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H D McCurdy

Publications and source records attributed to H D McCurdy.

11 recordsLinked to original sources
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↗
PubMed1979

The function of fimbriae in Myxococcus xanthus. II. The role of fimbriae in cell-cell interactions.

Anti-fimbriae antiserum specifically inhibited swarming but no gliding motility per se in Myxococcus xanthus. However, formation of motile aggregates on agar and clumps in liquid media correlated with the presence of fimbriae. Ethylenediaminetetraacetic acid which inhibited swarming also inhibited fimbriae formation. Direct electron-microscopic observations revealed that fimbriae establish contact with apposing cell surfaces. Intact but not depolymerized fimbriae exhibited hemagglutination activity against guinea pig erythrocytes. This activity was inhibited by mannose, N-acetyl-D-galactosamine, and to a lesser degree by fructose, raffinose, melibiose, and alpha-methyl-D-mannoside. It is concluded that fimbriae are organelles which function to establish and maintain intercellular contacts, perhaps by a lectin-like function, during the coordinated movement of cell aggregates' (swarming) in myxobacteria. This hypothesis is supported by the observations of other workers that genes determining movement of cells in groups also control fimbriation in M. xanthus.

Acetylglucosamine↗
PubMed1978

Cyclic nucleotides, cyclic nucleotide phosphodiesterase, and development in Myxococcus xanthus.

Exogenous cyclic nucleotide phosphodiesterase (PD) accelerated fruiting body (FB) formation and increased territory size of aggregates in Myxococcus xanthus. Both guanosine 3'5'-monophosphate (cGMP) and guanosine 5'-monophosphate (GMP) were antagonistic to the PD effect. Adenosine 3'5'-monophosphate (cAMP) increases FB numbers twofold in the absence but not in the presence of PD. PD induction is not affected by methionine or isoleucine, which inhibit, or by threonine, which stimulates, FB formation. There is an increase and subsequent decrease in cAMP levels during early glycerol-induced microcyst development but 10 mM theophylline or caffeine not only inhibited microcyst development but induced germination in the presence of glycerol. On the basis of these results and the reports of other investigators a tentative model is proposed based on a dual role for cyclic nucleotides in the development in M. xanthus.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1977

Fimbriation in gliding bacteria.

Of twenty-two strains of gliding prokaryotes examined, all but three were found to possess polar fimbriae. Fimbriae were not observed on two gliders, while Chloroflexus aurantiacus bore abundant peritrichous fimbriae. In some gliding bacteria, fimbriae were associated with 'holes' surrounded by an electron-transparent collar bearing 12 spike-like projections.

Bacteroidetes↗
PubMed1977

The diguanosine nucleotides: do they exist in aquatic fungi?

The aquatic fungi Achlya ambisexualis and Blastocladiella emersonii were grown in the presence of 32Pi and the 32P-labeled acid-soluble nucleotide fractions were analyzed by ion-exchange chromatography on DEAE-cellulose. Selected column fractions containing diguanosine tri- and tetra-phosphates (Gp3G and Gp4G) added as chromatographic markers were analyzed further for 32P by chromatography and (or) enzyme hydrolysis. The results of these experiments clearly indicate that neither Gp4G nor Gp3G is synthesized during vegetative growth of these organisms and cast doubt on the hypothesis that diguanosine nucleotides are important metabolic regulators in fungi.

Blastocladiella↗
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↗
PubMed1975

Ultrastructural studies of Chondromyces crocatus vegetative cells.

Electron microscopy of sectioned, chemically fixed Chondromyces crocatus revealed a microorganism with a typical gram-negative cell envelope. The cytoplasm contained, in addition to tubules and two types of granules, a membrane-associated structure (MAS) that, although less extensive, bears some resemblance to polar membranes observed in flagellated bacteria. Examination of swarming cells negatively stained in situ, as well as thin sections, established that cell division occurs by septum formation and that well-defined mesosomes are associated with the process. Polar pili and a compact, amorphous slime layer surrounding the cells were evident in shadowed preparations of in situ cells. The slime layer and pili, by providing cell-to-cell interconnections, may influence the organized gliding movement characteristic of C. crocatus and other myxobacteria.

Cell Division↗