- Volume 120, Issue 1, 1980

β-Ketoadipate induces catabolic enzymes in Pseudomonas putida. The compound is transported by a system which also concentrates adipate, a non-metabolizable analogue of -ketoadipate. The natural substrate, β-ketoadipate, competitively inhibits adipate transport with a K i of 0·04 mm, lower than the K m of 0·23 mm observed with adipate. Transport is inhibited competitively by succinate (K i 1·3 mm) and non-competitively by acetate (K i 5·3 mm). The system has a sharp pH optimum at 5·5. Transport activity is stimulated by a variety of ions, and salt concentrations in excess of 0·1 m are required to achieve optimal rates of influx. The transport system is inhibited by proton conductors and thiol reagents. Membrane vesicle preparations concentrate adipate when supplied with an oxidizable energy source. Induction of the transport system does not allow the rapid utilization of exogenous β-ketoadipate. Nevertheless, the system has been conserved in the evolution of divergent Pseudomonas species. The selective value of the β-ketoadipate transport system may lie in its apparent function in chemotaxis and in its ability to control intracellular concentrations of the inducing metabolite, β-ketoadipate.

Tetrahymena elliotti was used to assess the accuracy of the volume distribution measured with a Coulter counter. The volumes of the cells were shown to be underestimated because of their electrical conductivity. Theoretical considerations predicted the observed excessive skewness of the distributions. It is concluded that the only reliable parameter obtained from a Coulter volume distribution is the mean size.

A Bacillus subtilis plasmid capable of producing phenotypic erythromycin resistance was compared with an Eryr staphylococcal plasmid. The two plasmids did not interfere with the sporulation process in B. subtilis, in contrast to chromosomal erythromycin mutations.

The polymorphic fungus Aureobasidium pullulans has been fractionated into mycelium and single cells at three points in the growth cycle approximately corresponding to early, middle and late exponential phases. The ability of cells to divert assimilated glucose to form the extracellular polysaccharide pullulan varies throughout the cycle; the spores are the major source of polysaccharide, although the hyphae are also capable of producing it. Thus, the commencement of pullulan excretion, which has been associated with blastospore production in the early phases of the growth cycle, probably arises through some stimulation concurrent with, though not necessarily identical to, the initiation of spore formation.

The effect of gamma-radiation on fruiting body initiation in a basidiomycete, Hebeloma vinosophyllum, was investigated. Fruiting of this fungus is induced by visible light, but irradiation of the mycelium before or after light treatment delayed fruiting body initiation. The time required for fruiting body initiation increased with the radiation dose. The induction of fruiting bodies had two gamma-radiation sensitive stages, one immediately before fruiting body initiation and the other 15 to 20 h after the start of photoinduction.

Evidence was sought for gene-specific negative regulatory element of Dictyostelium discoideum similar to the repressor/operator systems that control some operons in rpkaryotes and their viruses. Mutants of D. discoideum that constitutively express the stage specific enzyme α-mannosidase-2 could provide such evidence. Reconstruction experiments demonstrated that the screening technique developed would detect mutants of that type. Over 2 × 105 surviovors of heavily mutagenized cell populations were grown and their progeny tested. No mutants of the desired type were obtained. The possible implications of this finding are discussed.

Schizosaccharomyces pombe grows and multiplies for many generations in the presence of chloramphenicol (CAP, 2 mg ml-1). CAP-grown cells exhibit nearly fully suppressed respiration, while fermentation occurs at the same rate as in untreated controls. The growth rate of the cultures is reduced in proportion to the diminished energy production, but the content of protein and bulk RNA per cell remain as in untreated cells. The effects of CAP are reversible. It is argued that CAP in S. pombe specifically inhibits mitochondrial protein synthesis without interfering with cytoplasmic protein synthesis.

CAP-treated cultures can be division-synchronized either by a selection technique or by a controlled temperature regimen and the synchronous divisions studied after removal of CAP.

Phenetic data on 75 strains of Erwinia and other representative genera of the Enterobacteriaceae were collected and analysed using two numerical taxonomic methods. In both methods the same subclusters were recovered. The subclusters, however, were defined at different similarity levels and were classified into clusters of different composition. Erwinia rubrifaciens strains formed a very tight, homogeneous subcluster, completely distinct and readily distinguishable from other Erwinia and enterobacteria species studied. DNA: DNA hybridizations between E. rubrifaciens and Erwinia and Shigella species were analysed to corroborate the numerical classifications. A good correlation between the numerical and DNA: DNA hybridization analyses was found and provided sufficient evidence for not supporting the previously proposed subspecific taxonomic position of E. rubrifaciens. The data clearly showed that E. rubrifaciens is a separate species in its own right. Based on the existence of very high genetic relatedness and high similarities in phenetic characters among E. rubrifaciens strains and the confinement of the pathogen to the state of California, the hypothesis is offered that E. rubrifaciens originated from a single source.