# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 538 | 0 | 1.0000 | The biochemical and genetic basis for high frequency thiomethyl galactoside resistance in lambda,lambdadg lysogens of Escherichia coli. In a culture of Escherichia coli K12 gal (lambdadg), cells which form large colonies on agar plates containing galactose and thiomethyl beta-D-galactoside (TMG) appear at high frequency. These clones are resistant to growth inhibition by TMG on galactose minimal medium. Biochemical studies of the steady-state levels of galactokinase and UDPgalactose 4-epimerase suggest that the resistant clones have extra copies of the genes for the galactose-metabolizing enzymes. The mutation for TMG resistance is not located in either the bacterial or the bacteriophage genome, but is probably due to an aberrant association between cell and prophage DNA. Mapping the TMG-resistant characteristic by phage P1 indicates that TMG-resistant bacteria posses at least two GAL+ OPERONS, ONE OF WHICH IS COTRANSDUCIBLe with bio+. In addition, TMG-resistant bacteria behave like lambdadg polylysogens when challenged with the phage lambdaI90c17. From these genetic experiments we conclude that TMG-resistant bacteria arise by duplication of the lambdadg prophage. Finally, gal+ bacteria which carry a single, additional, lambdadg prophage are TMG-resistant. TMG resistance is probably a gal+ gene dosage effect. | 1978 | 344832 |
| 617 | 1 | 0.9949 | Lytic action of cloned pneumococcal phage lysis genes in Streptococcus pneumoniae. The genes hbl3, cpl1 and cpl7 coding for the pneumococcal phage lytic enzymes HBL3, CPL1 and CPL7, respectively, have been cloned into shuttle plasmids that can replicate in Streptococcus pneumoniae and Escherichia coli. All these genes were expressed in E. coli under the control of either the lytP promoter of the lytA gene, which codes for the major pneumococcal autolysin, or the promoter of the tetracycline-resistance gene (tetP). In contrast, cpl1 and cpl7 genes that code for lysozymes were expressed in pneumococcus only under the control of tetP, whereas the hbl3 gene that codes for an amidase can be expressed using either promoter. The phage lysozymes or amidase expressed in S. pneumoniae M31, a mutant deleted in the lytA gene coding for short chains, were placed under physiological control since these transformed bacteria grew as normal 'diplo' cells during the exponential phase and underwent autolysis only after long incubation at 37 degrees C. The lysis genes appear to be expressed constitutively in the transformed pneumococci, since sharply defined lysis of these cultures could be induced prematurely during the exponential phase of growth by addition of sodium deoxycholate. | 1993 | 8472929 |
| 6203 | 2 | 0.9948 | Effect of induction of SOS response on expression of pBR322 genes and on plasmid copy number. Several lines of evidence are presented that indicate that the level of tetracycline resistance of Esherichia coli strains harboring plasmid pBR322 varies according to whether the SOS system of the host bacteria has been induced. These include use of strains in which the SOS system is expressed constitutively (lexA def.), is thermoinducible (recA441) or noninducible (lexA ind-), or is highly repressed (multiple copies of lexA+). Similar induction was observed with the product of another plasmid gene, beta-lactamase. The amounts of extractable plasmid DNA were also increased by SOS induction, and we propose that the SOS-induced increases in levels of tetracycline resistance and beta-lactamase activity are due to an increased plasmid copy number. | 1989 | 2695953 |
| 6205 | 3 | 0.9948 | Characterization of Caulobacter crescentus response to low temperature and identification of genes involved in freezing resistance. Free-living bacteria must respond to a wide range of temperature changes, and have developed specific mechanisms to survive in extreme environments. In this work we describe a remarkable resistance of mesophilic bacterium Caulobacter crescentus to several cycles of freezing at -80 degrees C, which was able to grow at low temperatures. Exponentially growing cells and late stationary-phase cells presented higher freezing resistance at both -20 and -80 degrees C than early stationary-phase cells. Cryotolerance was observed when log-phase cultures grown at 30 degrees C were preincubated at 5, 15 or 20 degrees C before freezing at -20 degrees C. A transposon library was screened to identify mutants sensitive to freezing at -80 degrees C and three strains presenting <10% survival were isolated. Identification of genes disrupted in each mutant showed that they encoded an AddA family DNA helicase, a DEAD/DEAH box RNA helicase and a putative RND (resistance, nodulation, cell division) efflux system component. These strains showed longer generation times than wild-type cells when growing at 15 degrees C, with the RNA helicase mutant presenting a severe growth defect. These analyses suggest that the singular intrinsic resistance to freezing of C. crescentus is in fact a consequence of several independent traits, especially the maintenance of a proper degree of supercoiling of nucleic acids. | 2008 | 18801049 |
| 333 | 4 | 0.9947 | Mutants of Escherichia coli altered in both genes coding for the elongation factor Tu. Genetic analysis of a mutant of Escherichia coli resistant to the antibiotic mocimycin is presented. This resistance is due to alterations in both tuf genes coding for the elongation factor Tu. Mocimycin resistance is recessive. Bacteria carryong only one tuf gene from the resistant mutant are still mocimycin sensitive. If the mutant gene is the tufA gene, the seisitive cells can be made resistant through inactivation of the tufB gene by insertion of the bacteriophage milliunits genome. Conditional mocimycin-resistant mutants ban also be isolated when the tufB gene is altered by an amber or a temperature-sensitive mutation. When only the tufB allele from the original mocimycin-resistant mutant is present, inactivation of the wild-type tufA gene fails to give viable mocimycin-resistant progeny. We conclude that the tufA mutant allele codes for a functional mocimycin-resistant EF-Tu, whereas the mutant tufB gene does not code for a functional product. | 1978 | 360222 |
| 6356 | 5 | 0.9947 | Contribution of chloride channel permease to fluoride resistance in Streptococcus mutans. Genes encoding fluoride transporters have been identified in bacterial and archaeal species. The genome sequence of the cariogenic Streptococcus mutans bacteria suggests the presence of a putative fluoride transporter, which is referred to as a chloride channel permease. Two homologues of this gene (GenBank locus tags SMU_1290c and SMU_1289c) reside in tandem in the genome of S. mutans The aim of this study was to determine whether the chloride channel permeases contribute to fluoride resistance. We constructed SMU_1290c- and SMU_1289c-knockout S. mutans UA159 strains. We also constructed a double-knockout strain lacking both genes. SMU_1290c or SMU_1289c was transformed into a fluoride transporter- disrupted Escherichia coli strain. All bacterial strains were cultured under appropriate conditions with or without sodium fluoride, and fluoride resistance was evaluated. All three gene-knockout S. mutans strains showed lower resistance to sodium fluoride than did the wild-type strain. No significant changes in resistance to other sodium halides were recognized between the wild-type and double-knockout strains. Both SMU_1290c and SMU_1289c transformation rescued fluoride transporter-disrupted E. coli cell from fluoride toxicity. We conclude that the chloride channel permeases contribute to fluoride resistance in S. mutans. | 2016 | 27190286 |
| 555 | 6 | 0.9946 | Mutations in dsbA and dsbB, but not dsbC, lead to an enhanced sensitivity of Escherichia coli to Hg2+ and Cd2+. The Dsb proteins are involved in disulfide bond formation, reduction and isomerisation in a number of Gram-negative bacteria. Mutations in dsbA or dsbB, but not dsbC, increase the proportion of proteins with free thiols in the periplasm compared to wild-type. We investigated the effects of mutations in these genes on the bacterial resistance to mercuric and cadmium salts. Mutations in genes involved primarily in disulfide formation (dsbA and dsbB) generally enhanced the sensitivity to Hg2+ and Cd2+ while a mutation of the dsbC gene (primarily an isomerase of disulfide bonds) had no effect. Mutations of the dsb genes had no effect on the expression of the mercury-resistance determinants of the transposon Tn501. | 1999 | 10234837 |
| 575 | 7 | 0.9946 | Identification and characterization of uvrA, a DNA repair gene of Deinococcus radiodurans. Deinococcus radiodurans is extraordinarily resistant to DNA damage, because of its unusually efficient DNA repair processes. The mtcA+ and mtcB+ genes of D. radiodurans, both implicated in excision repair, have been cloned and sequenced, showing that they are a single gene, highly homologous to the uvrA+ genes of other bacteria. The Escherichia coli uvrA+ gene was expressed in mtcA and mtcB strains, and it produced a high degree of complementation of the repair defect in these strains, suggesting that the UvrA protein of D. radiodurans is necessary but not sufficient to produce extreme DNA damage resistance. Upstream of the uvrA+ gene are two large open reading frames, both of which are directionally divergent from the uvrA+ gene. Evidence is presented that the proximal of these open reading frames may be irrB+. | 1996 | 8955293 |
| 563 | 8 | 0.9946 | Exit tunnel modulation as resistance mechanism of S. aureus erythromycin resistant mutant. The clinical use of the antibiotic erythromycin (ery) is hampered owing to the spread of resistance genes that are mostly mutating rRNA around the ery binding site at the entrance to the protein exit tunnel. Additional effective resistance mechanisms include deletion or insertion mutations in ribosomal protein uL22, which lead to alterations of the exit tunnel shape, located 16 Å away from the drug's binding site. We determined the cryo-EM structures of the Staphylococcus aureus 70S ribosome, and its ery bound complex with a two amino acid deletion mutation in its ß hairpin loop, which grants the bacteria resistance to ery. The structures reveal that, although the binding of ery is stable, the movement of the flexible shorter uL22 loop towards the tunnel wall creates a wider path for nascent proteins, thus enabling bypass of the barrier formed by the drug. Moreover, upon drug binding, the tunnel widens further. | 2019 | 31391518 |
| 371 | 9 | 0.9946 | 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 |
| 236 | 10 | 0.9946 | Glutamate decarboxylase-dependent acid resistance in orally acquired bacteria: function, distribution and biomedical implications of the gadBC operon. For successful colonization of the mammalian host, orally acquired bacteria must overcome the extreme acidic stress (pH < 2.5) encountered during transit through the host stomach. The glutamate-dependent acid resistance (GDAR) system is by far the most potent acid resistance system in commensal and pathogenic Escherichia coli, Shigella flexneri, Listeria monocytogenes and Lactococcus lactis. GDAR requires the activity of glutamate decarboxylase (GadB), an intracellular PLP-dependent enzyme which performs a proton-consuming decarboxylation reaction, and of the cognate antiporter (GadC), which performs the glutamatein /γ-aminobutyrateout (GABA) electrogenic antiport. Herein we review recent findings on the structural determinants responsible for pH-dependent intracellular activation of E. coli GadB and GadC. A survey of genomes of bacteria (pathogenic and non-pathogenic), having in common the ability to colonize or to transit through the host gut, shows that the gadB and gadC genes frequently lie next or near each other. This gene arrangement is likely to be important to ensure timely co-regulation of the decarboxylase and the antiporter. Besides the involvement in acid resistance, GABA production and release were found to occur at very high levels in lactic acid bacteria originally isolated from traditionally fermented foods, supporting the evidence that GABA-enriched foods possess health-promoting properties. | 2012 | 22995042 |
| 6222 | 11 | 0.9945 | 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 |
| 8232 | 12 | 0.9945 | Small acid-soluble proteins with intrinsic disorder are required for UV resistance in Myxococcus xanthus spores. Bacterial sporulation in Gram-positive bacteria results in small acid-soluble proteins called SASPs that bind to DNA and prevent the damaging effects of UV radiation. Orthologs of Bacillus subtilis genes encoding SASPs can be found in many sporulating and nonsporulating bacteria, but they are noticeably absent from spore-forming, Gram-negative Myxococcus xanthus. This is despite the fact that M. xanthus can form UV-resistant spores. Here we report evidence that M. xanthus produces its own unique group of low-molecular-weight, acid-soluble proteins that facilitate UV resistance in spores. These M. xanthus-specific SASPs vary depending upon whether spore formation is induced by starvation inside cell aggregations of fruiting bodies or is induced artificially by glycerol induction. Molecular predictions indicate that M. xanthus SASPs may have some association with the cell walls of M. xanthus spores, which may signify a different mechanism of UV protection than that seen in Gram-positive spores. | 2011 | 21515768 |
| 443 | 13 | 0.9945 | 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 |
| 372 | 14 | 0.9945 | A chromosomal locus required for copper resistance, competitive fitness, and cytochrome c biogenesis in Pseudomonas fluorescens. A chromosomal locus required for copper resistance and competitive fitness was cloned from a strain of Pseudomonas fluorescens isolated from copper-contaminated agricultural soil. Sequence analysis of this locus revealed six open reading frames with homology to genes involved in cytochrome c biogenesis in other bacteria, helC, cycJ, cycK, tipB, cycL, and cycH, with the closest similarity being to the aeg-46.5(yej) region of the Escherichia coli chromosome. The proposed functions of these genes in other bacteria include the binding, transport, and coupling of heme to apocytochrome c in the periplasm of these Gram-negative bacteria. Putative heme-binding motifs were present in the predicted products of cycK and cycL, and TipB contained a putative disulfide oxidoreductase active site proposed to maintain the heme-binding site of the apocytochrome in a reduced state for ligation of heme. Tn3-gus mutagenesis showed that expression of the genes was constitutive but enhanced by copper, and confirmed that the genes function both in copper resistance and production of active cytochrome c. However, two mutants in cycH were copper-sensitive and oxidase-positive, suggesting that the functions of these genes, rather than cytochrome c oxidase itself, were required for resistance to copper. | 1996 | 8692990 |
| 6357 | 15 | 0.9944 | Cloning and expression of the pediocin operon in Streptococcus thermophilus and other lactic fermentation bacteria. Production of pediocin in Pediococcus acidilactici is associated with pMBR1.0, which encodes prepediocin, a pediocin immunity protein, and two proteins involved in secretion and precursor processing. These four genes are organized as an operon under control of a single promoter. We have constructed shuttle vectors that contain all four structural genes, the chromosomal promoter ST(P2201) from Streptococcus thermophilus, and repA from the 2-kbp S. thermophilus plasmid pER8. The recombinant plasmid, pPC318, expressed and secreted active pediocin in Escherichia coli. Streptococcus thermophilus, Lactococcus lactis subsp. lactis, and Enterococcus faecalis were electrotransformed with pPC418, a modified vector fitted with an erythromycin resistance tracking gene. Pediocin was produced and secreted in each of the lactic acid bacteria, and production was stable for up to ten passages. The expression of pediocin in dairy fermentation microbes has important implications for bacteriocins as food preservatives in dairy products. | 1999 | 10489440 |
| 112 | 16 | 0.9944 | Glycopeptide resistance determinants from the teicoplanin producer Actinoplanes teichomyceticus. In enterococci and other pathogenic bacteria, high-level resistance to vancomycin and other glycopeptide antibiotics requires the action of the van genes, which direct the synthesis of peptidoglycan terminating in the depsipeptide D-alanyl-D-lactate, in place of the usual D-Ala-D-Ala. The Actinoplanes teichomyceticus tcp cluster, devoted to the biosynthesis of the glycopeptide antibiotic teicoplanin, contains van genes associated to a murF-like sequence (murF2). We show that A. teichomyceticus contains also a house-keeping murF1 gene, capable of complementing a temperature sensitive Escherichia coli murF mutant. MurF1, expressed in Streptomyces lividans, can catalyze the addition of either D-Ala-D-Ala or D-Ala-D-Lac to the UDP-N-acetyl-muramyl-L-Ala-D-Glu-d-Lys. However, similarly expressed MurF2 shows a small enzymatic activity only with D-Ala-D-lactate. Introduction of a single copy of the entire set of van genes confers resistance to teicoplanin-type glycopeptides to S. coelicolor. | 2004 | 15500981 |
| 719 | 17 | 0.9944 | Polyamines are critical for the induction of the glutamate decarboxylase-dependent acid resistance system in Escherichia coli. As part of our studies on the biological functions of polyamines, we have used a mutant of Escherichia coli that lacks all the genes for polyamine biosynthesis for a global transcriptional analysis on the effect of added polyamines. The most striking early response to the polyamine addition is the increased expression of the genes for the glutamate-dependent acid resistance system (GDAR) that is important for the survival of the bacteria when passing through the acid environment of the stomach. Not only were the two genes for glutamate decarboxylases (gadA and gadB) and the gene for glutamate-γ-aminobutyrate antiporter (gadC) induced by the polyamine addition, but the various genes involved in the regulation of this system were also induced. We confirmed the importance of polyamines for the induction of the GDAR system by direct measurement of glutamate decarboxylase activity and acid survival. The effect of deletions of the regulatory genes on the GDAR system and the effects of overproduction of two of these genes were also studied. Strikingly, overproduction of the alternative σ factor rpoS and of the regulatory gene gadE resulted in very high levels of glutamate decarboxylase and almost complete protection against acid stress even in the absence of any polyamines. Thus, these data show that a major function of polyamines in E. coli is protection against acid stress by increasing the synthesis of glutamate decarboxylase, presumably by increasing the levels of the rpoS and gadE regulators. | 2013 | 24097985 |
| 8372 | 18 | 0.9944 | A Plasmid-Encoded Putative Glycosyltransferase Is Involved in Hop Tolerance and Beer Spoilage in Lactobacillus brevis. Lactobacillus brevis beer-spoiling strains harbor plasmids that contain genes such as horA, horC, and hitA which are known to confer hop tolerance. The L. brevis beer-spoiling strain UCCLBBS124, which possesses four plasmids, was treated with novobiocin, resulting in the isolation of UCCLBBS124 derivatives exhibiting hop sensitivity and an inability to grow in beer. One selected derivative was shown to have lost a single plasmid, here designated UCCLBBS124_D, which harbors the UCCLBBS124_pD0015 gene, predicted to encode a glycosyltransferase. Hop tolerance and growth in beer were restored when UCCLBBS124_pD0015 was introduced in one of these hop-sensitive derivatives on a plasmid. We hypothesize that this gene modifies the surface composition of the polysaccharide cell wall, conferring protection against hop compounds. Furthermore, the introduction of this gene in trans in L. brevis UCCLB521, a strain that cannot grow in and spoil beer, was shown to furnish the resulting strain with the ability to grow in beer, while its expression also conferred phage resistance. This study underscores how the acquisition of certain mobile genetic elements plays a role in hop tolerance and beer spoilage for strains of this bacterial species.IMPORTANCELactobacillus brevis is a member of the lactic acid bacteria and is often reported as the causative agent of food or beverage spoilage, in particular, that of beer. Bacterial spoilage of beer may result in product withdrawal or recall, with concomitant economic losses for the brewing industry. A very limited number of genes involved in beer spoilage have been identified and primarily include those involved in hop resistance, such as horA, hitA, and horC However, since none of these genes are universal, it is clear that there are likely (many) other molecular players involved in beer spoilage. Here, we report on the importance of a plasmid-encoded glycosyltransferase associated with beer spoilage by L. brevis that is involved in hop tolerance. The study highlights the complexity of the genetic requirements to facilitate beer spoilage and the role of multiple key players in this process. | 2020 | 31757821 |
| 6196 | 19 | 0.9944 | New insights into the regulatory pathways associated with the activation of the stringent response in bacterial resistance to the PBP2-targeted antibiotics, mecillinam and OP0595/RG6080. OBJECTIVES: The diazabicyclooctane β-lactamase inhibitor OP0595 (RG6080) also acts as an antibiotic, targeting PBP2 in Enterobacteriaceae, but this activity is vulnerable to mutational resistance. We used WGS to investigate the basis of this resistance. METHODS: Twenty OP0595-selected mutants, comprising four derived from each of five different Escherichia coli strains, were sequenced on Illumina HiSeq. Reads from each mutant were mapped to the assembled genome of the corresponding parent. A variant-calling file generated with Samtools was parsed to determine genetic alterations. RESULTS: Besides OP0595, the mutants consistently showed decreased susceptibility to mecillinam, which likewise targets PBP2, and grew as stable round forms in the presence of subinhibitory concentrations of OP0595. Among the 20 mutants, 18 had alterations in genes encoding tRNA synthase and modification functions liable to induce expression of the RpoS sigma factor through activation of the stringent response or had mutations suppressing inactivators of RpoS or the stringent response signal-degrading enzyme, SpoT. TolB was inactivated in one mutant: this activates RcsBC regulation and was previously associated with mecillinam resistance. The mechanism of resistance remained unidentified in one mutant. Both the RpoS and RcsBC systems regulate genes of cell division, including ftsAQZ that can compensate for loss or inhibition of PBP2, allowing survival of the challenged bacteria as stable round forms, as seen. CONCLUSIONS: WGS identified the global stringent response signal, entailing induction of RpoS, as the main mediator of mutational resistance to OP0595 in E. coli. | 2016 | 27330062 |