Microbial transformation of steroids

A systematic study of transformation reactions of Actinomycetes with respect to the progesterone molecule was undertaken. The results obtained, i.e. the types of transformation reactions in different actinomycete species, were evaluated from the point of view of taxonomy. The actinomycetes tested were divided according to the transformation types into three groups: (1) a group of species transforming progesterone in the 16α-position; (2) a group of species transforming progesterone in the β-position; (3) a group of species in which no capacity to transform progesterone into another steroid derivative was established. From the point of view of Actinomycete classification the transformation reactions on the steroid molecule fulfil all the requirements of taxonomic features of Actinomycetes. They appear to be specific properties, independent of strictly cultivation conditions and common to all the strains of individual actinomycete species tested.     

A TAXONOMIST'S VIEW OF THE COLI-AEROGENES BACTERIA

SUMMARY: Examples are given of different names that might be applied to the same organisms when the scheme of classification is changed. In particular, the classification of the Coli-Aerogenes (1956) Sub-Committee of the Society for Applied Bacteriology and the proposed nomenclature are discussed.     

Competition for sulphur in a grass-clover association

Summary A 3 × 3 factorial experiment with nitrogen and sulphur fertilizers was carried out on a grass-clover association in an area where there is little if any cyclic return of sulphur. In the absence of sulphur, grass took up 98 per cent of the total uptake of sulphur, and nitrogen fixation by associated clover was negligible. In the absence of fertilizer nitrogen, dressings of sulphur as gypsum stimulated clover growth; at a low rate of application of sulphur, nitrogen fertilizer increased grass growth and clover was suppressed. This suppression was largely overcome with a higher dressing of sulphur. Sulphur therefore must be added to the group of elements (phosphorus, nitrogen and potassium) for which grass may compete intensely when grown with clover and when nitrogen fertilizers are applied to a grass-clover association adequate supplies of sulphur must be assured in order to minimise suppression of clover. Sulphate of ammonia may stimulate clover growth under these conditions. Solubility of gypsum was low in a dry season and residual effects were pronounced.     

Isolation of adenosine 5'-diphosphate-L-glycero-D-mannoheptose, the assumed substrate of heptose transferase(s), from Salmonella minnesota R595 and Shigella sonnei Re mutants

From heptose transferase-less Re mutants of Salmonella minnesota and Shigella sonnei, a mixture of nucleotide-linked heptoses was isolated. After paper chromatography in different solvent systems, ADP derivatives of D-glycero-D-mannoheptose and L-glycero-D-mannoheptose could be isolated in pure form. The structure of ADP-L-glycero-D-mannoheptose was verified by analytical methods and by transformation of ADP-D-glycero-D-mannoheptose with ADP-D-glycero-D-mannoheptose-6-epimerase.     

Tau, sigma, and delta. A family of repeated elements in yeast

We report here the isolation and structure of a new repeated DNA element, tau. This element, from Saccharomyces cerevisiae, is 371 base pairs long and is flanked on either end by the same invertedly repeated sequence found at the ends of some Ty and sigma elements in yeast, copia elements in Drosophila and spleen necrosis virus. The tau inverted repeats are themselves flanked by a 5-base pair directly repeated genomic sequence that is present only once in a cognate tau-allele. These structural characteristics, the presence of multiple copies of tau in the genome, and the isolation of tau+ and tau- allelic pairs suggest that tau may be capable of transposition either alone or in association with some larger element. Detailed sequence analysis of the tau, sigma, and delta elements revealed that all three contain significant regions of homology, suggesting that they are probably members of a single family derived from a common progenitor.     

An innovative lattice Boltzmann model for simulating Michaelis–Menten-based diffusion–advection kinetics and its application within a cartilage cell bioreactor

Lattice Boltzmann models (LBM) are rapidly showing their ability to simulate a lot of fluid dynamics problems that previously required very complex approaches. This study presents a LBM for simulating diffusion–advection transport of substrate in a 2-D laminar flow. The model considers the substrate influx into a set of active cells placed inside the flow field. A new innovative method was used to simulate the cells activity using the LBM by means of Michaelis–Menten kinetics. The model is validated with some numerical benchmark problems and proved highly accurate results. After validation the model was used to simulate the transport of oxygen substrates that diffuse in water to feed a set of active cartilage cells inside a new designed bioreactor.