# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 815 | 0 | 0.9342 | The sequence of the mer operon of pMER327/419 and transposon ends of pMER327/419, 330 and 05. Three different, independently isolated mercury-resistance-conferring plasmids, pMER327/419, pMER330 and pMER05, from cultures originating from the river Mersey (UK), contain identical regulatory merR genes and transposon ends. The mer determinant from pMER327/419 contains an additional potential ORF (ORF F) located between merP and merA when compared with the archetypal Tn501. Although these plasmids confer narrow-spectrum resistance (resistance to Hg2+, but not organomercurials) their merR genes encode a potential organomercurial-sensing protein. Transposition of the mer of pMER05 into plasmid RP4 was demonstrated and, as with Tn502 and Tn5053, insertion occurred at a specific region. The sequence of pMER05 is identical at the 'left' and 'right' termini and across merR to Tn5053, which was independently isolated from the chromosome of a Xanthomonas sp. bacteria from the Khaidarkan mercury mine in Kirgizia, former Soviet Union [Kholodii et al., J. Mol. Biol. 230 (1993a) 1103-1107]. The transpositional unit of pMER05 is, like that of Tn5053, bounded by DNA homologous to the imperfect 25-bp inverted repeats (IR) of the In2 integron, which brackets antibiotic-resistance cassettes in Tn21 subgroup transposons. At one end of the transposable element, and internal to the In2-like IR, is a 38-bp IR which closely resembles the IR that bounds Tn21. | 1994 | 8063107 |
| 817 | 1 | 0.9205 | Mercury resistance transposons in Bacilli strains from different geographical regions. A total of 65 spore-forming mercury-resistant bacteria were isolated from natural environments worldwide in order to understand the acquisition of additional genes by and dissemination of mercury resistance transposons across related Bacilli genera by horizontal gene movement. PCR amplification using a single primer complementary to the inverted repeat sequence of TnMERI1-like transposons showed that 12 of 65 isolates had a transposon-like structure. There were four types of amplified fragments: Tn5084, Tn5085, Tn(d)MER3 (a newly identified deleted transposon-like fragment) and Tn6294 (a newly identified transposon). Tn(d)MER3 is a 3.5-kb sequence that carries a merRETPA operon with no merB or transposase genes. It is related to the mer operon of Bacillus licheniformis strain FA6-12 from Russia. DNA homology analysis shows that Tn6294 is an 8.5-kb sequence that is possibly derived from Tn(d)MER3 by integration of a TnMERI1-type transposase and resolvase genes and in addition the merR2 and merB1 genes. Bacteria harboring Tn6294 exhibited broad-spectrum mercury resistance to organomercurial compounds, although Tn6294 had only merB1 and did not have the merB2 and merB3 sequences for organomercurial lyases found in Tn5084 of B. cereus strain RC607. Strains with Tn6294 encode mercuric reductase (MerA) of less than 600 amino acids in length with a single N-terminal mercury-binding domain, whereas MerA encoded by strains MB1 and RC607 has two tandem domains. Thus, Tn(d)MER3 and Tn6294 are shorter prototypes for TnMERI1-like transposons. Identification of Tn6294 in Bacillus sp. from Taiwan and in Paenibacillus sp. from Antarctica indicates the wide horizontal dissemination of TnMERI1-like transposons across bacterial species and geographical barriers. | 2016 | 26802071 |
| 3021 | 2 | 0.9200 | Sequencing and comparative analysis of IncP-1α antibiotic resistance plasmids reveal a highly conserved backbone and differences within accessory regions. Although IncP-1 plasmids are important for horizontal gene transfer among bacteria, in particular antibiotic resistance spread, so far only three plasmids from the subgroup IncP-1α have been completely sequenced. In this study we doubled this number. The three IncP-1α plasmids pB5, pB11 and pSP21 were isolated from bacteria of two different sewage treatment plants and sequenced by a combination of next-generation and capillary sequencing technologies. A comparative analysis including the previously analysed IncP-1α plasmids RK2, pTB11 and pBS228 revealed a highly conserved plasmid backbone (at least 99.9% DNA sequence identity) comprising 54 core genes. The accessory elements of the plasmid pB5 constitute a class 1 integron interrupting the parC gene and an IS6100 copy inserted into the integron. In addition, the tetracycline resistance genes tetAR and the ISTB11-like element are located between the klc operon and the trfA-ssb operon. Plasmid pB11 is loaded with a Tn5053-like mercury resistance transposon between the parCBA and parDE operons and contains tetAR that are identical to those identified in plasmid pB5 and the insertion sequence ISSP21. Plasmid pSP21 harbours an ISPa7 element in a Tn402 transposon including a class 1 integron between the partitioning genes parCBA and parDE. The IS-element ISSP21 (99.89% DNA sequence identity to ISSP21 from pB11), inserted downstream of the tetR gene and a copy of ISTB11 (identical to ISTB11 on pTB11) inserted between the genes pncA and pinR. On all three plasmids the accessory genes are almost always located between the backbone modules confirming the importance of the backbone functions for plasmid maintenance. The striking backbone conservation among the six completely sequenced IncP-1α plasmids is in contrast to the much higher diversity within the IncP-1β subgroup. | 2011 | 21115076 |
| 530 | 3 | 0.9182 | Location of the genes for anthranilate synthase in Streptomyces venezuelae ISP5230: genetic mapping after integration of the cloned genes. The anthranilate synthase (trpEG) genes in Streptomyces venezuelae ISP5230 were located by allowing a segregationally unstable plasmid carrying cloned S. venezuelae trpEG DNA and a thiostrepton resistance (tsr) marker to integrate into the chromosome. The integrated tsr was mapped by conjugation and transduction to a location close to tyr-2, between arg-6 and trpA13. A genomic DNA fragment containing trpC from S. venezuelae ISP5230 was cloned by complementation of a trpC mutation in Streptomyces lividans. Evidence from restriction enzyme analysis of the cloned DNA fragments, from Southern hybridization using the cloned trp DNA as probes, and from cotransduction frequencies, placed trpEG at a distance of 12-45 kb from the trpCBA cluster. The overall arrangement of tryptophan biosynthesis genes in the S. venezuelae chromosome differs from that in other bacteria examined so far. | 1993 | 8515229 |
| 820 | 4 | 0.9180 | Nucleotide sequence analysis of a transposon (Tn5393) carrying streptomycin resistance genes in Erwinia amylovora and other gram-negative bacteria. A class II Tn3-type transposable element, designated Tn5393 and located on plasmid pEa34 from streptomycin-resistant strain CA11 of Erwinia amylovora, was identified by its ability to move from pEa34 to different sites in plasmids pGEM3Zf(+) and pUCD800. Nucleotide sequence analysis reveals that Tn5393 consists of 6,705 bp with 81-bp terminal inverted repeats and generates 5-bp duplications of the target DNA following insertion. Tn5393 contains open reading frames that encode a putative transposase (tnpA) and resolvase (tnpR) of 961 and 181 amino acids, respectively. The two open reading frames are separated by a putative recombination site (res) consisting of 194 bp. Two streptomycin resistance genes, strA and strB, were identified on the basis of their DNA sequence homology to streptomycin resistance genes in plasmid RSF1010. StrA is separated from tnpR by a 1.2-kb insertion element designated IS1133. The tnpA-res-tnpR region of Tn5393 was detected in Pseudomonas syringae pv. papulans Psp36 and in many other gram-negative bacteria harboring strA and strB. Except for some strains of Erwinia herbicola, these other gram-negative bacteria lacked insertion sequence IS1133. The prevalence of strA and strB could be accounted for by transposition of Tn5393 to conjugative plasmids that are then disseminated widely among gram-negative bacteria. | 1993 | 8380801 |
| 816 | 5 | 0.9174 | High-Level Nickel Resistance in Alcaligenes xylosoxydans 31A and Alcaligenes eutrophus KTO2. Two new nickel-resistant strains of Alcaligenes species were selected from a large number (about 400) of strains isolated from ecosystems polluted by heavy metals and were studied on the physiological and molecular level. Alcaligenes xylosoxydans 31A is a heterotrophic bacterium, and Alcaligenes eutrophus KTO2 is an autotrophic aerobic hydrogen-oxidizing bacterium. Both strains carry-among other plasmids-a megaplasmid determining resistance to 20 to 50 mM NiCl(2) and 20 mM CoCl(2) (when growing in defined Tris-buffered media). Megaplasmids pTOM8, pTOM9 from strain 31A, and pGOE2 from strain KTO2 confer nickel resistance to the same degree to transconjugants of all strains of A. eutrophus tested but were not transferred to Escherichia coli. However, DNA fragments carrying the nickel resistance genes, cloned into broad-hostrange vector pVDZ'2, confer resistance to A. eutrophus derivatives as well as E. coli. The DNA fragments of both bacteria, TBA8, TBA9, and GBA (14.5-kb BamHI fragments), appear to be identical. They share equal size, restriction maps, and strong DNA homology but are largely different from fragment HKI of nickel-cobalt resistance plasmid pMOL28 of A. eutrophus CH34. | 1991 | 16348590 |
| 819 | 6 | 0.9172 | Trimethoprim resistance transposon Tn4003 from Staphylococcus aureus encodes genes for a dihydrofolate reductase and thymidylate synthetase flanked by three copies of IS257. Trimethoprim resistance mediated by the Staphylococcus aureus multi-resistance plasmid pSK1 is encoded by a structure with characteristics of a composite transposon which we have designated Tn4003. Nucleotide sequence analysis of Tn4003 revealed it to be 4717 bp in length and to contain three copies of the insertion element IS257 (789-790 bp), the outside two of which are flanked by directly repeated 8-bp target sequences. IS257 has imperfect terminal inverted repeats of 27-28 bp and encodes for a putative transposase with two potential alpha-helix-turn-alpha-helix DNA recognition motifs. IS257 shares sequence similarities with members of the IS15 family of insertion sequences from Gram-negative bacteria and with ISS1 from Streptococcus lactis. The central region of the transposon contains the dfrA gene that specifies the S1 dihydrofolate reductase (DHFR) responsible for trimethoprim resistance. The S1 enzyme shows sequence homology with type I and V trimethoprim-resistant DHFRs from Gram-negative bacteria and with chromosomally encoded DHFRs from Gram-positive and Gram-negative bacteria. 5' to dfrA is a thymidylate synthetase gene, designated thyE. | 1989 | 2548057 |
| 823 | 7 | 0.9168 | Characterization of the prtA and prtB genes of Erwinia chrysanthemi EC16. Two tandem metalloprotease-encoding structural genes, prtA and prtB, were sequenced from Erwinia chrysanthemi EC16. These were highly homologous to previously reported genes from the same bacteria, as well as to three other metalloprotease-encoding genes from enteric bacteria. The three tandem prt structural genes from strain EC16 were closely linked to a cluster of genes previously found to be essential for extracellular secretion of the metalloproteases. | 1993 | 8224883 |
| 821 | 8 | 0.9159 | DNA probes for studying streptothricin resistance evolution in enteric bacteria. Probes for the detection of streptothricin resistance genes have been derived from recombinant plasmids. These include the streptothricin resistance gene probe sat 1/2 derived from Tn 1826 and specific for both the sat-1 determinant of Tn 1825 and the sat-2 determinant of Tn 1826, and the probe sat D derived from and specific for the sat-1 determinant of transposon Tn 1825. A third streptothricin resistance gene probe, sat 3, represents the streptothricin resistance determinant sat-3 of the IncQ R plasmid pIE639. Hybridization studies did not reveal any sequence homology between sat-3 and the transposon-localized sat-1 and sat-2 determinants. Moreover, non of the different sat-determinants isolated from plasmids of gram negative bacteria hybridized with the analogous resistance determinant of Streptomyces noursei, which had been cloned and named nat by Krügel et al. (Gene, 1988, 62, 209-214). The sat 1/2 probe in combination with the sat D probe proved to be suitable for the identification and the differentiation of sat-1 and sat-2 determinants in different genetic environments. Streptothricin resistance genes related to those present on transposons Tn 1825 and Tn 1826 have been detected by hybridization with the probe sat 1/2 on plasmids isolated a long time ago before the application of streptothricins. The sat-3 determinant appears to be exclusively associated with the IncQ plasmid pIE639. | 1990 | 2166786 |
| 3027 | 9 | 0.9145 | Tn5045, a novel integron-containing antibiotic and chromate resistance transposon isolated from a permafrost bacterium. A novel antibiotic and chromate resistance transposon, Tn5045, was isolated from a permafrost strain of Pseudomonas sp. Tn5045 is a compound transposon composed of three distinct genetic elements. The backbone element is a Tn1013-like Tn3 family transposon, termed Tn1013∗, that contains the tnpA and the tnpR genes, encoding the transposase and resolvase, respectively, the res-site and four genes (orfA, B, C, D) related to different house-keeping genes. The second element is class 1 integron, termed InC∗, which is inserted into the Tn1013∗ res-region and contains 5'-CS-located integrase, 3'-CS-located qacE∆1 and sulfonamide resistance sulI genes, and a single cassette encoding the streptomycin resistance aadA2-gene. The third element is a TnOtChr-like Tn3 family transposon termed TnOtChr∗, which is inserted into the transposition module of the integron and contains genes of chromate resistance (chrB, A, C, F). Tn5045 is the first example of an ancient integron-containing mobile element and also the first characterized compound transposon coding for both antibiotic and chromate, resistance. Our data demonstrate that antibiotic and chromate resistance genes were distributed in environmental bacteria independently of human activities and provide important insights into the origin and evolution of antibiotic resistance integrons. | 2011 | 21262357 |
| 493 | 10 | 0.9142 | Mercury resistance transposons of gram-negative environmental bacteria and their classification. A total of 29 mercury resistance transposons were isolated from mercury-resistant environmental strains of proteobacteria collected in different parts of Eurasia and the USA and tested for hybridization with probes specific for transposase genes of known mercury resistance transposons. 9 were related to Tn21 in this test, 12 were related to Tn5053, 4 to Tn5041 and 1 to Tn5044; three transposons were negative in this test. Restriction mapping and DNA sequencing revealed that 12 transposons were identical or nearly identical to their corresponding relatives while the rest showed varying divergence from their closest relatives. Most of these previously unknown transposons apparently arose as a result of homologous or site-specific recombination. One of these, Tn5046, was completely sequenced, and shown to be a chimera with the mer operon and the transposition module derived from the transposons related to Tn5041 and to Tn5044, respectively. Transposon Tn5070, showing no hybridization with the specific probes used in this study, was also completely sequenced. The transposition module of Tn5070 was most closely related to that of Tn3 while the mer operon was most closely related to that of plasmid pMERPH. The merR of Tn5070 is transcribed in the same direction as the mer structural genes, which is typical for mer operons of gram-positive bacteria. Our data suggest that environmental bacteria may harbor many not yet recognized mercury resistance transposons and warrant their further inventory. | 2001 | 11763242 |
| 3015 | 11 | 0.9141 | Genetic structure and biological properties of the first ancient multiresistance plasmid pKLH80 isolated from a permafrost bacterium. A novel multidrug-resistance plasmid, pKLH80, previously isolated from Psychrobacter maritimus MR29-12 found in ancient permafrost, was completely sequenced and analysed. In our previous studies, we focused on the pKLH80 plasmid region containing streptomycin and tetracycline resistance genes, and their mobilization with an upstream-located ISPpy1 insertion sequence (IS) element. Here, we present the complete sequence of pKLH80 and analysis of its backbone genetic structure, including previously unknown features of the plasmid's accessory region, notably a novel variant of the β-lactamase gene blaRTG-6. Plasmid pKLH80 was found to be a circular 14 835 bp molecule that has an overall G+C content of 40.3 mol% and encodes 20 putative ORFs. There are two distinctive functional modules within the plasmid backbone sequence: (i) the replication module consisting of repB and the oriV region; and (ii) the mobilization module consisting of mobA, mobC and oriT. All of the aforementioned genes share sequence identities with corresponding genes of different species of Psychrobacter. The plasmid accessory region contains antibiotic resistance genes and IS elements (ISPsma1 of the IS982 family, and ISPpy1 and ISAba14 of the IS3 family) found in environmental and clinical bacterial strains of different taxa. We revealed that the sequences flanking blaRTG-6 and closely related genes from clinical bacteria are nearly identical. This fact suggests that blaRTG-6 from the environmental strain of Psychrobacter is a progenitor of blaRTG genes of clinical bacteria. We also showed that pKLH80 can replicate in different strains of Acinetobacter and Psychrobacter genera. The roles of IS elements in the horizontal transfer of antibiotic resistance genes are examined and discussed. | 2014 | 25063046 |
| 491 | 12 | 0.9138 | Class II broad-spectrum mercury resistance transposons in Gram-positive bacteria from natural environments. We have studied the mechanisms of the horizontal dissemination of a broad-spectrum mercury resistance determinant among Bacillus and related species. This mer determinant was first described in Bacillus cereus RC607 from Boston Harbor, USA, and was then found in various Bacillus and related species in Japan, Russia and England. We have shown that the mer determinant can either be located at the chromosome, or on a plasmid in the Bacillus species, and is carried by class II mercury resistance transposons: Tn5084 from B. cereus RC607 and B. cereus VKM684 (ATCC10702) and Tn5085 from Exiguobacterium sp. TC38-2b. Tn5085 is identical in nucleotide sequence to TnMERI1, the only other known mer transposon from Bacillus species, but it does not contain an intron like TnMERI1. Tn5085 is functionally active in Escherichia coli. Tn5083, which we have isolated from B. megaterium MK64-1, contains an RC607-like mer determinant, that has lost some mercury resistance genes and possesses a merA gene which is a novel sequence variant that has not been previously described. Tn5083 and Tn5084 are recombinants, and are comprised of fragments from several transposons including Tn5085, and a relative of a putative transposon from B. firmus (which contains similar genes to the cadmium resistance operon of Staphylococcus aureus), as well as others. The sequence data showed evidence for recombination both between transposition genes and between mer determinants. | 2001 | 11446519 |
| 3061 | 13 | 0.9133 | Tetracycline-resistance encoding plasmids from Paenibacillus larvae, the causal agent of American foulbrood disease, isolated from commercial honeys. Paenibacillus larvae, the causal agent of American foulbrood disease in honeybees, acquires tetracycline-resistance via native plasmids carrying known tetracycline-resistance determinants. From three P. larvae tetracycline-resistant strains isolated from honeys, 5-kb-circular plasmids with almost identical sequences, designated pPL373 in strain PL373, pPL374 in strain PL374, and pPL395 in strain PL395, were isolated. These plasmids were highly similar (99%) to small tetracycline-encoding plasmids (pMA67, pBHS24, pBSDMV46A, pDMV2, pSU1, pAST4, and pLS55) that replicate by the rolling circle mechanism. Nucleotide sequences comparisons showed that pPL373, pPL374, and pPL395 mainly differed from the previously reported P. larvae plasmid pMA67 in the oriT region and mob genes. These differences suggest alternative mobilization and/or conjugation capacities. Plasmids pPL373, pPL374, and pPL395 were individually transferred by electroporation and stably maintained in tetracycline-susceptible P. larvae NRRL B-14154, in which they autonomously replicated. The presence of nearly identical plasmids in five different genera of gram-positive bacteria, i.e., Bhargavaea, Bacillus, Lactobacillus, Paenibacillus, and Sporosarcina, inhabiting diverse ecological niches provides further evidence of the genetic transfer of tetracycline resistance among environmental bacteria from soils, food, and marine habitats and from pathogenic bacteria such as P. larvae. | 2014 | 25296446 |
| 531 | 14 | 0.9133 | p-Aminobenzoic acid and chloramphenicol biosynthesis in Streptomyces venezuelae: gene sets for a key enzyme, 4-amino-4-deoxychorismate synthase. Amplification of sequences from Streptomyces venezuelae ISP5230 genomic DNA using PCR with primers based on conserved prokaryotic pabB sequences gave two main products. One matched pabAB, a locus previously identified in S. venezuelae. The second closely resembled the conserved pabB sequence consensus and hybridized with a 3.8 kb NcoI fragment of S. venezuelae ISP5230 genomic DNA. Cloning and sequence analysis of the 3.8 kb fragment detected three ORFs, and their deduced amino acid sequences were used in BLAST searches of the GenBank database. The ORF1 product was similar to PabB in other bacteria and to the PabB domain encoded by S. venezuelae pabAB. The ORF2 product resembled PabA of other bacteria. ORF3 was incomplete; its deduced partial amino acid sequence placed it in the MocR group of GntR-type transcriptional regulators. Introducing vectors containing the 3.8 kb NcoI fragment of S. venezuelae DNA into pabA and pabB mutants of Escherichia coli, or into the Streptomyces lividans pab mutant JG10, enhanced sulfanilamide resistance in the host strains. The increased resistance was attributed to expression of the pair of discrete translationally coupled p-aminobenzoic acid biosynthesis genes (designated pabB/pabA) cloned in the 3.8 kb fragment. These represent a second set of genes encoding 4-amino-4-deoxychorismate synthase in S. venezuelae ISP5230. In contrast to the fused pabAB set previously isolated from this species, they do not participate in chloramphenicol biosynthesis, but like pabAB they can be disrupted without affecting growth on minimal medium. The gene disruption results suggest that S. venezuelae may have a third set of genes encoding PABA synthase. | 2001 | 11495989 |
| 818 | 15 | 0.9132 | Characterization of a staphylococcal plasmid related to pUB110 and carrying two novel genes, vatC and vgbB, encoding resistance to streptogramins A and B and similar antibiotics. We isolated and sequenced a plasmid, named pIP1714 (4,978 bp), which specifies resistance to streptogramins A and B and the mixture of these compounds. pIP1714 was isolated from a Staphylococcus cohnii subsp. cohnii strain found in the environment of a hospital where pristinamycin was extensively used. Resistance to both compounds and related antibiotics is encoded by two novel, probably cotranscribed genes, (i) vatC, encoding a 212-amino-acid (aa) acetyltransferase that inactivates streptogramin A and that exhibits 58.2 to 69.8% aa identity with the Vat, VatB, and SatA proteins, and (ii) vgbB, encoding a 295-aa lactonase that inactivates streptogramin B and that shows 67% aa identity with the Vgb lactonase. pIP1714 includes a 2,985-bp fragment also found in two rolling-circle replication and mobilizable plasmids, pUB110 and pBC16, from gram-positive bacteria. In all three plasmids, the common fragment was delimited by two direct repeats of four nucleotides (GGGC) and included (i) putative genes closely related to repB, which encodes a replication protein, and to pre(mob), which encodes a protein required for conjugative mobilization and site-specific recombination, and (ii) sequences very similar to the double- and single-strand origins (dso, ssoU) and the recombination site, RSA. The antibiotic resistance genes repB and pre(mob) carried by each of these plasmids were found in the same transcriptional orientation. | 1998 | 9661023 |
| 403 | 16 | 0.9131 | Nucleotide sequence and expression of the mercurial-resistance operon from Staphylococcus aureus plasmid pI258. The mercurial-resistance determinant from Staphylococcus aureus plasmid pI258 is located on a 6.4-kilobase-pair Bgl II fragment. The determinant was cloned into both Bacillus subtilis and Escherichia coli. Mercury resistance was found only in B. subtilis. The 6404-base-pair DNA sequence of the Bgl II fragment was determined. The mer DNA sequence includes seven open reading frames, two of which have been identified by homology with the merA (mercuric reductase) and merB (organomercurial lyase) genes from the mercurial-resistance determinants of Gram-negative bacteria. Whereas 40% of the amino acid residues overall were identical between the pI258 merA polypeptide product and mercuric reductases from Gram-negative bacteria, the percentage identity in the active-site positions and those thought to be involved in NADPH and FAD contacts was above 90%. The 216 amino acid organomercurial lyase sequence was 39% identical with that from a Serratia plasmid, with higher conservation in the middle of the sequences and lower homologies at the amino and carboxyl termini. The remaining five open reading frames in the pI258 mer sequence have no significant homologies with the genes from previously sequenced Gram-negative mer operons. | 1987 | 3037534 |
| 3028 | 17 | 0.9130 | Novel macrolide resistance module carried by the IncP-1beta resistance plasmid pRSB111, isolated from a wastewater treatment plant. The macrolide resistance plasmid pRSB111 was isolated from bacteria residing in the final effluents of a wastewater treatment plant. The 47-kb plasmid confers resistance to azithromycin, clarithromycin, erythromycin, roxithromycin, and tylosin when it is carried by Pseudomonas sp. strain B13 and is very similar to prototype IncP-1beta plasmid pB3, which was previously isolated from an activated-sludge bacterial community of a wastewater treatment plant. The two plasmids differ in their accessory regions, located downstream of the conjugative transfer module gene traC. Nucleotide sequence analysis of the pRSB111 accessory region revealed that it contains a new macrolide resistance module composed of the genes mphR(E), mph(E), and mrx(E), which putatively encode a transcriptional regulator, a macrolide phosphotransferase, and a transmembrane transport protein, respectively. Analysis of the contributions of the individual genes of the macrolide resistance module revealed that mph(E) and mrx(E) are required for high-level macrolide resistance. The resistance genes are flanked by two insertion sequences, namely, ISPa15 and ISRSB111. Two truncated transposable elements, IS6100 and remnants of a Tn3-like transposon, were identified in the vicinity of ISRSB111. The accessory element of pRSB111 apparently replaced the Tn402-like element present on the sister plasmid, pB3, as suggested by the conservation of Tn402-specific terminal inverted repeats on pRSB111. | 2007 | 17101677 |
| 494 | 18 | 0.9130 | The mercury resistance operon of the IncJ plasmid pMERPH exhibits structural and regulatory divergence from other Gram-negative mer operons. The bacterial mercury resistance determinant carried on the IncJ plasmid pMERPH has been characterized further by DNA sequence analysis. From the sequence of a 4097 bp Bg/II fragment which confers mercury resistance, it is predicted that the determinant consists of the genes merT, merP, merC and merA. The level of DNA sequence similarity between these genes and those of the mer determinant of Tn21 was between 56 center dot 4 and 62 center dot 4%. A neighbour-joining phylogenetic tree of merA gene sequences was constructed which suggested that pMERPH bears the most divergent Gram-negative mer determinant characterized to date. Although the determinant from pMERPH has been shown to be inducible, no regulatory genes have been found within the Bg/II fragment and it is suggested that a regulatory gene may be located elsewhere on the plasmid. The cloned determinant has been shown to express mercury resistance constitutively. Analysis of the pMERPH mer operator/promoter (O/P) region in vivo has shown constitutive expression from the mer PTCPA promoter, which could be partially repressed by the presence of a trans-acting MerR protein from a Tn21-like mer determinant. This incomplete repression of mer PTCPA promoter activity may be due to the presence of an extra base between the -35 and -10 sequences of the promoter and/or to variation in the MerR binding sites in the O/P region. Expression from the partially repressed mer PTCPA promoter could be restored by the addition of inducing levels of Hg2+ ions. Using the polymerase chain reaction with primers designed to amplify regions in the merP and merA genes, 1 center dot 37 kb pMERPH-like sequences have been amplified from the IncJ plasmid R391, the environmental isolate SE2 and from DNA isolated directly from non-cultivated bacteria in River Mersey sediment. This suggests that pMERPH-like sequences, although rare, are nevertheless persistent in natural environments. | 1996 | 8932707 |
| 460 | 19 | 0.9128 | Horizontal transfer of the photosynthesis gene cluster and operon rearrangement in purple bacteria. A 37-kb photosynthesis gene cluster was sequenced in a photosynthetic bacterium belonging to the beta subclass of purple bacteria (Proteobacteria), Rubrivivax gelatinosus. The cluster contained 12 bacteriochlorophyll biosynthesis genes (bch), 7 carotenoid biosynthesis genes (crt), structural genes for photosynthetic apparatuses (puf and puh), and some other related genes. The gene arrangement was markedly different from those of other purple photosynthetic bacteria, while two superoperonal structures, crtEF-bchCXYZ-puf and bchFNBHLM-lhaA-puhA, were conserved. Molecular phylogenetic analyses of these photosynthesis genes showed that the photosynthesis gene cluster of Rvi. gelatinosus was originated from those of the species belonging to the alpha subclass of purple bacteria. It was concluded that a horizontal transfer of the photosynthesis gene cluster from an ancestral species belonging to the alpha subclass to that of the beta subclass of purple bacteria had occurred and was followed by rearrangements of the operons in this cluster. | 2001 | 11343129 |