関: M. xanthus

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/09/26 13:09:00」(JST)

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Myxococcus xanthus is a gram-negative, rod-shaped species of myxobacteria that exhibits various forms of self-organizing behavior as a response to environmental cues. Under normal conditions with abundant food, it exists as a predatory, saprophytic single-species biofilm called a swarm. Under starvation conditions, it undergoes a multicellular development cycle.^[1]

Colony growth

A swarm of M. xanthus is a distributed system, containing millions of entities that communicate among themselves in a non-centralized fashion. Simple patterns of cooperative behavior among the members of the colony combine to generate complex group behaviors in a process known as "stigmergy". For example, the tendency for one cell to glide only when in direct contact with another results in the colony forming swarms called "wolf-packs" that may up to several inches wide. This behavior is advantageous to the members of the swarm, as it increases the concentration of extracellular digestive enzymes secreted by the bacteria, thus facilitating predatory feeding. Likewise, during stressful conditions, the bacteria undergo a process in which about 100,000 individual cells aggregate to form a structure called the fruiting body over the course of several hours. On the interior of the fruiting body, the rod-shaped cells differentiate into spherical, thick-walled spores. They undergo changes in the synthesis of new proteins, as well as alterations in the cell wall, which parallel the morphological changes. During these aggregations, dense ridges of cells move in ripples, which wax and wane over 5 hours.^[2]

Motility

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Social motility leads to a spatial distribution of cells with lots of clusters and few isolated single cells.

An important part of M. xanthus behavior is its ability to move on a solid surface by a mechanism called "gliding".^[3] Gliding Motility is a method of locomotion that allows for movement, without the help of a flagella, on a solid surface. Gliding Motility is separated into two groups for the M. xanthus: A-motility (adventurous) and S-motility (social).^[4] In A motility, single cells move, resulting in a distribution with many single cells. In S motility, single cells do not move, but cells that are close to one another move. This leads to a spatial distribution of cells with lots of clusters and few isolated single cells.^[4]

More than 37 genes are involved in the A-motility system, which comprises multiple motor elements that are arrayed along the entire cell body. Each motor element appears to be localized to the periplasmic space and is bound to the peptidoglycan layer. The motors are hypothesized to move on helical cytoskeletal filaments. Gliding force generated by these motors is coupled to adhesion sites that move freely in the outer membrane, and which provide a specific contact with the substratum, possibly aided by extracellular polysaccharide slime.^[5]^[6]

S-motility may represent a variation of twitching motility, since it is mediated by the extension and retraction of type IV pili that extend through the leading cell pole. The genes of the S-motility system appear to be homologs of genes involved in the biosynthesis, assembly, and function of twitching motility in other bacteria.^[5]^[6]

Cell differentiation, fruiting and sporulation

In the presence of prey (here E. coli), M. xanthus cells self-organize into periodic bands of traveling waves, termed ripples (left-hand side). In the areas without prey, M. xanthus cells are under nutrient stress and as a result self-organize into haystack-shaped, spore-filled structures termed fruiting bodies (right-hand side, yellow mounds).

In response to starvation, myxobacteria develop species-specific multicellular fruiting bodies. Starting from a uniform swarm of cells, some aggregate into fruiting bodies, while other cells remain in a vegetative state. Those cells that participate in formation of the fruiting body transform from rods into spherical, heat-resistant myxospores, while the peripheral cells remain rod-shaped.^[7] Although not as tolerant to environmental extremes as, say, Bacillus endospores, the relative resistance of myxospores to dessication and freezing enables myxobacteria to survive seasonally harsh environments. When a nutrient source becomes once again available, the myxospores germinate, shedding their spore coats to emerge into rod-shaped vegetative cells. The synchronized germination of thousands of myxospores from a single fruiting body enables the members of the new colony of myxobacteria to immediately engage in cooperative feeding.^[8]

Intercellular communication

It is very likely that cells communicate during the process of fruiting and sporulation, because a group of cells that starved together form myxospores inside fruiting bodies.^[1] Intercellular signal appears to be necessary to ensure that sporulation happens in the proper place and at the proper time.^[9] Research supports the existence of an extracellular signal, A-factor, which is necessary for developmental gene expression and for the development of a complete fruiting body.^[10]

Importance in research

The complex life cycles of the myxobacteria make them very attractive models for the study of gene regulation as well as cell to cell interactions. The traits of M. xanthus make it very easy to study, and therefore important to research. Laboratory strains of M. xanthus are available that are capable of planktonic growth in shaker culture, so that they are easy to grow in large numbers. The tools of classical and molecular genetics are relatively well-developed in M. xanthus.^[11]

Although the fruiting bodies of M. xanthus are relatively primitive compared with, say, the elaborate structures produced by Stigmatella aurantiaca and other myxobacteria, the great majority of genes known to be involved in development are conserved across species.^[12] In order to make agar cultures of M. xanthus grow into fruiting bodies, one simply can plate the bacteria on starvation media.^[13] Furthermore, it is possible to artificially induce the production of myxospores without the intervening formation of fruiting bodies, by adding compounds such as glycerol or various metabolites to the medium.^[14] In this way, different stages in the developmental cycle can be experimentally isolated.

The genome of M. xanthus has been completely sequenced.^[15] The size of its genome may reflect the complexity of its life cycle. At 9.14 megabase, it had the largest known prokaryotic genome until the sequencing of Sorangium cellulosum (12.3 Mb), which is also a myxobacterium.

Developmental cheating

Social cheating exists among M. Xanthus commonly. As long as mutants are not too common, if they are unable to perform the group beneficial function of producing spores, they will still reap the benefit of the population as a whole. Research has shown that 4 different types of M. Xanthus mutants showed forms of cheating during development, by being over-represented among spores relative to their initial frequency in the mixture.^[16]

M. xanthus and evolution

In 2003, two scientists, Velicer and Yu, deleted certain parts of the M. xanthus genome, making it unable to swarm effectively on soft agar. Individuals were cloned, and allowed to evolve. After a period of 64 weeks, two of the evolving populations had started to swarm outward almost as effectively as normal wild-type colonies. However, the patterns of the swarm were very different from those of the wild-type bacteria. This suggested that they had developed a new way of moving, and Velicer and Yu confirmed this by showing that the new populations had not regained the ability to make pili, which allows wild-type bacteria to swarm. This study addressed questions about the evolution of cooperation between individuals that had plagued scientists for years.

Strains

Myxococcus xanthus DK 1622

Myxococcus xanthus DZ2

Myxococcus xanthus DZF1

Myxococcus xanthus NewJersey2

References

^ ^a ^b Kroos, Lee; Kuspa, Adam; Kaiser, Dale (1986). "A global analysis of developmentally regulated genes in Myxococcus xanthus". Developmental Biology 117 (1): 252–266. Retrieved 26 May 2015.
^ Velicer GJ, Stredwick KL (2002). "Experimental social evolution with Myxococcus xanthus". Antonie Van Leeuwenhoek 81 (1–4): 155–64. doi:10.1023/A:1020546130033. PMID 12448714.
^ Shi, Wenyuan. "Myxococcus xanthus". University of California at Los Angeles. Retrieved 26 May 2015.
^ ^a ^b Kaiser, Dale (1979). "Social gliding is correlated with the presence of pili in Myxococcus xanthus" (PDF). Proc. Nat. Acad. Sci. 76 (11): 5952–5956. Retrieved 26 May 2015.
^ ^a ^b Spormann, A. M. (1999). "Gliding motility in bacteria: insights from studies of Myxococcus xanthus". Microbiol. Mol. Biol. Rev. 63 (3): 621–641. PMID 10477310.
^ ^a ^b Zusman, D. R.; Scott, A. E.; Yang, Z.; Kirby, J. R. (2007). "Chemosensory pathways, motility and development in Myxococcus xanthus". Nature Reviews Microbiology 5 (11): 862. doi:10.1038/nrmicro1770. PMID 17922045.
^ Julien, B.; Kaiser, A. D.; Garza, A. (2000). "Spatial control of cell differentiation in Myxococcus xanthus". Proceedings of the National Academy of Sciences 97 (16): 9098. doi:10.1073/pnas.97.16.9098.
^ Lee, Keesoo; Shimkets, Lawrence J. (1994). "Cloning and Characterization of the socA Locus Which Restores Development to Myxococcus xanthus C-Signaling Mutants" (PDF). Journal of Bacteriology 176 (8): 2200–2209. Retrieved 30 May 2015.
^ Hagan, David C.; Bretscher, Anthony P.; Kaiser, Dale (1978). "Synergism between morphogenetic mutants of Myxococcus xanthus". Developmental Biology 64 (2): 284–296. Retrieved 26 May 2015.
^ Kuspa, Adam; Kroos, Lee; Kaiser, Dale (1986). "Intercellular signaling is required for developmental gene expression in Myxococcus xanthus". Developmental Biology 117 (1): 267–276. Retrieved 26 May 2015.
^ Stephens, Karen; Kaiser, Dale (1987). "Genetics of gliding motility in Myxococcus xanthus: Molecular cloning of the mgl locus". Molecular and General Genetics 207: 256–266.
^ Huntley, S.; Hamann, N.; Wegener-Feldbrugge, S.; Treuner-Lange, A.; Kube, M.; Reinhardt, R.; Klages, S.; Muller, R.; Ronning, C. M.; Nierman, W. C.; Sogaard-Andersen, L. (2010). "Comparative Genomic Analysis of Fruiting Body Formation in Myxococcales". Molecular Biology and Evolution 28 (2): 1083–1097. doi:10.1093/molbev/msq292. PMID 21037205.
^ Inouye, Masayori; Inouye, Sumiko; Zusman, David R. (1979). "Gene expression during development of Myxococcus xanthus: Pattern of protein synthesis". Developmental Biology 68 (2): 579–591. Retrieved 26 May 2015.
^ Bui, N. K.; Gray, J.; Schwarz, H.; Schumann, P.; Blanot, D.; Vollmer, W. (2008). "The Peptidoglycan Sacculus of Myxococcus xanthus Has Unusual Structural Features and is Degraded during Glycerol-Induced Myxospore Development". Journal of Bacteriology 191 (2): 494. doi:10.1128/JB.00608-08. PMID 18996994.
^ Goldman, B. S.; Nierman, W. C.; Kaiser, D.; Slater, S. C.; Durkin, A. S.; Eisen, J. A.; Ronning, C. M.; Barbazuk, W. B.; Blanchard, M.; Field, C.; Halling, C.; Hinkle, G.; Iartchuk, O.; Kim, H. S.; MacKenzie, C.; Madupu, R.; Miller, N.; Shvartsbeyn, A.; Sullivan, S. A.; Vaudin, M.; Wiegand, R.; Kaplan, H. B. (2006). "Evolution of sensory complexity recorded in a myxobacterial genome". Proceedings of the National Academy of Sciences 103 (41): 15200. doi:10.1073/pnas.0607335103.
^ Velicer, G. J.; Kroos, L.; Lenski, R. E. (2000). "Developmental cheating in the social bacterium Myxococcus xanthus". Nature 404 (6778): 598–601. doi:10.1038/35007066.

External links

Model Organism Database
John Kirby at the University of Iowa
Dale Kaiser Lab at Stanford University
Watching social behaviour evolve
Taxonomic Information for Myxococcus xanthus

Videos

Myxococcus xanthus preying on an E. coli colony
Myxococcus xanthus fruiting body formation
Myxococcus xanthus ripples - Predation
Predatory bacterial crowdsourcing

English Journal

A recent evolutionary origin of a bacterial small RNA that controls multicellular fruiting body development.

Chen IC1, Griesenauer B2, Yu YT3, Velicer GJ4.Author information 1Department of Biology, Indiana University, Bloomington, IN 47405, USA; Institute of Integrative Biology (IBZ), ETH Zurich, CH-8092 Zurich, Switzerland. Electronic address: icchen@indiana.edu.2Department of Biology, Indiana University, Bloomington, IN 47405, USA.3Institute of Integrative Biology (IBZ), ETH Zurich, CH-8092 Zurich, Switzerland.4Department of Biology, Indiana University, Bloomington, IN 47405, USA; Institute of Integrative Biology (IBZ), ETH Zurich, CH-8092 Zurich, Switzerland.AbstractIn animals and plants, non-coding small RNAs regulate the expression of many genes at the post-transcriptional level. Recently, many non-coding small RNAs (sRNAs) have also been found to regulate a variety of important biological processes in bacteria, including social traits, but little is known about the phylogenetic or mechanistic origins of such bacterial sRNAs. Here we propose a phylogenetic origin of the myxobacterial sRNA Pxr, which negatively regulates the initiation of fruiting body development in Myxococcus xanthus as a function of nutrient level, and also examine its diversification within the Myxococcocales order. Homologs of pxr were found throughout the Cystobacterineae suborder (with a few possible losses) but not outside this clade, suggesting a single origin of the Pxr regulatory system in the basal Cystobacterineae lineage. Rates of pxr sequence evolution varied greatly across Cystobacterineae sub-clades in a manner not predicted by overall genome divergence. A single copy of pxr was found in most species with 17% of nucleotide positions being polymorphic among them. However three tandem paralogs were present within the genus Cystobacter and these alleles together exhibited an elevated rate of divergence. There appears to have been strong selection for maintenance of a predicted stem-loop structure, as polymorphisms accumulated preferentially at loop or bulge regions or as complementary substitutions within predicted stems. All detected pxr homologs are located in the intergenic region between the σ(54)-dependent response regulator nla19 and a predicted NADH dehydrogenase gene, but other neighboring gene content has diversified.
Molecular phylogenetics and evolution.Mol Phylogenet Evol.2014 Apr;73:1-9. doi: 10.1016/j.ympev.2014.01.001. Epub 2014 Jan 10.
In animals and plants, non-coding small RNAs regulate the expression of many genes at the post-transcriptional level. Recently, many non-coding small RNAs (sRNAs) have also been found to regulate a variety of important biological processes in bacteria, including social traits, but little is known ab
PMID 24418530

Genetic Redundancy, Proximity, and Functionality of lspA, the Target of Antibiotic TA, in the Myxococcus xanthus Producer Strain.

Xiao Y1, Wall D.Author information 1Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, USA.AbstractWe recently showed that type II signal peptidase (SPaseII) encoded by lspA is the target of an antibiotic called TA (myxovirescin), which is made by Myxococcus xanthus. SPaseII cleaves the signal peptide during bacterial lipoprotein processing. Bacteria typically contain one lspA gene; however, strikingly, the M. xanthus DK1622 genome contains four (lspA1 to lspA4). Since two of these genes, lspA3 and lspA4, are located in the giant TA biosynthetic gene cluster, we hypothesized they may play a role in TA resistance. To investigate the functions of the four M. xanthus lspA (lspA(Mx)) genes, we conducted sequence comparisons and found that they contained nearly all the conserved residues characteristic of SPaseII family members. Genetic studies found that an Escherichia coli ΔlspA mutation could be complemented by any of the lspA(Mx) genes in an lpp mutant background, but not in an E. coli lpp(+) background. Because Lpp is the most abundant E. coli lipoprotein, these results suggest the M. xanthus proteins do not function as efficiently as the host enzyme. In E. coli, overexpression of each of the LspA(Mx) proteins conferred TA and globomycin resistance, although LspA3 conferred the highest degree of resistance. In M. xanthus, each lspA(Mx) gene could be deleted and was therefore dispensable for growth. However, lspA3 or lspA4 deletion mutants each exhibited a tan phase variation bias, which likely accounts for their reduced-swarming and delayed-development phenotypes. In summary, we propose that all four LspA(Mx) proteins function as SPaseIIs and that LspA3 and LspA4 might also have roles in TA resistance and regulation, respectively.
Journal of bacteriology.J Bacteriol.2014 Mar;196(6):1174-83. doi: 10.1128/JB.01361-13. Epub 2014 Jan 3.
We recently showed that type II signal peptidase (SPaseII) encoded by lspA is the target of an antibiotic called TA (myxovirescin), which is made by Myxococcus xanthus. SPaseII cleaves the signal peptide during bacterial lipoprotein processing. Bacteria typically contain one lspA gene; however, stri
PMID 24391051

The groEL2 gene, but not groEL1, is required for biosynthesis of the secondary metabolite myxovirescin in Myxococcus xanthus DK1622.

Wang Y1, Li X, Zhang W, Zhou X, Li YZ.Author information 1State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan 250100, PR China.AbstractMyxococcus xanthus DK1622 possesses two copies of the groEL gene: groEL1, which participates in development, and groEL2, which is involved in the predatory ability of cells. In this study, we determined that the groEL2 gene is required for the biosynthesis of the secondary metabolite myxovirescin (TA), which plays essential roles in predation. The groEL2-knockout mutant strain was defective in producing a zone of inhibition and displayed decreased killing ability against Escherichia coli, while the groEL1-knockout mutant strain exhibited little difference from the wild-type strain DK1622. HPLC revealed that deletion of the groEL2 gene blocked the production of TA, which was present in the groEL1-knockout mutant. The addition of exogenous TA rescued the inhibition and killing abilities of the groEL2-knockout mutant against E. coli. Analysis of GroEL domain-swapping mutants indicated that the C-terminal equatorial domain of GroEL2 was essential for TA production, while the N-terminal equatorial or apical domains of GroEL2 were not sufficient to rescue TA production of the groEL2 knockout.
Microbiology (Reading, England).Microbiology.2014 Mar;160(Pt 3):488-95. doi: 10.1099/mic.0.065862-0. Epub 2014 Jan 14.
Myxococcus xanthus DK1622 possesses two copies of the groEL gene: groEL1, which participates in development, and groEL2, which is involved in the predatory ability of cells. In this study, we determined that the groEL2 gene is required for the biosynthesis of the secondary metabolite myxovirescin (T
PMID 24425771

Japanese Journal

Proteome Analyses of Soil Bacteria Grown in the Presence of Potato Suberin, a Recalcitrant Biopolymer

Ｍｉｃｒｏｂｅｓ　ａｎｄ　ｅｎｖｉｒｏｎｍｅｎｔｓ 31(4), 418-426, 2016
NAID 130005434983

Functional analysis of conserved motifs in a bacterial tyrosine kinase, BtkB, from Myxococcus xanthus

The journal of biochemistry 158(5), 385-392, 2015-11
NAID 40020646959

Characterizing activities of eukaryotic-like protein kinases with atypical catalytic loop motifs from Myxococcus xanthus

Journal of bioscience and bioengineering 119(5), 511-514, 2015-05
NAID 110009962602

Related Pictures

★リンクテーブル★

リンク元	「M. xanthus」「ミキソコッカス・ザンサス」
関連記事	「Myxococcus」

「M. xanthus」

Myxococcus xanthus
Scientific classification
Kingdom:	Bacteria
Phylum:	Proteobacteria
Class:	Delta Proteobacteria
Order:	Myxococcales
Family:	Myxococcaceae
Genus:	Myxococcus
Species:	M. xanthus
Binomial name
	Myxococcus xanthus; Beebe 1941