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At least 19 recordsLinked to original sources
PubMed1979

Social gliding is correlated with the presence of pili in Myxococcus xanthus.

Myxococcus xanthus, an organism whose motility involves cell interactions, normally bears pili. Myxococcal pili are found only at cell poles, are less than 10 nm in diameter, and may be longer than a cell. Myxococcus has two basic patterns of cell movement, adventurous (A-motility) and social (S-motility). Pili are found to be completely correlated with the presence of S-motility. (The S-motility pattern has many groups of cells, almost no single cells, and is governed by a set of genes called system S.) On the other hand, A-motility is in dependent of piliation. (The A-motility pattern has many single, isolated cells and it is governed by a second set of genes called system A.) Electron microscopic examination of more than 40 genetically different strains shows that all A+S+ (wild-type) and A-S+ strains have pili, but A+S- and A-S- strains lack them. Mutations in four different loci belonging to system S were tested and were found to stop productions of pili: the loci sg1A, sg1B, sg1G, and tg1. When brought into contact with tg1+ cells, cells of a tg1- strain, which lack pili, become phenotypically S+, produce pili, and become S-motile. Both motility and the production of pili are transient when initiated in this way. Thus it appears that pili permit cells that are close to one another to move.

Fimbriae, Bacterial↗
PubMed1979

Biosynthesis and self-assembly of protein S, a development-specific protein of Myxococcus xanthus.

Myxococcus xanthus is a Gram-negative bacterium that has a complex life cycle including a temporal sequence of cellular aggregation, mound formation, and myxosporulation. During development, protein S (molecuar weight 23,000) is induced and accumulates in very large amounts. Protein S was found in the soluble fraction of early developmental extracts and in the insoluble fraction in later extracts. This insoluble form of protein S can be solubilized by the addition of 1 M NaCl at 0 degrees C to extracts from aggregated cells (mound stage) or by the addition of 1 M NaCl at 30 degrees C to mature spores. Salt extraction (1 M NaCl) of protein S from mature spores was partially inhibited by the addition of Mg(2+) and almost completely inhibited by the addition of Ca(2+). The viability of spores was not changed by a salt extraction that removed their protein S. Examination of thin sections of mature spores and extracted spores by electron microscopy suggested that the protein S-deficient spores lacked a spore surface coat about 300 A thick. Purified protein S will spontaneously self-assemble onto protein S-deficient spores after removal of the NaCl by dialysis or by addition of 10 mM Ca(2+) to undialyzed samples. Glycerol-induced spores did not contain protein S and did not serve as primers for assembly of protein S. Quantitation of the self-assembly process showed almost stoichiometric binding of protein S to the protein S-deficient spores until saturation at 3.3 x 10(6) molecules per spore, a value 1.35 times higher than the normal level of proteins S found in mature spores. Protein S in the "reconstituted" spores was as protease resistant and sonication resistant as the protein S of native spores. Electron microscopy of the reconstituted spores revealed the assembly of new material on the spore surface. Adjacent spores were sometimes observed to be fused to each other through a common protein S layer. These results suggest that protein S serves a function in spore-spore interaction in the fruiting body.

Bacteria↗
PubMed1975

Myxospore induction in a nondispersed growing mutant of Myxococcus xanthus.

Myxococcus xanthus RB5, a rough-colony-forming, nondispersed growing mutant of strain FBt, forms macroscopic, multicellular masses of radially oriented cells in shake cultures. The cells appear to be held together by slime fibrils. Physical and enzymatic methods to disrupt the spheres were unsuccessful as were attempts to isolate dispersed growing mutants. During incubation of the spheres in starvation medium, the cells within convert to myxospores, indistinguishable from those formed in fruiting bodies. Myxospores were also induced in artifically constructed, dense masses of cells of a nonmotile strain.

Agar↗
PubMed1976

Morphogenesis in Myxococcus xanthus and Myxococcus virescens Myxobacterales.

1. Myxococcus xanthus B and M. virescens V2 were compared with a view to establishing the control of their morphogenetic cycles. Both organisms are typical myxococci and on solid media with low concentrations of nutrient they form fruiting bodies, within which vegetative cells convert to myxospores. Ultrathin sections of vegetative M. virescens resembled those of M. xanthus and contained prominent heavily stained bodies, presumed to be polyphosphate granules. Shadowed preparations showed fimbriae associated with M. xanthus but not with M. virescens. 2. M. xanthus B converted to myxospores in liquid medium in response to certain alcohols. M. virescens V2 produced phase-refractile spheres, which were not viable and had an unusual ultrastructure. 3. The distributions of fruiting bodies on solid media containing 0.02% Casitone were recorded for the two species and were compared with a Poisson distribution. Cells responded to differences in cell density in a manner suggestive of a response to a chemotactic attractant. Cells growing vegetatively and also cells forming fruiting bodies produced 3',5'-cyclic adenosine monophosphate (cAMP) as measured by the incorporation of exogeneous [3H] adenosine into cAMP. 4. The significance of these findings for theories of fruiting body formation are discussed.

Chemotaxis↗
PubMed1979

The function of fimbriae in Myxococcus xanthus. I. Purification and properties of M. xanthus fimbriae.

Myxococcus xanthus fimbriae have been purified and characterized as part of a study of the function of fimbriae in this prokaryote. Myxococcus xanthus produced two types of fimbriae, termed flaccid (F) and rigid (R) on the basis of electron microscopy. F and R fimbriae differed slightly in their response to pH and freeze-thaw regimes but were similar in their resistance to hydrolytic enzymes, amino acid composition, molecular weight, carbohydrate content, and antigenic determinants. Although the precise relationship between F and R fimbriae is unknown, the possibility is considered that F fimbriae might represent a "contracted" form of the R type. Studies designed to determine fimbriae function in M. xanthus are described in an accompanying report.

Amino Acids↗
PubMed1975

Chloramphenicol resistance in Myxococcus xanthus.

Derivatives of Myxococcus xanthus FB(t) resistant to chloramphenicol (25 mug/ml) arose spontaneously with a frequency of approximately 10(-7). One of these organisms (FB(t)Cam(1) (r)) was characterized. FB(t)Cam(1) (r) showed a unique type of phenotypic instability. After transfer from medium containing chloramphenicol to medium lacking the drug, resistance was lost after approximately one generation. The loss resulted in a sharp drop in the total number of chloramphenicol-resistant organisms and was not due to segregation of chloramphenicol-susceptible organisms during growth. Cell-free extracts of strain FB(t)Cam(1) (r) converted chloramphenicol to acetyl chloramphenicols in a fashion implicating activity of chloramphenicol acetyltransferase. This activity was lost simultaneously with the loss of chloramphenicol resistance after removal of the drug from cultures. Organisms with a similar phenotype to FB(t)Cam(1) (r) could be produced at high frequencies when strain FB(t) was exposed to low concentrations of chloramphenicol (2 to 5 mug/ml), to 3-acetylchloramphenicol (25 mug/ml), or to 1,3-diacetylchloramphenicol (25 mug/ml). Since strain FB(t) is capable of deacetylating acetyl chloramphenicols, these effects are probably all due to low concentrations of chloramphenicol. In the presence of chloramphenicol, FB(t)Cam(1) (r) produced fruiting bodies and myxospores on fruiting agar; however, glycerol-induced myxospore formation was inhibited. In the absence of the antibiotic, chloramphenicol resistance was maintained by glycerol-induced myxospores.

Chloramphenicol↗
PubMed1977

Pigmentation phenotype instability in Myxococcus xanthus.

Cells of Myxococcus xanthus FB2 produce tan or yellow colonies. Subcultures of tan colonies yielded tan and yellow colonies and subcultures of most yellow colonies yielded only yellow colonies. Strain FB2 variants in which the color type is more stable were obtained. Yellow cells were distinguishable from tan by the presence of pigment(s) with an absorption maximum at 379 nm. Fluctuation Test experiments and the presence of this pigment(s) in liquid cultures of FB2 indicated that tan phenotype cells spontaneously became or segregated yellow cells in liquid culture. The frequency of appearance of yellow cells was increased in low density cultures (less than 10(6)/ml). The increase cannot be explained by differences in growth rates of the two phenotypes. No evidence that cell-cell contact or culture medium constituents affect the appearance of the yellow phenotype was found. Ultraviolet irradiation of FB2 resulted in an increased proportion of cells producing yellow colonies among the survivors. Greater UV resistance of yellow cells and UV-induced conversion of tan to yellow accounts for this increase. Low level photoreactivation of viability and of the tan phenotype occurred. Incubation of FB2 in medium containing mitomycin C, nalidixic acid, phenethyl alcohol, or at 36.5 degrees C also resulted in conversion of tan to yellow cells.

Myxococcales↗
PubMed1977

Cell density-dependent growth of Myxococcus xanthus on casein.

When Myxococcus xanthus FB was grown on 0.2% casein it exhibited a phenomenon we call cooperative growth. That is, above 104 cells per ml, both strains that were studied exhibited increasing growth rates as a function of increasing cell numbers. Between 104 and 107 cells per ml, the mean doubling times of strains YS and TNS decreased from 15.2 to 8 h and 26 to 8.5 h, respectively. The extracellular proteinase activity of the two strains was equivalent and directly proportional to cell number. Cooperative growth was correlated with increased concentration of hydrolyzed casein in the medium, suggesting cooperative hydrolysis of casein. At low cell densities neither strain was capable of measurable growth on casein in liquid media, and we have calculated that the average concentration of hydrolyzed casein in the medium was indeed too low to support growth. At low cell densities, growth on hydrolyzed casein (Casitone) was normal and independent of cell concentration. Demonstration of cooperative growth at higher cell densities supports the suggestion that the communal behavior of myxobacteria results in more efficient feeding.

Caseins↗
PubMed1978

Synthesis and salvage of purines during cellular morphogenesis of Myxococcus xanthus.

Intact cells of Myxococcus xanthus were examined for de novo purine synthesis and salvage utilization. The cellular uptake rates of radioactive glycine (de novo purine precursor), adenine, and guanine were measured, and thin-layer chromatography and radioautography were used to examine cell extracts for de novo synthesized purine nucleotides. Intact vegatative cells, glycerol-induced myxospores, and germinating cells of M. xanthus CW-1 were able to carry out de novo purine and salvage synthesis. Germinating cells and glycerol-induced myxospores were metabolically more active or as active as vegetative cells with respect to purine anabolism. We conclude that M. xanthus is capable of synthesizing purine nucleotides and salvaging purines throughout the glycerol version of its life cycle.

Adenine↗
PubMed2025

The NmpRSTU multi-component signaling system of Myxococcus xanthus regulates expression of an oxygen utilization regulon.

UNLABELLED: Myxococcus xanthus has numerous two-component signaling systems (TCSs), many of which regulate the complex social behaviors of this soil bacterium. A subset of TCSs consists of NtrC-like response regulators (RRs) and their cognate histidine sensor kinases (SKs). We have previously demonstrated that a multi-component, phosphorelay TCS named NmpRSTU plays a role in M. xanthus social motility. NmpRSTU was discovered through a screen that identified mutations in nmp genes that restored Type-IV pili-dependent motility to a nonmotile strain. The Nmp pathway begins with the SK NmpU, which is predicted to be active in the presence of oxygen. NmpU phosphorylates another SK, NmpS, a hybrid kinase containing an RR domain and a HisKA-CA domain. These two kinases work in a reciprocal fashion: when NmpU is active, NmpS is inactive, and vice versa. Finally, the phosphorelay culminates in NmpS phosphorylating the NtrC-like RR NmpR. To better understand the role of NmpRSTU in M. xanthus physiology, we determined the NmpR regulon by combining in silico predictions of the NmpR consensus binding sequence with in vitro electromobility shift assays (EMSAs) and in vivo transcriptional reporters. We identified several NmpR-dependent, upregulated genes likely to be important in oxygen utilization. Additionally, we demonstrate NmpRSTU plays a role in fruiting body development, suggesting a role for oxygen sensing in this behavior. We propose that NmpRSTU senses oxygen-limiting conditions, and NmpR upregulates genes associated with optimal utilization of that oxygen. This may be necessary for M. xanthus physiology and behaviors in the highly dynamic soil where oxygen concentrations vary dramatically. IMPORTANCE: Bacteria use two-component signaling systems (TCSs) to respond to a multitude of environmental signals and subsequently regulate complex cellular physiology and behaviors. Myxococcus xanthus is a ubiquitous soil bacterium that encodes numerous two-component systems to respond to the conditions of its soil environment and coordinate multicellular behaviors such as coordinated motility, microbial predation, fruiting body development, and sporulation. To better understand how this bacterium uses a two-component system that has been linked to the sensing of oxygen concentrations, NmpRSTU, we determined the gene regulatory network of this system. We identified several genes regulated by NmpR that are likely important in oxygen utilization and for the M. xanthus response to varied oxygen concentrations in the dynamic soil environment.

Myxococcus xanthus↗
PubMed1976

The isolation and characterization of gliding motility mutants of Myxococcus xanthus.

Nonmotile and motility-altered mutants of Myxococcus xanthus have been obtained by the use of chemical mutagens, ultraviolet irradiation, and a procedure for selective spontaneous mutants. As judged by their behaviour on a variety of growth media, in both plate and slide culture, the mutants were divided into four groups. One group contains mutants which are truly nonmotile. Myxococcus xanthus NM, previously described as a nonmotile mutant, may be similar to type 3 mutants (described in text).

Hycanthone↗
PubMed1977

Effect of temperature on the growth of Myxococcus xanthus.

The cardinal growth characteristics of Myxococcus xanthus were examined from 14 to 40 degree C, and the examinations indicated that the organism is mesophilic in character. The maximum growth rate (0,3 doublings per h) was between 34 and 36 degree C and the temperature characteristic (micron) is 17,000 cal/mol (71,162 J/mol).

Myxococcales↗
PubMed1978

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.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1979

Myxobacterial hemagglutinin: a development-specific lectin of Myxococcus xanthus.

Fruiting body formation in the bacterium Myxococcus xanthus consists of a temporal sequence of cellular aggregation and sporulation. During the period of cellular aggregation, a major new development-specific protein that has lectin-like activity is synthesized. This protein, called myxobacterial hemagglutinin (MBHA), was able to agglutinate sheep or guinea pig erythrocytes but not horse, ox, chicken, or human erythrocytes. MBHA was undetectable in extracts of vegetative cells, cells starved in liquid buffer, or in glycerol-induced cells. However, cells starved on a fruiting medium produced large amounts of MBHA (about 5% of protein synthesis), starting at about 6-8 hr of development. The protein accumulated in the soluble fraction of cells, reaching a peak of 1-2% of total protein at about the time when aggregation was completed. At later times the amount of MBHA present in the soluble fraction declined although synthesis continued. The hemagglutinating activity of MBHA could not be inhibited with simple sugars or aminosugars but could be inhibited with fetuin, a fetal calf serum glycoprotein. The O-glycosidically linked trisaccharide glycopeptide of fetuin was shown to be inhibitory by itself. The penultimate galactose of this glycopeptide was directly implicated in the inhibitory activity, because the inhibition by asialofetuin was reduced to 1/60th by periodate oxidation and to 1/15th after beta-galactosidase treatment. MBHA is an abundant biochemical marker of development in M. xanthus. The fact that it is a lectin suggests that it may play a role in cell-cell recognition or agglutination.

Binding, Competitive↗
PubMed1977

Intracellular, periodic structures in the gliding bacterium Myxococcus xanthus.

Electron microscopic observations of thin sections of Myxococcus xanthus vegetative cells revealed the presence of cytoplasmic bundles of 4- to 5-nm-diameter filaments running longtitudinally below the cell membrane and terminating in association with the envelope near one pole. Part of each bundle demonstrated a herringbone-like periodicity (approximately 12-nm spacing). This structure was observed in cells from shake cultures and in gliding cells fixed by several methods. It is proposed that the structure may be attached to the envelope near both poles in gliding cells and that the motive force for motility may be provided by its contraction and relaxation. In one of four nongliding mutants examined, the periodicity was indistinct or lacking. In this mutant another structure, comprised of linearly arrayed beads, was observed in association with the filamentous bundle. Another structure, characterized by major, transverse bands (approximately 34 nm apart), occurred in patches that may traverse the diameter of the wild-type cells in which the structure was observed.

Cell Wall↗
PubMed1979

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.

Kinetics↗