Plasmids of the cyanobacterium Synechocystis sp. 6803

Three cryptic plasmids have been isolated from cyanobacterium Synechocystis sp. 6803::pSS2 (1.4 Md), pSS3 (36 Md), pSS4 (60 Md). Plasmid DNA was isolated in Cs-Cl-EB density gradient and analyzed by gel electrophoresis and electron microscopy by gel electrophoresis and electron microscopy techniques. The restriction map is constructed for plasmid pSS2 having the cleavage sites for Sau3a, HincII, HindIII, MspI restriction endonucleases. The plasmid may be used to construct the recombinant vector DNAs capable of autonomous replication in cyanobacterium Synechocystis sp. 6803. cells.     

Directed isolation of Micromonospora generic cultures on a selective medium with gentamycin

The results of using selective media with gentamicin for directed isolation of Micromonospora are presented. It was shown that the use of the selective media with gentamicin for isolation of actinomycetes from soils of usual humidity levels markedly increased the frequency of Micronomonospora detection. The use of the selective media with gentamicin for plating out silt substrates containing mainly Micromonospora had practically no effect on the increase in the number of the Micromonospora cultures grown. The number of antibiotic-producing Micromonospora isolated on the media with gentamicin was 3 times higher than that on the control media. The use of the selective media with gentamicin provided directed isolation of Micromonospora.     

Fertility of the flea, Xenopsylla gerbilli Minax, that parasitizes the great gerbil (Aphaniptera)]

It has been established experimentally that the fecundity of females of Xenopsylla gerbilli minax is wavy in its character from the beginning to end of their reproduction (peaks are replaced by falls). In spring and summer the egg laying proceeds on the 2nd--3rd day after the first bloodsucking of fleas and lasts to the end of their life. In autumn the first eggs develop on the 4th--6th day and do not develop at all at the end of the life. In winter months the egg production is somewhat slowed down but with the coming of spring become more intensive. Progeny obtained from one female during the experiment varies, depending on the conditions of the maintenance, from 20 to 130 individuals.     

Methodological procedures for detecting antibiotic producers among cultures of the family Micromonosporaceae]

Data on intensification of the search for active cultures among Micromonospora are presented. It was shown that the frequency of detecting the antibiotic-producing cultures among Micromonospora under conditions of fermentation on the corn-glucose medium inoculated with agar blocks amounted to 35 per cent. The use of nutrient media of different composition for growing submerged inoculum of Micromonospora demonstrated that the rate of its growth reached maximum on the peastarch medium. The use of this medium for growing submerged seed material for fermentation in the corn-glucose medium increased the frequency of detecting active cultures from 35 to 43.1 per cent. The assay of Micromonospora antibiotic activity twice, i.e. in 96 and 240 hours of the fermentation process increased the frequency of detecting active cultures up to 57.1 per cent and revealing greater variety of antibiotics. Fermentation of Micromonospora cultures simultaneously on 6 different nutrient media inoculated with submerged seed mycelium and assay of the activity for 2 times, i. e. in 96 and 240 hours allowed a detection of up to 76.2 per cent of active strains out of the total number of the isolates.