Improved methods of isolation and purification of myxobacteria and development of fruiting body formation of two strains

By using baiting techniques and different purification methods, a high number of myxobacterial strains have been isolated as pure cultures from soil of different regions of China. Because myxobacterial cells do not disperse easily in liquid media, a medium containing an enzymatic hydrolysate of casein (CEH) medium have been used for purification and purity tests combined in a single step. The key method, in which isolates are reintroduced to sterile rabbit dung to induce fruiting bodies formation, facilitates purification of myxobacteria. Sterile rabbit dung pellets are used to mimic the natural growth substance of these organisms which has the advantage that characteristic fruiting bodies emerge, which is a key characteristics in the taxonomy of myxobacteria. In this study, the optimum program of isolation and purification of some myxobacteria strains has been established which will facilitate screening programs. Moreover, the development of fruiting body formation of strain BD20 (Chondromyces) and strain BD54 (Cystobacter) have been recorded in this study.     

Myxobacterial Biodiversity in an Established Oak-Hickory Forest and a Savanna Restoration Site

The purpose of this study was to establish the myxobacterial biodiversity of an established oak-hickory forest and a savanna restoration site that has been cut and subsequently burned on four occasions between 1993 and 1998 in an attempt to restore the land to the native savanna ecosystem. Soil and bark samples were processed through standard methods specifically for myxobacteria and numbers and types of species were recorded for both locations. Species were identified through morphology of fruiting bodies, SDS-PAGE of whole cell protein profiles, and 16S rRNA gene sequences. Statistical analyses were employed and suggested that significantly greater numbers and types of myxobacteria are present on the bark of the trees in the established oak-hickory forest than the bark of trees in the savanna restoration site, while little difference in numbers and types of species were observed between the soil samples of the two locations.     

New locus important for Myxococcus social motility and development

The mts locus in salt-tolerant Myxococcus fulvus HW-1 was found to be critical for gliding motility, fruiting-body formation, and sporulation. The homologous genes in Myxococcus xanthus are also important for social motility and fruiting-body development. The mts genes were determined to be involved in cell-cell cohesion in both myxobacterial species.     

Role of phase variation in the resistance of Myxococcus xanthus fruiting bodies to Caenorhabditis elegans predation

The phenomenon of phase variation between yellow and tan forms of Myxococcus xanthus has been recognized for several decades, but it is not known what role this variation may play in the ecology of myxobacteria. We confirm an earlier report that tan variants are disproportionately more numerous in the resulting spore population of a M. xanthus fruiting body than the tan vegetative cells that contributed to fruiting body formation. However, we found that tan cells may not require yellow cells for fruiting body formation or starvation-induced sporulation of tan cells. Here we report three differences between the yellow and tan variants that may play important roles in the soil ecology of M. xanthus. Specifically, the yellow variant is more capable of forming biofilms, is more sensitive to lysozyme, and is more resistant to ingestion by bacteriophagous nematodes. We also show that the myxobacterial fruiting body is more resistant to predation by worms than are dispersed M. xanthus cells.     

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.     

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.     

Spatial Simulations of Myxobacterial Development

Many bacteria exhibit multicellular behaviour, with individuals within a colony coordinating their actions for communal benefit. One example of complex multicellular phenotypes is myxobacterial fruiting body formation, where thousands of cells aggregate into large three-dimensional structures, within which sporulation occurs. Here we describe a novel theoretical model, which uses Monte Carlo dynamics to simulate and explain multicellular development. The model captures multiple behaviours observed during fruiting, including the spontaneous formation of aggregation centres and the formation and dissolution of fruiting bodies. We show that a small number of physical properties in the model is sufficient to explain the most frequently documented population-level behaviours observed during development in Myxococcus xanthus.     

Characterization and description of Anaeromyxobacter dehalogenans gen. nov., sp. nov., an aryl-halorespiring facultative anaerobic myxobacterium

Five strains were isolated which form a physiologically and phylogenetically coherent group of chlororespiring microorganisms and represent the first taxon in the Myxobacteria capable of anaerobic growth. The strains were enriched and isolated from various soils and sediments based on their ability to grow using acetate as an electron donor and 2-chlorophenol (2-CPh) as an electron acceptor. They are slender gram-negative rods with a bright red pigmentation that exhibit gliding motility and form spore-like structures. These unique chlororespiring myxobacteria also grow with 2,6-dichlorophenol, 2,5-dichlorophenol, 2-bromophenol, nitrate, fumarate, and oxygen as terminal electron acceptors, with optimal growth occurring at low concentrations (<1 mM) of electron acceptor. 2-CPh is reduced by all strains as an electron acceptor in preference to nitrate, which is reduced to ammonium. Acetate, H(2), succinate, pyruvate, formate, and lactate were used as electron donors. None of the strains grew by fermentation. The 16S ribosomal DNA (rDNA) sequences of the five strains form a coherent cluster deeply branching within the family Myxococcaceae within the class Myxobacteria and are mostly closely associated with the Myxococcus subgroup. With the exception of anaerobic growth and lack of a characteristic fruiting body, these strains closely resemble previously characterized myxobacteria and therefore should be considered part of the Myxococcus subgroup. The anaerobic growth and 9.0% difference in 16S rDNA sequence from those of other myxobacterial genera are sufficient to place these strains in a new genus and species designated Anaeromyxobacter dehalogenans. The type strain is 2CP-1 (ATCC BAA-258).     

Structure of a community of testate amoebae in a sphagnum dominated bog in upper sura flow (Middle Volga Territory)

Fifty nine species of testate amoebae were found in a sphagnum moss bog located in the upper Sura flow (Volga highland). The active diversity in communities of sphagnum moss biotopes was formed by 24 species. Minimal species diversity (3 species) and maximum density of organisms were noted in the driest habitat. In the habitats with the medium humidity levels, the level of species richness was similar (13–16 species) and the total density was determined by redox characteristics of the environment: under the conditions of oxygen deficit, it was two to three times lower than in an oxidized environment. The species composition specificity in sphagnum moss biotopes was determined by the degree of humidity: in the driest habitats, Arcella arenaria predominated; in the biotopes with medium humidity, Nebela tenella and Hyalosphenia elegans; and in the most humid biotopes, Hyalosphenia papilio and Heleopera sphagni. Communities of testate amoebae differed by species composition and integral characteristics at different sphagnum moss horizons: the abundance and species richness increased with depth. The proportion of living individuals in the total number of tests was 35 to 75%.     

16S rRNA gene and 16S-23S rRNA gene internal transcribed spacer sequences analysis of the genus Myxococcus.

Phylogenetic relationships of the species belonging to the genus Myxococcus were elucidated based on the sequences of 16S rRNA genes and 16S-23S rRNA gene internal transcribed spacer (ITS) regions. The Myxococcus species were consequently classified into four distinct groups. The type strain of Myxococcus coralloides occupied an independent position (Group 1); it has been recently reclassified as Corallococcus coralloides. Group 2 comprised the type strains of both Myxococcus virescens and Myxococcus xanthus, and some strains assigned to Myxococcus flavescens. The type strain of M. flavescens was contained in Group 3 along with the strains of Myxococcus fulvus. Group 4 included the strains belonging to C. coralloides, M. fulvus, and M. stipitatus. The type strain of M. fulvus that was allocated outside Group 4 in the 16S rRNA gene tree belonged to Group 3 in the ITS tree. These results strongly suggest that the morphological characteristics of Myxococcus species are not consistent with the phylogenetic relationships. The Myxococcus species must therefore be redefined according to the phylogenetic relationships revealed in this study.     

Bacteriocins from Myxococcus fulvus (Myxobacterales)

Bacteriocin-like activities were found in several Myxococcus fulvus strains. One strain, Mxf16, exerted strong inhibitory effects on several myxobacterial strains. Synthesis of its bacteriocinic activity could not be induced by mitomycin. Electrophoresis and molecular sieve chromatography revealed at least three different bacteriocinic substances of low molecular weight.List of Abbreviations cas lm Casitone liquid medium - TCA trichloroacetic acid     

Short‐term assessment of dung beetle response to carbosulfan treatment against desert locust in Sudan

The beneficial role of dung beetles (Coleoptera: Scarabaeidae) is well known. Potential risks to these beetles from the widespread use of insecticides against the desert locust, a significant plant pest in Africa, the Near East and South West Asia, have not been studied previously. Short‐term responses of dung beetles to carbamate carbosulfan (Marshal®, ultra low‐volume formulation, 100 g active ingredient ha^?1) were assessed during desert locust control operations at five sites within two major biotopes: Acacia tortilis shrubland and cultivated wetland; on the Red Sea Coast of Sudan. The study took place during January–February 2004. At each site, fresh dung from Zebu cows was placed in areas targeted for desert locust control. Dung pats were placed in plots in two areas and left for 24 h, before and after insecticide application. Beetles were extracted by floatation. There was a significant decrease in abundance between the pre‐ and post‐spray period in treated areas for the Scarabaeinae species Onthophagus margaritifer (a dark colour morph). In contrast, it was found that Aphodius lucidus and beetles at the subfamily level of Aphodiinae increased in numbers after insecticide treatment. Mortality and sublethal impacts as well as a repellent effect of the insecticide may explain the decrease in Onthophagus margaritifer, while the increase in Aphodiinae beetles could be an indirect response to lower numbers of Scarabaeinae beetles in competing for the same resource. These organisms and the applied methodology may be useful for environmental monitoring of desert locust control, thus further studies are suggested. The assessment also revealed a marked difference between the two biotopes with high abundance and species richness of dung beetles in A. tortilis shrubland, while these measures were low in the cultivated wetland. Five new species of dung beetles for Sudan were found in this study.     

Reactions of the fauna on the bark of trees to the frequency of fires in a North American savanna

Summary The arthropod communities living on the bark of the oak species Quercus macrocarpa and Q. ellipsoidalis were investigated in a North American oak savanna. Differences were found in the community structure of the arthropods living on the bark of these two tree species, although they have the same fissured bark type. In the North American oak savanna ecosystem the most important disturbance factor is fire, which maintains species richness. Highest numbers of species and specimens were found at moderately disturbed sites. Three main ecological groups of arthropods living on the bark of trees can be distinguished in relation to the degree of disturbance: (1) Inhabitants of bark of trees restricted to undisturbed sites: they do not occur in fire-disturbed areas; (2) Inhabitants of bark of trees adapted to a moderate degree of disturbance: many species occur in high numbers only in moderately disturbed areas; and (3) Specialist inhabitants of bark of trees in heavily disturbed areas. The number of specimens of these species increases per trunk with the frequency of disturbance.     

新疆阿克苏地区盐碱地粘细菌分离鉴定

【目的】采用传统的纯培养技术,分离新疆阿克苏地区典型的盐碱地中的粘细菌,并初步分析盐碱地土壤中可培养粘细菌资源的多样性。【方法】采用传统的水琼脂法、滤纸法和改良的土壤浸出液法分离新疆阿克苏地区25份盐碱地的粘细菌。结合分析土样的酸碱度、含盐量、地理位置及其植被分布情况分析新疆阿克苏地区盐碱地粘细菌资源多样性。【结果】共分离到58株粘细菌,它们被鉴定为:粘球菌属(Myxococcus)33株;珊瑚球菌属(Corallococcus)14株;孢囊杆菌属(Cystobacter)6株;堆囊菌属(Sorangium)2株;侏囊菌属(Nannocystis)2株;多囊菌属(Polyangium)1株。其中粘球菌抗逆性强,分离的菌株数最多,在pH值7.5-8.5范围的盐碱地中普遍存在;其次为珊瑚球菌属;而侏囊菌属、多囊菌属的菌株较少见。【结论】新疆阿克苏地区盐碱地粘细菌多样性不高,可能受分离纯化方法、含盐量以及土壤性质影响较大。     

Disparity in Onset Timing and Frequency of Flowering and Fruiting Events in Two Bornean Peat‐Swamp Forests

The timing and frequency of flowering and fruiting events are key tropical forest characteristics that have substantial influence on fauna. Although our understanding of geographic variation in habitat‐wide timing and frequency of flowering and fruiting is advancing, corresponding information for individual tree species is limited. Thus, we compared climate and reproductive phenology of 16 tree species over 70 mo at two Bornean tropical peat‐swamp forest sites. We found significant inter‐site correlations in rainfall and temperature, and only small absolute temperature differences. In both sites, most species exhibited within‐site synchrony in flowering and fruiting onset. Broad‐scale flowering and fruiting onset frequency classifications showed high congruence between sites. Significant correlations in flowering and fruiting onset timing between sites were found for only 19 and 17 percent of the species, respectively. This remained the case when applying 1‐ and 2‐month lag periods for both sites, with neither site consistently lagging behind. Significant differences in the exact frequency of new flowering and fruiting events were detected for 44 and 58 percent of species, respectively, and no significant relationships between the onset timing synchrony and exact frequency of new reproductive events were found for either flowers or fruit. We conclude that inter‐site climatic and ecological similarities do not necessarily lead to high inter‐site synchrony in either onset timing or exact frequency of tree reproductive events. Potential reasons for this are discussed, as are the implications for understanding tropical forest ecology and improving forest restoration project seed collections.     

Myxobacteria: proficient producers of novel natural products with various biological activities--past and future biotechnological aspects with the focus on the genus Sorangium

Myxobacteria are gram-negative bacteria which are most noted for their ability to form fruiting bodies upon starvation. Within the last two decades, they increasingly gained attention as producers of natural products with biological activity. Here, recent and future biotechnological research on certain key myxobacteria and on their ability to produce natural products is reviewed with the focus on the production of myxovirescin, soraphen and epothilone. Aspects of product improvement and yield as well as statistics regarding secondary metabolite formation are discussed. Future research will deal with the exploitation of the biosynthetic potential of the myxobacteria, for example via the isolation of new myxobacterial species with different physiological properties. Additionally, the genetic potential of myxobacteria to form natural products can be exploited by the identification and activation of biosynthetic gene clusters. These can be found frequently within their genomes, which is shown by the analysis of the unfinished genomes of Myxococcus xanthus and Sorangium cellulosum. The current status of the S. cellulosum functional genome project with model strain So ce56 is discussed.     

Spatiotemporal distribution and dynamic changes of myxomycetes in subtropical forests of China

The spatiotemporal distribution and dynamic changes of species composition of myxomycetes in humid subtropical forests of Houhe National Nature Reserve in southern China were studied by collecting samples of bark and ground litter within four seasons for isolation of myxomycetes in moist chamber cultures and by collecting fruiting bodies in the field from June to October. A total of 725 specimens of myxomycete fruiting bodies representing 77 species of 25 genera were registered, among them 302 records/51 species from field collections and 423 records obtained from 600 moist chamber cultures of ground litter and bark of living trees, which resulted in 35 and 39 species, respectively. Cornuvia serpula and Perichaena microspora were recorded for the first time in China. Both myxomycete species richness and diversity were significantly different in ground litter among sites and field collections among months. NMDS combined with Permanova indicated that the site had a greater impact on the myxomycete community of bark and litter than the season, while the month of field collections had a greater impact than the sampling sites. CCA and VPA analysis showed that the bark-inhabiting myxomycete species were mainly affected by spatial variables, while the litter-inhabiting and field collected species were more affected by climatic factors.     

Effects of ingestion of seeds by sika deer (<Emphasis Type="Italic">Cervus nippon</Emphasis>) and dung presence on their germination in a herbaceous community

In a herbaceous community subjected to continual impacts of sika deer (Cervus nippon), I examined the effects of seed ingestion by deer on seeds by comparing the ripening and germination rates of seeds of two dominant species, Zoysia japonica and Hydrocotyle maritima, between seeds taken out of fecal pellets (deer-ingested seeds) and mature seeds collected directly from living plants (control seeds). Seeds of Z. japonica were likely to have tolerance to ingestion from earlier periods of seed maturity. In contrast, only ripened seeds of H. maritima may have tolerance to ingestion. When the seeds ripened, the germination rates of two species did not differ significantly between deer-ingested seeds and control seeds. Thus, although immature seeds may be crushed by ingestion, many mature seeds can be dispersed by sika deer with no alteration of germination rate. However, the other germination experiment showed that the germination rates were significantly higher for seeds of Juncus tenuis in artificially broken fecal pellets than for those kept confined in the pellets, and all seeds germinated from intact pellets were situated near the surface of the pellets. These results suggest that dung may physically prevent seeds inside from germinating and decomposition of dung enables herbaceous small seeds in the dung to germinate.     

High allozyme variation in populations of three spiny rat species from Upper Amazonia: association with ecology and evolution]

The allozyme variation in three spiny rat species of the genus Proechimys from Upper Amazonia was studied in relation to their ecology and evolution. The ecological environmental factors and biotopic distribution of species were analyzed. The unusually high allozyme variation was found in P. simonsi and P. sp. (2n = 34) inhabiting native forest biotopes. A relatively low allozyme variation in P. brevicauda was assumed to be associated with eurybiotic properties and the ability of this species to adapt to anthropogenic biotopes. Data on chromosome homeology and reconstruction of chromosome rearrangements in six spiny rat species were correlated with allozyme variation. The results suggested that chromosome rearrangements played the major role in evolution of the spiny rat species, and that the reorganization of the P. brevicauda genome was not random. P. simonsi and P. sp. (2n = 34), which live in native forest biotopes and carry an excessive genomik "informational load", were assumed to be highly susceptible to any novel external factors. These species are potentially able to produce new chromosome forms and are most significantly affected by deforestation.     

Ecology of mites (Acarina) on small mammals (Eulipotyphla, Rodentia) in Podunajská nížina plain

This study deals with the species distribution and structure of mite communities living in the fur of small mammals. Mesostigmatic mites (Acarina: Mesostigmata) of several small mammal species were studied at several sites of Slovakia situated in the Podunajská ní?na lowland. The aims deal with ecological evaluation of mesostigmatic mites and their small mammal hosts. The research was done from 2005 to 2007. Several small mammal species were caught at 16 sites in the research area. These represent 13 types of biotopes. On the captured small mammals we recorded 3,141 individuals of mesostigmatic mites (7 families and 22 species). The dominance and the diversity of the recorded mites were analysed. Mites being interpreted as the variable one were evaluated by cluster analysis and multifactor analysis (detrended correspondence analysis, principal components analysis, redundancy analysis). Small terrestrial mammals as hosts of mites represent “holders” of environmental factors, in the analysis they are being evaluated as explanatory variable mainly. They transform direct impact of the environment and for that reason the ecological evaluation of mites is specific comparing to other taxonomical and ecological groups of animals.