- Volume 136, Issue 10, 1990

In Anabaena cylindrica, protein synthesis continued during dark periods at 80 % of the rate observed in the light. Since nitrogen fixation ceases in the dark, this implies that fixed nitrogen accumulates during the light periods to supply amino acids for protein synthesis in the dark. Measurements of cyanophycin and the distribution of nitrogen in subcellular fractions indicated that cyanophycin does not represent a significant proportion of total cell nitrogen, nor does its concentration vary across the light/dark cycle. Similar results were obtained with Gloeothece; there was no evidence that cyanophycin accumulated during the dark to support protein synthesis in light. Cyanophycin does not, therefore, appear to serve as a dynamic temporary storage form of newly fixed nitrogen in the integration of light and dark metabolism. We also investigated an immunological approach to the measurement of cyanophycin and its turnover. Cyanophycin is immunogenic, and in the pure state could be assayed by radioimmunoassay, which had greater sensitivity than traditional assay procedures. The insolubility of cyanophycin at neutral pH, however, prevented the successful development of methods for quantifying cyanophycin turnover in cell extracts.

Cyanophycin, the nitrogen reserve compound in cyanobacteria, has a dynamic metabolism during transitions between the metabolic states of nitrogen deficiency and nitrogen repletion and vice versa. Cyanophycin was transiently synthesized when ammonia-grown Anabaena cylindrica or Synechocystis 6308 consumed a limited amount of ammonia. It was synthesized during the phase of declining ammonia concentration, and its degradation was complete by the time the external ammonia had been completely consumed. When nitrogen-starved cells of A. cylindrica or Synechocystis 6308 were given a usable source of fixed nitrogen, cyanophycin again accumulated transiently. This synthesis of cyanophycin was triggered by the suddenly renewed availability of fixed nitrogen, and not by the subsequent decline in the external concentration of fixed nitrogen. The cyanophycin was degraded when balanced exponential growth was again possible. Transient accumulations of cyanophycin with similar kinetics were also observed when ammonia was added to nitrogen-fixing A. cylindrica. It is suggested that cyanophycin serves as a dynamic reservoir which separates the environmental supply of fixed nitrogen from the metabolic demands of the cells, and that this provides a mechanism which enables cyanobacteria to maximize their share of any available fixed nitrogen. This would give cyanobacteria a competitive advantage over other organisms.

Ubiquinones extracted from 24 strains of Legionella pneumophila (including the type strains of serogroups 1–14 and one proposed new serogroup) and from 44 strains of other Legionella species (including 28 type strains and strains of five proposed new species) were analysed by reversed-phase thin-layer chromatography. Ubiquinone profiles as determined by this method were reproducible, both qualitatively and semi-quantitatively, and provided information to aid in the identification of species of Legionella. Results of ubiquinone profiles determined by different laboratories were compared. Some quantitative differences in results between laboratories were observed, which may be due to different analytical procedures. For this reason laboratories should establish their own library of ubiquinone profiles. New information is presented on the ubiquinone profiles of seven Legionella species: L. birminghamensis, L. brunensis, L. cincinnatiensis, L. moravica, L. quinlivanii, L. tucsonensis and proposed new species no. 1347, ‘L. worsleiensis’

The effect of hymexazol on the linear extension of hyphae of a range of Oomycetes was examined. Twenty-five species were compared using four fungicide concentrations. Cluster analysis was used to look for similarities between species. The response of each taxon to the different concentrations of hymexazol was modelled. The parameters of these curves were then subjected to multivariate analysis. Both analyses revealed close relationships between the sensitivity to the fungicide and the current classification of the Oomycetes. Comparisons were made with the effect of metalaxyl on the same isolates.

Genetic relationships among isolates assigned to Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus and H. paraphrophilus were determined by analysis of electrophoretically demonstrable allelic variation in 14 structural genes encoding metabolic enzymes. Among the 51 isolates analysed there were 25 electrophoretic types (ETs), among which mean genetic diversity per locus was 0·753. Cluster analysis of ETs demonstrated one well-defined group of 11 ETs representing solely the genotypes of all 17 isolates assigned to A. actinomycetemcomitans. The remaining 14 ETs represented the genotypes of the 34 isolates of H. aphrophilus and H. paraphrophilus. With the exception of ATCC 13252, all strains of H. aphrophilus were closely related, whereas strains assigned to H. paraphrophilus included distantly related lineages, some of which were similar to those of H. aphrophilus and should be assigned to this species. Thus, the study showed that there is no significant overall genetic similarity between A. actinomycetemcomitans and the two Haemophilus spp.