNA and introduce supercoiling. This pattern suggests histone-based chromatin is characteristic of Euryarchaeota rather than all archaea, reflecting diverse strategies for genome compaction under extreme conditions and differing sensitivity to thermal denaturation, influencing gene regulation and adaptation. Alba proteins abundant in Sulfolobus bind cooperatively to double-stranded DNA, bridging strands, regulating transcription and protecting against thermal denaturation, illustrating how crenarchaeota employ non-histone architectural proteins functionally analogous to histones yet structurally unrelated, diversifying chromatin strategies across archaeal phylum.

Ref: Sandman & Reeve, Curr Opin Microbiol 2006, Archaeal Histones; White & Bell, Trends Genet 2002, Chromatin in Archaea.

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