- Volume 128, Issue 9, 1982

A range of actinomycetes and Mycoplana strains were screened for nitrogenase activity. No positive results were obtained with actinomycetes, although some grew on media without added combined nitrogen. In contrast, most Mycoplana strains showed nitrogenase activity. Although the strains were unable to grow in anaerobic conditions, sustained nitrogen fixation required microaerobic conditions. The relationship of Mycoplana to actinomycetes is discussed.

Using 200 fresh isolates of Staphylococcus epidermidis, the relationship between type of growth in soft-agar medium and respiration, dehydrogenase activity and biotype was investigated. When strains of S. epidermidis were cultured in Brain Heart Infusion medium containing 0.15% (w/v) agar, the following different growth types were observed: compact colonial morphology with growth throughout the medium (type A), or with growth only at the surface (type B); and diffuse colonial morphology with growth throughout the medium (type C), growth only at the surface (type D), or growth from the surface to the middle of the tube (type E). Five representative strains of each growth type were studied and different results for cytochrome pattern, oxygen consumption and relative activities of lactic dehydrogenase and succinic dehydrogenase were obtained with different growth types. However, there was no correlation between growth type and biotype.

Entomophthora culicis, a fungus which parasitizes a variety of small adult dipteran insects, is characterized by the production of asexual spores (conidia) which are forcibly discharged. Of the four developmental possibilities available to conidia, only direct vegetative conidial germination leads to successful infection of a potential insect host. Fatty acids were found to exert profound physiological control over conidium development. In combination with chitin or chitosan, oleic acid (C18:1) consistently induced vegetative conidial germination. Palmitoleic acid (C16:1), linoleic acid (C18:2) and linolenic acid (C18:3) were toxic to conidia over a wide range of concentrations. An excess of oleic acid mitigated the toxic effects of linoleic acid. A possible role for lipid hydroperoxides in the mediation of conidial development by fatty acids is discussed.

The growth and development of mycelia of the dimorphic fungus Candida albicans in serumcontaining medium is described. Initially, colonies are undifferentiated (all hyphae in the mycelium having approximately the same diameter, extension rate, apical and intercalary compartment lengths) whereas older mycelia differentiate at the colony margin to produce leading hyphae that are wider, faster growing and have longer apical and intercalary compartment lengths than the branches they subtend. Early colony development exhibits unusual features: germ tube extension is linear (not exponential as in other fungi) and there is a prolonged delay between septation and the onset of branch formation. The subsequent patterns of growth and branching are similar in all other respects to those of other mycelial moulds. Mycelia have septa that delimit single nuclei within compartments. The septa do not prevent cytoplasmic flow and consequently allow the peripheral growth zone to span several compartments. From these results we conclude that filamentous growth of C. albicans in this medium is best described as truly mycelial.

A method is described for deletion mapping of essential genes in Escherichia coli. It involves the isolation of secondary-site insertions of λc1857 plac 5 into an F′ plasmid. The transposed lacZ gene is useful both for the ready screening of plasmid-phage cointegrates and for rapid analysis of deletions that extend from the site of phage integration into the bacterial genes carried on the substituted plasmid. Such deletions may be used to ‘hook-up’ bacterial cistrons to the powerful lac promoter. We report the application of this technique to the study of the btuB-rpoBC interval, a cluster of genes encoding components of the transcription-translation apparatus.

Glutamate synthase (GOGAT) activities in cell-free extracts of isolated heterocysts and whole filaments of the cyanobacterium Anabaena variabilis Kütz. (ATCC 29413) were determined by measuring [14C]glutamate production from 2-oxo[14C]glutarate or from [14C]glutamine, both of which are GOGAT substrates. There was negligible [14C]glutamate production from 2-oxo-[14C]glutarate in the presence of aminooxyacetate, which inhibits aminotransferase activity (<3% of that detectable in whole filament extracts). In experiments using [14C]glutamine, [14C]glutamate production by heterocyst extracts accounted for about 17% of that detected in whole filament extracts, even in the absence of 2-oxoglutarate, ferredoxin and sodium dithionite. It is concluded that virtually all the [14C]glutamate formed from [14C]glutamine in heterocyst extracts is independent of GOGAT activity.

Respiration-driven H+ translocation has been examined in an eup (‘energy uncoupled phenotype’) mutant of Escherichia coli and compared with that observed in its otherwise isogenic wildtype parent. Respiration-driven H+ translocation was unimpaired in the eup mutant strain. It appears that the role of the eup gene product lies in the utilization of energized protons pumped across the E. coli cytoplasmic membrane.

Succinate-driven calcium uptake by everted membrane vesicles from Escherichia coli was sensitive to 2 mm-KCN and a dimeric, mixed valence complex of ruthenium, Ru2(NH3)6Br5(H2O) (100 μm), but relatively insensitive to 100 μm-Ruthenium Red. The sensitivity of uptake to KCN and the slight inhibition caused by Ruthenium Red could be attributed to the different potencies of these compounds as respiratory inhibitors. Respiration was completely insensitive to the dimeric ruthenium complex, however, suggesting that this compound is an inhibitor of respiration-driven calcium transport.

A study was made of 516 randomly selected isolates of moderately halophilic bacteria from solar salterns showing salinities between 8·8 and 40·0% (w/v) total salts, located in S.E. Spain. After purification, many cytological, physiological, biochemical, nutritional and antibiotic sensitivity characters were determined for 106 selected saltern isolates and two reference strains. Data were coded and analysed by numerical techniques using the Jaccard coefficient (SJ ), and clusters of strains were obtained by average linkage (UPGMA) analysis. Nine major phenons were found at the 72·5% similarity level. The properties of each phenon are given, their taxonomic affinities are discussed, and typical reference strains are suggested. Almost all the strains were related to genera known to contain marine species. A large number of the strains could be tentatively assigned to the genus Vibrio, suggesting that this may be an abundant taxon of moderately halophilic Gram-negative rods in solar salterns.

Hybridization studies based on the use of crossing and the protoplast fusion technique revealed the relationship between the various taxa of the yeast genus Schizosaccharomyces Lindner. From a series of intra- and interspecific crosses as well as protoplast fusions, we concluded that a revision of the genus is required. Being interfertile, S. pombe and S. malidevorans have to be included in one species S. pombe. From the protoplast fusion results, this new taxon seems to be closely related to S. octosporus. The results obtained are discussed in connection with the characteristics of the low temperature spectra of the cytochromes.