Pigmentation changes in Brevibecteria induced by mutagenic treatment

Inducible pigmentation changes were observed in pigmented strains of Brevibacterium sp. M27 and B. flavum treated with N-methyl-N'-nitro-N-nitrosoguanidine. The highest frequency of induction was reached already at a survival of 30-40% with the maximal yield of 6-10%. As compared with the initial yellow colour, three new pigmentation types, viz. white, pink and orange, were observed. The yellow pigmented parent strains are most resistant to the lethal effects of UV radiation. By selecting pigmented mutants of all types on media containing antibiotics it was possible to obtain strains that were resistant either to tetracycline or to streptomycin. Auxotrophic pigmented mutants were also isolated. In multiple mutant strains of Brevibacterium sp. M27 a number of strainsexhibited a changed L-lysine production. In some strains the production was variable, whereasother strains did not produce L-lysine at all and stains with a limited production of other amino acids were also detected.     

Saprophytic production of Clavine alkaloids and activity of Hydroxymethylglutaryl-CoA reductase

In submerged Claviceps cultures the activity of hydroxymethylglutaryl-CoA reductase preceded the increase of alkaloid production and of sterol content. During the first alkaloid phase, cell mevalonate was involved in the biosynthesis of both alkaloids and steroids. In the second production phase, it was predominantly used for alkaloid synthesis. Hydroxymethylglutaryl-CoA reductase appears to be a suitable target for physiological manipulation to increase clavine alkaloid yields.     

TheX → Y → Z scheme after 23 years

Mathematical modelling of the course of the immune response is undoubtedly one of the most progressive and most promising areas of modern immunology. Mathematical models (along with computer programs) can be taken as "the only means of thoroughly testing and examining a large and intricate theory" (Partridge et al. 1984). The first phase of construction of mathematical models is the formulation of assumptions based on the knowledge of the facts to be modelled (manifested usually in a scheme of the presumed course of the modelled process). The first mathematical models of immune response were based on the hypothesis of a two-stage differentiation of cells participating in the humoral response, published in Prague 23 years ago (Sercarz and Coons 1962; Sterzl 1962) and illustrated by the X----Y----Z scheme. Many contemporary mathematical models still stem from this scheme which undoubtedly fits the fundamental data concerning the immune system.     

Effect of glucose on the amount of bacteria mineralizing 2,4-dichlorophenoxyacetic acid in soil

Plate numbers of bacteria and relative incidence of strains capable of mineralization of 2,4-dichlorophenoxyacetic acid (2,4-D) in chernozem samples incubated for 14 d with the herbicide (50 ppm) in the presence or absence of glucose (1000 ppm) were compared. Whereas the total number of bacteria increased 1.2-fold in the variant with 2,4-D and 2.4-fold in the variant with glucose and the herbicide, the number of 2,4-D-mineralizing bacteria increased 12.1-fold and 34.2-fold, respectively. In a collection of 96 isolates of soil bacteria substantially more strains capable of degradation of 2,4-D in the presence of glucose were detected as compared with the variant without it, indicating that processes of cometabolic type are involved during the degradation of this herbicide in the soil.     

The comparison of seed protein patterns within the genusArachis by polyacrylamide gel electrophoresis

The seed protein patterns of 12Arachis species were compared by polyacrylamide gel electrophoresis (PAGE), similarities between patterns were measured by the Jaccard index. Results obtained confirm the close relationships established between members of the genus on morphological grounds and support the more recent classification schemes.A. villosa andA. correntina could well be regarded as distinct species on grounds of protein differences whileA. macedoi andA. villosulicarpa (although members of the same section, Extranervosae) show considerable differentiation of their protein patterns. Surprisingly, the formA. ×batizogaea showed less similarity in protein pattern to those of its parental species than might have been expected. The principle value of seed protein pattern data appears to be in distinguishing species within sections.     

Differential tolerance ofArabidopsis thaliana crown gall tumors and calli to 5-bromo-2′-deoxyuridine

The degree of tolerance of two crown gall tumors and leaf calli ofArabidopsis thaliana to BUdR was compared. The nopaline producing teratoma tumor tolerated BUdR in concentration as high as 2.10^?4 M. The tolerance of octopine producing unorganized crown gall tumor to BUdR was lower, but both exceeded significantly the degree of tolerance to BUdR of untransformedA. thaliana calli, where 10^?5 M BUdR already show some inhibitory effect on the growth rate.     

New subspecies ofSparganium erectum L. from Iran

From the Caspian coastal region of Iran a new taxon,Sparganium erectum L. subsp.mazanderanicum Ponert, is described and illustrated. This new subspecies in some of its characters is near toSparganium erectum L. subsp.microcarpum (Neumann)Domin (with its east distribution trend); in other characters it is near toSparganium erectum L. subsp.neglectum (Beeby)Schinz etThell. (with ist south distribution trend). A comparative table of diacritical characters of these three subspecies is appended.