- Volume 132, Issue 12, 1986

Summary: The regulation of the NH+ 4-assimilating enzymes glutamate dehydrogenase (GDH), glutamine synthetase (GS) and glutamate synthase (GOGAT), and the cellular composition of Hyphomicrobium ZV620 grown in a chemostat with methanol and NH+ 4 as the supplied C- and N-sources were investigated. The influence of either C- or N-limitation (as a function of dilution rate) and of the C: N ratio (at a constant growth rate) was studied. NADP+-dependent GDH was active at high NH+ 4-concentrations and was repressed at low NH+ 4-concentrations. The activity increased with increasing dilution rates under C-limited growth conditions. Derepression of NADP+-dependent GDH was observed at low dilution rates under N-limited growth conditions. GS was more active at low NH+ 4-concentrations where both the total enzyme level (deadenylylated plus adenylylated forms) and the active fraction increased. C-limited growth resulted in low activities of GS, whereas activity in N-limited cells was consistently high. Dilution rate did not have a significant influence on the specific activity. The specific activity of GOGAT increased with decreasing NH+ 4 concentrations. Under both C- and N-limitation the specific activity of GOGAT increased with increasing growth rates. The C-content of the cells changed very little under the various growth conditions tested. The N-content and the protein content of the cells did not alter under C-limitation. N-limited growth conditions caused the cells to accumulate poly β-hydroxybutyrate. As a consequence, both the N-content and the protein content of the cells decreased.

Summary: Desulfovibrio vulgaris (Hildenborough) was grown on lactate with either a N2/CO2 or a H2/CO2 gas phase. H2 increased the growth yield on lactate and had a sparing effect on lactate utilization, without altering the growth rate or hydrogenase level. Growth on acetate plus CO2 with H2 as sole energy source did not require an extensive adaptation period. Addition of lactate to cultures growing on acetate and H2/CO2 resulted in a switch from acetate to lactate utilization. In lactate-limited medium under H2/CO2 biphasic growth was observed. Lactate was oxidized first with production of acetate, followed by a second phase of growth on the acetate. Under this condition H2 did not provide any supplementary energy during growth on lactate, as was evident from the ratio of lactate utilized to acetate produced.

Summary: A sulphur-oxidizing enzyme was purified to homogeneity from cell-free extracts of mixotrophically grown cells of sulfolobus brierleyi. The enzyme catalysed the oxidation of elemental sulphur to sulphite and had an MT of 560 000. Only one type of subunit (M/r 35000) could be detected. The pH and temperature optima for activity were 70 0-5 and 65°C respectively and an apparent Km for sulphur was calculated to be 0.05 M. Enzyme assays with 18O-enriched oxygen demonstrated directly that atmospheric oxygen was attached to sulphur. The first detectable reaction product was sulphite. These results provide evidence that sulphur oxidation in S. brierleyi is performed by an enzyme of the oxygenase type.

Summary: Analysis of cell extracts of Rhodomicrobium vannielii continuously labelled with [32P]orthophos-phate revealed that at least 25 polypeptides were phosphorylated, including abundant species of M r 88000, 66000, 55000 and 12700, and that the phosphate groups were ester-linked to serine, threonine and tyrosine. Pulse labelling with [32P]orthophosphate indicated that the protein phosphorylation profile was dependent upon the growth stage of the culture. Comparison of phosphopolypeptide profiles of reproductive and swarmer cells suggested that protein phosphorylation was drastically reduced in the swarmer cell. However, during the course of differentiation phosphopolypeptides became increasingly abundant, particularly two species of M r 55000 and 86000. Although protein kinase activities could be detected in vitro, there was little similarity between the in vitro pattern of phosphorylated polypeptides and that obtained in vivo.

Summary: At least 11 esterase isoenzymes have been resolved from conidia of six strains of Neurospora crassa on starch gel zymograms using β-naphthyl acetate as substrate. By means of inhibitor studies, three of them were determined to be acetylesterases and nine to be carboxylesterases. Carboxylesterases could be distinguished from acetylesterases by their positive reaction with α-naphthyl butyrate. The distribution of these multiple forms of esterases in conidia was clearly strain specific. Each strain contained two forms of acetylesterase and from zero to three forms of carboxylesterase. These esterases could not hydrolyse the naphthyl esters of aliphatic carboxylic acids larger than butyrate or that of benzoate. During the first 20 h of conidial germination, a marked decrease in esterolytic activity was observed for most of the carboxylesterases but not for the acetylesterases. This might indicate that digestion of aliphatic esters is involved in the initial stage of conidial germination.

Summary: Scanning electron microscopic studies showed that the morphology of Penicillium chrysogenum Thom in fermentation cultures changed in response to changes in COz concentration. At influent COz partial pressures between 0.03% (air) and 8 %, the predominant morphological form was filamentous, whereas at 15% CO2, swollen and stunted hyphae predominated, and a significant quantity of spherical or yeast-like cells was observed.

Summary: An action spectrum for photoinduced conidiophore formation in the fungus Alternaia cichorii was determined by exposing colonies to monochromatic radiation obtained from a diffraction grating monochromator. The action spectrum showed a peak near 290 nm with a noticeable shoulder between 310 and 330 nm and another one between 260 and 265 nm. This action spectrum has many common characters with those for photoinduced conidiophore formation of Helminthosporium oryzae and Alternaria tomato, where the induction of conidiophore formation is controlled by a blue-light-inducible, near-UV-reversible, photoreaction.

Summary: Two comptible mating-tyes of Physarum polycephalum, RSD4 and MA185, have recently been shown to have different surface properties by using aqueous two-phase partition. Changes in the surface properties of RSD4 amoebae were detected when in contact with cell culture medium from MA185 amoebae. The ability of MA185 culture medium to alter the surface of RSD4 amoebae was not affected by autoclaving or passage through a filter that removed molecules of M r greater than 10000. Activity was detected in medium from MA185 amoebae that had not previously been in contact with RSD4 amoebae. These results provide evidence for the existence of a low-Mr factor produced by MA185 amoebae which affects the surface of RSD4 amoebae.