Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Myxococcus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed1977

Myxospore coat synthesis in Myxococcus xanthus: enzymes associated with uridine 5'-diphosphate-N-acetylgalactosamine formation during myxospore development.

Activities of the enzymes glutamine synthetase (EC 6.3.1.2.), glucosamine 6-phosphate acetyltransferase (EC 2.3.1.4.), uridine 5'-diphosphate (UDP)-N-acetylglucosamine pyrophosphorylase (EC 2.7.23.), UDP-N-acetylglucosamine 4-epimerase (EC 5.1.3.7.), fructose 1,6-diphosphate phosphatase (EC 3.13.11.), L-glutamine-fructose 6-phosphate transamidase (EC 5.3.1.19.), alkaline phosphatase (EC 3.1.3.1.), and malic dehydrogenase (EC 1.1.1.37) were assayed in partially purified extracts prepared at different stages of myxospore formation and germination in liquid cultures of Myxococcus xanthus. The specific activities of the first six of these enzymes increased 4.5- to 7.5-fold after 2 h of induction with 0.5 M glycerol or 0.2 M dimethyl sulfoxide. The increase in specific activities of these six enzymes was not observed in a mutant unable to be induced with glycerol. During the first 2 to 4 h of induction and during the first hour of germination, the level of these enzymes decreased to the level characteristic of vegetative cells. It is suggested that the six enzymes are responsible for the increased conversion of fructose 1,6-diphosphate to UDP-N-acetylgalactosamine, the major precursor of the myxospore coat.

Acetylglucosamine↗
PubMed1977

Myxospore coat synthesis in Myxococcus xanthus: in vivo incorporation of acetate and glycine.

Myxospore coat synthesis in Myxococcus xanthus was studied by incorporation of [(14)C]acetate into intermediates in the biosynthesis of coat polysaccharide and into acid-insoluble material during vegetative growth and after glycerol induction of myxospores. During short labeling periods at 27 degrees C, the radioactivity was shown to be located primarily in N-acetyl groups rather than sugar moieties. Two hours after glycerol induction, the pools of N-acetylglucosamine 6-phosphate and uridine 5'-diphosphate-N-acetylgalactosamine (UDPGalNAc) plus uridine 5'-diphosphate-N-glucosamine increased about twofold and were labeled at twice the rate measured for vegetative cells. The increased rate of synthesis of UDPGalNAc and its precursors could be correlated with increased enzyme activities measured in vitro. Controlled acid hydrolysis revealed that the galactosamine portion of the myxospore coat was N-acetylated. After glycerol induction, the incorporation of acetate into acid-insoluble material increased threefold. This enhanced incorporation was sensitive to neither penicillin nor d-cycloserine. In contrast, bacitracin inhibited the incorporation of [(14)C]acetate into acid-insoluble material more effectively 2 h after myxospore induction than during vegetative growth. Chloramphenicol added to cells 90 min after induction blocked further increase in the rate of [(14)C]acetate incorporation. Since the myxospore coat contains glycine, polymer synthesis was also measured by chloramphenicol-insensitive [(14)C]glycine incorporation into acid-insoluble material. Although protein synthesis decreased after glycerol induction, glycine incorporation increased. Two hours after induction, glycine incorporation was only 75% inhibited by chloramphenicol and rifampin. The chloramphenicol-insensitive rate of incorporation of [(14)C]glycine increased during the first hour after myxospore induction and reached a peak rate after 2 to 3 h. The chloramphenicol-resistant incorporation of [(14)C]glycine was resistant to penicillin but sensitive to bacitracin.

Acetates↗
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↗
PubMed1978

Chromosome replication in Myxococcus xanthus.

The rates of DNA synthesis during the cell-division cycle were measured in Myxococcus xanthus growing in three different media permitting a twofold variation in doubling time. In all three media, simple DNA cycles were observed. Synthesis of DNA occurred during 85% of the cell-division cycle, independent of generation time, from 5 to 11 h. Cells were observed to contain one bacterial nucleoid at birth that later divided synchronously midway through the cell cycle. Nucleoid segregation appeared to begin before chromosome replication was completed. The DNA content of exponential-phase bacteria was determined to be about 20 +/- 3 X 10(-9) microgram per cell; newborn bacteria contained about 14 +/- 2 X 10(-9) microgram of DNA per cell. Exponential-phase bacteria showed about a 50% increase in DNA in the presence of chloramphenicol (50 microgram/ml). The number of randomly segregating chromosomes present in exponential-phase bacteria was determined by following the fate of prelabeled DNA during outgrowth in nonradioactive media. The results are consistent with a model in which cells are born with exactly one complete unreplicated chromosome. The molecular weight of such a chromosome is about 8.4 +/- 1.2 X 10(9).

Cell Cycle↗
PubMed1978

Purification and properties of an extracellular protease from Myxococcus virescens.

An extracellular protease from Myxococcus virescens was purified by phosphate precipitation, gel exclusion, and ion-exchange chromatography. The enzyme appeared homogeneous upon disc electrophoresis. The molecular weight of the protease was estimated to be 26,000. The enzyme was rapidly inactivated by ethylenediaminetetraacetate, but the activity could be partially restored by divalent cations. Diisopropylphosphorofluoridate inhibited enzyme activity completely. Michaelis-Menten kinetics were obeyed with casein and hemoglobin as substrates. First-order kinetics were obtained with elastin as the substrate, provided trypsin was in excess. Petidolytic activity indicated that the peptide bonds hydrolyzed by the enzyme were mainly those involving amino acids with nonpolar side chains.

Cations↗
PubMed1978

Nutrition of Myxococcus xanthus, a fruiting myxobacterium.

The minimal requirements for vegetative growth of Myxococcus xanthus have been sought. Isoleucine, leucine, and valine were required, and vitamin B12 was needed for the synthesis of methionine. Pyruvate was an excellent energy source and an efficient source of cellular carbon. Acetate, aspartate, glutamate, and most tricarboxylic acid cycle intermediates could also be utilized, but were less efficient sources of carbon and energy than was pyruvate. Many mono- and disaccharides were tested, but, in agreement with earlier results, none served as carbon-energy sources. A minimal medium (A1) has been devised that includes the essential amino acids and vitamin B12, with pyruvate and aspartate as carbon-energy sources. In this medium, M. xanthus could propagate indefinitely, and on it vegetative cells formed colonies with greater than 75% efficiency; hence, it is likely that no organic cofactors other than those present in A1 are required in more than trace amounts.

Amino Acids↗
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↗
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↗
PubMed1979

Rifampin-resistant mutants of Myxococcus xanthus defective in development.

Rifampin, an antibiotic which is known to bind to and inhibit RNA polymerase, was used to probe the molecular regulation of development in Myxococcus xanthus. Rifampin-resistant mutants were screened for defects in fruiting-body formation. About 20% of the isolates in the initial screenings showed major defects in developmental aggregation or sporulation. Eleven independent mutants with wild-type growth rates and stable phenotypes were analyzed by transduction. In these strains, the rifampin-resistant and nonfruiting phenotypes showed cotransduction frequencies equal to or greater than 99.0 to 99.9%. The RNA polymerase activities were resistant to rifampin in vitro, indicating that the RNA polymerase is altered in these strains. Although their fruiting phenotypes are heterogeneous, these strains can be divided into two classes based on the level of aggregation. The results suggest that RNA polymerase plays a significant role in the regulation of development in M. xanthus since mutations which cause no apparent changes in vegetative growth result in striking defects in fruiting-body formation.

DNA-Directed RNA Polymerases↗
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↗
PubMed1979

Myxococcus xanthus mutants with temperature-sensitive, stage-specific defects: evidence for independent pathways in development.

Fruiting-body formation in the bacterium Myxococcus xanthus consists of a temporal sequence of cellular aggregation and sporulation. To examine the developmental stages more closely, we established synchronous and reproducible conditions for fruiting-body formation. Mutants that are temperature sensitive for fruiting-body formation were isolated and analyzed under these conditions. The terminal morphologies of the mutant strains at the nonpermissive temperature were found to resemble intermediate stages of fruiting-body formation and therefore were grouped in the following phenotypic classes: (i) rough mutants, which show no aggregation; (ii) swirl mutants, which show defective aggregation; (iii) flat-mound mutants and translucent-mound mutants, mutants which aggregate but show very low levels of sporulation. The mutants were characterized by temperature-shift experiments and found to exhibit discrete and reproducible temperature-sensitive periods. The ends of the temperature-sensitive periods in the various mutants covered a broad range of the developmental cycle. No correlation was found between the terminal morphologies at the restrictive temperature and the timing of the temperature-sensitive periods. However, the terminal morphologies correlated well with sporulation. The rough and swirl mutants produced normal numbers of myxospores at 34 degrees C even though they failed to aggregate. In contrast, the flat-mound and translucent-mound mutants, which aggregate normally, produced very few spores. The translucent-mound mutants were also temperature sensitive for induction of glycerol spores. The results indicate that both aggregation and sporulation are initiated early in the developmental cycle and that these processes are largely independent of each other.

Glycerol↗
PubMed1980

Accumulation of guanosine tetraphosphate and guanosine pentaphosphate in Myxococcus xanthus during starvation and myxospore formation.

Cultures of Myxococcus xanthus develop multicellular fruiting bodies when starved for carbon and nitrogen sources on an agar surface. Under these conditions of severe starvation, cultures rapidly accumulated a compound identified as guanosine tetraphosphate by chromatographic migration of the compound and of its major acid and alkali breakdown products. The accumulation of guanosine tetraphosphate was reduced in the presence of tetracycline, indicating that it may be synthesized by mechanisms similar to those of Escherichia coli. The guanosine tetraphosphate level was also reduced in starved cultures of a mutant unable to fruit normally, although it has been determined whether the defect in guanosine tetraphosphate accumulation is responsible for the inability to fruit. Induction of spores by glycerol addition led to transient increases in both guanosine tetraphosphate and guanosine pentaphosphate at a stage following most cell shortening, but before spores had acquired full refractility.

Adenosine Triphosphate↗
PubMed1980

Guanosine pentaphosphate and guanosine tetraphosphate accumulation and induction of Myxococcus xanthus fruiting body development.

Development of multicellular fruiting bodies of Myxococcus xanthus can be induced by limitation of any of a number of different classes of amino acids. Investigated were amino acids that wild-type strains of M. xanthus are unable to synthesize (isoleucine, leucine, and valine), can synthesize at a low rate (phenylalanine), or can normally synthesize at an adequate rate (tryptophan and serine). In general, gradual rather than abrupt starvation for an essential amino acid was required for the induction of fruiting. Perhaps gradual starvation in general minimizes antagonism between amino acids present in the medium, as was documented for valine starvation. The previously reported induction of fruiting by a high concentration of threonine was shown to be specifically reversed by lysine. Threonine addition may starve cells for lysine by feedback inhibition of aspartokinase activity. Starvation for carbon-energy sources or inorganic phosphate also induced fruiting. As in other bacteria, amino acid starvation of M. xanthus leads to increases in cellular guanosine polyphosphate, usually consisting of large increases in the amount of guanosine pentaphosphate with smaller increases in the level of guanosine tetraphosphate. Guanosine polyphosphate accumulation is thus shown to be correlated with nutritional conditions that induce fruiting, and therefore may serve as an intracellular signal to trigger cells to end vegetative growth and initiate fruiting body development.

Amino Acids↗
PubMed1980

Purine-containing compounds, including cyclic adenosine 3',5'-monophosphate, induce fruiting of Myxococcus xanthus by nutritional imbalance.

Induction of Myxococcus xanthus fruiting by a number of different purine-containing compounds, including cyclic adenosine 3',5'-monophosphate, is defective in a mutant resistant to 2,6-diaminopurine. Furthermore, the purine-induced fruiting of wild-type cultures is uniquely blocked by a low concentration of added glycine. These results imply that different purine-containing compounds induce fruiting through a single mechanism involving nutritional imbalance.

Adenine↗
PubMed1980

Separation and properties of the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus.

We have developed methods for separating the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus. The total membrane fraction from ethylenediaminetetraacetic acid-lysozyme-treated cells was resolved into three major fractions by isopycnic density centrifugation. Between 85 and 90% of the succinate dehydrogenase and cyanide-sensitive reduced nicotinamide adenine dinucleotide oxidase activity was found in the first (I) fraction (rho = 1.221 g/ml) and 80% of the membrane-associated 2-keto-3-deoxyoctonate was found in the third (III) fraction (rho = 1.166 g/ml). The middle (II) fraction (rho = 1.185 g/ml) appeared to be a hybrid membrane fraction and contained roughly 10 to 20% of the activity of the enzyme markers and 2-keto-3-deoxyoctonate. No significant amounts of deoxyribonucleic acid or ribonucleic acid were present in the three isolated fractions, although 26% of the total cellular deoxyribonucleic acid and 3% of the total ribonucleic acid were recovered with the total membrane fraction. Phosphatidylethanolamine made up the bulk (60 to 70%) of the phospholipids in the membrane fractions. However, virtually all of the phosphatidylserine and cardiolipin were found in fraction I. Fraction III appeared to contain elevated amounts of lysophospholipids and contained almost three times the amount of total phospholipid as compared with fraction I. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved approximately 40 polypeptides in the total membrane fraction. Two-thirds of these polypeptides were enriched in fraction I, and the remainder was enriched in fraction III. Fraction II contained a banding pattern similar to the total membrane fraction. Electron microscopy revealed that vegetative cells of M. xanthus possessed an envelope similar to that of other gram-negative bacteria; however, the vesicular appearance of the isolated membranes was somewhat different from those reported for Escherichia coli and Salmonella typhimurium. The atypically low bouyant density of the outer membrane of M. xanthus is discussed with regard to the high phospholipid content of the outer membrane.

Bacterial Proteins↗
PubMed1980

Adenylate energy charge during fruiting body formation by Myxococcus xanthus.

The adenylate energy charge of developing Myxococcus xanthus cells was measured. The energy charge of vegetative cells (0.81) does not change significantly during the course of fruiting body formation. Furthermore, myxospores, which are resistant, resting cells present in the fruiting body, have a relatively high energy charge (0.73).

Adenosine Diphosphate↗
PubMed1980

Patterns of protein production in Myxococcus xanthus during spore formation induced by glycerol, dimethyl sulfoxide, and phenethyl alcohol.

Spore formation of Myxococcus xanthus can occur not only on agar plates during fruiting body formation, but also in a liquid culture by simply adding glycerol, dimethyl sulfoxide, or phenethyl alcohol to the culture. This chemically-induced spore formation occurs synchronously and much faster than that occurring during fruiting body formation. Dramatic changes in patterns of protein synthesis were observed during chemically-induced spore formation, as had previously been observed during fruiting body formation (Inouye et al., Dev. Biol. 68:579-591, 1979). However, the production of protein S, one of the major development-specific proteins during fruiting body formation, was not detected at all, although protein U, another development-specific protein, was produced in a late stage of spore formation as in the case of fruiting body formation. This indicates that the control of the gene expression during chemically-induced spore formation is significantly different from that during fruiting body formation. It was also found that during spore formation, every cell seems to have a potential to form a spore regardless of its age, since smaller cells as well as larger cells separated by sucrose density gradient centrifugation could equally form spores upon the addition of glycerol. Patterns of protein synthesis were almost identical for all the three chemicals. However, the final yield of spores was significantly different depending upon the chemicals used. When phenethyl alcohol was added with glycerol or dimethyl sulfoxide, the final yields were determined by the multiple effect of the two chemicals added. This suggests that although these chemicals are able to induce the gene functions required for spore formation, they may have inhibitory effects on some of the gene functions or the processes of spore formation.

Bacterial Proteins↗
PubMed1981

Genetic characterization of aggregation-defective developmental mutants of Myxococcus xanthus.

The transposon Tn5 was used to map temperature-sensitive mutants of Myxococcus xanthus defective in aggregation (C. E. Morrison and D. R. Zusman, J. Bacteriol. 140:1036-1042, 1979). Seven of the eight mutants showing a similar terminal phenotype (rough) were found to be tightly linked. These mapped in a group of loci which we have designated aggR1, aggR2, aggR3, and aggR4. Temperature-sensitive mutants having a different terminal phenotype were not liked to aggR. A search through a group of nonconditional rough mutants indicated that a much lower proportion of these (1 of 35) mapped in aggR. Thus, aggR is probably only one of many sites which can lead to the rough phenotype when mutated. Localized mutagenesis was used to isolate nine additional aggR mutants. All mapped within aggR1, aggR2, or aggR3, and none was found outside this region. Thus, we have characterized a cluster of developmental genes which are needed for aggregation in M. xanthus. The localization of a Tn5 insert adjacent to this region makes possible further manipulation of these genes.

Chromosome Mapping↗