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Biomedical subjects

J J Child

Publications and source records attributed to J J Child.

At least 19 recordsLinked to original sources
PubMed1979

Fatty acid composition of Rhizobium spp.

The fatty acid composition of 42 isolates belonging to the major plant affinity groups of Rhizobium has been determined and found to vary reproducible with culture age. Numerical taxonomic techniques applied to the 15 major fatty acid components of log-phase cultures of comparable physiological age showed that the rhizobia constitute a uniform group. However, two clusters comprising soybean-cowpea isolates and pea-bean isolates were evident. These observations, based on a simple analysis of only one group of chemical components, indicate relationships among rhizobia which differ from the conventional plant-affinity groupings but which are consistent with other proposed relationships established using a variety of biochemical and physiological criteria.

Fabaceae↗
PubMed1979

Nitrogen fixation by Rhizobium sp. 32H1. A morphological and ultrastructural comparison of asymbiotic and symbiotic nitrogen-fixing forms.

The induction of nitrogenase (C2H2) activity in asymbiotically cultured Rhizobium sp. 32H1 was found to be associated with morphological changes in the cells which were more pronounced than those seen in bacteroids. Polyphosphate granules were found in both bacteroids and cultured cells, but poly-beta-hydroxybutyrate vesicles were almost absent in bacteroids but were present in cultured cells. Freeze-etching techniques revealed no differences between the asymbiotically cultured nitrogen-fixing forms and bacteroids in that both the cell wall and cytoplasmic membrane cleavage planes were normal for gram-negative bacteria.

Cytoplasmic Granules↗
PubMed1979

Bacterial utilization of a hydrazine derivative as nitrogen source for growth.

The ability of microbes to metabolize the N--N bond seems rare. Pseudomonas sp. from soil can utilize 1,4,5,6-tetrahydro-6-oxo-3-pyridazinecarboxylic acid as C and N source. This appears to be the first report that a microbe can cleave a nitrogen--nitrogen bond in an organic compound and use the products for growth.

Aerobiosis↗
PubMed1978

Inducing effect of plant cells on nitrogenase activity by Spirillum and Rhizobium in vitro.

Eleven different plant cell tissue cultures of both legume and non-legume origin have been grown in direct association, and in separate but close proximal association with both Spirillum lipoferum and Rhizobium sp. 32H1. Basic similarities were found in the nutritional requirement for the induction of nitrogenase activity (C2H2) in both organisms. In the absence of plant cell cultures both organisms need to be provided with a pentose sugar and a tricarboxylic acid to induce high levels of nitrogen-fixing activity. Plant cell callus tissue appears only capable of supplying the tricarboxylic acid to induce high levels of nitrogen-fixing activity. Plant cell callus tissue appears only capable of supplying the tricarboxylic acids needed but not the sugar component. The plant tissue, however, seems able to activate certain carbohydrates, which in themselves are incapable of substituting for the pentose additive.

Enzyme Induction↗
PubMed1976

Effect of inhibitors of sterol biosynthesis on growth and sexuality of Pythium and Zygorhynchus.

Seven commercial inhibitors of sterol biosynthesis were tested for their effect upon vegatative growth and sexuality in Pythium acanthicum and Zygorhynchus moelleri. Five compounds (SKF 525, Chlorpropamide, Tolbutamide, Benzmalacene, AY 9944) inhibited both growth and sexuality of both fungi and two (SKF 7732 and SKF 7997) were ineffective. Pythium was more sensitive to the activity of the inhibitors than was Zygorhynchus. None of the compounds tested inhibited sexuality without similarly reducing vegetative growth.

Chlorpropamide↗
PubMed1976

Nitrogenase activity in cultured Rhizobium sp. strain 32H1: nutritional and physical considerations.

Nutritional and physical conditions affecting nitrogenase activity in the strain of "cowpea" rhizobia, 32H1, were examined using cultures grown on agar medium. Arabinose in the basic medium (CS7) could be replaced by ribose, xylose, or glycerol, but mannitol, glucose, sucrose, or galactose only supported low nitrogenase (C2H2 reduction) activity. Succinate could be replaced by pyruvate, fumarate, malate, or 2-oxoglutarate, but without any carboxylic acid, nitrogenase activity was low or undetectable unless a high level of arabinose was provided. Inositol was not essential. Several nitrogen sources could replace glutamine including glutamate, urea, (NH4)2SO4 and asparagine. The maximum nitrogenase activity of cultures grown in air at 30 degrees C was observed under assay conditions of pO2=0.20-0.25 atm and 30 degrees C incubation. Greatest activity occurred after a period of rapid bacterial growth, when viable cell count was relatively constant. Compared with results obtained on the CS7 medium, nitrogenase activity could be substantially increased and/or sustained for longer periods of time by using 12.5 MM succinate and 100 mM arabinose, by increasing phosphate concentration from 2 to 30-50 mM, or by culturing the bacteria at 25 degrees C.

Arabinose↗
PubMed1975

Ultrastructural aspects of wall regeneration by Pythium protoplasts.

Electron microscope studies were made of wall regeneration by Pythium protoplasts. Wall regeneration began with the formation of a loose network of fibrils on the surface of the protoplast followed by increase in density of the fibrillar mesh and deposition of granular mitrix material. The majority of the protoplasts did not develop beyond the loose fibrillar network stage, however a small percentage were able to complete wall formation and to form hyphal tubes. A clear zone of demarcation was visible between the fibrillar surface of the protoplast and the smooth surface at the base of the developing hyphal tube.

Cell Wall↗
PubMed1974

A simple technique for the establishment of nitrogenase in soybean callus culture.

A nitrogen-fixing association can be readily established in vitro between Rhizobium and cultured soybean root cells. Plant cells are grown as a thin callus on the surface of solid defined medium containing low levels of inorganic nitrogen and inoculated with bacteria during the active phase of growth. Acetylene reduction activities up to 275 nmoles ethylene/hr.g dry weight of cells have been recorded.The system is compact, uses inexpensive glassware, and facilitates multiple replication of samples. The use of a single medium throughout the experiments avoids unnecessary disturbance to the cells. The development of nitrogenase activity is relatively rapid and its activity can be recorded within a 3-week period.

Journal Article↗