RESUMO
The formation of polycellular forms by E. coli strain K-12 cells containing F-like plasmids pAP22-2 and pAP42 was studied by the method of small-angle laser scattering. The efficiency and patterns of the resultant cell associations depend on genetic characteristics of the studied plasmids.
Assuntos
Escherichia coli/genética , Plasmídeos/genética , Escherichia coli/metabolismo , Pili Sexual/metabolismoRESUMO
On the basis of transfer factor pAP42 and nonconjugative plasmids pRSF2124 and pUB781, the cointegrative plasmids pAP42/pRSF2124 and pAP42/pUB781 were constructed. Complex systems of plasmid transfer inhibition (funU and finV) were detected in the structure of cointegrative plasmids.
Assuntos
Elementos de DNA Transponíveis/genética , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica/genética , Plasmídeos/genética , Replicon/genética , Conjugação Genética/genética , Fator F/genéticaRESUMO
The role E. coli K-12 cell chromosome genetic region (tis-region) in expression of fin V-transfer inhibition system of F-like plasmid pAP53 was shown. The results obtained testify the linkage of tis region and Thr-Leu chromosomal segment.
Assuntos
Cromossomos Bacterianos , Escherichia coli/genética , Fator F/genética , Regulação Bacteriana da Expressão Gênica/genética , Leucina/genética , Treonina/genética , Genes Bacterianos , Ligação Genética , Recombinação GenéticaRESUMO
Natural plasmid complex pAP18 discovered in E. coli cells consists of F-like plasmid pAP18-1 (Tc, ColV) and N-like plasmid pAP18-2 (Sm) which differ in their genetic transfer. Plasmid pAP18-1 is able to inhibit transfer of plasmid pAP18-2 but not vice versa. These systems are active both in cells of serologically typed and untypable E. coli strains.
Assuntos
Conjugação Genética/genética , Escherichia coli/genética , Plasmídeos/genética , Tipagem de Bacteriófagos , Colífagos , Escherichia coli/classificação , Fator F/genética , Fímbrias Bacterianas , SorotipagemRESUMO
The results of investigation of serologically--typed and nontyped E. coli cells carrying F-like derepressed plasmid pAP42 testified to the influence of genome of some bacterial hosts on the expression of plasmid genetic region determining "sex" (plasmid--specific) pili synthesis and surface exclusion system (Sfx--system). Similar changes in bacterial cells phenotype can also result from the mutational changes of this plasmid.
Assuntos
Escherichia coli/genética , Fímbrias Bacterianas , Expressão Gênica , Plasmídeos , Colífagos/genética , Genes Bacterianos , Mutação , FenótipoRESUMO
With help of molecular cloning the genetic region controlling incompatibility of plasmid pAP18-1 (Inc FXI) was localized in EcoR1-fragment f5 (3.6 MD). The genetic region of incompatibility of its derepressed mutant pAP18-1drd (Inc FVII) is situated in EcoR1-fragment f2 (7,2 MD).
Assuntos
Plasmídeos , Clonagem Molecular , DNA Bacteriano/genética , Escherichia coli/genética , Genes Bacterianos , Mutação , Mapeamento por RestriçãoRESUMO
The study of structural and functional features of plasmid-specific pili synthetized by E. coli cells under control of 27 F-like plasmids was performed. All the plasmids determined the pili of "flexible" type which were classified into 3 groups on the basis of difference in cell sensitivity to pili-specific phages f1, f2, Q. The possible role of transposons in the variation of pili functional properties was supposed.
Assuntos
Fator F/genética , Fímbrias Bacterianas/ultraestrutura , Genes Bacterianos/genética , Plasmídeos/genética , Conjugação Genética , Elementos de DNA Transponíveis/genética , Escherichia coli/genética , Escherichia coli/ultraestrutura , Fímbrias Bacterianas/fisiologia , Regulação Bacteriana da Expressão Gênica/genética , Microscopia EletrônicaRESUMO
The F-like plasmids belonging to 5 different Sfx-groups were discovered. The existence of atypical plasmids belonging to different Sfx-groups was shown. The molecular cloning of plasmid DNA fragment (3.9 mD) determining SfxII phenotype was performed.
Assuntos
Escherichia coli/genética , Fator F , Regulação Bacteriana da Expressão Gênica , Clonagem Molecular , Conjugação Genética , FenótipoRESUMO
The results of complementation analysis of nitrosoguanidine-induced mutants of F-like drd-plasmid pAP18-1 (Tc, ColV) testified to the existence of at least 3 tra regions (tra1, tra2, tra3) and regulating locus fin V in the genome of this plasmid. By means of molecular cloning of tra2 region and locus fin V of plasmid pAP18-1drd were located in Sall-fragment f5 (3.9 MD).
Assuntos
Escherichia coli/genética , Fator F , Clonagem Molecular , Conjugação Genética , Elementos de DNA Transponíveis , Eletroforese , Genes Bacterianos/genética , Teste de Complementação Genética , Fenótipo , Mapeamento por RestriçãoRESUMO
The search of nonconjugated plasmids in antibiotic-resistant cells of wild E. coli strains was performed and their transposon maintenance has been studied. The possibility of existence of some different nonconjugated plasmids in one bacterial cells was shown and each plasmid could carry the same transposon. Insertion of one transposon into the conjugated plasmid pAP42 resulted in numerous deletions in the genome of this plasmid.
Assuntos
Conjugação Genética , Elementos de DNA Transponíveis , Escherichia coli/genética , Plasmídeos , Resistência Microbiana a Medicamentos/genética , Marcadores Genéticos , Peso Molecular , Mapeamento por RestriçãoRESUMO
Relation between induced mutations of plasmid pAP18-1 (Tc, Col) and alterations in it's restriction map was studied. Nitrosoguanidine induced mutations of transfer regulation system and incompatibility of this plasmid related with alteration in the situation of recognition sites for restrictases EcoR1 and Sal1 in map positions 42.2-4.3 and 12.9-17.9 MD. Insertions of transposons Tn5 and Tn9 into the plasmid DNA resulted in a decrease of incompatibility level.
Assuntos
Elementos de DNA Transponíveis , Fator F/efeitos dos fármacos , Mutação , Nitrosoguanidinas/farmacologia , Sequência de Bases/efeitos dos fármacos , Mapeamento Cromossômico , Conjugação Genética/efeitos dos fármacos , Enzimas de Restrição do DNA , DNA Bacteriano/efeitos dos fármacos , DNA Bacteriano/genética , Resistência Microbiana a Medicamentos/genética , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Marcadores Genéticos/efeitos dos fármacosRESUMO
Complementation analysis of a number of conjugative transfer functions was performed in derepressed (drd) mutants of E. coli F-like plasmids. The major part of double plasmid complexes investigated has revealed the formation of complementation transfer inhibitor of Fin V-type, or less frequently--the formation of Fin U-type inhibitor. An additional complementation analysis of drd plasmids defective at Fin V region genes has demonstrated at least three genes (denoted A, B, C) in the structure of this region.
Assuntos
Repressão Enzimática , Escherichia coli/genética , Teste de Complementação Genética , Mutação , PlasmídeosRESUMO
The data are reviewed on the genetic structure and regulation of tra-genes activity controlling the conjugative transfer of F, F-like plasmids as well as the transfer of some other bacterial plasmids. The effect of the systems inhibiting the conjugational transfer (fin-systems) of F and a number of derepressed F-like plasmids has been characterized on the basis of data obtained by the authors or published data. Possible mechanisms for the systems functioning in the regulation of tra-genes activity are discussed as well as the prospects of their further study.
Assuntos
Fator F , Genes Bacterianos , Genes Reguladores , Bactérias Gram-Negativas/genéticaRESUMO
The ability of standard plasmids of six Fin-groups to inhibit the functions of genes transferring derepressed F-like plasmids has been studied. It is shown that transposons incorporation into the structure of individual plasmids alters the regulatory system of plasmid tra-genes.