Territorial interactions between two Myxococcus Species.

It is unusual to find fruiting bodies of different myxobacteria occupying the same territory on natural samples. We were thus interested in determining whether myxobacteria establish territorial dominance and, if so, what the mechanism of that interaction is. We had previously observed that vegetative swarms of Myxococcus xanthus and Stigmatella aurantiaca placed close to each other on an agar surface initially merged but eventually separated. Further studies indicated that these two species also formed separate fruiting bodies when mixed together on developmental agar (unpublished observation). We examined the interactions between two more closely related myxobacteria, M. xanthus and M. virescens, in greater detail. When mixtures of a kanamycin-resistant strain of M. xanthus and a kanamycin-sensitive strain of M. virescens were placed together under developmental conditions, the cells sorted themselves out and established separate fruiting body territories. In addition, differential viable counts of a mixture of the two species during development indicated that each strain was producing an extracellular component that inhibited the growth and development of the other. Nevertheless, finally, M. virescens invariably outcompeted M. xanthus at all input ratios of M. xanthus/M. virescens tested. This is consistent with the observation that M. virescens is by far the more commonly encountered of the two species. The properties of the inhibitory substance from M. virescens are consistent with the possibility that it is a bacteriocin. Our working hypothesis is that the bacteriocin plays a role in the establishment of myxobacterial territoriality. If so, this is an example of an ecological function of bacteriocins.     

Distribution of multicopy single-stranded DNA among myxobacteria and related species.

Multicopy single-stranded DNA (msDNA) is a short single-stranded linear DNA originally discovered in Myxococcus xanthus and subsequently found in Stigmatella aurantiaca. It exists at an estimated 500 to 700 copies per chromosome (T. Yee, T. Furuichi, S. Inouye, and M. Inouye, Cell 38:203-209, 1984). We found msDNA in other myxobacteria, including Myxococcus coralloides, Cystobacter violaceus, Cystobacter ferrugineus (Cbfe17), Nannocystis exedens, and nine independently isolated strains of M. xanthus. The presence of msDNA in N. exedens would extend its phylogenetic distribution into another family of myxobacteria. Flexibacter elegans, a Cytophaga-like gliding bacteria which may be even more distantly related, also contained an msDNA but at a much lower copy number. msDNA was not detected in closely related strains of the myxobacteria Cystobacter fuscus and C. ferrugineus (Cbfe16 and Cbfe18) and the more distantly related eubacteria Herpetosiphon giganteus, Taxeobacter ocellatus, Lysobacter antibioticus, Lysobacter enzymogenes, Cytophaga johnsonae, Rhodopseudomonas sphaeroides, and Rhodospirillum rubrum. Thus far, msDNA has been found in certain gliding bacteria but not in others.     

The junctional pore complex and the propulsion of bacterial cells

Gliding motility is defined as translocation in the direction of the long axis of the bacterium while in contact with a surface. This definition leaves unspecified any mechanism and, indeed, it appears that there is more than one physiological system underlying the same type of motion. Currently, two distinct mechanisms have been discovered in myxobacteria. One requires the extension, attachment, and retraction of type IV pili to pull the cell forwards. Recent experimental evidence suggests that a second mechanism for gliding motility involves the extrusion of slime from an organelle called the 'junctional pore complex'. This review discusses the role of slime extrusion and the junctional pore complex in the gliding motility of both cyanobacteria and myxobacteria.     

The peptidoglycan sacculus of Myxococcus xanthus has unusual structural features and is degraded during glycerol-induced myxospore development

Upon nutrient limitation cells of the swarming soil bacterium Myxococcus xanthus form a multicellular fruiting body in which a fraction of the cells develop into myxospores. Spore development includes the transition from a rod-shaped vegetative cell to a spherical myxospore and so is expected to be accompanied by changes in the bacterial cell envelope. Peptidoglycan is the shape-determining structure in the cell envelope of most bacteria, including myxobacteria. We analyzed the composition of peptidoglycan isolated from M. xanthus. While the basic structural elements of peptidoglycan in myxobacteria were identical to those in other gram-negative bacteria, the peptidoglycan of M. xanthus had unique structural features. meso- or LL-diaminopimelic acid was present in the stem peptides, and a new modification of N-acetylmuramic acid was detected in a fraction of the muropeptides. Peptidoglycan formed a continuous, bag-shaped sacculus in vegetative cells. The sacculus was degraded during the transition from vegetative cells to glycerol-induced myxospores. The spherical, bag-shaped coats isolated from glycerol-induced spores contained no detectable muropeptides, but they contained small amounts of N-acetylmuramic acid and meso-diaminopimelic acid.     

人工微宇宙下粘细菌捕食对微生物群落结构的影响

【目的】人工微宇宙条件下测试粘细菌捕食对微生物群落结构的影响,模拟粘细菌捕食对微生态系统的调控作用。【方法】采用Lawn predation法,测定粘细菌EGB对9种猎物菌的捕食直径,以确定其对猎物菌的捕食能力。通过高通量测序技术分析粘细菌捕食引起的微生物群落结构变化。【结果】粘细菌EGB对9种不同猎物菌的捕食能力差异显著,粘细菌对热带芽孢杆菌的捕食能力显著高于其他细菌(P<0.05)。在含有9种猎物细菌的人工微宇宙系统中添加不等量粘细菌,均可显著降低细菌群落的多样性指数(Shannon)。PCoA结果表明粘细菌捕食可影响微宇宙微生物群落结构。人工微宇宙培养24 h后,7种猎物菌相对丰度显著降低(LefSe,P<0.05),但洋葱伯克霍尔德菌的相对丰度显著升高(P<0.05)。人工微宇宙实验的结果表明,粘细菌添加是造成其微生物群落结构改变的主要影响因素,且添加最小剂量的粘细菌(1 mL)也有显著的影响效果;随着培养时间的增加,洋葱伯克霍尔德菌是唯一能抵抗粘细菌捕食并具有较高丰度的猎物细菌。【结论】粘细菌捕食能够调控微宇宙中微生物的群落结构,为其对土壤生态的调控研究奠定了理论基础。     

Deoxyribonucleic Acid Homology Among the Fruiting Myxobacteria

Deoxyribonucleic acid similarities were determined by competition experiments. The several strains of fruiting myxobacteria tested showed from 23 to 89% homology with the reference strains Myxococcus xanthus (FB) and M. fulvus (M6).     

Exploring the diversity of myxobacteria in a soil niche by myxobacteria-specific primers and probes

The diversity of myxobacteria in a soil niche was explored using culture-dependent and -independent methods. Conventional cultivation for bacteriolytic myxobacteria produced six types of myxobacteria, which were identified as two Myxococcus spp., two Corallococcus spp., a Cystobacter sp. and a Nannocysts sp. Hybridization analysis of the soil bacterial 16S rRNA gene library with myxobacteria-specific probes revealed that myxobacteria accounted for less than 1% in the bacterial community. A Cystobacterineae 16S rRNA genes-rich library was further established from the soil DNA by polymerase chain reaction amplification with a Cystobacterineae-specific primer combined with a universal bacterial primer. Screening of the special library using Cystobacterineae- and Sorangineae-specific probes produced approximately 45% and 3% positive signals respectively. Sixty-four positive clones were randomly selected for sequencing. Except three repeats, the sequences were diverse ranging from 0.3% to 21.3%, and homologous with the known myxobacteria at 77.6-99.8%, including 57 in Cystobacterineae, one close to Nannocystis and three much more distant from the known myxobacteria. The sequences in the Cystobacterineae can further be divided into at least 12 groups, of which most were unreported. The results suggest that myxobacteria in nature are much more diverse than were ever known, even in one soil niche.     

Fruiting and non-fruiting myxobacteria: a phylogenetic perspective of cultured and uncultured members of this group

The diversity of myxobacteria present in campus garden soil was surveyed by both cultivation-based and cultivation-independent methods. Detailed phylogenetic analysis of cultured and uncultured myxobacteria 16S rRNA gene sequences revealed that many undescribed relatives of the myxobacteria exist in nature. Molecular systematic analyses also revealed that myxobacterial genera described to date on the basis of the morphology of multi-cellular fruiting bodies were mostly monophyletic. However, these known taxa comprised only in a small part of the sequences recovered directly from soil in a cultivation-independent approach, indicating that the group is much more diverse than previously thought. We propose that the myxobacteria exist in two forms: the fruiting and the non-fruiting types. Most of the uncultured myxobacteria may represent taxa which rarely form fruiting bodies, or may lack some or all of the developmental genes needed for fruiting body formation. In order to identify non-fruiting myxobacteria, new morphology-independent cultivation and isolation techniques need to be developed.     

Leben und Überleben im Boden

Myxobacteria - survivalists in soil Myxobacteria like Myxococccus xanthus are soil-living microorganisms featuring a complex lifestyle, including movement by coordinated swarming on surfaces, predatory feeding on other microorganisms, and the formation of multicellular fruiting bodies when unfavorable environmental conditions are encountered. Bioinformatic analysis of the large myxobacterial genomes has enabled fascinating insights into the molecular basis for the biosynthesis of complex secondary metabolite structures by myxobacteria, and has set the stage for the discovery of novel natural products. Moreover, well-characterized myxobacteria like M. xanthus increasingly play a role as “biochemical factories” for the biotechnological production of bioactive molecules using synthetic biology approaches.     

粘细菌基因组学研究进展

粘细菌(Myxobacteria)隶属于δ变形菌纲(Deltaproteobacteria)的粘球菌目(Myxococcales),是一类革兰氏阴性杆状细菌。它是继放线菌和真菌之后又一重要的活性次级代谢产物产生菌,尽管如此,由于分离纯化困难,粘细菌的研究进展一直较为缓慢。随着测序技术的进步和生物信息学的应用,大量粘细菌基因组被完成测序和报道。本文对粘细菌研究意义及该类资源开发价值、分离培养存在的困难进行了阐述,对粘细菌基因组注释及目前已测菌株的全基因组进行了归纳总结,同时介绍了基因组学在粘细菌生态、捕食机制、子实体形成以及次级代谢产物合成方面的研究进展。本文有助于了解基因组学在粘细菌研究中的重要价值,为联合应用多组学技术深入研究粘细菌代谢机制和社会性行为提供了参考,对粘细菌基础研究、资源发掘和开发利用具有重要意义。     

秦岭地区羊肚菌根系土样黏细菌的分离

通过分离陕西秦岭地区羊肚菌根系土样中的黏细菌,建立黏细菌的分离方法,分析羊肚菌根系土样中黏细菌的多样性。采集自陕西商洛地区种植羊肚菌根系土样,采用不同诱导方法分离土样中的黏细菌,比较不同方法的出菌率,通过菌落形态、显微照片对黏细菌进行观察,并结合16S rRNA序列,分析得到的黏细菌种类。采用活的大肠埃希菌作为诱导底物分离出的黏细菌数量最多,本次实验从羊肚菌根系土样中共分离纯化出17株黏细菌,包括5个属,其中黏球菌属(Myxococcus)12株,珊瑚球菌属(Corallococcus)2株,孢囊杆菌属(Cystobacter)1株,原囊菌属(Archangium)1株,标桩菌属(Stigmatella)1株。结果显示羊肚菌根系土壤有黏细菌存在,其中以黏球菌属居多,为后续探讨黏细菌与羊肚菌之间是否存在互生关系提供参考。     

粘细菌产生的水解酶类研究进展

粘细菌隶属于δ变形菌纲(Deltaproteobacteria),是重要的药源微生物类群,但是其分离培养困难,严重限制了粘细菌资源的发掘和开发利用。粘细菌是微生物捕食者,通过产生丰富多样的胞外水解酶,如淀粉酶、蛋白酶、几丁质酶、纤维素酶、磷酸酶、蛋白酶等来裂解其他微生物或分解纤维素等作为营养物质来源。目前,粘细菌分离纯化技术主要是利用被捕食菌或纤维素诱导法。可以说,粘细菌胞外水解酶是研究其分离培养方法的物质基础。然而,目前研究者们对粘细菌产生的水解酶类关注较少。本文主要对粘细菌产生的水解酶种类、性质及其功能进行归纳总结,为今后粘细菌分离培养技术和开发利用等相关研究提供参考。     

The fate of the cell envelopes of Myxococcus xanthus during microcyst germination

Summary By using an improved method for processing germinating microcysts for electron microscopy it was shown that no breakdown and resynthesis of the cell wall occured in M. xanthus during germination of microcysts. A third, dense cell wall layer, not described before for any species of myxobacteria, could be discerned when cells were fixed and embedded by a method described in Materials and Methods.     

Natural competence in strains of Actinobacillus pleuropneumoniae

The fatty acid (FA) profiles of myxobacteria contain FA species with double bonds at the Δ⁵ and Δ¹¹ positions, the latter being rather unusual among bacteria. Despite this knowledge, the mechanism for introduction of these double bonds has never been described before in myxobacteria. Searches for candidate genes in the genome of the model organism Myxococcus xanthus revealed 16 genes, which have been annotated as FA desaturases. However, due to redundant substrate specificity, functional analyses of these enzymes by construction of inactivation mutants did not lead to the identification of their function or substrate specificity. Therefore, we elucidated the regioselectivity of the desaturation reactions by heterologous expression of eight desaturases from M. xanthus in Pseudomonas putida and thus could prove five of them to be indeed active as desaturases, with three (MXAN_1742, MXAN_3495 and MXAN_5461) and two (MXAN_0317 and MXAN_6306) acting as Δ⁵ and Δ¹¹ desaturases, respectively. This is the first report about the heterologous expression and regioselectivity of FA desaturases in myxobacteria.     

Induction of Bacillus anthracis hemolytic activity with the use of Myxococcus xanthus

The development of a new method for the induction of the B. anthracis hemolytic activity with the use of M. xanthus and the differentiation of pure cultures of the causative agent of anthrax from those contaminated with myxobacteria is presented. To demonstrate the induction of the hemolytic acivity of B. anthracis with the use of M. xanthus, conditions for the symbiosis of B. anthracis cells STI, exhibiting no hemolytic activity, with M. xanthus non-hemolytic cells were created by mixing them and inoculating the symbiotic biomass on the surface of blood agar.     

不同分离方法对子实体形成和粘细菌分离的影响

【目的】基于模拟原位环境策略、可培养粘细菌的营养策略及细菌互作网络,改良分离培养基,以提高分离粘细菌的多样性。【方法】通过添加土壤浸提液、使用不同种类的诱导菌和改变诱导菌的接种方式设置分离方法,同时以传统的分离方法作对照。【结果】改良的分离方法比对照组诱导出了更多粘细菌子实体种类,采自4个地区的9份样品共分离纯化出40株粘细菌,按形态学和分子生物学,将其归类于原囊菌属(Archangium)、珊瑚菌属(Corallococcus)、软骨霉状菌属(Chondromyces)、粘球菌属(Myxococcus)、侏囊菌属(Nannocystis)、多囊菌属(Polyangium)、匣状球菌属(Pyxidicoccus)。【结论】与传统分离方法相比,添加土壤浸提液,诱导菌点接法能大大提高诱导出的粘细菌子实体种类的数目,革兰氏阳性菌和革兰氏阴性菌作为诱导菌对子实体种类影响较小,但是也发现革兰氏阳性菌特异性诱导出的子实体。虽然本研究通过对分离培养基的改良大大增加了子实体种类,但是纯化出的粘细菌种类远少于观察到的子实体种类,说明除改良分离方法外,还需进一步研究粘细菌的纯化方法,提高分离所得粘细菌的多样性,获取更多粘细菌新资源。     

PCR Detection of Type I Polyketide Synthase Genes in Myxobacteria

The diversity of type I modular polyketide synthase (PKS) was explored by PCR amplification of DNA encoding ketosynthase and acyltransferase domains in myxobacteria. The sequencing of the amplicons revealed that many PKS genes were distantly related to the published sequences. Thus, myxobacteria may be excellent resources for novel and diverse polyketides.     

Biology and global distribution of myxobacteria in soils

This review presents an overview of the present status of the biology of the myxobacteria, including the molecular biology of the systems that control and regulate myxobacterial gliding movement and morphogenesis. The present status of myxobacterial taxonomy and phylogeny is described. The evolutionary biology of the myxobacteria is emphasized with respect to their social behavior and the molecular basis of their signal chains. Most important within the metabolic physiology are the biologically active secondary metabolites of myxobacteria and their molecular mechanisms of action. The global distribution of myxobacteria in soils is described on the basis of data given in the literature as well as of comprehensive analyses of 1398 soil samples from 64 countries of all continents. The results are analyzed with respect to the spectrum and number of species depending on ecological and habitat-specific factors. The myxobacterial floras of different climate zones are compared. Included are myxobacterial species adapted to extreme biotopes. The efficiency of different methods used presently for isolation of myxobacteria is compared.     

粘细菌资源挖掘与多相分类研究进展

粘细菌(Myxobacteria)是一类具有复杂多细胞行为、能够广泛捕食各类细菌和真菌并能产生丰富次级代谢产物的药源微生物,具有重要研究和应用价值。然而,由于资源挖掘困难,多相分类研究进展缓慢,严重阻碍了粘细菌的开发利用。本文对粘细菌的特性、分离和纯化方法、目前存在的不足及改进措施进行阐述,并对粘细菌多相分类研究进展及存在的问题进行解析。另外,结合当前技术手段和发展现状,进一步对粘细菌的未来发展趋势进行展望,以期为相关研究提供参考。     

粘细菌生态多样性的初步研究

通过对河北,云南,青藏高原不同地区的粘细菌进行生态多样的研究,从42个样品中分离得到了10个属（Archangium,Myxococcus,Cystobacter,Corallococcus,Melittangium,Sorangium,Polyangium,Chondromyces,Angiococccus,Stigmatella)的150余株粘细菌,其中包括一些尚未有描述的菌株,有待鉴定,根据这些菌株的子实体结构,菌落形态,营养细胞,粘孢子形态等特征将它们初步鉴定到属,对这些特有自然生态环境的粘细菌按不同地点,植被,营养基质进行统计比较,结果表明,粘细菌生态分布极为广泛,具有丰富的生态多样性,以上结果为粘细菌生物资源的有效开发利用奠定了基础。