Methylation of macromolecules during development in Myxococcus xanthus.

Covalent modification of macromolecules can serve to alter their biological activities and is therefore frequently involved in regulation. I examined methylation of proteins and carbohydrates during development and vegetative growth in the procaryote Myxococcus xanthus. Striking differences in the patterns of protein methylation occurred when cell development was induced by nutrient deprivation on solid media and when cells were starved in liquid. In addition, a methylated, protease-resistant macromolecule which contained carbohydrate and which may have been an unusual type of lipopolysaccharide was observed on sodium dodecyl sulfate-polyacrylamide gels. A comparison of methylation patterns in various media and an analysis of the time course of methylation indicated that changes in methylation were part of the developmental pathway which includes aggregation. Induction of development in liquid by glycerol produced no changes in methylation.     

Sporulation of Myxococcus xanthus in liquid shake flask cultures.

When suspended in a liquid starvation medium, exponentially growing Myxococcus xanthus sporulated within 3 days. These myxospores were similar to spores developed within fruiting bodies, as determined by electron microscopy and the production of spore-specific protein S. This liquid sporulation system may be useful as a means of preparing large quantities of myxospores and extracellular fluid for biochemical studies, including isolation of chemical signals produced during the sporulation process.     

Changes in cyclic AMP levels during development in Myxococcus xanthus.

Cyclic AMP levels doubled in Myxococcus xanthus under conditions in which cells aggregate and form fruiting bodies. In liquid medium, glycerol- or dimethyl sulfoxide-induced sporulating cultures exhibited a sharp but transient rise in cyclic AMP concentration after 45 min.     

Production of syngenetic minerals with struvite by myxococcus coralloides D

The formation under laboratory conditions of newberyite, schertelite, and taylorite in conjunction with struvite by the bacterium Myxococcus coralloides D is reported for the first time. The presence of these syngenetic minerals with struvite was only detected in static liquid cultures.     

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.     

Changes in Activity of Glyoxylate Cycle Enzymes During Myxospore Development in Myxococcus xanthus

Activities of the glyoxylate cycle enzymes isocitrate lyase (EC 4.1.3.1) and malate synthase (EC 4.1.3.2) were assayed in extracts prepared at different stages of myxospore formation in liquid cultures of Myxococcus xanthus. Activities of both enzymes attained peak values during conversion of rods to spheres. Isocitrate lyase activity decreased after reaching its peak value. Malate synthase activity also declined but at a much slower rate. The loss of isocitrate lyase activity could be prevented by the addition of chloramphenicol to cultures early in myxospore formation (during the initial rise in enzyme activity), but not by such addition at later stages of myxospore formation. The increase in glyoxylate cycle enzymes was not observed in a mutant unable to form myxospores in liquid culture under conditions suitable for morphological conversion of the wild type, or in wild-type cells incubated in the absence of an inducer for myxospore formation. It is concluded that the changes in the glyoxylate cycle enzymes represent regulatory phenomena associated with the development of the myxospore.     

Competitive fates of bacterial social parasites: persistence and self-induced extinction of Myxococcus xanthus cheaters

Cooperative biological systems are susceptible to disruption by cheating. Using the social bacterium Myxococcus xanthus, we have tested the short-term competitive fates of mixed cheater and wild-type strains over multiple cycles of cooperative development. Cheater/wild-type mixes underwent several cycles of starvation-induced multicellular development followed by spore germination and vegetative population growth. The population sizes of cheater and wild-type strains in each pairwise mixture were measured at the end of each developmental phase and each growth phase. Cheater genotypes showed several distinct competitive fates, including cheater persistence at high frequencies with little effect on total population dynamics, cheater persistence after major disruption of total population dynamics, self-extinction of cheaters with wild-type survival, and total population extinction. Our results empirically demonstrate that social exploitation can destabilize a cooperative biological system and increase the risk of local extinction events.     

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.     

Fruiting-body formation and myxospore differentiation and germination in Mxyococcus xanthus viewed by scanning electron microscopy.

Streaming cells, fruiting bodies, and single cells undergoing myxospore differentiation and germination were examined in the FB strain of Myxococcus xanthus by scanning electron microscopy. Myxospores differentiated in fruiting bodies differed in size, in kinetics of germination, in the fate of the myxospore capsule, and in the external structure of the walls of newly emerged cells when compared with myxospores differentiated in liquid medium after glycerol induction. Vegetative cells outgrowing from glycerol-induced myxospores were regularly pleomorphic, a condition that persisted through the first cell division.     

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     

Developmental induction of Myxococcus xanthus myxospores.

Myxospore differentiation during the developmental cycle of Myxococcus xanthus is characterized by several distinguishable morphological stages. Two experimentally useful criteria of myxospore induction are the conversion of vegetative rods to optically refractile short rods or ovoids and the development of resistance to sonic lysis. The use of optical refractility as the first morphological criterion of myxospore induction has facilitated an analysis of induction on developmental plates. The time-dependent changes in the cell population from vegetative rods to the final products of development, autolysed cells and myxospores, were determined in liquid suspension by interrupting cells from developmental plates before the first appearance of myxospores. The treatment of cells involved a two-step induction system. The cells were first aerated in buffer at 32 degrees C (preinduction) and then aerated in 1% tryptone (Difco) at 32 degrees C (induction). At early plate times (0 to 18 h) there was little or no response to these treatments. After 18 h, many of the cells undergoing development on plates responded to preinduction in buffer by subsequent induction to myxospores in tryptone medium (intermediate cells). After 32 h, cells induced to myxospores in tryptone medium and did not require preinduction (competent cells). After 36 h, cells begin to undergo differentiation to myxospores on plates. These results indicate that there was a sequence of physiological changes in developing cells that are defined by the differential response of cells to treatment in liquid suspension. The liquid induction system described here provides a means to analyze the regulation of developmental myxospore induction.     

Increases in the intracellular concentration of glycerol during development in Myxococcus xanthus S. Courtney Frasch

Abstract The role of glycerol as a natural morphogen of myxospore formation in Myxococcus xanthus was examined. Glycerol was extracted from cells undergoing development and analyzed by gas chromatography. Glycerol is present in cells, and the intracellular level undergoes a series of transient increases during development. The data suggest a role for glycerol in myxosporulation and fruiting body morphogenesis supporting the notion that this chemical induction of sporulation may represent a physiological pathway in development.     

黄色粘球菌发育阶段外膜蛋白表达的变化

【目的】黄色粘球菌是研究原核发育的一种模式生物,对其膜蛋白的研究仍然十分缺乏。【方法】利用6种预测软件,在黄色粘球菌的基因组中筛选编码外膜蛋白(OMP)的基因。根据报告基因lacZ,检测这些基因在营养性生长和发育阶段的表达。【结果】基于生物信息学分析,筛选出11个编码外膜蛋白的基因。其中2个基因(MXAN3106和MXAN3883)在发育阶段表达量上升,它们分别编码Secretin家族和Fimbrial usher protein (FUP)家族转运蛋白。其余9个基因在发育起始阶段表达量降低或保持较低水平,它们均编码TonB依赖型受体或外排蛋白。【结论】这些数据提示,黄色粘球菌由生长到发育的转换过程,伴随着膜蛋白表达的显著变化。     

Programmed cell death: role for MazF and MrpC in Myxococcus multicellular development

Programmed cell death is of ultimate importance in embryonic development of animals. Now, programmed cell death has been shown to be an integral part of a multicellular developmental program in the bacterium Myxococcus xanthus.     

Differential expression of protein S genes during Myxococcus xanthus development

Protein S, the most abundant protein synthesized during development of the fruiting bacterium Myxococcus xanthus, is coded by two highly homologous genes called protein S gene 1 (ops) and protein S gene 2 (tps). The expression of these genes was studied with fusions of the protein S genes to the lacZ gene of Escherichia coli. The gene fusions were constructed so that expression of beta-galactosidase activity was dependent on protein S gene regulatory sequences. Both the gene 1-lacZ fusion and the gene 2-lacZ fusion were expressed exclusively during fruiting body formation (development) in M. xanthus. However, distinct patterns of induction of fusion protein activity were observed for the two genes. Gene 2 fusion activity was detected early during development on an agar surface and could also be observed during nutritional downshift in dispersed liquid culture. Gene 1 fusion activity was not detected until much later in development and was not observed after downshift in liquid culture. The time of induction of gene 1 fusion activity was correlated with the onset of sporulation, and most of the activity was spore associated. This gene fusion was expressed during glycerol-induced sporulation when gene 2 fusion activity could not be detected. The protein S genes appear to be members of distinct regulatory classes of developmental genes in M. xanthus.     

Protein U, a late-developmental spore coat protein of Myxococcus xanthus, is a secretory protein.

Protein U is a spore coat protein produced at the late stage of development of Myxococcus xanthus. This protein was isolated from developmental cells, and its amino-terminal sequence was determined. On the basis of this sequence, the gene for protein U (pru) was cloned and its DNA sequence was determined, revealing an open reading frame of 179 codons. The product from this open reading frame has a typical signal peptide of 25 amino acid residues at the amino terminal end, followed by protein U of 154 residues. This result indicates that protein U is produced as a secretory precursor, pro-protein U, which is then secreted across the membrane to assemble on the spore surface. This is in sharp contrast to protein S, a major spore coat protein produced early in development, which has no signal peptide, indicating that there are two distinct pathways for trafficking of spore coat proteins during the differentiation of M. xanthus.     

Production of acid and alkaline phosphatases byMyxococcus coralloides

Acid and alkaline phosphatase ofMyxococcus coralloides were examined during vegetative growth in a liquid medium. Two extracellular phosphatases and two cell-bound phosphatases, acid and alkaline in both cases, were produced. The phosphatase production was unaltered by the presence of high concentrations of inorganic phosphate. Both enzymes were produced constitutively. These two hydrolases were released into the growth medium during the exponential growth phase (approximately 10% of total activity). The production of these enzymes was modified by the presence of organic acids and metal ions in the medium.     

Cell surface antigens during submerged development of Myxococcus xanthus examined with monoclonal antibodies

Eighteen monoclonal antibodies directed against cell surface antigens of Myxococcus xanthus were followed by enzyme-linked immunosorbent assay. Three of the monoclonal antibodies were specifically directed against antigens present only on cells undergoing fruiting body development. These cell surface antigens became detectable by the early preaggregation stage (2 to 4 h) of development and increased until early aggregation (9 to 10 h), after which the concentrations of two of the cell surface antigens remained constant and the concentration of the third decreased. The remaining 15 monoclonal antibodies recognized cell surface antigens that were shared by vegetative and developing cells. Based on their relative concentrations during development, these shared antigens can be grouped into three classes. In the first class antigen concentration remained constant, in the second it decreased, and in the third it increased. Western blots of cell surface antigens were probed with monoclonal antibodies. Five monoclonal antibodies reacted with material in distinct bands, five monoclonal antibodies reacted with multiple, diffuse bands, and eight monoclonal antibodies were not reactive in Western blots.