Soliton-like and non-soliton regimes of interaction of taxis waves (illustrated with an example of bacterial population waves)

It has been shown in our previous studies that, during collision, bacterial population waves can penetrate each other or stop. In the present study, the mechanism of the two regimes of interaction is considered in detail. Based on the experimental and theoretical research, it has been shown that this interaction is a vivid example to confirm one of the characteristic properties of waves in cross-diffusion systems.     

Formation of demarcation zones when bacterial population waves are drawn together

Many motile bacteria (for instance, Escherichia coli) inoculated at some point in a semisolid nutrient medium can form population waves: bands or rings. The formation of these motile structures is due to chemotaxis. The population waves when they are drawn together can form two types of non-motile structures. Firstly, the population waves can collide. Secondly, in certain conditions, the waves can slow down and stop without coming into contact directly with each other. In this way demarcation zones are formed. The mechanism of the occurrence of the demarcation zones has been unknown. In this paper we show that formation of these zones is due to lack of nutrients (which at the same time act as attractants) within the narrow gap between individual bacterial populations.     

Action of the products of the vital activity of yeastlike fungi on the biosynthesis of levorin, levoristatin and fatty acids by a Streptomyces levoris culture

The data on the effect of the products of vital activity of Candida tropicalis, a yeast-like fungus, on the biosynthesis of levorin, levoristatin and fatty acids by Streptomyces levoris are presented. It was shown that the effect of the biostimulators was not specific with respect to production of levorin, since in the presence of the products of vital activity of C. tropicalis an increase in the synthesis of levoristatin and fatty acids was also observed. The qualitative and quantitative composition of the fatty acids of the mycelium of S. levoris was studied. Interrelation between the biosynthesis of levorin and synthesis of unsaturated fatty acids and branched chain fatty acids was noted.     

Comparative characteristics of some actnomycetes, producers of antifungal antibiotics related to chondamycin]

Three actinomycetous strains designated as LIA-0773, LIA-0783 and LIA-0780 were isolated from various soil samples. The cultures actively inhibited the growth of Trichophyton gipseum and produced a non-polyenic antibiotic of the chondamycin type. The strains were identified with Act. griseochromogenes Fukunaga et. al., 1955. The cultures differed within the species by some morphological, cultural, physiological and antibiotic properties, as well as by the component composition of the antibiotic produced. Thus, strain LIA-0773 had larger spiral sporophores, satisfactorily hydrolized starch and inverted sucrose. The strain inhibited the growth of not only the fungi but also grampositive bacteria and mycobacteria and produced an antibiotic composed of 6 components. Strain LIA-0780 had small sporophores with close spirals and low amilolytic activity. It inhibited only the growth of the fungi and produced a monocomponent antibiotic. Strain LIA-0783 was intermediate. By its biological properties it was closer to strain LIA-0780. The antibiotic produced by it consisted of 6 components, while by its physico-chemical properties the antibiotic was close to that produced by strain LIA-0780. All the 3 actinomycetous cultures were considered as different variants of Act. griseochromogenes Fukunaga et al., 1955.     

The pea (Pisum sativum L.) genes sym33 and sym40 control infection thread formation and root nodule function

Two novel non-allelic mutants that were unable to fix nitrogen (Fix^?) were obtained after EMS (ethyl methyl sulfonate) mutagenesis of pea (Pisum sativum L.). Both mutants, SGEFix^?–1 and SGEFix^?–2, form two types of nodules: SGEFix^?–1 forms numerous white and some pink nodules, while mutant SGEFix^?–2 forms white nodules with a dark pit at the distal end and also some pinkish nodules. Both mutations are monogenic and recessive. In both lines the manifestation of the mutant phenotype is associated with the root genotype. White nodules of SGEFix^?–1 are characterised by hypertrophied infection threads and infection droplets, mass endocytosis of bacteria, abnormal morphological differentiation of bacteroids, and premature degradation of nodule symbiotic structures. The structure of the pink nodules of SGEFix^?–1 does not differ from that of the parental line, SGE. White nodules of SGEFix^?–2 are characterised by “locked” infection threads surrounded with abnormally thick plant cell walls. In these nodules there is no endocytosis of bacteria into host-cell cytoplasm. The pinkish nodules of SGEFix^?–2 are characterised by virtually undifferentiated bacteroids and premature degradation of nodule tissues. Thus, the novel pea symbiotic genes, sym40 and sym33, identified after complementation analysis in SGEFix^?–1 and SGEFix^?–2 lines, respectively, control early nodule developmental stages connected with infection thread formation and function.     

A synthetic derivative of plant allylpolyalkoxybenzenes induces selective loss of motile cilia in sea urchin embryos.

Polyalkoxybenzenes are plant components displaying a wide range of biological activities. In these studies, we synthesized apiol and dillapiol isoxazoline analogues of combretastatins and evaluated their effect on sea urchin embryos. We have shown that p-methoxyphenyl isoxazoline caused sea urchin embryo immobilization due to the selective excision of motile cilia, whereas long immotile sensory cilia of apical tuft remained intact. This effect was completely reversed by washing the embryos. The compound did not alter cell division, blastulae hatching, and larval morphogenesis. In our hands, the molecule would serve as a convenient tool for in vivo studying morphogenetic processes in the sea urchin embryo. We anticipate that both the assay and the described derivative could be used for studies in ciliary function in embryogenesis.