# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 371 | 0 | 1.0000 | Single amino acid substitutions in the enzyme acetolactate synthase confer resistance to the herbicide sulfometuron methyl. Sulfometuron methyl, a sulfonylurea herbicide, blocks growth of bacteria, yeast, and higher plants by inhibition of acetolactate synthase (EC 4.1.3.18), the first common enzyme in the biosynthesis of branched-chain amino acids. Spontaneous mutations that confer increased resistance to the herbicide were obtained in cloned genes for acetolactate synthase from Escherichia coli and Saccharomyces cerevisiae. The DNA sequence of a bacterial mutant gene and a yeast mutant gene revealed single nucleotide differences from their respective wild-type genes. The mutations result in single amino acid substitutions in the structurally homologous aminoterminal regions of the two proteins, but at different positions. The bacterial mutation results in reduced levels of acetolactate synthase activity, reduced sensitivity to sulfometuron methyl, and unaltered resistance to feedback inhibition by valine. The yeast mutation results in unaltered levels of acetolactate synthase activity, greatly reduced sensitivity to sulfometuron methyl, and slightly reduced sensitivity to valine. | 1986 | 16593715 |
| 186 | 1 | 0.9990 | Plasmid-encoded resistance to arsenic and antimony. Resistance determinants to the toxic oxyanionic salts of arsenic and antimony are found on plasmids of both gram-negative and gram-positive organisms. In most cases these provide resistance to both the oxyanions of +III oxidation state, antimonite and arsenite, and the +V oxidation state, arsenate. In both gram-positive and -negative bacteria, resistance is correlated with efflux of the anions from cells. The determinant from the plasmid R773, isolated from a gram-negative organism, has been studied in detail. It encodes an oxyanion-translocating ATPase with three subunits, a catalytic subunit, the ArsA protein, a membrane subunit, the ArsB subunit, and a specificity factor, the ArsC protein. The first two form a membrane-bound complex with arsenite-stimulated ATPase activity. The determinants from gram-positive bacteria have only the arsB and arsC genes and encode an efflux system without the participation of an ArsA homologue. | 1992 | 1531541 |
| 180 | 2 | 0.9990 | Bacterial resistances to inorganic mercury salts and organomercurials. Environmental and clinical isolates of mercury-resistant (resistant to inorganic mercury salts and organomercurials) bacteria have genes for the enzymes mercuric ion reductase and organomercurial lyase. These genes are often plasmid-encoded, although chromosomally encoded resistance determinants have been occasionally identified. Organomercurial lyase cleaves the C-Hg bond and releases Hg(II) in addition to the appropriate organic compound. Mercuric reductase reduces Hg(II) to Hg(O), which is nontoxic and volatilizes from the medium. Mercuric reductase is a FAD-containing oxidoreductase and requires NAD(P)H and thiol for in vitro activity. The crystal structure of mercuric ion reductase has been partially solved. The primary sequence and the three-dimensional structure of the mercuric reductase are significantly homologous to those of other flavin-containing oxidoreductases, e.g., glutathione reductase and lipoamide dehydrogenase. The active site sequences are the most conserved region among these flavin-containing enzymes. Genes encoding other functions have been identified on all mercury ion resistance determinants studied thus far. All mercury resistance genes are clustered into an operon. Hg(II) is transported into the cell by the products of one to three genes encoded on the resistance determinants. The expression of the operon is regulated and is inducible by Hg(II). In some systems, the operon is inducible by both Hg(II) and some organomercurials. In gram-negative bacteria, two regulatory genes (merR and merD) were identified. The (merR) regulatory gene is transcribed divergently from the other genes in gram-negative bacteria. The product of merR represses operon expression in the absence of the inducers and activates transcription in the presence of the inducers. The product of merD coregulates (modulates) the expression of the operon. Both merR and merD gene products bind to the same operator DNA. The primary sequence of the promoter for the polycistronic mer operon is not ideal for efficient transcription by the RNA polymerase. The -10 and -35 sequences are separated by 19 (gram-negative systems) or 20 (gram-positive systems) nucleotides, 2 or 3 nucleotides longer than the 17-nucleotide optimum distance for binding and efficient transcription by the Escherichia coli sigma 70-containing RNA polymerase. The binding site of MerR is not altered by the presence of Hg(II) (inducer). Experimental data suggest that the MerR-Hg(II) complex alters the local structure of the promoter region, facilitating initiation of transcription of the mer operon by the RNA polymerase. In gram-positive bacteria MerR also positively regulates expression of the mer operon in the presence of Hg(II). | 1992 | 1311113 |
| 443 | 3 | 0.9990 | Deletion mutant analysis of the Staphylococcus aureus plasmid pI258 mercury-resistance determinant. Deletion mutant analysis of the mercury-resistant determinant (mer operon) from the Staphylococcus aureus plasmid pI258 was used to verify the location of the merA and merB genes and to show the existence of mercuric ion transport gene(s). ORF5 was confirmed to be a transport gene and has an amino acid product sequence homologous to the merT gene products from several gram-negative bacteria and a Bacillus species. Deletion analysis established that inactivation of merA on a broad-spectrum mer resistance determinant resulted in a mercury-hypersensitive phenotype. Gene dosage had no apparent effect on the level of resistance conferred by the intact mer operon or on the expression of an inducible phenotype, except that when the intact pI258 mer operon was on a high copy number plasmid, uninduced cells possessed a volatilization rate that was at most only 3.5-fold less than that observed for induced cells. There was no need for mercury ion transport proteins for full resistance when the mer operon was expressed in a high copy number plasmid. | 1991 | 1954576 |
| 373 | 4 | 0.9990 | The ybiT gene of Erwinia chrysanthemi codes for a putative ABC transporter and is involved in competitiveness against endophytic bacteria during infection. We investigated the role in bacterial infection of a putative ABC transporter, designated ybiT, of Erwinia chrysanthemi AC4150. The deduced sequence of this gene showed amino acid sequence similarity with other putative ABC transporters of gram-negative bacteria, such as Escherichia coli and Pseudomonas aeruginosa, as well as structural similarity with proteins of Streptomyces spp. involved in resistance to macrolide antibiotics. The gene contiguous to ybiT, designated as pab (putative antibiotic biosynthesis) showed sequence similarity with Pseudomonas and Streptomyces genes involved in the biosynthesis of antibiotics. A ybiT mutant (BT117) was constructed by marker exchange. It retained full virulence in potato tubers and chicory leaves, but it showed reduced ability to compete in planta against the wild-type strain or against selected saprophytic bacteria. These results indicate that the ybiT gene plays a role in the in planta fitness of the bacteria. | 2002 | 11916677 |
| 380 | 5 | 0.9989 | Expression of a chloramphenicol-resistance determinant carried on hybrid plasmids in gram-positive and gram-negative bacteria. To analyse the control of chloramphenicol (Cm) resistance conferred by the Staphylococcus aureus plasmid pUB112, a detailed restriction map of this plasmid has been constructed, and the position and orientation of the cat gene have been determined. An MboI restriction fragment carrying the entire cat gene of pUB112 was then cloned in another S. aureus plasmid, the kanamycin (Km) resistance vector pUB110. Depending on the orientation of the incorporated cat fragment, the level of Cm resistance varied dramatically in Bacillus subtilis cells. This effect could not be eliminated by deleting parts of the vector DNA, and only the introduction of a transcription termination signal led to orientation-independent Cm resistance. One such construct was further developed to yield a shuttle vector, replicating both in Escherichia coli and B. subtilis. Using this vector the expression of incorporated genes can be determined in both Gram-positive and Gram-negative bacteria. By in vitro transcription experiments using pUB110 DNA linearized with various restriction endonucleases as template, two pUB110 promoters could be localized and their orientations determined: one promoter controls a gene whose function is unknown, the other regulates the transcription of the KmR gene. | 1984 | 6442250 |
| 386 | 6 | 0.9989 | A mutant neomycin phosphotransferase II gene reduces the resistance of transformants to antibiotic selection pressure. The neo (neomycin-resistance) gene of transposon Tn5 encodes the enzyme neomycin phosphotransferase II (EC 2.7.1.95), which confers resistance to various aminoglycoside antibiotics, including kanamycin and G418. The gene is widely used as a selectable marker in the transformation of organisms as diverse as bacteria, yeast, plants, and animals. We found a mutation that involves a glutamic to aspartic acid conversion at residue 182 in the protein encoded by the chimeric neomycin phosphotransferase II genes of several commonly used transformation vectors. The mutation substantially reduces phosphotransferase activity but does not appear to affect the stability of the neomycin phosphotransferase II mRNA or protein. Plants and bacteria transformed with the mutant gene are less resistant to antibiotics than those transformed with the normal gene. A simple restriction endonuclease digestion distinguishes between the mutant and the normal gene. | 1990 | 2159150 |
| 285 | 7 | 0.9989 | Streptothricin resistance as a novel selectable marker for transgenic plant cells.  Streptothricins are known as antimicrobial agents produced by Streptomyces spp. Bacterial resistance to streptothricin is mediated by specific enzymes exhibiting an acetyltransferase activity which renders the drug non-toxic for bacteria. The nucleotide sequence of several streptothricin resistance genes from bacteria have been described. Certain cells of eukaryotic parasites (such as Ustilago maydis or Leishmania spp.) are sensitive to streptothricin and the introduction of the bacterial resistance gene sat2 renders them resistant. We show that numerous species of plants are sensitive to low concentrations of streptothricin. Moreover, introduction of the bacterial resistance gene sat3 under the control of the 35S cauliflower mosaic virus promoter protects these cells from the toxic action of streptothricin. Therefore, sat3-mediated streptothricin resistance appears to be a promising selective marker for genetic manipulation of plant cells. | 2000 | 30754912 |
| 6324 | 8 | 0.9989 | Genetic and biochemical basis of tetracycline resistance. Properties of several, well characterized, tetracycline resistance determinants were compared. The determinants in Tn1721 and Tn10 (both from Gram-negative bacteria) each contain two genes; one encodes a repressor that regulates both its own transcription and that of a membrane protein that confers resistance by promoting efflux of the drug. Determinants from Gram-positive bacteria also encode efflux proteins, but expression of resistance is probably regulated by translational attenuation. The likely tetracycline binding site (a common dipeptide) in each efflux protein was predicted. The presence of the common binding site is consistent with the ability of an efflux protein originating in Bacillus species to be expressed in Escherichia coli. | 1986 | 3542941 |
| 385 | 9 | 0.9989 | Introduction of a mini-gene encoding a five-amino acid peptide confers erythromycin resistance on Bacillus subtilis and provides temporary erythromycin protection in Proteus mirabilis. A 15-bp mini-gene was introduced into Bacillus subtilis and into stable protoplast-like L-forms of Proteus mirabilis. This mini-gene encoded the peptide MVLFV and modeled a fragment of Escherichia coli 23S rRNA responsible for E. coli erythromycin (Ery) resistance. Expression of the introduced mini-gene conferred permanent Ery resistance on B. subtilis. In L-forms of P. mirabilis, the Ery-protective effect was maintained in the course of several generations. Herewith, the mechanism of Ery resistance mediated by expression of specific short peptides was shown to exist in evolutionary distant bacteria. Three new plasmids were constructed containing the gene under study transcriptionally fused with the genes encoding glutamylendopeptidase of Bacillus licheniformis or delta-endotoxin of Bacillus thuringiensis. The Ery resistance pentapeptide (E-peptide) mini-gene served as an efficient direct transcriptional reporter and allowed to select bacillar glutamylendopeptidase with improved productivity. The mini-genes encoding E-peptides may be applied as selective markers to transform both Gram-positive and Gram-negative bacteria. The small size of the E-peptide mini-genes makes them attractive selective markers for vector construction. | 2000 | 10620668 |
| 185 | 10 | 0.9989 | The chromosomal arsenic resistance genes of Thiobacillus ferrooxidans have an unusual arrangement and confer increased arsenic and antimony resistance to Escherichia coli. The chromosomal arsenic resistance genes of the acidophilic, chemolithoautotrophic, biomining bacterium Thiobacillus ferrooxidans were cloned and sequenced. Homologues of four arsenic resistance genes, arsB, arsC, arsH, and a putative arsR gene, were identified. The T. ferrooxidans arsB (arsenite export) and arsC (arsenate reductase) gene products were functional when they were cloned in an Escherichia coli ars deletion mutant and conferred increased resistance to arsenite, arsenate, and antimony. Therefore, despite the fact that the ars genes originated from an obligately acidophilic bacterium, they were functional in E. coli. Although T. ferrooxidans is gram negative, its ArsC was more closely related to the ArsC molecules of gram-positive bacteria. Furthermore, a functional trxA (thioredoxin) gene was required for ArsC-mediated arsenate resistance in E. coli; this finding confirmed the gram-positive ArsC-like status of this resistance and indicated that the division of ArsC molecules based on Gram staining results is artificial. Although arsH was expressed in an E. coli-derived in vitro transcription-translation system, ArsH was not required for and did not enhance arsenic resistance in E. coli. The T. ferrooxidans ars genes were arranged in an unusual manner, and the putative arsR and arsC genes and the arsBH genes were translated in opposite directions. This divergent orientation was conserved in the four T. ferrooxidans strains investigated. | 2000 | 10788346 |
| 637 | 11 | 0.9989 | Identification of Bacillus subtilis sigma-dependent genes that provide intrinsic resistance to antimicrobial compounds produced by Bacilli. Bacillus subtilis produces many antibiotics of varying structures and specificity. Here we identify a prominent role for sigma(W), an extracytoplasmic function (ECF) sigma factor, in providing intrinsic resistance to antimicrobial compounds produced by other Bacilli. By using a panel of B. subtilis mutants disrupted for each of the 30 known sigma(W)-dependent operons we identified resistance genes for at least three different antimicrobial compounds. The ydbST and fosB genes contribute to resistance to antimicrobial compound(s) produced by B. amyloliquefaciens FZB42, the yqeZyqfAB operon provides resistance to the SPbeta prophage-encoded bacteriocin sublancin, and the yknWXYZ operon and yfhL provide resistance to the antimicrobial peptide SdpC. YfhL encodes a paralogue of SdpI, a membrane protein that provides immunity to SdpC. In competition experiments, we identify sigma(W) as a key factor in allowing B. subtilis to resist antibiotic killing and encroachment by competing strains. Together with the previous observation that sigma(W) provides inducible resistance against the Streptomyces antibiotic fosfomycin, these studies support the notion that sigma(W) controls an antibiosis regulon important in the microbial ecology of soil bacteria. | 2006 | 16629676 |
| 440 | 12 | 0.9989 | Nucleotide sequence analysis reveals similarities between proteins determining methylenomycin A resistance in Streptomyces and tetracycline resistance in eubacteria. Previous studies had localised the gene (mmr) for resistance to methylenomycin A (Mm) to a 2.5-kb PstI fragment in the middle of a cluster of Mm biosynthetic genes from the Streptomyces coelicolor plasmid SCP1. In this paper, the gene has been more precisely located by sub-cloning, and the nucleotide sequence of the whole fragment has been determined. The predicted mmr-specified protein (Mr 49238) would be hydrophobic, with some homology at the amino acid level to tetracycline-resistance proteins from both Gram-positive and Gram-negative bacteria. Comparisons of hydropathy plots of the amino acid sequences reinforces the idea that the proteins are similar. It is suggested that Mm resistance may be conferred by a membrane protein, perhaps controlling efflux of the antibiotic. No significant homology was detected by hybridisation analysis between mmr and a cloned oxytetracycline (OTc)-resistance gene (tetB) of the OTc producer Streptomyces rimosus, and no cross-resistance was conferred by these genes. Sequences on both sides of mmr appear to encode proteins. The direction of translation in each case would be opposite to that of mmr translation. This suggests that mmr is transcribed as a monocistronic mRNA from a bidirectional promoter. An extensive inverted repeat sequence between the stop codons of mmr and the converging gene may function as a bidirectional transcription terminator. | 1987 | 2828187 |
| 704 | 13 | 0.9989 | Aminoarabinose is essential for lipopolysaccharide export and intrinsic antimicrobial peptide resistance in Burkholderia cenocepacia(†). One common mechanism of resistance against antimicrobial peptides in Gram-negative bacteria is the addition of 4-amino-4-deoxy-L-arabinose (L-Ara4N) to the lipopolysaccharide (LPS) molecule. Burkholderia cenocepacia exhibits extraordinary intrinsic resistance to antimicrobial peptides and other antibiotics. We have previously discovered that unlike other bacteria, B. cenocepacia requires L-Ara4N for viability. Here, we describe the isolation of B. cenocepacia suppressor mutants that remain viable despite the deletion of genes required for L-Ara4N synthesis and transfer to the LPS. The absence of L-Ara4N is the only structural difference in the LPS of the mutants compared with that of the parental strain. The mutants also become highly sensitive to polymyxin B and melittin, two different classes of antimicrobial peptides. The suppressor phenotype resulted from a single amino acid replacement (aspartic acid to histidine) at position 31 of LptG, a protein component of the multi-protein pathway responsible for the export of the LPS molecule from the inner to the outer membrane. We propose that L-Ara4N modification of LPS provides a molecular signature required for LPS export and proper assembly at the outer membrane of B. cenocepacia, and is the most critical determinant for the intrinsic resistance of this bacterium to antimicrobial peptides. | 2012 | 22742453 |
| 292 | 14 | 0.9989 | Mechanisms underlying expression of Tn10 encoded tetracycline resistance. Tetracycline-resistance determinants encoding active efflux of the drug are widely distributed in gram-negative bacteria and unique with respect to genetic organization and regulation of expression. Each determinant consists of two genes called tetA and tetR, which are oriented with divergent polarity, and between them is a central regulatory region with overlapping promoters and operators. The amino acid sequences of the encoded proteins are 43-78% identical. The resistance protein TetA is a tetracycline/metal-proton antiporter located in the cytoplasmic membrane, while the regulatory protein TetR is a tetracycline inducible repressor. TetR binds via a helix-turn-helix motif to the two tet operators, resulting in repression of both genes. A detailed model of the repressor-operator complex has been proposed on the basis of biochemical and genetic data. The tet genes are differentially regulated so that repressor synthesis can occur before the resistance protein is expressed. This has been demonstrated for the Tn10-encoded tet genes and may be a common property of all tet determinants, as suggested by the similar locations of operators with respect to promoters. Induction is mediated by a tetracycline-metal complex and requires only nanomolar concentrations of the drug. This is the most sensitive effector-inducible system of transcriptional regulation known to date. The crystal structure of the TetR-tetracycline/metal complex shows the Tet repressor in the induced, non-DNA binding conformation. The structural interpretation of many noninducible TetR mutants has offered insight into the conformational changes associated with the switch between inducing and repressing structures of TetR. Tc is buried in the core of TetR, where it is held in place by multiple contacts to the protein. | 1994 | 7826010 |
| 6222 | 15 | 0.9989 | A Sco homologue plays a role in defence against oxidative stress in pathogenic Neisseria. Sco proteins are found in mitochondria and in a variety of oxidase positive bacteria. Although Sco is required for the formation of the Cu(A) centre in a cytochrome oxidase of the aa(3) type, it was observed that oxidases with a Cu(A) centre are not present in many bacteria that contain a Sco homologue. Two bacteria of this type are the pathogens Neisseria meningitidis and Neisseria gonorrhoeae. The sco genes of N. gonorrhoeae strain 1291 and N. meningitidis strain MC58 were cloned, inactivated by inserting a kanamycin resistance cassette and used to make knockout mutants by allelic exchange. Both N. gonorrhoeae and N. meningitidis sco mutants were highly sensitive to oxidative killing by paraquat, indicating that Sco is involved in protection against oxidative stress in these bacteria. | 2003 | 12832079 |
| 6201 | 16 | 0.9989 | Overexpression of mfpA Gene Increases Ciprofloxacin Resistance in Mycobacterium smegmatis. Fluoroquinolones (FQs) are antibiotics useful in the treatment of drug-resistant tuberculosis, but FQ-resistant mutants can be selected rapidly. Although mutations in the DNA gyrase are the principal cause of this resistance, pentapeptide proteins have been found to confer low-level FQ resistance in Gram-negative bacteria. MfpA is a pentapeptide repeat protein conserved in mycobacterial chromosomes, where it is adjacent to a group of four highly conserved genes termed a conservon. We wished to characterize the transcriptional regulation of the mfpA gene and relate its expression to ciprofloxacin resistance in M. smegmatis. Reverse transcription PCR showed that mfpA gene is part of an operon containing the conservon genes. Using a transcriptional fusion, we showed that a promoter was located 5' to the mfpEA operon. We determined the promoter activity under different growth conditions and found that the expression of the operon increases slightly in late growth phases in basic pH and in subinhibitory concentrations of ciprofloxacin. Finally, by cloning the mfpA gene in an inducible vector, we showed that induced expression of mfpA increases the ciprofloxacin Minimal Inhibitory Concentration. These results confirm that increased expression of the mfpA gene, which is part of the mfpEA operon, increases ciprofloxacin resistance in M. smegmatis. | 2021 | 33824663 |
| 6209 | 17 | 0.9989 | Evaluation of Mycobacterium tuberculosis genes involved in resistance to killing by human macrophages. A coinfection assay was developed to examine Mycobacterium tuberculosis genes suspected to be involved in resistance to killing by human macrophages. THP-1 macrophages were infected with a mixture of equal numbers of recombinant Mycobacterium smegmatis LR222 bacteria expressing an M. tuberculosis gene and wild-type M. smegmatis LR222 bacteria expressing the xylE gene. At various times after infection, the infected macrophages were lysed and the bacteria were plated. The resulting colonies were sprayed with catechol to determine the number of recombinant colonies and the number of xylE-expressing colonies. M. smegmatis bacteria expressing the M. tuberculosis glutamine synthetase A (glnA) gene or open reading frame Rv2962c or Rv2958c demonstrated significantly increased survival rates in THP-1 macrophages relative to those of xylE-expressing bacteria. M. smegmatis bacteria expressing M. tuberculosis genes for phospholipase C (plcA and plcB) or for high temperature requirement A (htrA) did not. | 2000 | 10603413 |
| 376 | 18 | 0.9989 | Construction of a reporter plasmid for screening in vivo promoter activity in Francisella tularensis. Francisella tularensis is a facultative intracellular bacterium that survives and multiplies inside macrophages. Here we constructed a new promoter probe plasmid denoted pKK214 by introduction of a promoter-less chloramphenicol acetyltransferase (cat) gene into the shuttle vector pKK202. A promoter library was created in F. tularensis strain LVS by cloning random chromosomal DNA fragments into pKK214. Approximately 15% of the recombinant bacteria showed chloramphenicol resistance in vitro. The promoter library was also used to infect macrophages in the presence of chloramphenicol and after two cycles of infection the library contained essentially only chloramphenicol resistance clones which shows that pKK214 can be used to monitor F. tularensis genes that are expressed during infection. | 2001 | 11728719 |
| 689 | 19 | 0.9989 | Regulatory and DNA repair genes contribute to the desiccation resistance of Sinorhizobium meliloti Rm1021. Sinorhizobium meliloti can form a nitrogen-fixing symbiotic relationship with alfalfa after bacteria in the soil infect emerging root hairs of the growing plant. To be successful at this, the bacteria must be able to survive in the soil between periods of active plant growth, including when conditions are dry. The ability of S. meliloti to withstand desiccation has been known for years, but genes that contribute to this phenotype have not been identified. Transposon mutagenesis was used in combination with novel screening techniques to identify four desiccation-sensitive mutants of S. meliloti Rm1021. DNA sequencing of the transposon insertion sites identified three genes with regulatory functions (relA, rpoE2, and hpr) and a DNA repair gene (uvrC). Various phenotypes of the mutants were determined, including their behavior on several indicator media and in symbiosis. All of the mutants formed an effective symbiosis with alfalfa. To test the hypothesis that UvrC-related excision repair was important in desiccation resistance, uvrA, uvrB, and uvrC deletion mutants were also constructed. These strains were sensitive to DNA damage induced by UV light and 4-NQO and were also desiccation sensitive. These data indicate that uvr gene-mediated DNA repair and the regulation of stress-induced pathways are important for desiccation resistance. | 2009 | 19028909 |