ABSTRACT
The ardA genes are present in a wide variety of conjugative plasmids and play an important role in overcoming the restriction barrier. To date, there is no information on the chromosomal ardA genes. It is still unclear whether they keep their antirestriction activity and why bacterial chromosomes contain these genes. In the present study, we confirmed the antirestriction function of the ardA gene from the Bifidobacterium bifidum chromosome. Transcriptome analysis in Escherichia coli showed that the range of regulated genes varies significantly for ardA from conjugative plasmid pKM101 and from the B. bifidum chromosome. Moreover, if the targets for both ardA genes match, they often show an opposite effect on regulated gene expression. The results obtained indicate two seemingly mutually exclusive conclusions. On the one hand, the pleiotropic effect of ardA genes was shown not only on restriction-modification system, but also on expression of a number of other genes. On the other hand, the range of affected genes varies significally for ardA genes from different sources, which indicates the specificity of ardA to inhibited targets. Author Summary. Conjugative plasmids, bacteriophages, as well as transposons, are capable to transfer various genes, including antibiotic resistance genes, among bacterial cells. However, many of those genes pose a threat to the bacterial cells, therefore bacterial cells have special restriction systems that limit such transfer. Antirestriction genes have previously been described as a part of conjugative plasmids, and bacteriophages and transposons. Those plasmids are able to overcome bacterial cell protection in the presence of antirestriction genes, which inhibit bacterial restriction systems. This work unveils the antirestriction mechanisms, which play an important role in the bacterial life cycle. Here, we clearly show that antirestriction genes, which are able to inhibit cell protection, exist not only in plasmids but also in the bacterial chromosomes themselves. Moreover, antirestrictases have not only an inhibitory function but also participate in the regulation of other bacterial genes. The regulatory function of plasmid antirestriction genes also helps them to overcome the bacterial cell protection against gene transfer, whereas the regulatory function of genomic antirestrictases has no such effect.
ABSTRACT
The bioluminescence induced by luciferases of marine bacteria promotes repair of UV damaged DNA of Escherichia coli AB1886 uvrA6. It is shown that bacterial photolyase that implements photoreactivation activity is the major contributor to DNA repair. However, the intensity of bioluminescence increasing induced by UV-irradiation (SOS-induction) in bacterial cells is not enough for efficient photoreactivation.
Subject(s)
Adenosine Triphosphatases/metabolism , DNA-Binding Proteins/metabolism , Escherichia coli Proteins/metabolism , Escherichia coli/genetics , Luciferases, Bacterial/metabolism , SOS Response, Genetics , Ultraviolet Rays , Adenosine Triphosphatases/genetics , Adenosine Triphosphatases/radiation effects , DNA-Binding Proteins/genetics , DNA-Binding Proteins/radiation effects , Escherichia coli/radiation effects , Escherichia coli Proteins/genetics , Escherichia coli Proteins/radiation effects , Luciferases, Bacterial/genetics , Luciferases, Bacterial/radiation effects , Photobacterium/enzymologyABSTRACT
When transformed into Escherichia coli K12 strains, the mercury resistance transposon Tn5053@ exhibits high antirestriction activity against the EcoKI type I restriction and modification system. The products of the genes merR and ardD contribute to the antirestriction activity of Tn5053. The merR gene encodes the MerR protein, the transcription regulator of the mer operon genes. The ardD gene is responsible for ArdD protein synthesis and is located within the tni operon. In the following study, it was demonstrated that the antirestriction activity of the transposon Tn5053 is absent in E. coli K12 strains with the mutant genes clpX, clpP, and recA. The antirestriction effect of Tn5053 is not enhanced by 2-aminopurine. The Tn5053 antirestriction activity is not altered in E. coli K12 with the mutant dam gene; however, it is decreased in the E. coli K12 mutD. It is assumed that the activities of the MerR and ArdD proteins lead to the formation of a significant amount of unmodified DNA in the bacterial cell, causing the SOS-dependent reduction of the EcoKI (R2M2S) enzyme activity associated with ClpXP-induced proteolysis of the R-subuinit.
Subject(s)
DNA Transposable Elements/physiology , Drug Resistance, Bacterial/physiology , Endopeptidase Clp/metabolism , Escherichia coli K12/metabolism , Escherichia coli Proteins/metabolism , Mercury , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Endopeptidase Clp/genetics , Escherichia coli K12/genetics , Escherichia coli Proteins/genetics , Operon/physiology , Proteolysis , Site-Specific DNA-Methyltransferase (Adenine-Specific)/genetics , Site-Specific DNA-Methyltransferase (Adenine-Specific)/metabolismABSTRACT
Antirestriction proteins ArdA and ArdB are specific inhibitors of the type I restriction-modification enzymes. The transmissible plasmid R64 ardA and yfeB (ardB) genes were cloned in pUC18 and pZE21 vectors. It was shown that the R64 ArdA and ArdB proteins inhibit only restriction activity of the type I restriction-modification enzyme (EcoKI) in Escherichia coli K12 cells. The dependence of the effectiveness of the antirestriction activity of the ArdA and ArdB proteins on the intracellular concentration was determined. Antirestriction activity of ArdB is independent from the ClpXP protease. Transcription of yfeB (ardB) gene in R64 plasmid is realized from the yfeA promoter.
