Additional Nucleotide Sequences in Precursor 16S Ribosomal RNA from <Emphasis Type="Italic">Escherichia coli</Emphasis>

MATURE 5S, 16S and 23S ribosomal RNA species present in E. coli ribosomes are the end products of complex biosyn-thetic pathways. They are formed by reduction in length, and methylation of longer RNA chains transcribed on the ribosomal RNA cistrons of E. coli DNA. While these modifications take place the ribosome structure is formed by progressive addition of ribosomal proteins and conformational changes in the resulting ribonucleoprotein precursor particles¹.     

The nature of the microbial stimulus affecting sporophore formation in Agaricus bisporus (Lange) Sing

An apparatus is described in which pure cultures of Agaricus bisporus were maintained on composted media in filtered atmospheres free from (a) noxious concentrations of carbon dioxide, and (b) contaminating microorganisms. When grown on compost alone, cultures of A. bisporus did not produce sporophores. Their formation was however stimulated by a covering layer of an unsterilized mixture of peat and chalk (=‘casing’ soil). Autoclaving or fumigating ‘casing’ with propylene oxide decreased populations of contaminating bacteria and prevented sporophore formation. Populations of micro-organisms isolated from unsterile ‘casing’ contained bacteria which when added to pure cultures of A. bisporus stimulated fruit-body formation. Numbers of these stimulators increased when cultured on a carbon-free liquid medium exposed to atmospheres with ethanol, ethyl acetate and acetone or containing the volatile metabolites of A. bisporus. The ability to utilize these volatile chemicals was exploited in a selective technique for isolating sporophore stimulators where aqueous suspensions of mixed bacterial populations were exposed to atmospheres of these materials for 5 days, before aliquots were added to agar media subsequently gelled. The stimulatory bacteria were identified as, or closely related to, Pseudomonas putida.     

Effects of some systemic imidazole and triazole fungicides on white clover and symbiotic nitrogen fixation by Rhizobium trifolii

Effects of prochloraz, imazalil, diclobutrazol, triadimefon and propiconazole were studied. Compared with most systemic fungicides previously tested they were all relatively toxic to R. trifolii on agar. Effects of soil residues of the compounds on the growth and nitrogen fixing capacity of white clover were measured. The lowest concentration of the fungicides used was that which would be present if all the active ingredient from a single application remained unchanged and evenly distributed in the top 5 cm of soil. This concentration of diclobutrazol decreased the size and weight of 11-wk-old clover plants. The rate of nitrogen fixation was reduced by twice this concentration and root nodulation by four times this amount. None of the other fungicides had any significant effect. The possibility of field application of diclobutrazol to cereals causing damage to clover crops is discussed. It is questionable whether harmful soil residues will ever accumulate from normal usage of the fungicide but exceeding the recommended rate of application, or application to cereals undersown with clover, might cause undesirable effects on the clover.     

Novel microsatellite loci identified from the Australian eastern small‐eyed snake (Elapidae: Rhinocephalus nigrescens) and cross species amplification in the related genus Suta

A total of 15 microsatellite primers pairs were developed for the Australian small‐eyed snake Rhinoplocephalus nigrescens. Five primers were used to screen 93 individuals of R. nigrescens and were also tested against eight species of the closely related genus Suta. Allelic diversity in R. nigrescens was high in three loci (12–27) and there was high heterozygosity (0.58–0.82). Observed heterozygosity did not deviate from Hardy–Weinberg expectations for the five loci tested. These primers will be useful in studies of population genetics and mating systems of small‐eyed snakes and related species.