Biomedical subjects
A A Prozorov
Publications and source records attributed to A A Prozorov.
[Conjugative transfer of the large plasmid p19 in various Bacillus subtilis strains].
Cryptic conjugative plasmid p19 from the environmental Bacillus subtilis strain 19 was labeled with the cat gene conferring resistance to chloramphenicol. The resulting plasmid, p19cat, was used to estimate the transfer frequency, to study the dynamics of plasmid transfer, and to detect some specific features of conjugation between various B. subtilis strains.
Plasmid transfer in bacilli by a self-transmissible plasmid p19 from a Bacillus subtilis soil strain.
The cryptic 95-kb plasmid p19 of the Bacillus subtilis 19 soil strain promotes the transfer of a small kanamycin resistance plasmid pUB110. To facilitate direct selection for p19 transfer, a plasmid derivative carrying the chloramphenicol resistance gene was constructed. The frequency of transfer of the large plasmid between cells of B. subtilis 19 approached 100% but was more than two orders of magnitude lower when the strain B. subtilis 168 was a recipient. However, when the restriction-deficient strain B. subtilis 168 was a recipient, the transfer efficiency was almost completely recovered. The effectiveness of pUB110 mobilization was virtually not altered in all these cases. pC194 was not mobilized by p19. The kinetics of p19 conjugative transfer is also presented.
[Inter- and intraspecies conjugal transfer of different plasmids in bacilli].
Conjugal transfer of plasmid pUB110 between different strains of bacilli was studied. The plasmid transfer was possible not only between various strains of B. subtilis, but also when many other species of bacilli served as recipients. Conjugation of a donor strain B. subtilis 19 (p19pUB110) was accompanied by a transfer of plasmid p19 along with plasmid pUB110 to the B. subtilis recipient strains lacking a large plasmid p19. If, like the donor cells, the recipient B. subtilis strain carried plasmid p19, the frequency of conjugation decreased. The small plasmid pBC16 was also capable of conjugative transfer. However, if this plasmid carried the mob gene with an inverted region, the frequency of its transmission dramatically decreased. If the donor strain contained another small plasmid, pV, which also carried the mob gene, the efficiency of transmission was partially restored.
[The ISBsu2 mobile element is present in a plasmid of a soil strain and in the chromosomes of several other strains of Bacillus subtilis].
Chromosomes of several Bacillus subtilis strains were shown to contain homologs of the ISBsu2 mobile genetic element, which was earlier revealed in a cryptic plasmid of a soil strain of B. subtilis.
[High frequency conjugative mobilization in natural strains of Bacillus subtilis, bearing a large plasmid].
Conjugative properties of the strain Bacillus subtilis that carrying a large plasmid approximately 95 kb in size and isolated in Belarus from forest soil were described. The staphylococcal plasmid pUB110 that had previously been introduced into this strain was transferred to recipient cells of the Bacillus subtilis 168 strain with a frequency of approximately 10(-2). The transfer occurred with approximately the same frequency both upon donor and recipient cell contact on the surface of membranes and in a liquid medium. The latter fact makes this system suitable as a model for studying conjugal mobilization in bacilli. A large plasmid cannot be transferred to recipients. An optimal temperature for conjugation of donor and recipient cells was 37 degrees C, but conjugation also proceeded at lower temperatures, up to 21 degrees C.
[A large conjugative plasmid from a soil strain of Bacillus subtilis].
A large plasmid 35.5 kb in size was found in the soil Bacillus subtilis strain. This plasmids was shown to be capable of conjugal mobilization of small plasmids.
Complete sequence of Bacillus subtilis plasmid p1414 and comparison with seven other plasmid types found in Russian soil isolates of Bacillus subtilis.
We determined the complete sequence of a cryptic 7949-bp plasmid isolated from naturally occurring Bacillus subtilis found in Russian soil from Moscow. We found 15 putative open reading frames (ORFs), all of which were preceded by a ribosome binding site. One encodes the gene (rep) which should be essential for vegetative rolling circle replication (RCR). The putative double-stranded origin as well as a palT1-like single-stranded origin was also identified. The predicted product of another ORF showed similarity to a moblization protein while a third showed similarity to a ubiquitous family of small proteins whose members have so far been associated with stress response. We used fragments with these latter ORFs to probe representatives of seven other groups of cryptic RCR plasmids from geographically related B. subtilis isolates. All plasmids carried the mob function, suggesting a common ancestor for the rep/mob region but the putative hsp was present only on some of the plasmids. This suggests that the putative hsp gene is not an essential plasmid component and may therefore be present as a phenotypic marker-perhaps providing response to stress. This adds weight to the growing evidence that these small Bacillus plasmids may not be cryptic but may provide an adaptive advantage for the host in its natural environment.
[Simultaneous presence of three cryptic plasmids of various size in a soil strain of Bacillus subtilis].
The Bacillus subtilis 1387 soil strain, which contains three cryptic plasmids simultaneously, was described. Two small plasmids (6.3 and 8.5 kb) were homologous to each other, and a large plasmid (30 kb) had no homology with them. The plasmids were separately transmitted into cells of the Bac. subtilis 168 strain, and some plasmid characteristics were analyzed.
[DNA uptake by bacterial cells: a natural process and laboratory techniques].
The mechanisms of DNA uptake during natural transformation of various bacterial species and the methods of the artificial introduction of DNA into bacterial cells and protoplasts are considered. The evolution of views on the bacterial competence and its genetic control during history of investigation of the transformation is discussed.
[Divergence between "early" genes from defective phages of various strains of soil bacilli, close to Bacillus subtilis 168].
The extent of xre gene divergence was studied in nine soil bacillus strains with different degrees of relationship to Bacillus subtilis 168. This gene product is a repressor of defective phages. Bac. subtilis 168 recipient strains were transformed by DNA from these bacillus strains for the xhi-1479 marker and ten markers of amino acid and nitrous bases metabolism. The efficiency of soil strain DNA hybridization with Bac. subtilis 168 DNA was assessed. Eight strains were close to Bac. subtilis 168 with respect to the efficiency of heterotransformation for all markers and hybridization, and one strain (1621) strongly differed from other strains with regard to these parameters. As determined by the degree of differences in heterotransformation for all markers, the nucleotide sequence of the xre gene diverged in the evolution process at a rate similar to that of the nucleotide sequences of the housekeeping genes. All examined genes were shown to have similar selective value.
[Defective phages of bacilli: cell parasites or chromosomal components].
A review of data on defective phages of bacilli is presented. The genetics and morphology of this group of phages, the peculiarities of their induction, and data of sequence analysis of the segment of the bacterial chromosome in which the phage genome is localized are considered. It is concluded that the genome of defective phages should probably be considered a part of the bacterial chromosome rather than the genome of a parasite virus of the bacteria.
[Homology in natural cryptic plasmids of Bacillus subtilis].
Peculiarities of DNA homology in a number of cryptic plasmids isolated from soil bacillary strains and related or identical to Bacillus subtilis were studied. Fragments generated after digestion of one of these plasmids, p1414, were employed as a probe for blot hybridization with identical fragments of other plasmids. The data obtained suggest that nearly all the studied plasmids possess a common homology site that occupies a significant plasmid portion. Regions of detectable and weak homology were located throughout this site. Moreover, plasmid p1414 was shown to carry a large site that lacks homology with plasmids belonging to two groups. Eventually, one of these plasmids demonstrates complete lack of homology with the remaining plasmids.
[Determination and comparative analysis of the nucleotide sequence for minireplicon fragments of the cryptic plasmid p1414 from the soil strain of Bacillus subtilis].
Nucleotide sequences of two minireplicon fragments of the p1414 cryptic plasmid of Bacillus subtilis were determined. The fragments corresponded to the region containing ori(+) and the gene coding for Rep protein. Comparing sequences of the fragments with corresponding sequences of other ss+ plasmids suggested that ori(+) of p1414 belongs to the family of endogenous cryptic B. subtilis plasmids, which form an individual, closely related subgroup in the group of ori(+) sequences of the pC194 type. It was found that the amino acid sequence of a conservative FLTLTV motif located, together with its flanking sequences, at the N ends of Rep proteins encoded by different ss+ plasmids, is similar to those of several transmembrane proteins and signal peptides. These results, together with computer data on predicting the secondary and tertiary structure of the N-terminal domain of the p1414 Rep protein, suggest that the domain can serve as a "membrane anchor" during plasmid replication.
[Genomic structure of bacteria: uniformity or diversity?].
This paper is a survey of data, indicating that, in contrast to widely adopted ideas, bacterial chromosomes and plasmids are not only circular, but also linear. Moreover, certain bacteria contain at least two different chromosomes per cell. Examples of other unusual genome properties in certain representatives of bacteria are also considered.
[RecA-independent induction of the new plasmid rAS1 after introduction of a fragment of the cryptic plasmid p1414 into Bacillus subtilis 168 cells].
Bacillus subtilis 168 was transformed with fragments from the minireplicon of the cryptic plasmid p1414; these fragments were ligated into the cat gene of plasmid pC194. As a result, the 4.6 kb plasmid pAS1 appeared with a low frequency. The plasmid was homologous to the chromosomal DNA of B. subtilis 168, but had no homology with p1414. Plasmid pAS1 had extensive homology (3.2 kb) with plasmid pUB110 and its restriction map in this region of homology correlated well with the restriction map of pUB110. Plasmid pAS1 occurred both in rec+ and recA- cells. We suppose that pAS1 was generated because of the illegitimate recombination between p1414 and the replicon pUB110 incorporated in the chromosome of B. subtilis 168, and the resulting substitution of marker KmR of pUB110 for marker CmR of pC194.
[Allozyme variability in strains of soil bacilli related to Bacillus subtilis].
Allozyme variability in 37 strains of soil bacilli related to Bacillus subtilis was studied. A study of electrophoretic mobility of corresponding enzymes showed that, with one exception the strains did not differ essentially from the standard strain Bacillus subtilis 168 Marburg, in accordance with the results on electrophoretic mobility of corresponding enzymes. However, considerable genetic diversity was revealed at the intraspecific level in the population of bacilli under study. Of the 8 isoenzyme loci, 7 were polymorphic, and the average number of alleles per locus was 3.14. The extent of genetic diversity and the Nei's genetic distance were, on average 0.28 and 0.46, respectively. Significant correlation (r = 0.836) between the value of genetic distance and the level of the DNA-DNA hybridization of the strains was demonstrated.
[Plasmid pAS1, excised from Bacillus subtilis 168 chromosomes].
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