Biology:Hydrobacteria

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Short description: Clade of bacteria

Hydrobacteria
EscherichiaColi NIAID.jpg
Escherichia coli cells magnified 25,000 times
Scientific classification e
Domain: Bacteria
Clade: Hydrobacteria
Battistuzzi and Hedges 2009[1]
Superphyla/Phyla

Hydrobacteria is a taxon containing approximately one-third of prokaryote species, mostly gram-negative bacteria and their relatives.[1] It was found to be the closest relative of an even larger group of Bacteria, Terrabacteria, which are mostly gram positive bacteria.[2][1] The name Hydrobacteria (hydro = "water") refers to the moist environment inferred for the common ancestor of those species. In contrast, species of Terrabacteria possess adaptations for life on land.[2][1]

The content of Hydrobacteria has grown to include these superphyla and phyla: Acidobacteriota, Aquificota, Bdellovibrionota, Campylobacterota, Deferribacterota, Dependentiae, Desulfobacterota, Desulfuromonadota, Elusimicrobiota, FCB superphylum, Myxococcota, Nitrospirota, Proteobacteria, PVC superphylum, and Spirochaetota.[3][4]

Some unrooted molecular phylogenetic analyses[5][6] have not supported this dichotomy of Terrabacteria and Hydrobacteria, but the most recent genomic analyses,[3][4] including those that have focused on rooting the tree,[3] have found these two groups to be monophyletic.

Hydrobacteria and Terrabacteria were inferred to have diverged approximately 3 billion years ago, suggesting that land (continents) had been colonized by prokaryotes at that time.[1] Together, Hydrobacteria and Terrabacteria form a large group containing 97% of prokaryotes and 99% of all species of Bacteria known by 2009, and placed in the taxon Selabacteria, in allusion to their phototrophic abilities (selas = light).[7] Currently, the bacterial phyla that are outside of Hydrobacteria + Terrabacteria, and thus justifying the taxon Selabacteria, are debated and may or may not include Fusobacteria.[3][4]

"Gracilicutes," which was described in 1978 by Gibbons and Murray,[8] is sometimes used in place of Hydrobacteria. However, "Gracilicutes" included cyanobacteria (a member of Terrabacteria) and was not constructed under the now generally accepted three-domain system.[8] More recently, a redefinition of "Gracilicutes" was proposed[9] but it did not include a molecular phylogeny or statistical analyses. Also, it did not follow the three-domain system, claiming instead that the lineage of eukaryotes + Archaea is nested within Bacteria as a close relative of Actinomycetota, a tree not supported in any molecular phylogeny.

Phylogeny

  • A timetree redrawn showing the division of Hydrobacteria and Terrabacteria.

    A timetree redrawn from Battistuzzi and Hedges (2009) shows the division of Hydrobacteria and Terrabacteria.[2][1]

The definition of two major divisions within the domain Bacteria, Hydrobacteria and Terrabacteria, has come largely from rooted phylogenetic analyses of genomes.[2][1][3][4] Unrooted analyses have not fully supported this division,[6][5] drawing attention to the importance of rooted trees of life.

The two recent analyses of bacterial phylogeny both supported the division of Hydrobacteria and Terrabacteria.[3][4] However, they interpreted the evolution of the cell wall differently, with one concluding that the last common ancestor of Bacteria was a monoderm (gram-positive bacteria[3]) and the other concluding that it was a diderm (gram-negative bacteria[4]). The following tree is redrawn from one of those two recent studies,[3] showing the phylogeny of bacterial phyla and superphyla, with the position of Fusobacteria being unresolved and DST being the closest relative of Terrabacteria:

  • A phylogeny of bacterial phyla and superphyla according to Coleman et al. (2021).[3] Hydrobacteria was referred to as "Gracilicutes" in that study.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Battistuzzi, F. U.; Hedges, S. B. (1 February 2009). "A Major Clade of Prokaryotes with Ancient Adaptations to Life on Land". Molecular Biology and Evolution 26 (2): 335–343. doi:10.1093/molbev/msn247. PMID 18988685. 
  2. ↑ 2.0 2.1 2.2 2.3 Battistuzzi, Fabia U; Feijao, Andreia; Hedges, S Blair (2004). "A genomic timescale of prokaryote evolution: insights into the origin of methanogenesis, phototrophy, and the colonization of land". BMC Evolutionary Biology 4 (1): 44. doi:10.1186/1471-2148-4-44. PMID 15535883. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Coleman, Gareth A.; Davín, Adrián A.; Mahendrarajah, Tara A.; Szánthó, Lénárd L.; Spang, Anja; Hugenholtz, Philip; Szöllősi, Gergely J.; Williams, Tom A. (7 May 2021). "A rooted phylogeny resolves early bacterial evolution". Science 372 (6542): eabe0511. doi:10.1126/science.abe0511. PMID 33958449. https://research-information.bris.ac.uk/en/publications/51e9e402-36b7-47a6-91de-32b8cf7320d2. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Léonard, Raphaël R.; Sauvage, Eric; Lupo, Valérian; Perrin, Amandine; Sirjacobs, Damien; Charlier, Paulette; Kerff, Frédéric; Baurain, Denis (18 February 2022). "Was the Last Bacterial Common Ancestor a Monoderm after All?". Genes 13 (2): 376. doi:10.3390/genes13020376. PMID 35205421. 
  5. ↑ 5.0 5.1 Hug, Laura A.; Baker, Brett J.; Anantharaman, Karthik; Brown, Christopher T.; Probst, Alexander J.; Castelle, Cindy J.; Butterfield, Cristina N.; Hernsdorf, Alex W. et al. (May 2016). "A new view of the tree of life". Nature Microbiology 1 (5): 16048. doi:10.1038/nmicrobiol.2016.48. PMID 27572647. 
  6. ↑ 6.0 6.1 Zhu, Qiyun; Mai, Uyen; Pfeiffer, Wayne; Janssen, Stefan; Asnicar, Francesco; Sanders, Jon G.; Belda-Ferre, Pedro; Al-Ghalith, Gabriel A. et al. (December 2019). "Phylogenomics of 10,575 genomes reveals evolutionary proximity between domains Bacteria and Archaea". Nature Communications 10 (1): 5477. doi:10.1038/s41467-019-13443-4. PMID 31792218. Bibcode: 2019NatCo..10.5477Z. 
  7. ↑ Battistuzzi, FU; Hedges, SB (2009). "Eubacteria". in Hedges, SB; Kumar, S. The Timetree of Life. New York: Oxford University Press. pp. 106–115. 
  8. ↑ 8.0 8.1 Gibbons, N. E.; Murray, R. G. E. (1 January 1978). "Proposals Concerning the Higher Taxa of Bacteria". International Journal of Systematic Bacteriology 28 (1): 1–6. doi:10.1099/00207713-28-1-1. 
  9. ↑ Cavalier-Smith, Thomas (2006). "Rooting the tree of life by transition analyses". Biology Direct 1 (1): 19. doi:10.1186/1745-6150-1-19. PMID 16834776. 

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