Myxobacteria
Myxococcus xanthus
Scientific classification Edit this classification
Domain: Bacteria
Phylum: Myxococcota
Class: Myxococcia
Waite et al. 2020[1]
Order: Myxococcales
Tchan et al. 1948
Families & genera
Synonyms

"Myxococcidae" Cavalier-Smith 2020

The myxobacteria ("slime bacteria") are a group of bacteria that predominantly live in the soil and feed on insoluble organic substances. The myxobacteria have very large genomes relative to other bacteria, e.g. 9–10 million nucleotides except for Anaeromyxobacter[2] and Vulgatibacter.[3] One species of myxobacteria, Minicystis rosea,[4] has the largest known bacterial genome with over 16 million nucleotides. The second largest is another myxobacteria Sorangium cellulosum.[5][6]

Myxobacteria can move by gliding.[7] They typically travel in swarms (also known as wolf packs), containing many cells kept together by intercellular molecular signals. Individuals benefit from aggregation as it allows accumulation of the extracellular enzymes that are used to digest food; this in turn increases feeding efficiency. Myxobacteria produce a number of biomedically and industrially useful chemicals, such as antibiotics, and export those chemicals outside the cell.[8]

Myxobacteria are used to study the polysaccharide production in gram-negative bacteria like the model Myxococcus xanthus which have four different mechanisms[9] of polysaccharide secretion and where a new Wzx/Wzy mechanism producing a new polysaccharide was identified in 2020.[9]

Myxobacteria are also good models to study the multicellularity in the bacterial world.[10]

Life cycle

When nutrients are scarce, myxobacterial cells aggregate into fruiting bodies (not to be confused with those in fungi), a process long-thought to be mediated by chemotaxis but now considered to be a function of a form of contact-mediated signaling.[11][12] These fruiting bodies can take different shapes and colors, depending on the species. Within the fruiting bodies, cells begin as rod-shaped vegetative cells, and develop into rounded myxospores with thick cell walls. These myxospores, analogous to spores in other organisms, are more likely to survive until nutrients are more plentiful. The fruiting process is thought to benefit myxobacteria by ensuring that cell growth is resumed with a group (swarm) of myxobacteria, rather than as isolated cells. Similar life cycles have developed among certain amoebae, called cellular slime molds.

At a molecular level, initiation of fruiting body development in Myxococcus xanthus is regulated by Pxr sRNA.[13][14]

Myxobacteria such as Myxococcus xanthus and Stigmatella aurantiaca are used as model organisms for the study of development.

Various myxobacterial species as sketched by Roland Thaxter in 1892: Chondromyces crocatus (figs. 1–11), Stigmatella aurantiaca (figs. 12–19 and 25-28), Melittangium lichenicola (figs. 20–23), Archangium gephyra (fig. 24), Myxococcus coralloides (figs. 29-33), Polyangium vitellinum (figs. 34-36), and Myxococcus fulvus (figs. 37-41). Thaxter was the first taxonomist to recognize the bacterial nature of the myxobacteria. Previously, they had been misclassified as members of the fungi imperfecti.[15]

It has been suggested that the last common ancestor of myxobacteria was an aerobe and that their anaerobic predecessors lived syntrophically with early eukaryotes.[16]

Clinical use

Metabolites secreted by Sorangium cellulosum known as epothilones have been noted to have antineoplastic activity. This has led to the development of analogs which mimic its activity. One such analog, known as Ixabepilone is a U.S. Food and Drug Administration approved chemotherapy agent for the treatment of metastatic breast cancer.[17]

Myxobacteria are also known to produce gephyronic acid, an inhibitor of eukaryotic protein synthesis and a potential agent for cancer chemotherapy.[18]

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[19] and National Center for Biotechnology Information (NCBI)[20]

16S rRNA based LTP_08_2023[21][22][23] 120 marker proteins based GTDB 08-RS214[24][25][26]
Myxo-
Deferrisomatales

Deferrisomataceae

Bradymonadales

Bradymonadaceae

Myxococcales
Cystobacterineae

Vulgatibacteraceae

Anaeromyxobacteraceae

Myxococcaceae

Nannocystineae

Kofleriaceae Reichenbach 2007

Nannocystaceae

Sorangiineae

Polyangiaceae (incl. Sandaracinaceae)

-coccota
Myxo-
Bradymonadia
Bradymonadales

Microvenatoraceae Wang, Chen & Du 2022

Bradymonadaceae Wang et al. 2015

Polyangiia
Haliangiales

Haliangiaceae Waite et al. 2020 (incl. Kofleriaceae)

Nannocystales

Nannocystaceae Reichenbach 2006

Polyangiales

Sandaracinaceae Mohr et al. 2012

Polyangiaceae Jahn 1924

Myxococcia
Myxococcales

Anaeromyxobacteraceae Yamamoto et al. 2014

Vulgatibacteraceae Yamamoto et al. 2014

Myxococcaceae Jahn 1924

-coccota

See also

References

  1. ↑ Waite DW, Chuvochina M, Pelikan C, Parks DH, Yilmaz P, Wagner M, Loy A, Naganuma T, Nakai R, Whitman WB, Hahn MW, Kuever J, Hugenholtz P. (2020). "Proposal to reclassify the proteobacterial classes Deltaproteobacteria and Oligoflexia, and the phylum Thermodesulfobacteria into four phyla reflecting major functional capabilities". Int J Syst Evol Microbiol. 70 (11): 5972–6016. doi:10.1099/ijsem.0.004213. PMID 33151140.
  2. ↑ Thomas SH, Wagner RD, Arakaki AK, Skolnick J, Kirby JR, Shimkets LJ, Sanford RA, Löffler FE (May 2008). "The mosaic genome of Anaeromyxobacter dehalogenans strain 2CP-C suggests an aerobic common ancestor to the delta-proteobacteria". PLOS ONE. 3 (5): e2103. Bibcode:2008PLoSO...3.2103T. doi:10.1371/journal.pone.0002103. PMC 2330069. PMID 18461135.
  3. ↑ "Vulgatibacter incomptus strain DSM 27710, complete genome". 2015-08-19. {{cite journal}}: Cite journal requires |journal= (help)
  4. ↑ Shilpee Pal, Gaurav Sharma & Srikrishna Subramanian (2021-09-13). "Complete genome sequence and identification of polyunsaturated fatty acid biosynthesis genes of the myxobacterium Minicystis rosea DSM 24000T". BMC Genomics. 22 (1): 655. doi:10.1186/s12864-021-07955-x. PMC 8436480. PMID 34511070.
  5. ↑ Schneiker S, Perlova O, Kaiser O, Gerth K, Alici A, Altmeyer MO, et al. (November 2007). "Complete genome sequence of the myxobacterium, Sorangium cellulosum". Nat. Biotechnol. 25 (11): 1281–9. doi:10.1038/nbt1354. PMID 17965706.
  6. ↑ Land M, Hauser L, Jun SR, Nookaew I, Leuze MR, Ahn TH, Karpinets T, Lund O, Kora G, Wassenaar T, Poudel S, Ussery DW (March 2015). "Insights from 20 years of bacterial genome sequencing". Funct. Integr. Genomics. 15 (2): 141–61. doi:10.1007/s10142-015-0433-4. PMC 4361730. PMID 25722247.
  7. ↑ Mauriello EM, Mignot T, Yang Z, Zusman DR (June 2010). "Gliding motility revisited: how do the myxobacteria move without flagella?". Microbiol. Mol. Biol. Rev. 74 (2): 229–49. doi:10.1128/MMBR.00043-09. PMC 2884410. PMID 20508248.
  8. ↑ Reichenbach H (September 2001). "Myxobacteria, producers of novel bioactive substances". J. Ind. Microbiol. Biotechnol. 27 (3): 149–56. doi:10.1038/sj.jim.7000025. PMID 11780785. S2CID 34964313.
  9. 1 2 Islam ST, Vergara Alvarez I, Saïdi F, Guiseppi A, Vinogradov E, Sharma G, et al. (June 2020). "Modulation of bacterial multicellularity via spatio-specific polysaccharide secretion". PLOS Biology. 18 (6): e3000728. doi:10.1371/journal.pbio.3000728. PMC 7310880. PMID 32516311.
  10. ↑ Islam ST, Vergara Alvarez I, Saïdi F, Guiseppi A, Vinogradov E, Sharma G, et al. (June 2020). "Modulation of bacterial multicellularity via spatio-specific polysaccharide secretion". PLOS Biology. 18 (6): e3000728. doi:10.1371/journal.pbio.3000728. PMC 7310880. PMID 32516311.
  11. ↑ Kiskowski MA, Jiang Y, Alber MS (December 2004). "Role of streams in myxobacteria aggregate formation". Phys Biol. 1 (3–4): 173–83. Bibcode:2004PhBio...1..173K. doi:10.1088/1478-3967/1/3/005. PMID 16204837. S2CID 18846289.
  12. ↑ Sozinova O, Jiang Y, Kaiser D, Alber M (August 2005). "A three-dimensional model of myxobacterial aggregation by contact-mediated interactions". Proc. Natl. Acad. Sci. U.S.A. 102 (32): 11308–12. Bibcode:2005PNAS..10211308S. doi:10.1073/pnas.0504259102. PMC 1183571. PMID 16061806.
  13. ↑ Yu YT, Yuan X, Velicer GJ (May 2010). "Adaptive evolution of an sRNA that controls Myxococcus development". Science. 328 (5981): 993. Bibcode:2010Sci...328..993Y. doi:10.1126/science.1187200. PMC 3027070. PMID 20489016.
  14. ↑ Fiegna F, Yu YT, Kadam SV, Velicer GJ (May 2006). "Evolution of an obligate social cheater to a superior cooperator". Nature. 441 (7091): 310–4. Bibcode:2006Natur.441..310F. doi:10.1038/nature04677. PMID 16710413. S2CID 4371886.
  15. ↑ Thaxter R (1892). "On the Myxobacteriaceæ, a New Order of Schizomycetes". Botanical Gazette. 17 (12): 389–406. doi:10.1086/326866. ISSN 0006-8071.
  16. ↑ Hoshino, Y.; Gaucher, E.A. (2021). "Evolution of bacterial steroid biosynthesis and its impact on eukaryogenesis". PNAS. 118 (25): e2101276118. doi:10.1073/pnas.2101276118. ISSN 0027-8424. PMC 8237579. PMID 34131078.
  17. ↑ "FDA Approval for Ixabepilone". National Cancer Institute.
  18. ↑ Sasse F, Steinmetz H, Höfle G, Reichenbach H (January 1995). "Gephyronic acid, a novel inhibitor of eukaryotic protein synthesis from Archangium gephyra (myxobacteria). Production, isolation, physico-chemical and biological properties, and mechanism of action". J. Antibiot. 48 (1): 21–5. doi:10.7164/antibiotics.48.21. PMID 7868385.
  19. ↑ J.P. Euzéby. "Deltaproteobacteria". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2022-09-09.
  20. ↑ Sayers; et al. "Deltaproteobacteria". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2022-09-09.
  21. ↑ "The LTP". Retrieved 20 November 2023.
  22. ↑ "LTP_all tree in newick format". Retrieved 20 November 2023.
  23. ↑ "LTP_08_2023 Release Notes" (PDF). Retrieved 20 November 2023.
  24. ↑ "GTDB release 08-RS214". Genome Taxonomy Database. Retrieved 10 May 2023.
  25. ↑ "bac120_r214.sp_label". Genome Taxonomy Database. Retrieved 10 May 2023.
  26. ↑ "Taxon History". Genome Taxonomy Database. Retrieved 10 May 2023.
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