Myxococcus

Myxococcus is a genus of bacteria in the family Myxococcaceae. Myxococci are Gram-negative, spore-forming, chemoorganotrophic, obligate aerobes. They are elongated rods with rounded or tapered ends, and they are nonflagellated. The cells move by gliding and can predate other bacteria. The genus has been isolated from soil.

Myxococcus
Fruiting bodies of M. xanthus
Scientific classification Edit this classification
Domain: Bacteria
Phylum: Myxococcota
Class: Myxococcia
Order: Myxococcales
Family: Myxococcaceae
Genus: Myxococcus
Thaxter 1892
Type species
Myxococcus fulvus
(Cohn 1875) Jahn 1911
Species
Synonyms
  • Myxococcus section "Simplices" Jahn 1911
  • Myxococcus section "Stipitatae" Jahn 1911

At least eleven species had been identified with confidence by late 2020 and each had been characterised to some extent. As well as using traditional biochemical tests, strains of some species had been compared using whole genome sequences. This approach has provided evidence that the genus, like most bacterial genera, has a core set of genes found in all members of the genus, along with others that are confined to particular species. The identity of Myxococcus species therefore continues to change. An example where taxonomy may be changed is that comparisons of genome sequences and biochemical tests indicated that M. xanthus and M. virescens were not distinguishable.[1][2]

One notable characteristic of Myxococcus is its formation of fruiting bodies. Myxococcus are known to form fruiting bodies using chemical signals. The cells communicate with each other, and in response to stress factors, most often starvation, begin to form fruiting bodies. These fruiting bodies then allow Myxococcus to transform into round spores resistant to the environment.[3] The genetic programs underlying fruiting body formation in the Myxococci exhibit an unexpected level of plasticity, strongly suggesting that the genetic program underlying fruiting body formation in various Myxococci is not conserved, leading to diverse reactions in all Myxococcus species.[4] Rather than chemotaxis used by other microorganisms for cell-cell communication, Myxococcus, specifically M. xanthus, a species of Myxococcus, has been found to use direct cell-to-cell communication to form fruiting bodies.[3]

In addition, Myxococcus prey interacts with one another by sending quorum signals using acyl homoserine lactones (AHLs). It was discovered that AHLs increased some Myxococcus colonies' predatory behavior and growth rates. Therefore, the predatory behavior of these Myxococcus bacteria appears to be enhanced by the presence of xenic quorum signaling molecules. Some Myxococcus bacteria employ AHLs as indicators of nearby prey, possibly listening in on talks between prey creatures in the wild.[5]

This cooperation between different individual Myxococcus allows them to act as a singular organism and perform functions as such, including but not limited to homeostasis repair. While fruiting body development occurs through the Myxococcus genus, it can take on a variety of structures, and dome-shaped mounds have been observed in some species.[6] Social interactions are major in the myxobacteria's life cycle. In significant groupings compared to wolf packs, cells prey on other bacteria during vegetative growth. When starved, cells produce a macroscopic fruiting body dense with spores. The current state of knowledge on cell-cell signaling during development is reflected in these behavioral activities.[7]

Myxococcus is a single celled predatory bacteria that are facultative bacteria. Myxococcus are social microbes and often seen as exhibiting “wolf-pack” behavior.[8] They are able to communicate with each other via quorum sensing. Myxococcus are seen as predatory microbial communities because of their behavior. They are able to form several distinct multicellular structures. Myxococcus are found in soil. Single cells combine and form large clusters using quorum sensing. When nutrients are unavailable, these cells become fruiting bodies that contain approximately 50,000 cells.[9] One study found that after placing the bacteria in starving conditions they aggregated into mounds of 100,000 cells.[10]

Myxococcus Quorum Sensing

Myxococcus are able to prey[11] and thrive on soil bacteria, plant pathogens, cyanobacteria. Multiple studies have shown that under laboratory conditions Myxococcus can thrive off these prey species.[11] Myxococcus are able to prey using gliding motility. There are two [10] of these systems: (i) social (S)-motility and adventurous (A)-motility. Social motility is based on IV pili and adventurous motility is based on slime-secretion.

Myxococcus is a soil-dwelling bacterium that can aggregate into fruiting bodies when food is scarce. This process is regulated by quorum sensing, a type of cell-to-cell communication that allows bacteria to coordinate their behavior in response to population density.[12]

In Myxococcus, quorum sensing is mediated by two signaling molecules: A-factor and C-signal. A-factor is a small, diffusible molecule that is produced by all cells in the population. When the concentration of A-factor reaches a certain threshold, it binds to receptors on the surface of cells and triggers a cascade of events that leads to aggregation.[13]

C-signal is a larger, cell-surface protein that is not diffusible. It is produced by a subset of cells in the population and binds to receptors on the surface of other cells. This interaction triggers a cascade of events that leads to the formation of fruiting bodies. Quorum sensing is essential for the survival of Myxococcus. By aggregating into fruiting bodies, the bacteria can protect themselves from predators and desiccation. They can also produce spores that can survive in harsh environments until conditions improve. Quorum sensing is a complex process that is still not fully understood. However, it is clear that it plays an important role in the life cycle of Myxococcus and other bacteria.[14][15]

In addition to its role in aggregation and fruiting body formation, quorum sensing also regulates other aspects of Myxococcus development, such as motility, chemotaxis, and virulence. Quorum sensing is also used by Myxococcus to communicate with other bacteria, such as its prey.[16] This allows the bacteria to coordinate their activities and improve their chances of survival.

Myxococcus secretes antibiotics and bacteriolytic enzymes to kill their prey. Because of this, there has been speculation of using Myxococcus as novel antibacterial strategies.[11]

Sources

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[17] and National Center for Biotechnology Information (NCBI)[18]

16S rRNA based LTP_01_2022[19][20][21] 120 marker proteins based GTDB 07-RS207[22][23][24]

M. stipitatus Thaxter 1897

M. fulvus (Cohn 1875) Jahn 1911

Pyxidicoccus fallax corrig. Reichenbach 2007

Pyxidicoccus trucidator Chambers et al. 2020

M. eversor Chambers et al. 2021

M. llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogochensis
Chambers et al. 2021

M. vastator Chambers et al. 2021

M. macrosporus (Krzemieniewska & Krzemieniewski 1926) Zahler & McCurdy 1974

M. virescens Thaxter 1892

M. xanthus Beebe 1941

M. stipitatus

M. eversor

M. fulvus

Pyxidicoccus fallax

Pyxidicoccus caerfyrddinensis
Chambers et al. 2020

Pyxidicoccus trucidator

"M. hansupus" Sharma et al. 2016

M. macrosporus

M. virescens

M. xanthus

See also

References
  1. Chambers, James; Sparks, Natalie; Sydney, Natashia; Livingstone, Paul G.; Cookson, Alan R.; Whitworth, David E. (2020). "Comparative genomics and pan-genomics of the Myxococcaceae, including a description of five novel species: Myxococcus eversor sp. nov., Myxococcus llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogochensis sp. nov., Myxococcus vastator sp. nov., Pyxidicoccus caerfyrddinensis sp. nov. and Pyxidicoccus trucidator sp. nov". Genome Biology and Evolution. evaa212 (12): 2289–2302. doi:10.1093/gbe/evaa212. PMC 7846144. PMID 33022031.
  2. Sharma, Gaurav; Narwani, Tarun; Subramanian, Srikrishna (2016). "Complete Genome Sequence and Comparative Genomics of a Novel Myxobacterium Myxococcus hansupus". PLOS ONE. 11 (2): e0148593. Bibcode:2016PLoSO..1148593S. doi:10.1371/journal.pone.0148593. PMC 4765838. PMID 26900859.
  3. Sozinova, Olga; Jiang, Yi; Kaiser, Dale; Alber, Mark (14 November 2006). "A three-dimensional model of myxobacterial fruiting-body formation". Proceedings of the National Academy of Sciences. 103 (46): 17255–17259. Bibcode:2006PNAS..10317255S. doi:10.1073/pnas.0605555103. PMC 1859919. PMID 17088558.
  4. Huntley, Stuart; Hamann, Nils; Wegener-Feldbrügge, Sigrun; Treuner-Lange, Anke; Kube, Michael; Reinhardt, Richard; Klages, Sven; Müller, Rolf; Ronning, Catherine M.; Nierman, William C.; Søgaard-Andersen, Lotte (February 2011). "Comparative Genomic Analysis of Fruiting Body Formation in Myxococcales". Molecular Biology and Evolution. 28 (2): 1083–1097. doi:10.1093/molbev/msq292. PMID 21037205.
  5. Lloyd, Daniel G.; Whitworth, David E. (2017-03-14). "The Myxobacterium Myxococcus xanthus Can Sense and Respond to the Quorum Signals Secreted by Potential Prey Organisms". Frontiers in Microbiology. 8: 439. doi:10.3389/fmicb.2017.00439. PMC 5348527. PMID 28352265.
  6. Cao, Pengbo; Dey, Arup; Vassallo, Christopher N.; Wall, Daniel (November 2015). "How Myxobacteria Cooperate". Journal of Molecular Biology. 427 (23): 3709–3721. doi:10.1016/j.jmb.2015.07.022. PMC 4658263. PMID 26254571.
  7. Shimkets, Lawrence J. (October 1999). "Intercellular Signaling During Fruiting-Body Development of Myxococcus xanthus". Annual Review of Microbiology. 53 (1): 525–549. doi:10.1146/annurev.micro.53.1.525. PMID 10547700.
  8. Marshall, Rupert C.; Whitworth, David E. (April 2019). "Is 'Wolf‐Pack' Predation by Antimicrobial Bacteria Cooperative? Cell Behaviour and Predatory Mechanisms Indicate Profound Selfishness, Even when Working Alongside Kin". BioEssays. 41 (4): 1800247. doi:10.1002/bies.201800247. PMID 30919490. S2CID 85544906.
  9. Curtis, Patrick D.; Taylor, Rion G.; Welch, Roy D.; Shimkets, Lawrence J. (December 2007). "Spatial organization of Myxococcus xanthus during fruiting body formation". Journal of Bacteriology. 189 (24): 9126–9130. doi:10.1128/JB.01008-07. PMC 2168639. PMID 17921303.
  10. Sliusarenko, Oleksii; Zusman, David R.; Oster, George (15 January 2007). "Aggregation during Fruiting Body Formation in Myxococcus xanthus Is Driven by Reducing Cell Movement". Journal of Bacteriology. 189 (2): 611–619. doi:10.1128/JB.01206-06. PMC 1797407. PMID 17098901.
  11. Thiery, Susanne; Kaimer, Christine (2020). "The Predation Strategy of Myxococcus xanthus". Frontiers in Microbiology. 11: 2. doi:10.3389/fmicb.2020.00002. PMC 6971385. PMID 32010119.
  12. Smith, Robert P.; Barraza, Ivana; Quinn, Rebecca J.; Fortoul, Marla C. (2020). "The mechanisms and cell signaling pathways of programmed cell death in the bacterial world". Cell Death Regulation in Health and Disease - Part B. International Review of Cell and Molecular Biology. Vol. 352. pp. 1–53. doi:10.1016/bs.ircmb.2019.12.002. ISBN 978-0-12-819929-9. PMID 32334813. S2CID 212759298.
  13. Lloyd, Daniel G.; Whitworth, David E. (2017). "The Myxobacterium Myxococcus xanthus Can Sense and Respond to the Quorum Signals Secreted by Potential Prey Organisms". Frontiers in Microbiology. 8: 439. doi:10.3389/fmicb.2017.00439. PMC 5348527. PMID 28352265.
  14. Bassler, Bonnie L.; Miller, Melissa B. (2013). "Quorum Sensing". The Prokaryotes. pp. 495–509. doi:10.1007/978-3-642-30123-0_60. ISBN 978-3-642-30122-3.
  15. Miller, Melissa B.; Bassler, Bonnie L. (October 2001). "Quorum Sensing in Bacteria". Annual Review of Microbiology. 55 (1): 165–199. doi:10.1146/annurev.micro.55.1.165. PMID 11544353.
  16. Lloyd, Daniel G.; Whitworth, David E. (14 March 2017). "The Myxobacterium Myxococcus xanthus Can Sense and Respond to the Quorum Signals Secreted by Potential Prey Organisms". Frontiers in Microbiology. 8: 439. doi:10.3389/fmicb.2017.00439. PMC 5348527. PMID 28352265.
  17. A.C. Parte; et al. "Myxococcus". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2022-09-09.
  18. Sayers; et al. "Myxococcus". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2022-09-09.
  19. "The LTP". Retrieved 23 February 2022.
  20. "LTP_all tree in newick format". Retrieved 23 February 2022.
  21. "LTP_01_2022 Release Notes" (PDF). Retrieved 23 February 2022.
  22. "GTDB release 07-RS207". Genome Taxonomy Database. Retrieved 20 June 2022.
  23. "bac120_r207.sp_labels". Genome Taxonomy Database. Retrieved 20 June 2022.
  24. "Taxon History". Genome Taxonomy Database. Retrieved 20 June 2022.
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