# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 123 | 0 | 0.9260 | Genes for all metals--a bacterial view of the periodic table. The 1996 Thom Award Lecture. Bacterial chromosomes have genes for transport proteins for inorganic nutrient cations and oxyanions, such as NH4+, K+, Mg2+, Co2+, Fe3+, Mn2+, Zn2+ and other trace cations, and PO4(3-), SO4(2-) and less abundant oxyanions. Together these account for perhaps a few hundred genes in many bacteria. Bacterial plasmids encode resistance systems for toxic metal and metalloid ions including Ag+, AsO2-, AsO4(3-), Cd2+, Co2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, TeO3(2-), Tl+ and Zn2+. Most resistance systems function by energy-dependent efflux of toxic ions. A few involve enzymatic (mostly redox) transformations. Some of the efflux resistance systems are ATPases and others are chemiosmotic ion/proton exchangers. The Cd(2+)-resistance cation pump of Gram-positive bacteria is membrane P-type ATPase, which has been labeled with 32P from [gamma-32P]ATP and drives ATP-dependent Cd2+ (and Zn2+) transport by membrane vesicles. The genes defective in the human hereditary diseases of copper metabolism, Menkes syndrome and Wilson's disease, encode P-type ATPases that are similar to bacterial cadmium ATPases. The arsenic resistance system transports arsenite [As(III)], alternatively with the ArsB polypeptide functioning as a chemiosmotic efflux transporter or with two polypeptides, ArsB and ArsA, functioning as an ATPase. The third protein of the arsenic resistance system is an enzyme that reduces intracellular arsenate [As(V)] to arsenite [As(III)], the substrate of the efflux system. In Gram-negative cells, a three polypeptide complex functions as a chemiosmotic cation/protein exchanger to efflux Cd2+, Zn2+ and Co2+. This pump consists of an inner membrane (CzcA), an outer membrane (CzcC) and a membrane-spanning (CzcB) protein that function together. | 1998 | 9523453 |
| 124 | 1 | 0.9219 | A bacterial view of the periodic table: genes and proteins for toxic inorganic ions. Essentially all bacteria have genes for toxic metal ion resistances and these include those for Ag+, AsO2-, AsO4(3-), Cd2+ Co2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, TeO3(2-), Tl+ and Zn2+. The largest group of resistance systems functions by energy-dependent efflux of toxic ions. Fewer involve enzymatic transformations (oxidation, reduction, methylation, and demethylation) or metal-binding proteins (for example, metallothionein SmtA, chaperone CopZ and periplasmic silver binding protein SilE). Some of the efflux resistance systems are ATPases and others are chemiosmotic ion/proton exchangers. For example, Cd2+-efflux pumps of bacteria are either inner membrane P-type ATPases or three polypeptide RND chemiosmotic complexes consisting of an inner membrane pump, a periplasmic-bridging protein and an outer membrane channel. In addition to the best studied three-polypeptide chemiosmotic system, Czc (Cd2+, Zn2+, and Co2), others are known that efflux Ag+, Cu+, Ni2+, and Zn2+. Resistance to inorganic mercury, Hg2+ (and to organomercurials, such as CH3Hg+ and phenylmercury) involve a series of metal-binding and membrane transport proteins as well as the enzymes mercuric reductase and organomercurial lyase, which overall convert more toxic to less toxic forms. Arsenic resistance and metabolizing systems occur in three patterns, the widely-found ars operon that is present in most bacterial genomes and many plasmids, the more recently recognized arr genes for the periplasmic arsenate reductase that functions in anaerobic respiration as a terminal electron acceptor, and the aso genes for the periplasmic arsenite oxidase that functions as an initial electron donor in aerobic resistance to arsenite. | 2005 | 16133099 |
| 517 | 2 | 0.9113 | Adaptation to metal(loid)s in strain Mucilaginibacter rubeus P2 involves novel arsenic resistance genes and mechanisms. Arsenic is a ubiquitous environmental toxi substance that affects human health. Compared to inorganic arsenicals, reduced organoarsenicals are more toxic, and some of them are recognized as antibiotics, such as methylarsenite [MAs(III)] and arsinothricin (2-amino-4-(hydroxymethylarsinoyl)butanoate, or AST). To date, organoarsenicals such as MAs(V) and roxarsone [Rox(V)] are still used in agriculture and animal husbandry. How bacteria deal with both inorganic and organoarsenic species is unclear. Recently, we identified an environmental isolate Mucilaginibacter rubeus P2 that has adapted to high arsenic and antinomy levels by triplicating an arsR-mrarsU(Bact)-arsN-arsC-(arsRhp)-hp-acr3-mrme1(Bact)-mrme2(Bact)gene cluster. Heterologous expression of mrarsM(Bact), mrarsU(Bact), mrme1(Bact) and mrme2(Bact), encoding putative arsenic resistance determinants, in the arsenic hypersensitive strain Escherichia coli AW3110 conferred resistance to As(III), As(V), MAs(III) or Rox(III). Our data suggest that metalloid exposure promotes plasticity in arsenic resistance systems, enhancing host organism adaptation to metalloid stress. | 2024 | 37865075 |
| 107 | 3 | 0.9110 | Common ancestry of iron oxide- and iron-sulfide-based biomineralization in magnetotactic bacteria. Magnetosomes are prokaryotic organelles produced by magnetotactic bacteria that consist of nanometer-sized magnetite (Fe(3)O(4)) or/and greigite (Fe(3)S(4)) magnetic crystals enveloped by a lipid bilayer membrane. In magnetite-producing magnetotactic bacteria, proteins present in the magnetosome membrane modulate biomineralization of the magnetite crystal. In these microorganisms, genes that encode for magnetosome membrane proteins as well as genes involved in the construction of the magnetite magnetosome chain, the mam and mms genes, are organized within a genomic island. However, partially because there are presently no greigite-producing magnetotactic bacteria in pure culture, little is known regarding the greigite biomineralization process in these organisms including whether similar genes are involved in the process. Here using culture-independent techniques, we now show that mam genes involved in the production of magnetite magnetosomes are also present in greigite-producing magnetotactic bacteria. This finding suggest that the biomineralization of magnetite and greigite did not have evolve independently (that is, magnetotaxis is polyphyletic) as once suggested. Instead, results presented here are consistent with a model in which the ability to biomineralize magnetosomes and the possession of the mam genes was acquired by bacteria from a common ancestor, that is, the magnetotactic trait is monophyletic. | 2011 | 21509043 |
| 579 | 4 | 0.9104 | Control of expression of a periplasmic nickel efflux pump by periplasmic nickel concentrations. There is accumulating evidence that transenvelope efflux pumps of the resistance, nodulation, cell division protein family (RND) are excreting toxic substances from the periplasm across the outer membrane directly to the outside. This would mean that resistance of Gram-negative bacteria to organic toxins and heavy metals is in fact a two-step process: one set of resistance factors control the concentration of a toxic substance in the periplasm, another one that in the cytoplasm. Efficient periplasmic detoxification requires periplasmic toxin sensing and transduction of this signal into the cytoplasm to control expression of the periplasmic detoxification system. Such a signal transduction system was analyzed using the Cnr nickel resistance system from Cupriavidus (Wautersia, Ralstonia, Alcaligenes) metallidurans strain CH34. Resistance is based on nickel efflux mediated by the CnrCBA efflux pump encoded by the cnrYHXCBAT metal resistance determinant. The products of the three genes cnrYXH transcriptionally regulate expression of cnr. CnrY and CnrX are membrane-bound proteins probably functioning as anti sigma factors while CnrH is a cnr-specific extracytoplasmic functions (ECF) sigma factors. Experimental data provided here indicate a signal transduction chain leading from nickel in the periplasm to transcription initiation at the cnr promoters cnrYp and cnrCp, which control synthesis of the nickel efflux pump CnrCBA. | 2005 | 16158236 |
| 806 | 5 | 0.9084 | A two-component small multidrug resistance pump functions as a metabolic valve during nicotine catabolism by Arthrobacter nicotinovorans. The genes nepAB of a small multidrug resistance (SMR) pump were identified as part of the pAO1-encoded nicotine regulon responsible for nicotine catabolism in Arthrobacter nicotinovorans. When [(14)C]nicotine was added to the growth medium the bacteria exported the (14)C-labelled end product of nicotine catabolism, methylamine. In the presence of the proton-motive force inhibitors 2,4-dinitrophenol (DNP), carbonyl cyanide m-chlorophenylhydrazone (CCCP) or the proton ionophore nigericin, export of methylamine was inhibited and radioactivity accumulated inside the bacteria. Efflux of [(14)C]nicotine-derived radioactivity from bacteria was also inhibited in a pmfR : cmx strain with downregulated nepAB expression. Because of low amine oxidase levels in the pmfR : cmx strain, gamma-N-methylaminobutyrate, the methylamine precursor, accumulated. Complementation of this strain with the nepAB genes, carried on a plasmid, restored the efflux of nicotine breakdown products. Both NepA and NepB were required for full export activity, indicating that they form a two-component efflux pump. NepAB may function as a metabolic valve by exporting methylamine, the end product of nicotine catabolism, and, in conditions under which it accumulates, the intermediate gamma-N-methylaminobutyrate. | 2007 | 17464069 |
| 655 | 6 | 0.9082 | Identification of a cell envelope protein (MtrF) involved in hydrophobic antimicrobial resistance in Neisseria gonorrhoeae. The mtrCDE-encoded efflux pump of Neisseria gonorrhoeae provides gonococci with a mechanism to resist structurally diverse antimicrobial hydrophobic agents (HAs). Strains of N. gonorrhoeae that display hypersusceptibility to HAs often contain mutations in the efflux pump genes, mtrCDE. Such strains frequently contain a phenotypically suppressed mutation in mtrR, a gene that encodes a repressor (MtrR) of mtrCDE gene expression, and one that would normally result in HA resistance. We have recently examined HA-hypersusceptible clinical isolates of gonococci that contain such phenotypically suppressed mtrR mutations, in order to determine whether genes other than mtrCDE are involved in HA resistance. These studies led to the discovery of a gene that we have designated mtrF, located downstream of the mtrR gene, that is predicted to encode a 56.1 kDa cytoplasmic membrane protein containing 12 transmembrane domains. Expression of mtrF was enhanced in a strain deficient in MtrR production, indicating that this gene, together with the closely linked mtrCDE operon, is subject to MtrR-dependent transcriptional control. Orthologues of mtrF were identified in a number of diverse bacteria. Except for the AbgT protein of Escherichia coli, their products have been identified as hypothetical proteins with unknown function(s). Genetic evidence is presented that MtrF is important in the expression of high-level detergent resistance by gonococci. We propose that MtrF acts in conjunction with the MtrC-MtrD-MtrE efflux pump, to confer on gonococci high-level resistance to certain HAs. | 2003 | 12493784 |
| 218 | 7 | 0.9077 | Bacterial silver resistance: molecular biology and uses and misuses of silver compounds. Resistance to silver compounds as determined by bacterial plasmids and genes has been defined by molecular genetics. Silver resistance conferred by the Salmonella plasmid pMGH100 involves nine genes in three transcription units. A sensor/responder (SilRS) two-component transcriptional regulatory system governs synthesis of a periplasmic Ag(I)-binding protein (SilE) and two efflux pumps (a P-type ATPase (SilP) plus a three-protein chemiosmotic RND Ag(I)/H+ exchange system (SilCBA)). The same genes were identified on five of 19 additional IncH incompatibility class plasmids but thus far not on other plasmids. Of 70 random enteric isolates from a local hospital, isolates from catheters and other Ag-exposed sites, and total genomes of enteric bacteria, 10 have recognizable sil genes. The centrally located six genes are found and functional in the chromosome of Escherichia coli K-12, and also occur on the genome of E. coli O157:H7. The use of molecular epidemiological tools will establish the range and diversity of such resistance systems in clinical and non-clinical sources. Silver compounds are used widely as effective antimicrobial agents to combat pathogens (bacteria, viruses and eukaryotic microorganisms) in the clinic and for public health hygiene. Silver cations (Ag+) are microcidal at low concentrations and used to treat burns, wounds and ulcers. Ag is used to coat catheters to retard microbial biofilm development. Ag is used in hygiene products including face creams, "alternative medicine" health supplements, supermarket products for washing vegetables, and water filtration cartridges. Ag is generally without adverse effects for humans, and argyria (irreversible discoloration of the skin resulting from subepithelial silver deposits) is rare and mostly of cosmetic concern. | 2003 | 12829274 |
| 330 | 8 | 0.9076 | A DHA14 drug efflux gene from Xanthomonas albilineans confers high-level albicidin antibiotic resistance in Escherichia coli. AIMS: Identification of a gene for self-protection from the antibiotic-producing plant pathogen Xanthomonas albilineans, and functional testing by heterologous expression. METHODS AND RESULTS: Albicidin antibiotics and phytotoxins are potent inhibitors of prokaryote DNA replication. A resistance gene (albF) isolated by shotgun cloning from the X. albilineans albicidin-biosynthesis region encodes a protein with typical features of DHA14 drug efflux pumps. Low-level expression of albF in Escherichia coli increased the MIC of albicidin 3000-fold, without affecting tsx-mediated albicidin uptake into the periplasm or resistance to other tested antibiotics. Bioinformatic analysis indicates more similarity to proteins involved in self-protection in polyketide-antibiotic-producing actinomycetes than to multi-drug resistance pumps in other gram-negative bacteria. A complex promoter region may co-regulate albF with genes for hydrolases likely to be involved in albicidin activation or self-protection. CONCLUSIONS: AlbF is the first apparent single-component antibiotic-specific efflux pump from a gram-negative antibiotic producer. It shows extraordinary efficiency as measured by resistance level conferred upon heterologous expression. SIGNIFICANCE AND IMPACT OF THE STUDY: Development of the clinical potential of albicidins as potent bactericidial antibiotics against diverse bacteria has been limited because of low yields in culture. Expression of albF with recently described albicidin-biosynthesis genes may enable large-scale production. Because albicidins are X. albilineans pathogenicity factors, interference with AlbF function is also an opportunity for control of the associated plant disease. | 2006 | 16834602 |
| 805 | 9 | 0.9076 | LexR Positively Regulates the LexABC Efflux Pump Involved in Self-Resistance to the Antimicrobial Di-N-Oxide Phenazine in Lysobacter antibioticus. Myxin, a di-N-oxide phenazine isolated from the soil bacterium Lysobacter antibioticus, exhibits potent activity against various microorganisms and has the potential to be developed as an agrochemical. Antibiotic-producing microorganisms have developed self-resistance mechanisms to protect themselves from autotoxicity. Antibiotic efflux is vital for such protection. Recently, we identified a resistance-nodulation-division (RND) efflux pump, LexABC, involved in self-resistance against myxin in L. antibioticus. Expression of its genes, lexABC, was induced by myxin and was positively regulated by the LysR family transcriptional regulator LexR. The molecular mechanisms, however, have not been clear. Here, LexR was found to bind to the lexABC promoter region to directly regulate expression. Moreover, myxin enhanced this binding. Molecular docking and surface plasmon resonance analysis showed that myxin bound LexR with valine and lysine residues at positions 146 (V146) and 195 (K195), respectively. Furthermore, mutation of K195 in vivo led to downregulation of the gene lexA. These results indicated that LexR sensed and bound with myxin, thereby directly activating the expression of the LexABC efflux pump and increasing L. antibioticus resistance against myxin. IMPORTANCE Antibiotic-producing bacteria exhibit various sophisticated mechanisms for self-protection against their own secondary metabolites. RND efflux pumps that eliminate antibiotics from cells are ubiquitous in Gram-negative bacteria. Myxin is a heterocyclic N-oxide phenazine with potent antimicrobial and antitumor activities produced by the soil bacterium L. antibioticus. The RND pump LexABC contributes to the self-resistance of L. antibioticus against myxin. Herein, we report a mechanism involving the LysR family regulator LexR that binds to myxin and directly activates the LexABC pump. Further study on self-resistance mechanisms could help the investigation of strategies to deal with increasing bacterial antibiotic resistance and enable the discovery of novel natural products with resistance genes as selective markers. | 2023 | 37166326 |
| 167 | 10 | 0.9075 | Ion efflux systems involved in bacterial metal resistances. Studying metal ion resistance gives us important insights into environmental processes and provides an understanding of basic living processes. This review concentrates on bacterial efflux systems for inorganic metal cations and anions, which have generally been found as resistance systems from bacteria isolated from metal-polluted environments. The protein products of the genes involved are sometimes prototypes of new families of proteins or of important new branches of known families. Sometimes, a group of related proteins (and presumedly the underlying physiological function) has still to be defined. For example, the efflux of the inorganic metal anion arsenite is mediated by a membrane protein which functions alone in Gram-positive bacteria, but which requires an additional ATPase subunit in some Gram-negative bacteria. Resistance to Cd2+ and Zn2+ in Gram-positive bacteria is the result of a P-type efflux ATPase which is related to the copper transport P-type ATPases of bacteria and humans (defective in the human hereditary diseases Menkes' syndrome and Wilson's disease). In contrast, resistance to Zn2+, Ni2+, Co2+ and Cd2+ in Gram-negative bacteria is based on the action of proton-cation antiporters, members of a newly-recognized protein family that has been implicated in diverse functions such as metal resistance/nodulation of legumes/cell division (therefore, the family is called RND). Another new protein family, named CDF for 'cation diffusion facilitator' has as prototype the protein CzcD, which is a regulatory component of a cobalt-zinc-cadmium resistance determinant in the Gram-negative bacterium Alcaligenes eutrophus. A family for the ChrA chromate resistance system in Gram-negative bacteria has still to be defined. | 1995 | 7766211 |
| 556 | 11 | 0.9072 | An ArsR/SmtB family member regulates arsenic resistance genes unusually arranged in Thermus thermophilus HB27. Arsenic resistance is commonly clustered in ars operons in bacteria; main ars operon components encode an arsenate reductase, a membrane extrusion protein, and an As-sensitive transcription factor. In the As-resistant thermophile Thermus thermophilus HB27, genes encoding homologues of these proteins are interspersed in the chromosome. In this article, we show that two adjacent genes, TtsmtB, encoding an ArsR/SmtB transcriptional repressor and, TTC0354, encoding a Zn(2+) /Cd(2+) -dependent membrane ATPase are involved in As resistance; differently from characterized ars operons, the two genes are transcribed from dedicated promoters upstream of their respective genes, whose expression is differentially regulated at transcriptional level. Mutants defective in TtsmtB or TTC0354 are more sensitive to As than the wild type, proving their role in arsenic resistance. Recombinant dimeric TtSmtB binds in vitro to both promoters, but its binding capability decreases upon interaction with arsenate and, less efficiently, with arsenite. In vivo and in vitro experiments also demonstrate that the arsenate reductase (TtArsC) is subjected to regulation by TtSmtB. We propose a model for the regulation of As resistance in T. thermophilus in which TtSmtB is the arsenate sensor responsible for the induction of TtArsC which generates arsenite exported by TTC0354 efflux protein to detoxify cells. | 2017 | 28696001 |
| 166 | 12 | 0.9069 | Cupriavidus metallidurans: evolution of a metal-resistant bacterium. Cupriavidus metallidurans CH34 has gained increasing interest as a model organism for heavy metal detoxification and for biotechnological purposes. Resistance of this bacterium to transition metal cations is predominantly based on metal resistance determinants that contain genes for RND (resistance, nodulation, and cell division protein family) proteins. These are part of transenvelope protein complexes, which seem to detoxify the periplasm by export of toxic metal cations from the periplasm to the outside. Strain CH34 contains 12 predicted RND proteins belonging to a protein family of heavy metal exporters. Together with many efflux systems that detoxify the cytoplasm, regulators and possible metal-binding proteins, RND proteins mediate an efficient defense against transition metal cations. To shed some light into the origin of genes encoding these proteins, the genomes of C. metallidurans CH34 and six related proteobacteria were investigated for occurrence of orthologous and paralogous proteins involved in metal resistance. Strain CH34 was not much different from the other six bacteria when the total content of transport proteins was compared but CH34 had significantly more putative transition metal transport systems than the other bacteria. The genes for these systems are located on its chromosome 2 but especially on plasmids pMOL28 and pMOL30. Cobalt-nickel and chromate resistance determinants located on plasmid pMOL28 evolved by gene duplication and horizontal gene transfer events, leading to a better adaptation of strain CH34 to serpentine-like soils. The czc cobalt-zinc-cadmium resistance determinant, located on plasmid pMOL30 in addition copper, lead and mercury resistance determinants, arose by duplication of a czcICAB core determinant on chromosome 2, plus addition of the czcN gene upstream and the genes czcD, czcRS, czcE downstream of czcICBA. C. metallidurans apparently evolved metal resistance by horizontal acquisition and by duplication of genes for transition metal efflux, mostly on the two plasmids, and decreased the number of uptake systems for those metals. | 2009 | 18830684 |
| 6014 | 13 | 0.9067 | Whole genome sequencing and analysis of plant growth promoting bacteria isolated from the rhizosphere of plantation crops coconut, cocoa and arecanut. Coconut, cocoa and arecanut are commercial plantation crops that play a vital role in the Indian economy while sustaining the livelihood of more than 10 million Indians. According to 2012 Food and Agricultural organization's report, India is the third largest producer of coconut and it dominates the production of arecanut worldwide. In this study, three Plant Growth Promoting Rhizobacteria (PGPR) from coconut (CPCRI-1), cocoa (CPCRI-2) and arecanut (CPCRI-3) characterized for the PGP activities have been sequenced. The draft genome sizes were 4.7 Mb (56% GC), 5.9 Mb (63.6% GC) and 5.1 Mb (54.8% GB) for CPCRI-1, CPCRI-2, CPCRI-3, respectively. These genomes encoded 4056 (CPCRI-1), 4637 (CPCRI-2) and 4286 (CPCRI-3) protein-coding genes. Phylogenetic analysis revealed that both CPCRI-1 and CPCRI-3 belonged to Enterobacteriaceae family, while, CPCRI-2 was a Pseudomonadaceae family member. Functional annotation of the genes predicted that all three bacteria encoded genes needed for mineral phosphate solubilization, siderophores, acetoin, butanediol, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, chitinase, phenazine, 4-hydroxybenzoate, trehalose and quorum sensing molecules supportive of the plant growth promoting traits observed in the course of their isolation and characterization. Additionally, in all the three CPCRI PGPRs, we identified genes involved in synthesis of hydrogen sulfide (H2S), which recently has been proposed to aid plant growth. The PGPRs also carried genes for central carbohydrate metabolism indicating that the bacteria can efficiently utilize the root exudates and other organic materials as energy source. Genes for production of peroxidases, catalases and superoxide dismutases that confer resistance to oxidative stresses in plants were identified. Besides these, genes for heat shock tolerance, cold shock tolerance and glycine-betaine production that enable bacteria to survive abiotic stress were also identified. | 2014 | 25162593 |
| 343 | 14 | 0.9066 | Cloning and molecular characterization of three arylamine N-acetyltransferase genes from Bacillus anthracis: identification of unusual enzymatic properties and their contribution to sulfamethoxazole resistance. The arylamine N-acetyltransferases (NATs) are xenobiotic-metabolizing enzymes that catalyze the N-acetylation of arylamines and their N-hydroxylated metabolites. These enzymes play a key role in detoxication of numerous drugs and xenobiotics. We report here the cloning, functional expression, and characterization of three new NAT genes (termed banatA, banatB, and banatC) from the pathogen Bacillus anthracis. The sequences of the corresponding proteins are approximately 30% identical with those of characterized eukaryotic and prokaryotic NAT enzymes, and the proteins were recognized by an anti-NAT antibody. The three genes were endogenously expressed in B. anthracis, and NAT activity was found in cell extracts. The three NAT homologues exhibited distinct structural and enzymatic properties, some of which have not previously been observed with other NAT enzymes. Recombinant BanatC displayed strong NAT activity toward several prototypic NAT substrates, including the sulfonamide antibiotic sulfamethoxazole (SMX). As opposed to BanatC, BanatB also had acetyl-CoA (AcCoA) and p-nitrophenyl acetate (PNPA) hydrolysis activity in the absence of arylamine substrates, indicating that it may act as an AcCoA hydrolase. BanatA was devoid of NAT or AcCoA/PNPA hydrolysis activities, suggesting that it may be a new bacterial NAT-like protein with unknown function. Expression of BanatC in Escherichia coli afforded higher-than-normal resistance to SMX in the recombinant bacteria, whereas an inactive mutant of the enzyme did not. These data indicate that BanatC could contribute to the resistance of B. anthracis to SMX. | 2007 | 17511472 |
| 9997 | 15 | 0.9065 | RNAi screen of DAF-16/FOXO target genes in C. elegans links pathogenesis and dauer formation. The DAF-16/FOXO transcription factor is the major downstream output of the insulin/IGF1R signaling pathway controlling C. elegans dauer larva development and aging. To identify novel downstream genes affecting dauer formation, we used RNAi to screen candidate genes previously identified to be regulated by DAF-16. We used a sensitized genetic background [eri-1(mg366); sdf-9(m708)], which enhances both RNAi efficiency and constitutive dauer formation (Daf-c). Among 513 RNAi clones screened, 21 displayed a synthetic Daf-c (SynDaf) phenotype with sdf-9. One of these genes, srh-100, was previously identified to be SynDaf, but twenty have not previously been associated with dauer formation. Two of the latter genes, lys-1 and cpr-1, are known to participate in innate immunity and six more are predicted to do so, suggesting that the immune response may contribute to the dauer decision. Indeed, we show that two of these genes, lys-1 and clc-1, are required for normal resistance to Staphylococcus aureus. clc-1 is predicted to function in epithelial cohesion. Dauer formation exhibited by daf-8(m85), sdf-9(m708), and the wild-type N2 (at 27°C) were all enhanced by exposure to pathogenic bacteria, while not enhanced in a daf-22(m130) background. We conclude that knockdown of the genes required for proper pathogen resistance increases pathogenic infection, leading to increased dauer formation in our screen. We propose that dauer larva formation is a behavioral response to pathogens mediated by increased dauer pheromone production. | 2010 | 21209831 |
| 581 | 16 | 0.9064 | Inorganic polyphosphates and heavy metal resistance in microorganisms. The mechanisms of heavy metal resistance in microbial cells involve multiple pathways. They include the formation of complexes with specific proteins and other compounds, the excretion from the cells via plasma membrane transporters in case of procaryotes, and the compartmentalization of toxic ions in vacuoles, cell wall and other organelles in case of eukaryotes. The relationship between heavy metal tolerance and inorganic polyphosphate metabolism was demonstrated both in prokaryotic and eukaryotic microorganisms. Polyphosphates, being polyanions, are involved in detoxification of heavy metals through complex formation and compartmentalization. The bacteria and fungi cultivated in the presence of some heavy metal cations contain the enhanced levels of polyphosphate. In bacteria, polyphosphate sequesters heavy metals; some of metal cations stimulate an exopolyphosphatase activity, which releases phosphate from polyphosphates, and MeHPO(4)(-) ions are then transported out of the cells. In fungi, the overcoming of heavy metal stresses is associated with the accumulation of polyphosphates in cytoplasmic inclusions, vacuoles and cell wall and the formation of cation/polyphosphate complexes. The effects of knockout mutations and overexpression of the genes encoding polyphosphate-metabolizing enzymes on heavy metal resistance are discussed. | 2018 | 30151754 |
| 331 | 17 | 0.9064 | MmpS4 promotes glycopeptidolipids biosynthesis and export in Mycobacterium smegmatis. The MmpS family (mycobacterial membrane protein small) includes over 100 small membrane proteins specific to the genus Mycobacterium that have not yet been studied experimentally. The genes encoding MmpS proteins are often associated with mmpL genes, which are homologous to the RND (resistance nodulation cell division) genes of Gram-negative bacteria that encode proteins functioning as multidrug efflux system. We showed by molecular genetics and biochemical analysis that MmpS4 in Mycobacterium smegmatis is required for the production and export of large amounts of cell surface glycolipids, but is dispensable for biosynthesis per se. A new specific and sensitive method utilizing single-chain antibodies against the surface-exposed glycolipids was developed to confirm that MmpS4 was dispensable for transport to the surface. Orthologous complementation demonstrated that the MmpS4 proteins are exchangeable, thus not specific to a defined lipid species. MmpS4 function requires the formation of a protein complex at the pole of the bacillus, which requires the extracytosolic C-terminal domain of MmpS4. We suggest that MmpS proteins facilitate lipid biosynthesis by acting as a scaffold for coupled biosynthesis and transport machinery. | 2010 | 21062372 |
| 510 | 18 | 0.9064 | ArsZ from Ensifer adhaerens ST2 is a novel methylarsenite oxidase. Trivalent methylarsenite [MAs(III)] produced by biomethylation is more toxic than inorganic arsenite [As(III)]. Hence, MAs(III) has been proposed to be a primordial antibiotic. Other bacteria evolved mechanisms to detoxify MAs(III). In this study, the molecular mechanisms of MAs(III) resistance of Ensifer adhaerens ST2 were investigated. In the chromosome of E. adhaerens ST2 is a gene encoding a protein of unknown function. Here, we show that this gene, designated arsZ, encodes a novel MAs(III) oxidase that confers resistance by oxidizing highly toxic MAs(III) to relatively nontoxic MAs(V). Two other genes, arsRK, are adjacent to arsZ but are divergently encoded in the opposite direction. Heterologous expression of arsZ in Escherichia coli confers resistance to MAs(III) but not to As(III). Purified ArsZ catalyses thioredoxin- and NAPD(+) -dependent oxidation of MAs(III). Mutational analysis of ArsZ suggests that Cys59 and Cys123 are involved in the oxidation of MAs(III). Expression of arsZ, arsR and arsK genes is induced by MAs(III) and As(III) and is likely controlled by the ArsR transcriptional repressor. These results demonstrate that ArsZ is a novel MAs(III) oxidase that contributes to E. adhaerens tolerance to environmental organoarsenicals. The arsZRK operon is widely present in bacteria within the Rhizobiaceae family. | 2022 | 35355385 |
| 191 | 19 | 0.9062 | Mariprofundus ferrooxydans PV-1 the first genome of a marine Fe(II) oxidizing Zetaproteobacterium. Mariprofundus ferrooxydans PV-1 has provided the first genome of the recently discovered Zetaproteobacteria subdivision. Genome analysis reveals a complete TCA cycle, the ability to fix CO(2), carbon-storage proteins and a sugar phosphotransferase system (PTS). The latter could facilitate the transport of carbohydrates across the cell membrane and possibly aid in stalk formation, a matrix composed of exopolymers and/or exopolysaccharides, which is used to store oxidized iron minerals outside the cell. Two-component signal transduction system genes, including histidine kinases, GGDEF domain genes, and response regulators containing CheY-like receivers, are abundant and widely distributed across the genome. Most of these are located in close proximity to genes required for cell division, phosphate uptake and transport, exopolymer and heavy metal secretion, flagellar biosynthesis and pilus assembly suggesting that these functions are highly regulated. Similar to many other motile, microaerophilic bacteria, genes encoding aerotaxis as well as antioxidant functionality (e.g., superoxide dismutases and peroxidases) are predicted to sense and respond to oxygen gradients, as would be required to maintain cellular redox balance in the specialized habitat where M. ferrooxydans resides. Comparative genomics with other Fe(II) oxidizing bacteria residing in freshwater and marine environments revealed similar content, synteny, and amino acid similarity of coding sequences potentially involved in Fe(II) oxidation, signal transduction and response regulation, oxygen sensation and detoxification, and heavy metal resistance. This study has provided novel insights into the molecular nature of Zetaproteobacteria. | 2011 | 21966516 |