1
|
Vassallo CN, Troselj V, Weltzer ML, Wall D. Rapid diversification of wild social groups driven by toxin-immunity loci on mobile genetic elements. ISME JOURNAL 2020; 14:2474-2487. [PMID: 32565537 DOI: 10.1038/s41396-020-0699-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Revised: 05/22/2020] [Accepted: 06/03/2020] [Indexed: 01/05/2023]
Abstract
Many species form distinct social groups that provide fitness advantages to individuals. However, the evolutionary processes that generate new social groups are not well understood. Here we examined recently diverged natural isolates of the model social bacterium, Myxococcus xanthus, to probe the genetic mechanisms and evolutionary processes of kin discrimination that occurred naturally in soil. We show that social incompatibilities were formed from horizontal gene transfer of effectors belonging to three distinct polymorphic toxin systems; outer membrane exchange, type VI secretion and rearrangement hotspot systems. Strikingly, the unique toxin effectors and their respective immunity genes that are responsible for social incompatibilities reside on mobile genetic elements, which make up nearly all of the genotypic variation between isolates within clades. By disrupting these three toxin systems, we engineered social harmony between strains that were originally incompatible. In addition, a horizontal allele swap of a single kin recognition receptor changed social interactions and competition outcomes. Our results provide a case study for how horizontal gene transfer led to social diversification in a natural context. Finally, we show how genomic information of kin discriminatory loci can be used to predict social interactions.
Collapse
Affiliation(s)
- Christopher N Vassallo
- Department of Molecular Biology, University of Wyoming, 1000 E University Avenue, Laramie, WY, 82071, USA.,Department of Biology, Massachusetts Institute of Technology, 31 Ames St., Cambridge, MA, 02142, USA
| | - Vera Troselj
- Department of Molecular Biology, University of Wyoming, 1000 E University Avenue, Laramie, WY, 82071, USA.,The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - Michael L Weltzer
- Department of Molecular Biology, University of Wyoming, 1000 E University Avenue, Laramie, WY, 82071, USA
| | - Daniel Wall
- Department of Molecular Biology, University of Wyoming, 1000 E University Avenue, Laramie, WY, 82071, USA.
| |
Collapse
|
2
|
Self-identity barcodes encoded by six expansive polymorphic toxin families discriminate kin in myxobacteria. Proc Natl Acad Sci U S A 2019; 116:24808-24818. [PMID: 31744876 DOI: 10.1073/pnas.1912556116] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Myxobacteria are an example of how single-cell individuals can transition into multicellular life by an aggregation strategy. For these and all organisms that consist of social groups of cells, discrimination against, and exclusion of, nonself is critical. In myxobacteria, TraA is a polymorphic cell surface receptor that identifies kin by homotypic binding, and in so doing exchanges outer membrane (OM) proteins and lipids between cells with compatible receptors. However, TraA variability alone is not sufficient to discriminate against all cells, as traA allele diversity is not necessarily high among local strains. To increase discrimination ability, myxobacteria include polymorphic OM lipoprotein toxins called SitA in their delivered cargo, which poison recipient cells that lack the cognate, allele-specific SitI immunity protein. We previously characterized 3 SitAI toxin/immunity pairs that belong to 2 families. Here, we discover 4 additional SitA families. Each family is unique in sequence, but share the characteristic features of SitA: OM-associated toxins delivered by TraA. We demonstrate that, within a SitA family, C-terminal nuclease domains are polymorphic and often modular. Remarkably, sitA loci are strikingly numerous and diverse, with most genomes possessing >30 and up to 83 distinct sitAI loci. Interestingly, all SitA protein families are serially transferred between cells, allowing a SitA inhibitor cell to poison multiple targets, including cells that never made direct contact. The expansive suites of sitAI loci thus serve as identify barcodes to exquisitely discriminate against nonself to ensure populations are genetically homogenous to conduct cooperative behaviors.
Collapse
|
3
|
Bacteriophages of Myxococcus xanthus, a Social Bacterium. Viruses 2018; 10:v10070374. [PMID: 30021959 PMCID: PMC6070905 DOI: 10.3390/v10070374] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/12/2018] [Accepted: 07/16/2018] [Indexed: 01/21/2023] Open
Abstract
Bacteriophages have been used as molecular tools in fundamental biology investigations for decades. Beyond this, however, they play a crucial role in the eco-evolutionary dynamics of bacterial communities through their demographic impact and the source of genetic information they represent. The increasing interest in describing ecological and evolutionary aspects of bacteria–phage interactions has led to major insights into their fundamental characteristics, including arms race dynamics and acquired bacterial immunity. Here, we review knowledge on the phages of the myxobacteria with a major focus on phages infecting Myxococcus xanthus, a bacterial model system widely used to study developmental biology and social evolution. In particular, we focus upon the isolation of myxophages from natural sources and describe the morphology and life cycle parameters, as well as the molecular genetics and genomics of the major groups of myxophages. Finally, we propose several interesting research directions which focus on the interplay between myxobacterial host sociality and bacteria–phage interactions.
Collapse
|
4
|
Self-identity reprogrammed by a single residue switch in a cell surface receptor of a social bacterium. Proc Natl Acad Sci U S A 2017; 114:3732-3737. [PMID: 28320967 DOI: 10.1073/pnas.1700315114] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The ability to recognize close kin confers survival benefits on single-celled microbes that live in complex and changing environments. Microbial kinship detection relies on perceptible cues that reflect relatedness between individuals, although the mechanisms underlying recognition in natural populations remain poorly understood. In myxobacteria, cells identify related individuals through a polymorphic cell surface receptor, TraA. Recognition of compatible receptors leads to outer membrane exchange among clonemates and fitness consequences. Here, we investigated how a single receptor creates a diversity in recognition across myxobacterial populations. We first show that TraA requires its partner protein TraB to function in cell-cell adhesion. Recognition is shown to be traA allele-specific, where polymorphisms within TraA dictate binding selectivity. We reveal the malleability of TraA recognition, and seemingly minor changes to its variable region reprogram recognition outcomes. Strikingly, we identify a single residue (A/P205) as a molecular switch for TraA recognition. Substitutions at this position change the specificity of a diverse panel of environmental TraA receptors. In addition, we engineered a receptor with unique specificity by simply creating an A205P substitution, suggesting that modest changes in TraA can lead to diversification of new recognition groups in nature. We hypothesize that the malleable property of TraA has allowed it to evolve and create social barriers between myxobacterial populations and in turn avoid adverse interactions with relatives.
Collapse
|
5
|
Vassallo CN, Cao P, Conklin A, Finkelstein H, Hayes CS, Wall D. Infectious polymorphic toxins delivered by outer membrane exchange discriminate kin in myxobacteria. eLife 2017; 6:29397. [PMID: 28820387 PMCID: PMC5562445 DOI: 10.7554/elife.29397] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 07/13/2017] [Indexed: 01/07/2023] Open
Abstract
Myxobacteria are known for complex social behaviors including outer membrane exchange (OME), in which cells exchange large amounts of outer membrane lipids and proteins upon contact. The TraA cell surface receptor selects OME partners based on a variable domain. However, traA polymorphism alone is not sufficient to precisely discriminate kin. Here, we report a novel family of OME-delivered toxins that promote kin discrimination of OME partners. These SitA lipoprotein toxins are polymorphic and widespread in myxobacteria. Each sitA is associated with a cognate sitI immunity gene, and in some cases a sitB accessory gene. Remarkably, we show that SitA is transferred serially between target cells, allowing the toxins to move cell-to-cell like an infectious agent. Consequently, SitA toxins define strong identity barriers between strains and likely contribute to population structure, maintenance of cooperation, and strain diversification. Moreover, these results highlight the diversity of systems evolved to deliver toxins between bacteria.
Collapse
Affiliation(s)
| | - Pengbo Cao
- Department of Molecular Biology, University of Wyoming, Laramie, United States
| | - Austin Conklin
- Department of Molecular Biology, University of Wyoming, Laramie, United States
| | - Hayley Finkelstein
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, United States
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, United States
| | - Daniel Wall
- Department of Molecular Biology, University of Wyoming, Laramie, United States,
| |
Collapse
|
6
|
Sibling Rivalry in Myxococcus xanthus Is Mediated by Kin Recognition and a Polyploid Prophage. J Bacteriol 2016; 198:994-1004. [PMID: 26787762 DOI: 10.1128/jb.00964-15] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 01/07/2016] [Indexed: 01/24/2023] Open
Abstract
UNLABELLED Myxobacteria form complex social communities that elicit multicellular behaviors. One such behavior is kin recognition, in which cells identify siblings via their polymorphic TraA cell surface receptor, to transiently fuse outer membranes and exchange their contents. In addition, outer membrane exchange (OME) regulates behaviors, such as inhibition of wild-type Myxococcus xanthus (DK1622) from swarming. Here we monitored the fate of motile cells and surprisingly found they were killed by nonmotile siblings. The kill phenotype required OME (i.e., was TraA dependent). The genetic basis of killing was traced to ancestral strains used to construct DK1622. Specifically, the kill phenotype mapped to a large "polyploid prophage," Mx alpha. Sensitive strains contained a 200-kb deletion that removed two of three Mx alpha units. To explain these results, we suggest that Mx alpha expresses a toxin-antitoxin cassette that uses the OME machinery of M. xanthus to transfer a toxin that makes the population "addicted" to Mx alpha. Thus, siblings that lost Mx alpha units (no immunity) are killed by cells that harbor the element. To test this, an Mx alpha-harboring laboratory strain was engineered (by traA allele swap) to recognize a closely related species, Myxococcus fulvus. As a result, M. fulvus, which lacks Mx alpha, was killed. These TraA-mediated antagonisms provide an explanation for how kin recognition specificity might have evolved in myxobacteria. That is, recognition specificity is determined by polymorphisms in traA, which we hypothesize were selected for because OME with non-kin leads to lethal outcomes. IMPORTANCE The transition from single cell to multicellular life is considered a major evolutionary event. Myxobacteria have successfully made this transition. For example, in response to starvation, individual cells aggregate into multicellular fruiting bodies wherein cells differentiate into spores. To build fruits, cells need to recognize their siblings, and in part, this is mediated by the TraA cell surface receptor. Surprisingly, we report that TraA recognition can also involve sibling killing. We show that killing originates from a prophage-like element that has apparently hijacked the TraA system to deliver a toxin to kin. We hypothesize that this killing system has imposed selective pressures on kin recognition, which in turn has resulted in TraA polymorphisms and hence many different recognition groups.
Collapse
|
7
|
Zhao JY, Zhong L, Shen MJ, Xia ZJ, Cheng QX, Sun X, Zhao GP, Li YZ, Qin ZJ. Discovery of the autonomously replicating plasmid pMF1 from Myxococcus fulvus and development of a gene cloning system in Myxococcus xanthus. Appl Environ Microbiol 2008; 74:1980-7. [PMID: 18245244 PMCID: PMC2292591 DOI: 10.1128/aem.02143-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2007] [Accepted: 01/23/2008] [Indexed: 11/20/2022] Open
Abstract
Myxobacteria are very important due to their unique characteristics, such as multicellular social behavior and the production of diverse and novel bioactive secondary metabolites. However, the lack of autonomously replicating plasmids has hindered genetic manipulation of myxobacteria for decades. To determine whether indigenous plasmids are present, we screened about 150 myxobacterial strains, and a circular plasmid designated pMF1 was isolated from Myxococcus fulvus 124B02. Sequence analysis showed that this plasmid was 18,634 bp long and had a G+C content of 68.7%. Twenty-three open reading frames were found in the plasmid, and 14 of them were not homologous to any known sequence. Plasmids containing the gene designated pMF1.14, which encodes a large unknown protein, were shown to transform Myxococcus xanthus DZ1 and DK1622 at high frequencies ( approximately 10(5) CFU/microg DNA), suggesting that the locus is responsible for the autonomous replication of pMF1. Shuttle vectors were constructed for both M. xanthus and Escherichia coli. The pilA gene, which is essential for pilus formation and social motility in M. xanthus, was cloned into the shuttle vectors and introduced into the pilA-deficient mutant DK10410. The transformants subsequently exhibited the ability to form pili and social motility. Autonomously replicating plasmid pMF1 provides a new tool for genetic manipulation in Myxococcus.
Collapse
Affiliation(s)
- Jing-Yi Zhao
- State Key Laboratory of Microbial Technology, College of Life Science, Shandong University, Jinan 250100, People's Republic of China.
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Tiennault-Desbordes E, Cenatiempo Y, Laalami S. Initiation factor 2 of Myxococcus xanthus, a large version of prokaryotic translation initiation factor 2. J Bacteriol 2001; 183:207-13. [PMID: 11114918 PMCID: PMC94867 DOI: 10.1128/jb.183.1.207-213.2001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have isolated the structural gene for translation initiation factor IF2 (infB) from the myxobacterium Myxococcus xanthus. The gene (3.22 kb) encodes a 1,070-residue protein showing extensive homology within its G domain and C terminus to the equivalent regions of IF2 from Escherichia coli. The protein cross-reacts with antibodies raised against E. coli IF2 and was able to complement an E. coli infB mutant. The M. xanthus protein is the largest IF2 known to date. This is essentially due to a longer N-terminal region made up of two characteristic domains. The first comprises a 188-amino-acid sequence consisting essentially of alanine, proline, valine, and glutamic acid residues, similar to the APE domain observed in Stigmatella aurantiaca IF2. The second is unique to M. xanthus IF2, is located between the APE sequence and the GTP binding domain, and consists exclusively of glycine, proline, and arginine residues.
Collapse
Affiliation(s)
- E Tiennault-Desbordes
- Institut de Biologie Moléculaire et d'Ingénierie Génétique, ESA CNRS 6031, Université de Poitiers, 86022 Poitiers Cedex, France
| | | | | |
Collapse
|
9
|
Magrini V, Storms ML, Youderian P. Site-specific recombination of temperate Myxococcus xanthus phage Mx8: regulation of integrase activity by reversible, covalent modification. J Bacteriol 1999; 181:4062-70. [PMID: 10383975 PMCID: PMC93897 DOI: 10.1128/jb.181.13.4062-4070.1999] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Temperate Myxococcus xanthus phage Mx8 integrates into the attB locus of the M. xanthus genome. The phage attachment site, attP, is required in cis for integration and lies within the int (integrase) coding sequence. Site-specific integration of Mx8 alters the 3' end of int to generate the modified intX gene, which encodes a less active form of integrase with a different C terminus. The phage-encoded (Int) form of integrase promotes attP x attB recombination more efficiently than attR x attB, attL x attB, or attB x attB recombination. The attP and attB sites share a common core. Sequences flanking both sides of the attP core within the int gene are necessary for attP function. This information shows that the directionality of the integration reaction depends on arm sequences flanking both sides of the attP core. Expression of the uoi gene immediately upstream of int inhibits integrative (attP x attB) recombination, supporting the idea that uoi encodes the Mx8 excisionase. Integrase catalyzes a reaction that alters the primary sequence of its gene; the change in the primary amino acid sequence of Mx8 integrase resulting from the reaction that it catalyzes is a novel mechanism by which the reversible, covalent modification of an enzyme is used to regulate its specific activity. The lower specific activity of the prophage-encoded IntX integrase acts to limit excisive site-specific recombination in lysogens carrying a single Mx8 prophage, which are less immune to superinfection than lysogens carrying multiple, tandem prophages. Thus, this mechanism serves to regulate Mx8 site-specific recombination and superinfection immunity coordinately and thereby to preserve the integrity of the lysogenic state.
Collapse
Affiliation(s)
- V Magrini
- Department of Microbiology, Molecular Biology, and Biochemistry, University of Idaho, Moscow, Idaho 83844-3052, USA
| | | | | |
Collapse
|
10
|
Bremaud L, Laalami S, Derijard B, Cenatiempo Y. Translation initiation factor IF2 of the myxobacterium Stigmatella aurantiaca: presence of a single species with an unusual N-terminal sequence. J Bacteriol 1997; 179:2348-55. [PMID: 9079922 PMCID: PMC178973 DOI: 10.1128/jb.179.7.2348-2355.1997] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The structural gene for translation initiation factor IF2 (infB) was isolated from the myxobacterium Stigmatella aurantiaca on a 5.18-kb BamHI genomic restriction fragment. The infB gene (ca. 3.16 kb) encodes a 1,054-residue polypeptide with extensive homology within its G domain and C terminus with the equivalent regions of IF2s from Escherichia coli, Bacillus subtilis, Bacillus stearothermophilus, and Streptococcus faecium. The N-terminal region does not display any significant homology to other known proteins. The S. aurantiaca infB gene encodes a single protein which cross-reacted with antiserum to E. coli IF2 and was able to complement an E. coli infB mutant. The S. aurantiaca IF2 is distinguished from all other IF2s by a sequence of 160 residues near the N terminus that has an unusual composition, made up essentially of alanine, proline, valine, and glutamic acid. Within this sequence, the pattern PXXXAP is repeated nine times. Complete deletion of this sequence did not affect the factor's function in initiation of translation and even increased its capacity to complement the E. coli infB mutant.
Collapse
Affiliation(s)
- L Bremaud
- Institut de Biologie Moléculaire et d'Ingénierie Génétique, URA CNRS 1172, Université de Poitiers, France
| | | | | | | |
Collapse
|
11
|
Bremaud L, Fremaux C, Laalami S, Cenatiempo Y. Genetic and molecular analysis of the tRNA-tufB operon of the myxobacterium Stigmatella aurantiaca. Nucleic Acids Res 1995; 23:1737-43. [PMID: 7784178 PMCID: PMC306930 DOI: 10.1093/nar/23.10.1737] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The tufB gene, encoding elongation factor Tu (EF-Tu), from the myxobacterium Stigmatella aurantiaca was cloned and sequenced. It is preceded by four tRNA genes, the first ever described in myxobacteria. The tRNA synthesized from these genes and the general organization of the locus seem identical to that of Escherichia coli, but differences of potential importance were found in the tRNA sequences and in the intergenic regions. The primary structure of EF-Tu was deduced from the tufB DNA sequence. The factor is composed of 396 amino acids, with a predicted molecular mass of 43.4 kDa, which was confirmed by expression of tufB in maxicells. Sequence comparisons between S.aurantiaca EF-Tu and other bacterial homologues from E.coli, Salmonella typhimurium and Thermus thermophilus displayed extensive homologies (75.9%). Among the variable positions, two Cys residues probably involved in the temperature sensitivity of E.coli and S.typhimurium EF-Tu are replaced in T.thermophilus and S.aurantiaca EF-Tu. Since two or even three tuf genes have been described in other bacterial species, the presence of multiple tuf genes was sought for. Southern and Northern analysis are consistent with two tuf genes in the genome of S.aurantiaca. Primer extension experiments indicate that the four tRNA genes and tufB are organized in a single operon.
Collapse
Affiliation(s)
- L Bremaud
- Institut de Biologie Moléculaire et d'Ingénierie Génétique-CNRS URA 1172, Université de Poitiers, France
| | | | | | | |
Collapse
|
12
|
He Q, Chen H, Kuspa A, Cheng Y, Kaiser D, Shimkets LJ. A physical map of the Myxococcus xanthus chromosome. Proc Natl Acad Sci U S A 1994; 91:9584-7. [PMID: 7937810 PMCID: PMC44857 DOI: 10.1073/pnas.91.20.9584] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
A physical map of the 9.2-Mbp Myxococcus xanthus DK1622 chromosome at a resolution of 25 kbp was constructed by using a strategy that is applicable to virtually all microorganisms. Segments of the chromosome were used as hybridization probes to subdivide a yeast artificial chromosome (YAC) library into groups of linked clones. The clones were aligned by comparing their EcoRI restriction patterns. The groups of YAC clones ("contigs") were oriented and aligned with the genomic restriction map by means of common genetic and physical markers such as rare restriction sites and transposon insertions. Over 95% of the genome is represented by cloned DNA. Sixty genetic loci including > 100 genes, many of which play a role in fruiting body development, have been mapped in this way. Additional genes can now be located on the chromosome map by hybridization of their sequences to the ordered set of YAC chromosomes. The mapped genetic loci account for approximately 2% of the genome.
Collapse
Affiliation(s)
- Q He
- Department of Microbiology, University of Georgia, Athens 30602
| | | | | | | | | | | |
Collapse
|
13
|
Lucas N, Mazaud-Aujard C, Bremaud L, Cenatiempo Y, Julien R. Protein purification, gene cloning and sequencing of an acidic endoprotease from Myxococcus xanthus DK101. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 222:247-54. [PMID: 8020464 DOI: 10.1111/j.1432-1033.1994.tb18863.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
An acidic endoprotease (MAEP) secreted during vegetative growth by Myxococcus xanthus DK101 was purified to homogeneity by a series of chromatographic procedures. The endoprotease cleaved the Phe-Met bond of kappa-casein under acidic conditions (pH 5.9). Its apparent molecular mass and its isoelectric point have been estimated to be 12 kDa and 4.5, respectively. From the N-terminal amino acid sequence, a set of two primers for polymerase chain reaction have been designed. Amplification of the corresponding DNA fragment (84 bp) generated a probe, then used to screen an expression DNA library of M. xanthus and to isolate a recombinant plasmid which contained a 2127-bp insert. The nucleotide sequence included an open reading frame (ORF) of 585 nucleotides, encoding 195 amino acids, that exhibited a high degree of similarity with the N-terminal amino acid sequence of the purified MAEP. The polypeptide sequence inferred from this ORF revealed that the mature enzyme should contain 131 amino acids arising from a 195-amino-acid precursor protein.
Collapse
Affiliation(s)
- N Lucas
- Institut de Biotechnologie, Faculté des Sciences, Limoges, France
| | | | | | | | | |
Collapse
|
14
|
Abstract
The genome of Myxococcus xanthus, which is 9,454 kbp, is one of the largest bacterial genomes. The organization of the DNA and the distribution of genes encoding social and developmental behaviors were examined by using pulsed field gel electrophoresis. Intact genomic DNA was digested with AseI into 16 restriction fragments, which were separated by contour-clamped homogeneous electric field electrophoresis, purified, and radiolabeled. Each AseI fragment was hybridized to SpeI-digested DNA and to an M. xanthus genomic library contained in yeast artificial chromosomes. Some SpeI restriction fragments and yeast artificial chromosome clones contained AseI sites and hybridized with two different AseI restriction fragments, providing evidence for the juxtaposition of these AseI restriction fragments in the chromosome. The deduced AseI physical map is circular, suggesting that this bacterium contains a single, circular chromosome. Transposable elements shown by transduction to be in or near genes of interest were located on specific AseI restriction fragments by restriction analysis and Southern hybridization. Most AseI restriction fragments contained genes involved in social and developmental behaviors.
Collapse
Affiliation(s)
- H W Chen
- Department of Microbiology, University of Georgia, Athens 30602
| | | | | | | |
Collapse
|
15
|
|
16
|
Kalos M, Zissler J. Transposon tagging of genes for cell-cell interactions in Myxococcus xanthus. Proc Natl Acad Sci U S A 1990; 87:8316-20. [PMID: 2172982 PMCID: PMC54946 DOI: 10.1073/pnas.87.21.8316] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The prokaryote Myxococcus xanthus is a model for cell interactions important in multicellular behavior. We used the transposon TnphoA to specifically identify genes for cell-surface factors involved in cell interactions. From a library of 10,700 insertions of TnphoA, we isolated 36 that produced alkaline phosphatase activity. Three TnphoA insertions tagged cell motility genes, called cgl, which control the adventurous movement of cells. The products of the tagged cgl genes could function in trans upon other cells and were localized primarily in the cell envelope and extracellular space, consistent with TnphoA tagging genes for extracellular factors controlling motility.
Collapse
Affiliation(s)
- M Kalos
- Department of Microbiology, University of Minnesota Medical School, Minneapolis 55455
| | | |
Collapse
|
17
|
Chen H, Keseler IM, Shimkets LJ. Genome size of Myxococcus xanthus determined by pulsed-field gel electrophoresis. J Bacteriol 1990; 172:4206-13. [PMID: 2165472 PMCID: PMC213243 DOI: 10.1128/jb.172.8.4206-4213.1990] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Genomic DNA of the myxobacterium Myxococcus xanthus was digested with the rare cutting restriction endonuclease AseI or SpeI, and the restriction products were separated by pulsed-field gel electrophoresis. Transposons Tn5-132 and Tn5 lac, which contain AseI restriction sites, were used to determine the number of restriction fragments in each band. The size of the genome was determined by adding the molecular sizes of the restriction products. The genomes of strains DK101, MD2, and DZF1 have identical restriction patterns and were estimated to be 9,454 +/- 101 kilobase pairs from the AseI digestions and 9,453 +/- 106 kilobase pairs from the SpeI digestions. DK1622, which was derived from DK101 by treatment with UV light, has suffered a 220- to 222-kilobase-pair deletion that removed an AseI and an SpeI restriction site. The deleted DNA may consist exclusively of Mx alpha-associated sequences.
Collapse
Affiliation(s)
- H Chen
- Department of Microbiology, University of Georgia, Athens 30602
| | | | | |
Collapse
|