Myxococcus xanthus - The Swarming Bacteria: Difference between revisions

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==Fruting==
==Fruting==
Fruiting is the method at which Mxyococcus xanthus reproduces. This occurs when nutrients are unavailable or scarce. When no food is obtainable the individual <i>Myxococcus xanthus</i> cells organize themselves into larger masses. On average about 105 (100,000) cells assemble to form the larger mass. This large mass is called a fruiting body. <ref name=d>[https://search.proquest.com/docview/305215572?fromopenview=true&pq-origsite=gscholar White, D. 1993. Myxospore and fruiting body morphogenesis, p. 307-332. In M. Dworkin and D. Kaiser (ed.), Myxobacteria II. ASM Press, Washington, D.C.]</ref> As the cells are forming the fruiting body they are actually being selected for based on related and unrelated cells. This creates uniform and species specific fruiting bodies among all of the cells. About 10% of the rod shaped cells that form the fruiting body then transform into sporangioles which also contain smaller myxospores. Around 30% of the original cells become the rods located on the outside of the mass of cells. The rest of the cells encased inside die off and become a source of nutrients for the remaining cells. It is believed that the cells come together to make sure a new colony is made by many cells opposed to one. Unlike other spore forming bacteria the rod-shaped cells directly transform into spherical myxospores.<br> <br>The fruiting body is formed when groups of cells start to spiral together and travel to certain points called aggregation centers. . <ref name=f>[https://search.proquest.com/docview/305215572?fromopenview=true&pq-origsite=gscholar Reichenbach, H. 1966. Myxococcus spp. (Myxobacteriales). Schwarmentwicklung und Bildung von Protocysten. Publikationen zu wissenschafilichen Filmen, Gottingen. lA:557-578.]</ref>  As these aggregation centers form they become three-dimensional due to the meeting of different waves of cells. <ref name=g>[https://pubmed.ncbi.nlm.nih.gov/14761986/ Kaiser, D., and R. Welch. 2004. Dynamics of fruiting body morphogenesis. J Bacteriol 186:919-27.]</ref> After the fruiting body is completed two new cells have been formed. The myxospores which are found inside of the fruiting body and the peripheral rods which are found around the outside of the fruiting body. . <ref name=h>[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC207943/ O'Connor, K. A., and D. R. Zusman. 1991. Development in Myxococcus xanthus involves differentiation into two cell types, peripheral rods and spores. J Bacteriol 173:3318-33.]</ref> br> <br> Around 6-12 hours after the cells were starved of nutrients and the fruiting body is formed the rods that were unused become lysed. . <ref name=i>[https://pubmed.ncbi.nlm.nih.gov/806967/ Wireman, J. W., and M. Dworkin. 1975. Morphogenesis and developmental interactions in myxobacteria. Science 189:516-23.]</ref> It has been found that the lysing cells are able to donate spore coated proteins to their own spores increasing the strength of the cell. <ref name=j>[https://search.proquest.com/docview/305215572?fromopenview=true&pq-origsite=gscholar Rosenbluh, A., and E. Rosenberg. 1993. Developmental lysis and autocides, p. 213-233. In M. Dworkin and D. Kaiser (ed.), Myxobacteria II. American Society of Microbiology, Washington, D. C.]</ref>After 72 hours the spores are finally mature enough to germinate and once they do it creates new population of cells which start to swarm together in order to gain nutrients needed to grow. <ref name=k>[https://jb.asm.org/content/166/3/837.short L J Shimkets Correlation of energy-dependent cell cohesion with social motility in Myxococcus xanthus. Journal of Bacteriology Jun 1986, 166 (3) 837-841]</ref>In terms of fruiting body formation, the cells need to be stimulated by being close to another cell which initiates S-motility, also called twitching motility. <ref name=l>[https://elifesciences.org/articles/50374#bib11 Diodati ME, Gill RE, Plamann L, Singer M. 2008. Initiation and early developmental events. In: Whitworth D. E (Ed). Myxobacteria: Multicellularity and Differentiation. ASM Press.]</ref>
Fruiting is the method at which Mxyococcus xanthus reproduces. This occurs when nutrients are unavailable or scarce. When no food is obtainable the individual <i>Myxococcus xanthus</i> cells organize themselves into larger masses. On average about 105 (100,000) cells assemble to form the larger mass. This large mass is called a fruiting body. <ref name=d>[https://search.proquest.com/docview/305215572?fromopenview=true&pq-origsite=gscholar White, D. 1993. Myxospore and fruiting body morphogenesis, p. 307-332. In M. Dworkin and D. Kaiser (ed.), Myxobacteria II. ASM Press, Washington, D.C.]</ref> As the cells are forming the fruiting body they are actually being selected for based on related and unrelated cells. This creates uniform and species specific fruiting bodies among all of the cells. About 10% of the rod shaped cells that form the fruiting body then transform into sporangioles which also contain smaller myxospores. Around 30% of the original cells become the rods located on the outside of the mass of cells. The rest of the cells encased inside die off and become a source of nutrients for the remaining cells. It is believed that the cells come together to make sure a new colony is made by many cells opposed to one. Unlike other spore forming bacteria the rod-shaped cells directly transform into spherical myxospores.<br> <br>The fruiting body is formed when groups of cells start to spiral together and travel to certain points called aggregation centers. . <ref name=f>[https://search.proquest.com/docview/305215572?fromopenview=true&pq-origsite=gscholar Reichenbach, H. 1966. Myxococcus spp. (Myxobacteriales). Schwarmentwicklung und Bildung von Protocysten. Publikationen zu wissenschafilichen Filmen, Gottingen. lA:557-578.]</ref>  As these aggregation centers form they become three-dimensional due to the meeting of different waves of cells. <ref name=g>[https://pubmed.ncbi.nlm.nih.gov/14761986/ Kaiser, D., and R. Welch. 2004. Dynamics of fruiting body morphogenesis. J Bacteriol 186:919-27.]</ref> After the fruiting body is completed two new cells have been formed. The myxospores which are found inside of the fruiting body and the peripheral rods which are found around the outside of the fruiting body. . <ref name=h>[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC207943/ O'Connor, K. A., and D. R. Zusman. 1991. Development in Myxococcus xanthus involves differentiation into two cell types, peripheral rods and spores. J Bacteriol 173:3318-33.]</ref> br> <br> Around 6-12 hours after the cells were starved of nutrients and the fruiting body is formed the rods that were unused become lysed. . <ref name=i>[https://pubmed.ncbi.nlm.nih.gov/806967/ Wireman, J. W., and M. Dworkin. 1975. Morphogenesis and developmental interactions in myxobacteria. Science 189:516-23.]</ref> It has been found that the lysing cells are able to donate spore coated proteins to their own spores increasing the strength of the cell. <ref name=j>[https://search.proquest.com/docview/305215572?fromopenview=true&pq-origsite=gscholar Rosenbluh, A., and E. Rosenberg. 1993. Developmental lysis and autocides, p. 213-233. In M. Dworkin and D. Kaiser (ed.), Myxobacteria II. American Society of Microbiology, Washington, D. C.]</ref>After 72 hours the spores are finally mature enough to germinate and once they do it creates new population of cells which start to swarm together in order to gain nutrients needed to grow. <ref name=k>[https://jb.asm.org/content/166/3/837.short L J Shimkets Correlation of energy-dependent cell cohesion with social motility in Myxococcus xanthus. Journal of Bacteriology Jun 1986, 166 (3) 837-841]</ref>In terms of fruiting body formation, the cells need to be stimulated by being close to another cell which initiates S-motility, also called twitching motility. <ref name=l>[https://elifesciences.org/articles/50374#bib11 Diodati ME, Gill RE, Plamann L, Singer M. 2008. Initiation and early developmental events. In: Whitworth D. E (Ed). Myxobacteria: Multicellularity and Differentiation. ASM Press.]</ref>
<br><br>In terms of why <i>Myxococcus xanthus</i> uses the fruiting body method there are a couple hypotheses. One is that it reduces the competition between other organisms by multiplying until they out number other organisms. <ref name=m>[https://onlinelibrary.wiley.com/doi/full/10.1111/j.1420-9101.2006.01104.x GARDNER, A. and WEST, S.A. (2006), Demography, altruism, and the benefits of budding. Journal of Evolutionary Biology, 19: 1707-1716.]</ref>Another is that the spore may protect them from outside threats or stresses that may arise. <ref name=n>[https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.522.4&rep=rep1&type=pdf Ward MJ, Lew H, Zusman DR. Disruption of aldA Influences the Developmental Process in Myxococcus xanthus. J. Bacteriol. 2000, 182(2):546.]</ref> Lastly, it is possible that all of the processes that lead up to myxococcus formation is only to maintain their specialized lifestyle and make sure they are able to grow well. <ref name=o>[https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.000208?crawler=true Keane R, Berleman J. The predatory life cycle of Myxococcus xanthus. Microbiology. 2016, 162:1.]</ref>     
<br><br>In terms of why <i>Myxococcus xanthus</i> uses the fruiting body method there are a couple hypotheses. One is that it reduces the competition between other organisms by multiplying until they out number other organisms. <ref name=m>[https://onlinelibrary.wiley.com/doi/full/10.1111/j.1420-9101.2006.01104.x GARDNER, A. and WEST, S.A. (2006), Demography, altruism, and the benefits of budding. Journal of Evolutionary Biology, 19: 1707-1716.]</ref>Another is that the spore may protect them from outside threats or stresses that may arise. <ref name=n>[https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.522.4&rep=rep1&type=pdf Ward MJ, Lew H, Zusman DR. Disruption of aldA Influences the Developmental Process in Myxococcus xanthus. J. Bacteriol. 2000, 182(2):546.]</ref> Lastly, it is possible that all of the processes that lead up to myxococcus formation is only to maintain their specialized lifestyle and make sure they are able to grow well. <ref name=o>[https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.000208?crawler=true Keane R, Berleman J. The predatory life cycle of Myxococcus xanthus. Microbiology. 2016, 162:1.]</ref>  
 
==Life Cycle==
<i>Myxococcus xanthus</i> lives in a never-ending cycle. It “starts” when there are many individual vegetative cells, which just means a cell that is actively growing. The cells then scout for prey in order to obtain nutrients or they branch off together in much larger quantity. The cells then find a prey and attempt to attack it by rippling through the organism. If the cells do not find any prey they are forced to come together in order to begin fruiting. Once the aggregates are formed the cells within them start to become spores and then as soon as nutrients are available the spores are germinated and made into many vegetative cells again.      
<i>Myxococcus xanthus</i> has two ways of directly multiplying. They are able to attack neighboring cells and feed on the nutrients that the cells excreted. They can also come together when nutrients are infrequent and form fruiting bodies that contain myxospores. The myxospores are able to live for a long time while under harsh conditions giving them the best chance of survival.<ref name=g/> The fact that <i>Myxococcus xanthus</i> is able to do perform either method makes it a highly studied organism due to its complexity.
 





Revision as of 21:38, 7 April 2021


By [Patrick Nally]

Introduction

Myxococcus xanthus is a specific species of myxobacteria that are single celled but exist in “swarms” or “packs”. Myxococcus xanthus are rod-shaped and are gram-negative. M. xanthus was discovered in 1892 by Roland Thaxter. [1] M. xanthus are found in soil or any place plentiful with organic matter. They live best when the ph of the soil is around 7-8 and the temperature is around 30C. [2] M. xanthus is also a chemoorganotroph, which means they are organisms that oxidize the chemical bonds in organic compounds that they then use for energy. Myxococcus xanthus live together by living in a small biofilm or slime sheet. [3] They move as one in search of nutrients, but when nutrients are not immediately available the cells are able to transform and come together as one large mass in order to survive.

Classification


Kingdom: Bacteria

Phylum: Proteobacteria

Class: Delta Proteobacteria

Order: Myxococcales

Family: Myxococcaceae

Genus: Myxococcus

Species: M. xanthus

Ecology & Genome


Myxococcus xanthus is found in the Myxococcales order. Myxococcales can be characterized by the following: have specific ways of communicating with each other and are very social, they are morphogenetic, and they are able to move around via gliding. Many of these requirements for being in this order can be due to the habitat and nutrient availability. The gliding helps locate and attack other organisms within their general area. Myxococcus xanthus is also considered a predator since they eat other microbes in their environment. Myxococcus xanthus has been described as a social bacteria as well. [4]This means that each cell relies on each other in order to survive.

All myxobacteria, with one exception, have the largest genomes in comparison to other prokaryotes. Since myxobacteria are so complex and organized the large genome could be due to how they survive and live in harsh environments. [5]Since they are able to live together in tough conditions the genomes have high plasticity which results in changes in the genome such as the formation of the fruiting body. Four different myxobacteria species genomes were compared and it was found that 452 genes were found in all of them. [6]This means that these genes could be responsible for the formation of the fruiting body.

Myxococcus xanthus had its genome sequenced IN 2001 and it was found to be 9.14 Mb. This is much larger than other deltaproteobacteria. It was found that specific genes were selected for rather than random gene duplication. These genes included sensing for small molecules, transcription control, and cell to cell signaling[7]The entire genome consists of 7,500 genes in total. Myxococcus xanthus also contains genes that aid in synthesizing amino acids as well as secreting growth inhibitors. There is also recent evidence that Myxococcus xanthus has a mechanism for breaking down protein. [8]It has also been found that fluids located within Myxococcus xanthus are able to lyse cell wall by hydrolyzing the peptidoglycan. [9] Each cell is only able to secrete so much, hence the reason they travel together in groups.

Fruting

Fruiting is the method at which Mxyococcus xanthus reproduces. This occurs when nutrients are unavailable or scarce. When no food is obtainable the individual Myxococcus xanthus cells organize themselves into larger masses. On average about 105 (100,000) cells assemble to form the larger mass. This large mass is called a fruiting body. [10] As the cells are forming the fruiting body they are actually being selected for based on related and unrelated cells. This creates uniform and species specific fruiting bodies among all of the cells. About 10% of the rod shaped cells that form the fruiting body then transform into sporangioles which also contain smaller myxospores. Around 30% of the original cells become the rods located on the outside of the mass of cells. The rest of the cells encased inside die off and become a source of nutrients for the remaining cells. It is believed that the cells come together to make sure a new colony is made by many cells opposed to one. Unlike other spore forming bacteria the rod-shaped cells directly transform into spherical myxospores.

The fruiting body is formed when groups of cells start to spiral together and travel to certain points called aggregation centers. . [11] As these aggregation centers form they become three-dimensional due to the meeting of different waves of cells. [12] After the fruiting body is completed two new cells have been formed. The myxospores which are found inside of the fruiting body and the peripheral rods which are found around the outside of the fruiting body. . [13] br>
Around 6-12 hours after the cells were starved of nutrients and the fruiting body is formed the rods that were unused become lysed. . [14] It has been found that the lysing cells are able to donate spore coated proteins to their own spores increasing the strength of the cell. [15]After 72 hours the spores are finally mature enough to germinate and once they do it creates new population of cells which start to swarm together in order to gain nutrients needed to grow. [16]In terms of fruiting body formation, the cells need to be stimulated by being close to another cell which initiates S-motility, also called twitching motility. [17]

In terms of why Myxococcus xanthus uses the fruiting body method there are a couple hypotheses. One is that it reduces the competition between other organisms by multiplying until they out number other organisms. [18]Another is that the spore may protect them from outside threats or stresses that may arise. [19] Lastly, it is possible that all of the processes that lead up to myxococcus formation is only to maintain their specialized lifestyle and make sure they are able to grow well. [20]

Life Cycle

Myxococcus xanthus lives in a never-ending cycle. It “starts” when there are many individual vegetative cells, which just means a cell that is actively growing. The cells then scout for prey in order to obtain nutrients or they branch off together in much larger quantity. The cells then find a prey and attempt to attack it by rippling through the organism. If the cells do not find any prey they are forced to come together in order to begin fruiting. Once the aggregates are formed the cells within them start to become spores and then as soon as nutrients are available the spores are germinated and made into many vegetative cells again. Myxococcus xanthus has two ways of directly multiplying. They are able to attack neighboring cells and feed on the nutrients that the cells excreted. They can also come together when nutrients are infrequent and form fruiting bodies that contain myxospores. The myxospores are able to live for a long time while under harsh conditions giving them the best chance of survival.[12] The fact that Myxococcus xanthus is able to do perform either method makes it a highly studied organism due to its complexity.



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  1. Thaxter, R On the Myxobacteriaceae, a new order of Schizomycetes. Botanical Gazette. 1892, 17:12, 389-406.
  2. Janssen GR, Wireman JW, Dworkin M Effect of temperature on the growth of Myxococcus xanthus. Journal of Bacteriology. 1977, 130(1) 561-562.
  3. Shimkets L.J., Dworkin M., Reichenbach H. (2006) The Myxobacteria. In: Dworkin M., Falkow S., Rosenberg E., Schleifer KH., Stackebrandt E. (eds) The Prokaryotes. Springer, New York, NY.
  4. Wolgemuth CW, Igoshin O, Oster, G. The Motility of Mollicutes. Biophysical Journal. 2003, 85(2)828:842.
  5. Zhou, X.‐w., Li, S.‐g., Li, W., Jiang, D.‐m., Han, K., Wu, Z.‐h. and Li, Y.‐z. (2014), Predominant soil myxobacteria. Environmental Microbiology Reports, 6: 45-56.
  6. Stuart Huntley, Nils Hamann, Sigrun Wegener-Feldbrügge, Anke Treuner-Lange, Michael Kube, Richard Reinhardt, Sven Klages, Rolf Müller, Catherine M. Ronning, William C. Nierman, Lotte Søgaard-Andersen, Comparative Genomic Analysis of Fruiting Body Formation in Myxococcales, Molecular Biology and Evolution, Volume 28, Issue 2, February 2011, Pages 1083–1097.
  7. B. S. Goldman, W. C. Nierman, D. Kaiser, S. C. Slater, A. S. Durkin, J. A.Eisen, C. M. Ronning, W. B. Barbazuk, M. Blanchard, C. Field, C. Halling, G.Hinkle, O. Iartchuk, H. S. Kim, C. Mackenzie, R. Madupu, N. Miller, A.Shvartsbeyn, S. A. Sullivan, M. Vaudin, R. Wiegand, H. B. Kaplan. Evolution of sensory complexity recorded in a myxobacterial genome. Proceedings of the National Academy of Sciences Oct 2006, 103 (41) 15200-15205
  8. Krug D, Zurek G, Revermann O, Vos M, Velicer GJ, Müller R. Discovering the hidden secondary metabolome of Myxococcus xanthus: a study of intraspecific diversity. Appl Environ Microbiol. 2008;74(10):3058-3068. doi:10.1128/AEM.02863-07.
  9. Rosenberg E, Keller KH, Dworkin M. Cell density-dependent growth of Myxococcus xanthus on casein. J Bacteriol. 1977 Feb;129(2):770-7. doi: 10.1128/JB.129.2.770-777.1977. PMID: 402357; PMCID: PMC235010.
  10. White, D. 1993. Myxospore and fruiting body morphogenesis, p. 307-332. In M. Dworkin and D. Kaiser (ed.), Myxobacteria II. ASM Press, Washington, D.C.
  11. Reichenbach, H. 1966. Myxococcus spp. (Myxobacteriales). Schwarmentwicklung und Bildung von Protocysten. Publikationen zu wissenschafilichen Filmen, Gottingen. lA:557-578.
  12. 12.0 12.1 Kaiser, D., and R. Welch. 2004. Dynamics of fruiting body morphogenesis. J Bacteriol 186:919-27.
  13. O'Connor, K. A., and D. R. Zusman. 1991. Development in Myxococcus xanthus involves differentiation into two cell types, peripheral rods and spores. J Bacteriol 173:3318-33.
  14. Wireman, J. W., and M. Dworkin. 1975. Morphogenesis and developmental interactions in myxobacteria. Science 189:516-23.
  15. Rosenbluh, A., and E. Rosenberg. 1993. Developmental lysis and autocides, p. 213-233. In M. Dworkin and D. Kaiser (ed.), Myxobacteria II. American Society of Microbiology, Washington, D. C.
  16. L J Shimkets Correlation of energy-dependent cell cohesion with social motility in Myxococcus xanthus. Journal of Bacteriology Jun 1986, 166 (3) 837-841
  17. Diodati ME, Gill RE, Plamann L, Singer M. 2008. Initiation and early developmental events. In: Whitworth D. E (Ed). Myxobacteria: Multicellularity and Differentiation. ASM Press.
  18. GARDNER, A. and WEST, S.A. (2006), Demography, altruism, and the benefits of budding. Journal of Evolutionary Biology, 19: 1707-1716.
  19. Ward MJ, Lew H, Zusman DR. Disruption of aldA Influences the Developmental Process in Myxococcus xanthus. J. Bacteriol. 2000, 182(2):546.
  20. Keane R, Berleman J. The predatory life cycle of Myxococcus xanthus. Microbiology. 2016, 162:1.
  21. 21.0 21.1 Hodgkin, J. and Partridge, F.A. "Caenorhabditis elegans meets microsporidia: the nematode killers from Paris." 2008. PLoS Biology 6:2634-2637.
  22. Bartlett et al.: Oncolytic viruses as therapeutic cancer vaccines. Molecular Cancer 2013 12:103.