Biology:Myxobacteria

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Short description: Order of bacteria

Myxobacteria
Myxococcus xanthus.png
Myxococcus xanthus
Scientific classification
Kingdom:
Bacteria
Phylum:
Proteobacteria
Class:
Deltaproteobacteria
Order:
Myxococcales

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[1] and Vulgatibacter.[2] One species of myxobacteria, Minicystis rosea,[3] has the largest known bacterial genome with over 16 million nucleotides. The second largest is another myxobacteria Sorangium cellulosum.[4][5] Myxobacteria are included among the delta group of proteobacteria, a large taxon of Gram-negative forms.

Myxobacteria can move by gliding.[6] 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.[7]

Myxobacteria are used to study the polysaccharide production in gram-negative bacteria like the model Myxococcus Xanthus which have four different machineries[8] of polysaccharide secretion and where a new Wzx/Wzy machinery producing a new polysaccharide was identified in 2020.[8]

Myxobacteria are also good models to study the multicellularity in the bacterial world.[9]

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.[10][11] 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.[12][13]

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.[14]

It has been suggested that the last common ancestor of myxobacteria was an aerobe and that their anaerobic predecessors lived syntrophically with early eukaryotes.[15]

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.[16]

Myxobacteria are also known to produce gephyronic acid, an inhibitor of eukaryotic protein synthesis and a potential agent for cancer chemotherapy.[17]


References

  1. ↑ "The mosaic genome of Anaeromyxobacter dehalogenans strain 2CP-C suggests an aerobic common ancestor to the delta-proteobacteria". PLOS ONE 3 (5): e2103. May 2008. doi:10.1371/journal.pone.0002103. PMID 18461135. Bibcode: 2008PLoSO...3.2103T. 
  2. ↑ (in en-US) Vulgatibacter incomptus strain DSM 27710, complete genome. 2015-08-19. https://www.ncbi.nlm.nih.gov/nuccore/CP012332.1. 
  3. ↑ (in en-US) Minicystis rosea strain DSM 24000, complete genome. 2017-01-04. https://www.ncbi.nlm.nih.gov/nuccore/CP016211.1. 
  4. ↑ "Complete genome sequence of the myxobacterium, Sorangium cellulosum". Nat. Biotechnol. 25 (11): 1281–9. November 2007. doi:10.1038/nbt1354. PMID 17965706. 
  5. ↑ "Insights from 20 years of bacterial genome sequencing". Funct. Integr. Genomics 15 (2): 141–61. March 2015. doi:10.1007/s10142-015-0433-4. PMID 25722247. 
  6. ↑ "Gliding motility revisited: how do the myxobacteria move without flagella?". Microbiol. Mol. Biol. Rev. 74 (2): 229–49. June 2010. doi:10.1128/MMBR.00043-09. PMID 20508248. 
  7. ↑ "Myxobacteria, producers of novel bioactive substances". J. Ind. Microbiol. Biotechnol. 27 (3): 149–56. September 2001. doi:10.1038/sj.jim.7000025. PMID 11780785. 
  8. ↑ 8.0 8.1 "Modulation of bacterial multicellularity via spatio-specific polysaccharide secretion". PLOS Biology 18 (6): e3000728. June 2020. doi:10.1371/journal.pbio.3000728. PMID 32516311. 
  9. ↑ "Modulation of bacterial multicellularity via spatio-specific polysaccharide secretion". PLOS Biology 18 (6): e3000728. June 2020. doi:10.1371/journal.pbio.3000728. PMID 32516311. 
  10. ↑ "Role of streams in myxobacteria aggregate formation". Phys Biol 1 (3–4): 173–83. December 2004. doi:10.1088/1478-3967/1/3/005. PMID 16204837. Bibcode: 2004PhBio...1..173K. 
  11. ↑ "A three-dimensional model of myxobacterial aggregation by contact-mediated interactions". Proc. Natl. Acad. Sci. U.S.A. 102 (32): 11308–12. August 2005. doi:10.1073/pnas.0504259102. PMID 16061806. Bibcode: 2005PNAS..10211308S. 
  12. ↑ "Adaptive evolution of an sRNA that controls Myxococcus development". Science 328 (5981): 993. May 2010. doi:10.1126/science.1187200. PMID 20489016. Bibcode: 2010Sci...328..993Y. 
  13. ↑ "Evolution of an obligate social cheater to a superior cooperator". Nature 441 (7091): 310–4. May 2006. doi:10.1038/nature04677. PMID 16710413. Bibcode: 2006Natur.441..310F. 
  14. ↑ "On the Myxobacteriaceæ, a New Order of Schizomycetes" (in en). Botanical Gazette 17 (12): 389–406. 1892. doi:10.1086/326866. ISSN 0006-8071. 
  15. ↑ 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. PMID 34131078. 
  16. ↑ "FDA Approval for Ixabepilone". http://www.cancer.gov/cancertopics/druginfo/fda-ixabepilone. 
  17. ↑ "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. January 1995. doi:10.7164/antibiotics.48.21. PMID 7868385. 

External links

Wikidata ☰ Q1068698 entry




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