[Structural stability of DNA of the transposon derivatives of pCA25 plasmid].

Mutants of Erwinia carotovora subsp. carotovra 48A carrying plasmid pCA25 and its transposon variant and resistant to mitomycin C, nalidixic acid and streptomycin were used in the research. It has been shown that the presence of transposon in plasmid pCA25 (strain 48A-7/4b[pCA25::Tn9]) does not practically affect the frequency of appearance of the stable bacterial mutants under the effect of all three antibiotics. Several variants, the plasmid profile of which differs from the initial one were found only in the case of this strain clones resistant to mitomycin C. Electrophoretic mobility of the plasmid DNA of the mutant clones 31 and 32 decreased and approached mobility of the initial plasmid pCA25, the mutant plasmid 13 had high electrophoretic mobility compared to pCA25::Tn9. Some plasmids are the deletion variants of pCA25::Tn9, one of two IS1-elements of the transposon Tn9 being absent in them. The obtained results indicate that the studied plasmid pCA25 is stable, is not eliminated from the cells under different treatments and confirm once more the hypothesis of the prophage origin of the plasmid. The paper is presented in Russian.

[Peculiarities of morphogenetical development of erwiniophage ZF40 virulent mutants ].

The distortion of morphopoiesis or tail attachment to the capsid is a characteristic feature of morphogenetical development not only of a reproductive infection but also of the lysogenic induction of the defective bacteriophage Erwinia carotovora subsp. carotovora (Ecc). A model system for studying morphogenetical development and assembling of the virion was created on the basis of the phage ZF40 and its two virulent mutants ZF40-421 and ZF40(5/5), as well as the indicator culture Ecc M2-4/50 R1 being nontraditional host for these phages. It has helped to establish that the diameter of the phage capsid is not a conservative value. The presence of capsids of two types with the average diameters 60.3 and 65.0 nm is characteristic of the virmutant ZF40c(5/5)/50RI, while in the course of morphogenesis the phage ZF40-421/50RI forms only one type of heads of 65 nm in size. These heads are probably not firmly connected to the tails since the degree of the secondary destruction of the virions of the phage Zf40-421/50RI is considerably higher, than that of the virions of the phage ZF40c(5/5)/50RI. The number of capsids being 60.3 nm in diameter prevails considerably in the latter. The both virulent mutants as a whole are essentially more stable than their isogenic partners obtained on Ecc RC5297 which helps to make a conclusion about considerable influence of specific bacterial proteins of the host-cell on morphogenesis and morphopoiesis.

[Detection of bacteriophages of siphoviridae family in Erwinia carotovora subsp. carotovora].

It was established that the polylysogenic phage system of culture Erwinia carotovora subsp. carotovora 91P includes: a) defective bacteriophages of Myoviridae family, which are displayed as macromolecular carotovoricins b) valuable highly unstable temperate phage, which can be attributed to the family Myoviridae, and which, perhaps, is an analogue of phage ZF40 [6], and c) resistant to osmotic shock temperate phage of family Siphoviridae. This phage, called TIRI, consists of isometric head 50 nm in diameter and a rigid tail structure 203 nm long. A characteristic feature of the phage tail is an evident transverse striation, which is also indicative for the tail-like particle of the defective temperate phage of the strain 48A-7/4b. In general, the phage system of E carotovora subsp. carotovora is similar to Pseudomonas aeruginosa with its R- and F-bacteriocins, and phages of the families Myoviridae and Siphoviridae.

[Abortive infection in Erwinia carotovora, as a source of nanoparticles of phage nature].

A possibility to obtain nanoparticles of phage nature using abortive phage infection was shown for the first time. It was found out that the nonspecific host Erwinia carotovora subsp. carotovora J2 being infected by phage ZF 40-RT80, the cells form a 100-fold surplus of capsid structures. Using the electron microscope the authors have found two types of phage capsids which differ from each other and have different modal diameters--47.5 and 71.5 nm. The found capsids pack the phage DNA which releases them under treatment of the preparations by DNAse I. A simple method of purification of capsid structures from mature virions which are formed in inconsiderable quantity in the process of abortive phage infection is proposed. The obtained results create preconditions for obtaining capsid nanoparticles as well as for studying the stages of morphogenesis and morphopoiesis of phage ZF40 without attracting special phage mutants.

[Preliminary characteristic of DNA-containing virus-like particles of Erwinia carotovora].

DNA-containing particles formed by the expression of the defect prophages of E. carotovora subsp. carotovora (Ecc) have been revealed for the first time. Two types of virus-like particles (VLP) occur in this phytopathogenic bacterium. Capsides of the first type VLP are weakly identified at agarose electrophoretic separation while DNA released from them are presented by distinct reflexes. Mobility of the second type particles is close to that of separate capsids of the temperate phage ZF40. DNA packed in these VLP are slightly mobile in agarose gels and are, most likely, typologically close to the open ring forms. Molecules of DNA particles of the both types possess the size equal to or more than 50 t.p.n. It is shown that DNA-containing VLP prevail in lysates obtained at lysogenic induction of cells by nalidixic acid, while the induction by mitomycin C is mainly characterized by formation of biologically active tails of defective temperate phages. The obtained result create preconditions for studying molecular-genetic organization of defective prophages and their significance in ecology of the important phytopathogen E. carotovora.

[Characteristic of endogenous plasmids of Pseudomonas aeruginosa collection strains].

Investigation of 70 collection strains of Pseudomonas aeruginosa of various origin on content of extrachromosomal DNA has shown that about 20% of them contain plasmids of discrete dimensions: 3.80; 5.89; 6.756; 23.4; 30.2; 32.3; 39.8; 40.7; 94.3 bk. Plasmid-containing strains have been found only among clinical isolates which accompanied the outbreaks of infections diseases in 1968 (Kyiv city). A preliminary analysis proves that plasmids can characterize the ecological niche with persistence of the strains of P. aeruginosa.