51
|
Hendrick CA, Haskins WP, Vidaver AK. Conjugative Plasmid in Corynebacterium flaccumfaciens subsp. oortii That Confers Resistance to Arsenite, Arsenate, and Antimony(III). Appl Environ Microbiol 2010; 48:56-60. [PMID: 16346601 PMCID: PMC240307 DOI: 10.1128/aem.48.1.56-60.1984] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gene transfer systems for phytopathogenic corynebacteria have not been reported previously. In this paper we describe a conjugative 46-megadalton plasmid (pDG101) found in Corynebacterium flaccumfaciens subsp. oortii CO101 that mediates resistance to arsenite, arsenate, and antimony(III). Transfer of the plasmid from CO101 to four other strains from the C. flaccumfaciens group occurred between cells immobilized on nitrocellulose filters or on agar surfaces. Transconjugant strains expressed the same levels of metal resistance as the donor strain and were able to act as donor strains in subsequent matings. The physical presence of the plasmid was detected by agarose gel electrophoresis. Arsenite-sensitive derivatives of the donor and transconjugant strains were obtained after heat treatment; these were cured of pDG101.
Collapse
Affiliation(s)
- C A Hendrick
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0722
| | | | | |
Collapse
|
52
|
Hamlett NV. Alteration of a salt marsh bacterial community by fertilization with sewage sludge. Appl Environ Microbiol 2010; 52:915-23. [PMID: 16347183 PMCID: PMC239138 DOI: 10.1128/aem.52.4.915-923.1986] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of long-term fertilization with sewage sludge on the aerobic, chemoheterotrophic portion of a salt marsh bacterial community were examined. The study site in the Great Sippewissett Marsh, Cape Cod, Mass., consisted of experimental plots that were treated with different amounts of commercial sewage sludge fertilizer or with urea and phosphate. The number of CFUs, percentage of mercury- and cadmium-resistant bacteria, and percentage of antibiotic-resistant bacteria were all increased in the sludge-fertilized plots. Preliminary taxonomic characterization showed that sludge fertilization markedly altered the taxonomic distribution and reduced diversity within both the total heterotrophic and the mercury-resistant communities. In control plots, the total heterotrophic community was fairly evenly distributed among taxa and the mercury-resistant community was dominated by Pseudomonas spp. In sludge-fertilized plots, both the total and mercury-resistant communities were dominated by a single Cytophaga sp.
Collapse
Affiliation(s)
- N V Hamlett
- Department of Biology, Swarthmore College, Swarthmore, Pennsylvania 19081, and Marine Biological Laboratory, Woods Hole, Massachusetts 02543
| |
Collapse
|
53
|
Perlin MH, Clark DR, McKenzie C, Patel H, Jackson N, Kormanik C, Powell C, Bajorek A, Myers DA, Dugatkin LA, Atlas RM. Protection of Salmonella by ampicillin-resistant Escherichia coli in the presence of otherwise lethal drug concentrations. Proc Biol Sci 2009; 276:3759-68. [PMID: 19656787 DOI: 10.1098/rspb.2009.0997] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Microbial systems have become the preferred testing grounds for experimental work on the evolution of traits that benefit other group members. This work, based on conceptual and theoretical models of frequency-dependent selection within populations, has proven fruitful in terms of understanding the dynamics of group beneficial or 'public goods' traits within species. Here, we expand the scope of microbial work on the evolution of group-beneficial traits to the case of multi-species communities, particularly those that affect human health. We examined whether beta-lactamase-producing Escherichia coli could protect ampicillin-sensitive cohorts of other species, particularly species that could cause human disease. Both beta-lactamase-secreting E. coli and, surprisingly, those engineered to retain it, allowed for survival of a large number of ampicillin-sensitive cohorts of Salmonella enterica serovar Typhimurium, including both laboratory and clinical isolates. The Salmonella survivors, however, remained sensitive to ampicillin when re-plated onto solid medium and there was no evidence of gene transfer. Salmonella survival did not even require direct physical contact with the resistant E. coli. The observed phenomenon appears to involve increased release of beta-lactamase from the E. coli when present with S. enterica. Significantly, these findings imply that resistant E. coli, that are not themselves pathogenic, may be exploited, even when they are normally selfish with respect to other E. coli. Thus, Salmonella can gain protection against antibiotics from E. coli without gene transfer, a phenomenon not previously known. As a consequence, antibiotic-resistant E. coli can play a decisive role in the survival of a species that causes disease and may thereby interfere with successful treatment.
Collapse
Affiliation(s)
- Michael H Perlin
- Department of Biology, Program on Disease Evolution, University of Louisville, Louisville, KY, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
54
|
Joshi PM, Juwarkar AA. In vivo studies to elucidate the role of extracellular polymeric substances from Azotobacter in immobilization of heavy metals. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:5884-9. [PMID: 19731692 DOI: 10.1021/es900063b] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The role of extracellular polymeric substances (EPS) produced by the heavy metal-resistant strain of Azotobacter spp. in restricting the uptake of cadmium (Cd) and chromium (Cr) by wheat plants cultivated in soils contaminated with the respective heavy metals has been demonstrated. A heavy metal-resistant strain of Azotobacter spp. was isolated and identified. Minimum inhibitory concentrations (MIC) of Cd2+ and CrO4(2-) were determined to be 20 and 10 mg L(-1), respectively. Under in vitro conditions, the EPS produced by the strain could bind 15.17 +/- 0.58 mg g(-1) of Cd2+ and 21.9 +/- 0.08 mg g(-1) of CrO4(2-). Fourier transform infrared spectra of the EPS revealed the presence of functional groups like carboxyl (-COOH) and hydroxyl (-OH), primarily involved in metal ion binding. Under pot culture experiments, the isolated strain of Azotobacter was added to the metal-contaminated soils in the form of free cells and immobilized cells. The total Azotobacter count and plant metal concentrations under different treatments showed a negative coefficient between the Azotobacter population and plant Cd (-0.496) and Cr (-0.455). Thus it could be inferred that Azotobacter spp. is involved in metal ion complexation either through EPS or through cell wall lipopolysaccharides (LPS).
Collapse
Affiliation(s)
- Prachi M Joshi
- Environmental Biotechnology Division, National Environmental Engineering Research Institute (NEERI), Nehru Marg, Nagpur-440020, India
| | | |
Collapse
|
55
|
Martinez JL. The role of natural environments in the evolution of resistance traits in pathogenic bacteria. Proc Biol Sci 2009; 276:2521-30. [PMID: 19364732 DOI: 10.1098/rspb.2009.0320] [Citation(s) in RCA: 274] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Antibiotics are among the most valuable compounds used for fighting human diseases. Unfortunately, pathogenic bacteria have evolved towards resistance. One important and frequently forgotten aspect of antibiotics and their resistance genes is that they evolved in non-clinical (natural) environments before the use of antibiotics by humans. Given that the biosphere is mainly formed by micro-organisms, learning the functional role of antibiotics and their resistance elements in nature has relevant implications both for human health and from an ecological perspective. Recent works have suggested that some antibiotics may serve for signalling purposes at the low concentrations probably found in natural ecosystems, whereas some antibiotic resistance genes were originally selected in their hosts for metabolic purposes or for signal trafficking. However, the high concentrations of antibiotics released in specific habitats (for instance, clinical settings) as a consequence of human activity can shift those functional roles. The pollution of natural ecosystems by antibiotics and resistance genes might have consequences for the evolution of the microbiosphere. Whereas antibiotics produce transient and usually local challenges in microbial communities, antibiotic resistance genes present in gene-transfer units can spread in nature with consequences for human health and the evolution of environmental microbiota that are largely ignored.
Collapse
Affiliation(s)
- Jose L Martinez
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Darwin 3, Cantoblanco, 28049 Madrid, Spain.
| |
Collapse
|
56
|
Toth M, Chow JW, Mobashery S, Vakulenko SB. Source of phosphate in the enzymic reaction as a point of distinction among aminoglycoside 2''-phosphotransferases. J Biol Chem 2009; 284:6690-6. [PMID: 19158087 DOI: 10.1074/jbc.m808148200] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aminoglycoside 2''-phosphotransferases are clinically important enzymes that cause high levels of resistance to aminoglycoside antibiotics by the organisms that harbor them. These enzymes phosphorylate aminoglycosides, and the modified antibiotics show significant reduction in the binding ability to target the bacterial ribosome. This report presents a detailed characterization of the antibiotic resistance profile and the aminoglycoside and nucleotide triphosphate substrate profiles of four common aminoglycoside 2''-phosphotransferases widely distributed in clinically important Gram-positive microorganisms. Although the antibiotic resistance phenotypes exhibited by these enzymes are similar, their aminoglycoside and nucleotide triphosphate substrate profiles are distinctive. Contrary to the dogma that these enzymes use ATP as the source of phosphate in their reactions, two of the four aminoglycoside 2'-phosphotransferases utilize GTP as the phosphate donor. Of the other two enzymes, one exhibits preference for ATP, and the other can utilize either ATP or GTP as nucleotide triphosphate substrate. A new nomenclature for these enzymes is put forth that takes into account the differences among these enzymes based on their respective substrate preferences. These nucleotide triphosphate preferences should have ramifications for understanding of the evolution, selection, and dissemination of the genes for these important resistance enzymes.
Collapse
Affiliation(s)
- Marta Toth
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | | | | | | |
Collapse
|
57
|
McIntosh D, Cunningham M, Ji B, Fekete FA, Parry EM, Clark SE, Zalinger ZB, Gilg IC, Danner GR, Johnson KA, Beattie M, Ritchie R. Transferable, multiple antibiotic and mercury resistance in Atlantic Canadian isolates of Aeromonas salmonicida subsp. salmonicida is associated with carriage of an IncA/C plasmid similar to the Salmonella enterica plasmid pSN254. J Antimicrob Chemother 2008; 61:1221-8. [PMID: 18375380 DOI: 10.1093/jac/dkn123] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES The aim of this study was to examine the molecular basis for multiple antibiotic and mercury resistance in Canadian isolates of Aeromonas salmonicida subsp. salmonicida. METHODS Phenotypic and genotypic methods were employed to identify plasmid-associated antibiotic and mercury resistance genes and to determine the organization of those genes in multidrug-resistant (MDR) A. salmonicida isolates. RESULTS The MDR phenotype was transferable via conjugation using Escherichia coli, Aeromonas hydrophila and Edwardseilla tarda as recipients. Antibiotic and mercury resistance genes were carried by a conjugative IncA/C plasmid. Three distinct antibiotic resistance cassettes were characterized; first a class I integron containing an aadA7 gene encoding for an aminoglycoside-3'-adenyltransferase, the second cassette showed 99.9% nucleotide sequence homology to a cassette previously identified in the Salmonella enterica IncA/C plasmid pSN254, containing floR, tetA, sulII and strA/strB sequences. The third cassette showed 100% nucleotide sequence similarity to a transposon-like element, containing a bla(CMY-2) beta-lactamase in association with sugE and blc sequences. This element is known to be widely distributed among clinical and food-borne Salmonella and other Enterobacteriaceae throughout Asia and the United States. Mercury resistance was linked to the presence of a mer operon that showed 100% nucleotide sequence homology to the mer operon carried by plasmid pSN254. CONCLUSIONS Each MDR A. salmonicida isolate carried the same plasmid, which was related to plasmid pSN254. This is the first report of plasmid-mediated florfenicol-resistant A. salmonicida in North America. In addition, it is the first report of a plasmid-associated AmpC beta-lactamase sequence in a member of the Aeromonadaceae.
Collapse
Affiliation(s)
- Douglas McIntosh
- Research and Productivity Council, 921 College Hill Road, Fredericton, NB, Canada E3B 6Z9.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
58
|
Mindlin SZ, Petrova MA, Bass IA, Gorlenko ZM. Origin, evolution, and migration of drug resistance genes. RUSS J GENET+ 2006. [DOI: 10.1134/s1022795406110081] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
59
|
Ledwidge R, Patel B, Dong A, Fiedler D, Falkowski M, Zelikova J, Summers AO, Pai EF, Miller SM. NmerA, the metal binding domain of mercuric ion reductase, removes Hg2+ from proteins, delivers it to the catalytic core, and protects cells under glutathione-depleted conditions. Biochemistry 2005; 44:11402-16. [PMID: 16114877 DOI: 10.1021/bi050519d] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ligand binding and catalytic properties of heavy metal ions have led to the evolution of metal ion-specific pathways for control of their intracellular trafficking and/or elimination. Small MW proteins/domains containing a GMTCXXC metal binding motif in a betaalphabetabetaalphabeta fold are common among proteins controlling the mobility of soft metal ions such as Cu(1+), Zn(2+), and Hg(2+), and the functions of several have been established. In bacterial mercuric ion reductases (MerA), which catalyze reduction of Hg(2+) to Hg(0) as a means of detoxification, one or two repeats of sequences with this fold are highly conserved as N-terminal domains (NmerA) of uncertain function. To simplify functional analysis of NmerA, we cloned and expressed the domain and catalytic core of Tn501 MerA as separate proteins. In this paper, we show Tn501 NmerA to be a stable, soluble protein that binds 1 Hg(2+)/domain and delivers it to the catalytic core at kinetically competent rates. Comparison of steady-state data for full-length versus catalytic core MerA using Hg(glutathione)(2) or Hg(thioredoxin) as substrate demonstrates that the NmerA domain does participate in acquisition and delivery of Hg(2+) to the catalytic core during the reduction catalyzed by full-length MerA, particularly when Hg(2+) is bound to a protein. Finally, comparison of growth curves for glutathione-depleted Escherichia coli expressing either catalytic core, full-length, or a combination of core plus NmerA shows an increased protection of cells against Hg(2+) in the media when NmerA is present, providing the first evidence of a functional role for this highly conserved domain.
Collapse
Affiliation(s)
- Richard Ledwidge
- Department of Pharmaceutical Chemistry, University of California-San Francisco, 600 16th Street, San Francisco, California 94143-2280, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
60
|
Tu ZL, Li JN, Chin KH, Chou CC, Lee CC, Shr HL, Lyu PC, Gao FP, Wang AHJ, Chou SH. Cloning, expression, crystallization and preliminary X-ray analysis of a putative multiple antibiotic resistance repressor protein (MarR) from Xanthomonas campestris. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:706-8. [PMID: 16511135 PMCID: PMC1952447 DOI: 10.1107/s1744309105019548] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Accepted: 06/21/2005] [Indexed: 11/10/2022]
Abstract
The multiple antibiotic resistance operon (marRAB) is a member of the multidrug-resistance system. When induced, this operon enhances resistance of bacteria to a variety of medically important antibiotics, causing a serious global health problem. MarR is a marR-encoded protein that represses the transcription of the marRAB operon. Through binding with salicylate and certain antibiotics, however, MarR can derepress and activate the marRAB operon. In this report, the cloning, expression, crystallization and preliminary X-ray analysis of XC1739, a putative MarR repressor protein present in the Xanthomonas campestris pv. campestris, a Gram-negative bacterium causing major worldwide disease of cruciferous crops, are described. The XC1739 crystals diffracted to a resolution of at least 1.8 A. They are orthorhombic and belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 39.5, b = 54.2 and c = 139.5 A, respectively. They contain two molecules in the asymmetric unit from calculation of the self-rotation function.
Collapse
Affiliation(s)
- Zhi-Le Tu
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan
| | - Juo-Ning Li
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan
| | - Ko-Hsin Chin
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan
| | - Chia-Cheng Chou
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
- Core Facility for Protein Crystallography, Academia Sinica, Nankang, Taipei, Taiwan
| | - Cheng-Chung Lee
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
- Core Facility for Protein Crystallography, Academia Sinica, Nankang, Taipei, Taiwan
| | - Hui-Lin Shr
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
- Core Facility for Protein Crystallography, Academia Sinica, Nankang, Taipei, Taiwan
| | - Ping-Chiang Lyu
- Department of Life Science, National Tsing Hua University, Hsin-Chu, Taiwan
| | - Fei Philip Gao
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
| | - Andrew H.-J. Wang
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
- Core Facility for Protein Crystallography, Academia Sinica, Nankang, Taipei, Taiwan
| | - Shan-Ho Chou
- Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan
| |
Collapse
|
61
|
Sheldon IM, Bushnell M, Montgomery J, Rycroft AN. Minimum inhibitory concentrations of some antimicrobial drugs against bacteria causing uterine infections in cattle. Vet Rec 2004; 155:383-7. [PMID: 15499809 DOI: 10.1136/vr.155.13.383] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The minimum inhibitory concentrations (MICs) of oxytetracycline, cephapirin, cephapirin/mecillinam, cefquinome, ceftiofur and enrofloxacin, candidate antibiotics for the principal bacteria associated with uterine infections: Escherichia coli, Arcanobacterium pyogenes and the anaerobic bacteria Fusobacterium necrophorum and Prevotella melaninogenicus, were determined by the agar dilution method. The bacteria were isolated from animals with clinical metritis and/or endometritis. For E coli, cefquinome and enrofloxacin had the lowest MIC90 and MIC50 values (< 0.06 microg/ml), and oxytetracycline and cephapirin had the highest values. For A pyogenes, oxytetracycline had the highest MIC50 value (16 microg/ml), but all the cephalosporins had values below 0.06 microg/ml. For the anaerobic bacteria, enrofloxacin and oxytetracycline had the highest MIC50 values but all the cephalosporins had values of 0.06 microg/ml or below.
Collapse
Affiliation(s)
- I M Sheldon
- Department of Veterinary Clinical Sciences, Royal Veterinary College, Hawkshead Lane, Hatfield AL9 7TA
| | | | | | | |
Collapse
|
62
|
Bizily SP, Kim T, Kandasamy MK, Meagher RB. Subcellular targeting of methylmercury lyase enhances its specific activity for organic mercury detoxification in plants. PLANT PHYSIOLOGY 2003; 131:463-71. [PMID: 12586871 PMCID: PMC166823 DOI: 10.1104/pp.010124] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2002] [Revised: 07/18/2002] [Accepted: 10/17/2002] [Indexed: 05/21/2023]
Abstract
Methylmercury is an environmental pollutant that biomagnifies in the aquatic food chain with severe consequences for humans and other animals. In an effort to remove this toxin in situ, we have been engineering plants that express the bacterial mercury resistance enzymes organomercurial lyase MerB and mercuric ion reductase MerA. In vivo kinetics experiments suggest that the diffusion of hydrophobic organic mercury to MerB limits the rate of the coupled reaction with MerA (Bizily et al., 2000). To optimize reaction kinetics for organic mercury compounds, the merB gene was engineered to target MerB for accumulation in the endoplasmic reticulum and for secretion to the cell wall. Plants expressing the targeted MerB proteins and cytoplasmic MerA are highly resistant to organic mercury and degrade organic mercury at 10 to 70 times higher specific activity than plants with the cytoplasmically distributed wild-type MerB enzyme. MerB protein in endoplasmic reticulum-targeted plants appears to accumulate in large vesicular structures that can be visualized in immunolabeled plant cells. These results suggest that the toxic effects of organic mercury are focused in microenvironments of the secretory pathway, that these hydrophobic compartments provide more favorable reaction conditions for MerB activity, and that moderate increases in targeted MerB expression will lead to significant gains in detoxification. In summary, to maximize phytoremediation efficiency of hydrophobic pollutants in plants, it may be beneficial to target enzymes to specific subcellular environments.
Collapse
Affiliation(s)
- Scott P Bizily
- Genetics Department, University of Georgia, Athens, Georgia 30602, USA
| | | | | | | |
Collapse
|
63
|
Abstract
Erythromycin, which was introduced over 50 years ago, was the first macrolide to be used clinically. "New" macrolides, for the treatment of patients with various infectious diseases, were not clinically introduced until 40 years later. The pharmacokinetic and adverse events profile of erythromycin initially limited its use to an alternative agent for patients with allergy to beta-lactam agents. However, the emergence of atypical and/or new pathogens and the ongoing escalation of acquired antimicrobial resistance has impacted on the empirical and organism directed therapy of infectious diseases. Azithromycin and clarithromycin were developed by enhancing the basic macrolide structure. Some of the basic features associated with these new agents include a pharmacokinetic profiles that allow once or twice daily dosing with a much lower incidence of side effects and a substantially broader spectrum of activity which includes some Gram-negative bacilli, atypical pathogens and new, unconventional or uncommon pathogens. Clinical trial data has supported the use of "new" macrolides in a wide range of clinical indications, however, some specific indications are currently restricted to treatment with either azithromycin or clarithromycin. Macrolide resistance is a class effect and depending on the mechanism will confer either low or high level resistance. While resistance is problematic, it does not always result in clinical failure. The macrolides are a valuable class of antimicrobial agent and play an important role in the management of infectious diseases.
Collapse
Affiliation(s)
- Joseph M Blondeau
- Department of Clinical Microbiology, Saskatoon District Health and St. Paul's Hospital (Grey Nuns), Saskatoon, Saskatchewan, Canada.
| | | | | | | |
Collapse
|
64
|
Mateu E, Martin M. Why is anti-microbial resistance a veterinary problem as well? JOURNAL OF VETERINARY MEDICINE. B, INFECTIOUS DISEASES AND VETERINARY PUBLIC HEALTH 2001; 48:569-81. [PMID: 11708676 DOI: 10.1046/j.1439-0450.2001.00475.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Resistance to anti-microbial agents has become one of the main issues in public health strategies world-wide. Much attention has been paid to the emergence of pathogenic micro-organisms such as enterococci or Salmonella that have developed resistance mechanisms that render them almost untreatable with current antibiotics. One of the alleged reasons for such an emergence is the non-medical use of antibiotics, especially in animals. However, only recently have veterinary forums and journals begun to discuss this topic. On the other hand, anti-microbial resistance has also become a problem in veterinary medicine and the number of reports indicating high rates of resistance among animal-originated micro-organisms is considerable. The present review deals with the mechanisms of resistance known for antibiotics in common veterinary use, the problem of anti-microbial resistance in veterinary medicine and the links between the use of antibiotics in animals and the emergence of anti-microbial resistance in humans.
Collapse
Affiliation(s)
- E Mateu
- Departament de Sanitat i Anatomia Animals, UAB, Bellaterra, Spain
| | | |
Collapse
|
65
|
Verma T, Srinath T, Gadpayle RU, Ramteke PW, Hans RK, Garg SK. Chromate tolerant bacteria isolated from tannery effluent. BIORESOURCE TECHNOLOGY 2001; 78:31-35. [PMID: 11265785 DOI: 10.1016/s0960-8524(00)00168-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The occurrence of metal tolerant and antibiotic resistant organisms was investigated in tannery effluent. Seventy-seven isolates comprising heterotrophs (41) and coliforms (36) which were tolerant to chromate level of > 50 microg/ml were selected for detailed study. The majority of the coliforms were resistant to higher levels of chromate (200 microg/ml) whereas around 3% of the heterotrophs were resistant to Cr6+ at a level of > 150 microg/ml. All chromate tolerant heterotrophs were also tolerant to Cu2+ (100%) whereas only 58.53% coliforms were tolerant to Cu2+. Except in the case of Cd2+ a higher number of heterotrophs were found tolerant to other heavy metals tested. Both groups of isolates were found sensitive to mercury. Resistance to cephaloridine was more abundant (P < 0.001) in coliforms as compared to heterotrophs. On the other hand a significantly higher number (P < 0.01) of heterotrophs showed resistance to streptomycin and carbencillin. All coliforms were sensitive to chloramphenicol. Around 80%) and 31.70% of coliforms and heterotrophs exhibited a relationship to the combination of metals and antibiotics. Both heterotrophs and coliforms tolerant to Hg2+ were also resistant to polymixin-B.
Collapse
Affiliation(s)
- T Verma
- Photobiology Division, Industrial Toxicology Research Centre, Lucknow, India
| | | | | | | | | | | |
Collapse
|
66
|
|
67
|
McDonnell G, Russell AD. Antiseptics and disinfectants: activity, action, and resistance. Clin Microbiol Rev 1999; 12:147-79. [PMID: 9880479 PMCID: PMC88911 DOI: 10.1128/cmr.12.1.147] [Citation(s) in RCA: 2646] [Impact Index Per Article: 105.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Antiseptics and disinfectants are extensively used in hospitals and other health care settings for a variety of topical and hard-surface applications. A wide variety of active chemical agents (biocides) are found in these products, many of which have been used for hundreds of years, including alcohols, phenols, iodine, and chlorine. Most of these active agents demonstrate broad-spectrum antimicrobial activity; however, little is known about the mode of action of these agents in comparison to antibiotics. This review considers what is known about the mode of action and spectrum of activity of antiseptics and disinfectants. The widespread use of these products has prompted some speculation on the development of microbial resistance, in particular whether antibiotic resistance is induced by antiseptics or disinfectants. Known mechanisms of microbial resistance (both intrinsic and acquired) to biocides are reviewed, with emphasis on the clinical implications of these reports.
Collapse
Affiliation(s)
- G McDonnell
- STERIS Corporation, St. Louis Operations, St. Louis, Missouri 63166, USA.
| | | |
Collapse
|
68
|
Moscoso H, Saavedra C, Loyola C, Pichuantes S, Vásquez C. Biochemical characterization of tellurite-reducing activities of Bacillus stearothermophilus V. Res Microbiol 1998; 149:389-97. [PMID: 9766238 DOI: 10.1016/s0923-2508(98)80321-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Bacillus stearothermophilus V is a naturally occurring Gram-positive rod which exhibits resistance to potassium tellurite. Crude extracts of this bacterium catalyse the NADH-dependent, protease-sensitive reduction of K2TeO3 in vitro. Two fractions which showed the ability to reduce potassium tellurite (H1 and H2) were obtained. Fraction H1 behaved as a macroaggregate exhibiting a very high molecular mass that could not be estimated accurately. Upon electrophoresis in polyacrylamide gels in the presence of SDS, however, it was resolved into three distinct bands of 60, 41 and 37.5 kDa. On the other hand, an M(r) of 121 was determined for fraction H2 by means of gel filtration and high-pressure liquid chromatography. In SDS-PAGE a unique protein band of 60 kDa was observed, suggesting that it is actually a dimer. Both fractions showed pH and temperature optima of 7.5 and 57 degrees C, respectively. Concentrations of 2.5 M NaCl or 0.35 mM SDS inhibited fraction H2 almost completely, while fraction H1 retained 20% of its activity under the same conditions. Concentrations of 5 mM EDTA caused the activity of both fractions to increase 2-fold. In addition to reducing tellurite, they were also able to reduce Na2SeO3 and Na2SO3 in vitro.
Collapse
Affiliation(s)
- H Moscoso
- Laboratorio de Microbiología Molecular, Facultad de Química y Biología, Universidad de Santiago de Chile
| | | | | | | | | |
Collapse
|
69
|
Amoroso AM, Gutkind GO. Chromogenic detection of aminoglycoside phosphotransferases. Antimicrob Agents Chemother 1998; 42:228-30. [PMID: 9527764 PMCID: PMC105392 DOI: 10.1128/aac.42.2.228] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
A coupled chromogenic reaction (based on an agar overlay combining NADH, pyruvate kinase, lactate dehydrogenase, phosphoenolpyruvate, ATP, and kanamycin sulfate with thiazolyl blue-phenazine methosulfate for detection of NADH consumption) was optimized for the detection of aminoglycoside phosphotransferases (APHs). When used after analytical isoelectrofocusing of bacterial extracts from APH-producing strains, this method revealed one band in each of two strains with a genetically confirmed APH (3') I and two bands in another strain with both APH (3') I and APH (3') VI, whereas no bands were detected in susceptible control strains or in aminoglycoside-resistant microorganisms without APH genes.
Collapse
Affiliation(s)
- A M Amoroso
- Cátedra de Microbiología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina
| | | |
Collapse
|
70
|
|
71
|
Platteeuw C, Michiels F, Joos H, Seurinck J, de Vos WM. Characterization and heterologous expression of the tetL gene and identification of iso-ISS1 elements from Enterococcus faecalis plasmid pJH1. Gene 1995; 160:89-93. [PMID: 7628724 DOI: 10.1016/0378-1119(95)00208-n] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The tetracycline-resistance (TcR) determinant of the Enterococcus faecalis plasmid pJH1 has been identified and located on a 2.2-kb RsaI-EcoRI fragment. The fragment was cloned in Escherichia coli, and specified TcR in this host. The nucleotide (nt) sequence of the cloned fragment showed the presence of an open reading frame (ORF) of 1374 bp, designated tetL. The nt sequence of tetL from pJH1 was identical to that of the tetL present on pLS1 from Streptococcus agalactiae. Upstream of the pJH1 tetL, part of another ORF was found that, except for two single-nt substitutions, was identical to an iso-ISS1 element from Lactococcus lactis. Hybridization studies indicated the presence of several ISS1-like elements in plasmid pJH1, but not on the En. faecalis chromosome. To study its usefulness as a marker in Gram+ organisms, the pJH1 tetL was cloned on the broad-host-range plasmid pNZ124, resulting in pNZ280, that was found to give resistance to 40 micrograms Tc/ml in Lc. lactis and Bacillus subtilis.
Collapse
Affiliation(s)
- C Platteeuw
- Molecular Genetics Group, NIZO, Ede, The Netherlands
| | | | | | | | | |
Collapse
|
72
|
Welage L, Carver P, Welch K. Antibacterial activity of sucralfate versus aluminum chloride in simulated gastric fluid. Eur J Clin Microbiol Infect Dis 1994; 13:1046-52. [PMID: 7889966 DOI: 10.1007/bf02111825] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Studies have previously demonstrated that sucralfate possesses intrinsic antibacterial activity. This study was designed to indirectly assess whether aluminum is the active antibacterial component of sucralfate and to further evaluate factors that may influence this agent's antibacterial activity. Utilizing an in vitro model, the antibacterial activity of sucralfate, an equivalent quantity of aluminum in the form of aluminum chloride, and a control were compared. In addition, the influences of bacterial species (Enterobacter cloacae and Pseudomonas aeruginosa), time (0-24 h) and environmental pH (3,5,7) on the agents' antibacterial activities were evaluated. Equivalent quantities of aluminum, as either sucralfate or aluminum chloride, were added to two of three flasks containing approximately 10(5) cfu/ml of bacteria in pH-adjusted simulated gastric fluid. The third flask served as a control. Samples were obtained over 24 h, diluted and subcultured onto agar plates. The experiments demonstrated that bacterial growth was influenced by pH, time and treatment (aluminum chloride or sucralfate). Regardless of pH or bacterial species, bacterial death occurred within 20 min following the addition of aluminum chloride. In contrast, bacterial death following the addition of sucralfate was more variable and appeared to be pH dependent. In conclusion, sucralfate and aluminum chloride both possess antibacterial activity, even at pH values that normally support bacterial growth in gastric fluid. Although differences in the antibacterial activity of the two agents may in part be related to drug-induced changes in pH, these differences also support data suggesting that aluminum release from sucralfate is incomplete and is dependent on pH.
Collapse
Affiliation(s)
- L Welage
- College of Pharmacy, Department of Pharmacy, University of Michigan Medical Center, Ann Arbor
| | | | | |
Collapse
|
73
|
Van Dyck E, Bogaerts J, Smet H, Tello WM, Mukantabana V, Piot P. Emergence of Haemophilus ducreyi resistance to trimethoprim-sulfamethoxazole in Rwanda. Antimicrob Agents Chemother 1994; 38:1647-8. [PMID: 7979300 PMCID: PMC284607 DOI: 10.1128/aac.38.7.1647] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The in vitro susceptibilities of 112 clinical isolates of Haemophilus ducreyi to six antimicrobial agents were determined. These isolates were obtained in Kigali, Rwanda, during three studies on genital ulcer disease performed in 1986 (18 isolates), 1988 (23 isolates), and 1991 (71 isolates). All H. ducreyi isolates were susceptible to azithromycin, ceftriaxone, ciprofloxacin, and erythromycin; all isolates obtained in 1986 were also susceptible to trimethoprim and to the combination trimethoprim-sulfamethoxazole. In contrast, 39 and 9% of the isolates obtained in 1988 and 59 and 48% of the isolates obtained in 1991 were resistant to trimethoprim (MIC, > or = 4.0 mg/liter) and trimethoprim-sulfamethoxazole (MIC, < or = 4.0/76 mg/liter), respectively. These data indicate that trimethoprim-sulfamethoxazole can no longer be recommended for use in the treatment of chancroid in Rwanda, and possibly elsewhere in Africa.
Collapse
Affiliation(s)
- E Van Dyck
- Division of Microbiology, Institute of Tropical Medicine, Antwerp, Belgium
| | | | | | | | | | | |
Collapse
|
74
|
|
75
|
Dhakephalkar PK, Chopade BA. High levels of multiple metal resistance and its correlation to antibiotic resistance in environmental isolates of Acinetobacter. Biometals 1994; 7:67-74. [PMID: 8118175 DOI: 10.1007/bf00205197] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Forty strains of Acinetobacter were isolated from different environmental sources. All the strains were classified into four genospecies, i.e., A. baumannii (33 isolates), A. calcoaceticus (three isolates), A. junii (three isolates) and A. genospecies3 (one isolate). Susceptibility of these 40 strains to salts of 20 heavy metals and 18 antibiotics was tested by the agar dilution method. All environmental isolates of Acinetobacter were resistant to multiple metal ions (minimum 13 metal ions) while all but one of the strains were resistant to multiple antibiotics (minimum four antibiotics). The maximum number of strains were found to be sensitive to mercury (60% strains) while all strains were resistant to copper, lead, boron and tungsten even at 10 mM concentration. Salts of these four metal ions may be added to the growth medium to facilitate selective isolation of Acinetobacter. Rifampicin and nalidixic acid were the most toxic antibiotics, inhibiting 94.5 and 89.5% of the acinetobacters, respectively. A. genospecies3 was found to be the most resistant species, tolerating high concentrations of all the 20 metal ions and also to a greater number of antibiotics than any other species of Acinetobacter tested. An inhibitory concentration (10 mM) of Ni(2+) and Zn(2+) was observed to inhibit the growth of all of the clinical isolates but allowed the growth of the environmental isolates, facilitating the differentiation between pathogenic and non-pathogenic acinetobacters.
Collapse
|
76
|
Dale GE, Then RL, Stüber D. Characterization of the gene for chromosomal trimethoprim-sensitive dihydrofolate reductase of Staphylococcus aureus ATCC 25923. Antimicrob Agents Chemother 1993; 37:1400-5. [PMID: 8363365 PMCID: PMC187982 DOI: 10.1128/aac.37.7.1400] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The gene for the trimethoprim-sensitive (Tmps) chromosomal dihydrofolate reductase (DHFR) of Staphylococcus aureus ATCC 25923 was cloned and characterized. The structural gene encodes a polypeptide of 159 amino acid residues and has a calculated molecular weight of 18,251. The amino acid sequences of this Tmps DHFR and those of the trimethoprim-resistant type S1 DHFR encoded by transposon Tn4003 are 80% identical. In contrast to the trimethoprim-resistant enzyme, the Tmps DHFR can be highly overexpressed in Escherichia coli, with most of the recombinant protein occurring in a soluble and an active form.
Collapse
Affiliation(s)
- G E Dale
- Department of New Technologies, F. Hoffmann-La Roche Ltd., Basel, Switzerland
| | | | | |
Collapse
|
77
|
Ledent P, Raquet X, Joris B, Van Beeumen J, Frère JM. A comparative study of class-D beta-lactamases. Biochem J 1993; 292 ( Pt 2):555-62. [PMID: 8389139 PMCID: PMC1134246 DOI: 10.1042/bj2920555] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Three class-D beta-lactamases (OXA2, OXA1 and PSE2) were produced and purified to protein homogeneity. 6 beta-Iodopenicillanate inactivated the OXA2 enzyme without detectable turnover. Labelling of the same beta-lactamase with 6 beta-iodo[3H]penicillanate allowed the identification of Ser-70 as the active-site serine residue. In agreement with previous reports, the apparent M(r) of the OXA2 enzyme as determined by molecular-sieve filtration, was significantly higher than that deduced from the gene sequence, but this was not due to an equilibrium between a monomer and a dimer. The heterogeneity of the OXA2 beta-lactamase on ion-exchange chromatography contrasted with the similarity of the catalytic properties of the various forms. A first overview of the enzymic properties of the three 'oxacillinases' is presented. With the OXA2 enzyme, 'burst' kinetics, implying branched pathways, seemed to prevail with many substrates.
Collapse
Affiliation(s)
- P Ledent
- Laboratoire d'Enzymologie, Université de Liège, Belgium
| | | | | | | | | |
Collapse
|
78
|
|
79
|
Shaw KJ, Rather PN, Hare RS, Miller GH. Molecular genetics of aminoglycoside resistance genes and familial relationships of the aminoglycoside-modifying enzymes. Microbiol Rev 1993; 57:138-63. [PMID: 8385262 PMCID: PMC372903 DOI: 10.1128/mr.57.1.138-163.1993] [Citation(s) in RCA: 513] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The three classes of enzymes which inactivate aminoglycosides and lead to bacterial resistance are reviewed. DNA hybridization studies have shown that different genes can encode aminoglycoside-modifying enzymes with identical resistance profiles. Comparisons of the amino acid sequences of 49 aminoglycoside-modifying enzymes have revealed new insights into the evolution and relatedness of these proteins. A preliminary assessment of the amino acids which may be important in binding aminoglycosides was obtained from these data and from the results of mutational analysis of several of the genes encoding aminoglycoside-modifying enzymes. Recent studies have demonstrated that aminoglycoside resistance can emerge as a result of alterations in the regulation of normally quiescent cellular genes or as a result of acquiring genes which may have originated from aminoglycoside-producing organisms or from other resistant organisms. Dissemination of these genes is aided by a variety of genetic elements including integrons, transposons, and broad-host-range plasmids. As knowledge of the molecular structure of these enzymes increases, progress can be made in our understanding of how resistance to new aminoglycosides emerges.
Collapse
Affiliation(s)
- K J Shaw
- Schering-Plough Research Institute, Kenilworth, New Jersey 07033
| | | | | | | |
Collapse
|
80
|
Bennett PM, Chopra I. Molecular basis of beta-lactamase induction in bacteria. Antimicrob Agents Chemother 1993; 37:153-8. [PMID: 8452343 PMCID: PMC187630 DOI: 10.1128/aac.37.2.153] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Affiliation(s)
- P M Bennett
- Department of Pathology and Microbiology, School of Medical Sciences, University of Bristol, United Kingdom
| | | |
Collapse
|
81
|
Turner RJ, Hou Y, Weiner JH, Taylor DE. The arsenical ATPase efflux pump mediates tellurite resistance. J Bacteriol 1992; 174:3092-4. [PMID: 1533216 PMCID: PMC205967 DOI: 10.1128/jb.174.9.3092-3094.1992] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The ars operon of the resistance plasmid R773 was found to produce moderate levels of resistance to tellurite. A MIC of 64 micrograms of TeO3(2-) per ml was found for Escherichia coli cells harboring plasmids which contained all three of the structural genes (arsA, arsB, and arsC) of the anion-translocating ATPase. MICs specified by plasmids carrying only one or two structural elements or the cloning vector alone were 2 to 4 micrograms/ml. The rate of TeO3(2-) uptake was found to be on the order of 55% less for cultures containing the resistance plasmids.
Collapse
Affiliation(s)
- R J Turner
- Department of Biochemistry, University of Alberta, Edmonton, Canada
| | | | | | | |
Collapse
|
82
|
Burman LG, Haeggman S, Kuistila M, Tullus K, Huovinen P. Epidemiology of plasmid-mediated beta-lactamases in enterobacteria Swedish neonatal wards and relation to antimicrobial therapy. Antimicrob Agents Chemother 1992; 36:989-92. [PMID: 1510425 PMCID: PMC188816 DOI: 10.1128/aac.36.5.989] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
TEM-1, OXA-1, SHV-1, and related beta-lactamases in fecal isolates from 953 infants in 22 Swedish neonatal intensive care units were studied by DNA hybridization. TEM-1- and OXA-1-positive isolates were always Escherichia coli and represented 86 and 8%, respectively, of the ampicillin-resistant isolates of this species. SHV-1 was found in 16% of the Klebsiella sp. (mainly Klebsiella pneumoniae) isolates. TEM-1 and SHV-1 occurred in 14 and 16 units and in up to 64 and 26% of the neonates, respectively. On average, two to four different biochemical phenotypes per species per ward were positive for each beta-lactamase. All but 1 of the 33 E. coli phenotypes found to be TEM-1 positive were uniformly positive for the beta-lactamase gene, whereas some of the phenotypes found to be positive for OXA-1 (2 of 3) and SHV-1 (6 of 70) were occasionally negative for the respective genes. The occurrence of the three beta-lactamases studied tended to be associated with local ampicillin usage (correlation coefficient, 0.31 to 0.39; P greater than 0.05). Of the neonates receiving ampicillin, 30% carried TEM-1-positive E. coli, compared with 13% for cephalosporin-treated neonates and 15% for untreated neonates (P less than or equal to 0.001). The corresponding rates for SHV-1 in Klebsiella spp. were 18, 13, and 9% (P less than or equal to 0.01). Ampicillin is thus a significant risk factor for the maintenance of the most prevalent gram-negative plasmid-mediated beta-lactamases in hospitalized neonates.
Collapse
Affiliation(s)
- L G Burman
- National Bacteriological Laboratory, Stockholm, Sweden
| | | | | | | | | |
Collapse
|
83
|
Kingsley MT, Bohlool BB. Extracellular Polysaccharide Is Not Responsible for Aluminum Tolerance of
Rhizobium leguminosarum
bv. Phaseoli CIAT899. Appl Environ Microbiol 1992; 58:1095-101. [PMID: 16348680 PMCID: PMC195560 DOI: 10.1128/aem.58.4.1095-1101.1992] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Strain UHM-5, a pSym
-
Exo
-
derivative of the aluminum-tolerant
Rhizobium leguminosarum
bv. phaseoli strain CIAT899, was equally tolerant of aluminum (Al) as the parental culture. Dialyzed culture supernatants of the wild-type cells grown in YEM broth (10
9
cells ml
-1
) contained 185 μg of glucose equivalents ml
-1
whereas UHM-5 culture supernatants yielded 2 μg of glucose ml
-1
. The Exo
-
derivative and the parental strain gave essentially similar growth in medium containing from 0 to 300 μM Al, indicating that the pSym of CIAT899, and extracellular polysaccharide, were not involved in the aluminum tolerance of this strain. However, increasing the level of Al from 80 to 150 μM increased the lag phase, induced a slight killing of the inoculum, and depressed the final populations by about fivefold. Doubling the aluminum concentration from 150 to 300 μM presented a severe aluminum stress to CIAT899 and UHM-5: the inoculum level dropped 10-fold, indicating killing of the inoculum, and remained depressed for ca. 4 days before continuing to grow slowly; the final population was decreased 15-fold relative to that of cultures grown in medium containing 80 μM Al. The production by CIAT899 of other extracellular or intracellular aluminum tolerance factors was investigated in culture by using aluminum-sensitive rhizobia as stress indicators. These experiments, conducted at 80 μM Al, demonstrated that CIAT899 produced neither extracellular nor intracellular products that could alleviate toxicity for the Al-sensitive indicator rhizobia.
Collapse
Affiliation(s)
- M T Kingsley
- Department of Microbiology, University of Hawaii, Honolulu, Hawaii 96822
| | | |
Collapse
|
84
|
Bissonnette L, Roy PH. Characterization of In0 of Pseudomonas aeruginosa plasmid pVS1, an ancestor of integrons of multiresistance plasmids and transposons of gram-negative bacteria. J Bacteriol 1992; 174:1248-57. [PMID: 1310501 PMCID: PMC206418 DOI: 10.1128/jb.174.4.1248-1257.1992] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Many multiresistance plasmids and transposons of gram-negative bacteria carry related DNA elements that appear to have evolved from a common ancestor by site-specific integration of discrete cassettes containing antibiotic resistance genes or sequences of unknown function. The site of integration is flanked by conserved segments coding for an integraselike protein and for sulfonamide resistance, respectively. These segments, together with the antibiotic resistance genes between them, have been termed integrons (H. W. Stokes and R. M. Hall, Mol. Microbiol. 3:1669-1683, 1989). We report here the characterization of an integron, In0, from Pseudomonas aeruginosa plasmid pVS1, which has an unoccupied integration site and hence may be an ancestor of more complex integrons. Codon usage of the integrase (int) and sulfonamide resistance (sul1) genes carried by this integron suggests a common origin. This contrasts with the codon usage of other antibiotic resistance genes that were presumably integrated later as cassettes during the evolution and spread of these DNA elements. We propose evolutionary schemes for (i) the genesis of the integrons by the site-specific integration of antibiotic resistance genes and (ii) the evolution of the integrons of multiresistance plasmids and transposons, in relation to the evolution of transposons related to Tn21.
Collapse
Affiliation(s)
- L Bissonnette
- Département de Biochimie, Faculté des Sciences et de Génie, Université Laval, Sainte-Foy, Québec, Canada
| | | |
Collapse
|
85
|
Whelan KF, Colleran E. Restriction endonuclease mapping of the HI2 incompatibility group plasmid R478. J Bacteriol 1992; 174:1197-204. [PMID: 1735713 PMCID: PMC206412 DOI: 10.1128/jb.174.4.1197-1204.1992] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
A restriction map of the 272-kb IncHI2 plasmid R478 was constructed by using the enzymes ApaI, XbaI, SalI, and XhoI. The map was derived from cloned restriction fragments from R478 inserted into cosmid and plasmid vectors as well as from double-digestion analysis of R478 and R478 miniplasmids. All previously known resistance determinants were cloned from R478, and their positions were located on the restriction map. A region involved in incompatibility was cloned and mapped. The location of a previously unreported arsenite resistance gene was also determined. The genes encoding tellurite resistance, colicin B resistance, and phage inhibition were found to be associated with a 6.7-kb SalI fragment of R478.
Collapse
Affiliation(s)
- K F Whelan
- Department of Microbiology, University College Galway, Ireland
| | | |
Collapse
|
86
|
Abstract
The results of molecular genetics have frequently been difficult to explain by conventional evolutionary theory. New findings about the genetic conservation of protein structure and function across very broad taxonomic boundaries, the mosaic structure of genomes and genetic loci, and the molecular mechanisms of genetic change all point to a view of evolution as involving the rearrangement of basic genetic motifs. A more detailed examination of how living cells restructure their genomes reveals a wide variety of sophisticated biochemical systems responsive to elaborate regulatory networks. In some cases, we know that cells are able to accomplish extensive genome reorganization within one or a few cell generations. The emergence of bacterial antibiotic resistance is a contemporary example of evolutionary change; molecular analysis of this phenomenon has shown that it occurs by the addition rearrangement of resistance determinants and genetic mobility systems rather than by gradual modification of pre-existing cellular genomes. In addition, bacteria and other organisms have intricate repair systems to prevent genetic change by sporadic physicochemical damage or errors of the replication machinery. In their ensemble, these results show that living cells have (and use) the biochemical apparatus to evolve by a genetic engineering process. Future research will reveal how well the regulatory systems integrate genomic change into basic life processes during evolution.
Collapse
Affiliation(s)
- J A Shapiro
- Department of Biochemistry and Molecular Biology, University of Chicago, IL 60637
| |
Collapse
|
87
|
Abstract
Azithromycin contains an aza-methyl substitution in the 15-membered aglycone ring and as such it is the prototype antibiotic of the azalide class, similar in mechanism of activity to the macrolides. It demonstrates a broad spectrum of activity against many aerobic and anaerobic Gram-positive species, and also inhibits a number of important aerobic and anaerobic Gram-negative bacteria. Significantly, azithromycin shows good activity against Haemophilus influenzae, an organism against which older macrolide antibiotics have proved disappointing. It is highly effective in inhibiting clinically significant intracellular pathogens such as Chlamydia trachomatis and Legionella. Bactericidal activity is seen for certain streptococci and for H. influenzae. Closely linked with azithromycin's microbiologic activity are its novel pharmacokinetics. Azithromycin moves rapidly from blood to tissue compartments where it remains for prolonged periods. Although serum concentrations remain low, the levels attained in the tissues (often greater than 2 mg/kg) are higher than the minimum inhibitory concentration for many common pathogens, and delivery of drug to infection sites by phagocytic cells contributes to these concentrations. This penetration into eukaryotic and prokaryotic cells may be responsible for azithromycin's expanded spectrum of activity, particularly against intracellular organisms. The use of antibiotic blood levels as breakpoints for susceptibility would appear to be inappropriate in the case of azalides. Rather, levels of drug at the tissue site of infection should be considered as guides to predicting efficacy. The in vitro activity of azithromycin, together with its unique tissue pharmacodynamics, define an agent that should demonstrate utility in infections of the respiratory tract, skin and skin structures, and certain sexually transmitted diseases.
Collapse
Affiliation(s)
- H C Neu
- Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York 10032
| |
Collapse
|
88
|
Hächler H, Cohen SP, Levy SB. marA, a regulated locus which controls expression of chromosomal multiple antibiotic resistance in Escherichia coli. J Bacteriol 1991; 173:5532-8. [PMID: 1715857 PMCID: PMC208267 DOI: 10.1128/jb.173.17.5532-5538.1991] [Citation(s) in RCA: 136] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Stable chromosomal multiple-antibiotic-resistant (Mar) mutants of Escherichia coli, derived by exposing susceptible cells to low concentrations of tetracycline or chloramphenicol, express cross-resistance to structurally unrelated antibiotics. The entire resistance phenotype is reversed to susceptibility by insertion of transposon Tn5 into a locus, designated marA, near 34 min on the chromosome (A. M. George and S. B. Levy, J. Bacteriol. 155:541-548, 1983). Strains in which 39 kbp of chromosomal DNA, including marA, had been deleted were unable to produce Mar mutants. The deletion strain could be complemented in trans by introduction of intact marA+ on plasmid F'506. Junction fragments from a strain containing marA::Tn5 were cloned, exploiting kanamycin resistance on Tn5 for selection. They were used as probes to search a phasmid library of E. coli K-12 for recombinants containing the marA+ region. Two phasmids which contained regions hybridizing to this probe were identified and shown to complement delta marA in a deletion strain. From one phasmid, several marA-containing fragments were cloned: those of greater than or equal to 7.8 kbp restored the ability to form Mar mutants in a deletion strain. These Mar mutants were shown to be dependent on the cloned marA fragment. Chromosomal as well as recombinant Mar mutants showed increased expression of a marA-specific mRNA species of about 1.4 kb, which was barely or not detectable in wild-type strains. Exposure of mutants and, to a lesser extent, parental strains to tetracycline or chloramphenicol resulted in elevated levels of mRNA which hybridized to the marA probe. These results indicate that the marA locus is needed for production of Mar mutants and is regulated, responding to at least two antibiotics to which it controls resistance.
Collapse
Affiliation(s)
- H Hächler
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
| | | | | |
Collapse
|
89
|
Gadaleta P, Kaufman S, Martini P, Zorzópulos J. A staphylococcal plasmid that replicates and expresses ampicillin, gentamicin and amikacin resistance in Escherichia coli. FEMS Microbiol Lett 1991. [DOI: 10.1111/j.1574-6968.1991.tb04651.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
|
90
|
An upstream regulatory sequence stimulates expression of the perfringolysin O gene of Clostridium perfringens. Infect Immun 1991; 59:137-42. [PMID: 1987025 PMCID: PMC257717 DOI: 10.1128/iai.59.1.137-142.1991] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The structural gene for perfringolysin O (pfoA), a thiol-activated hemolysin of Clostridium perfringens, was cloned into Escherichia coli JM109 on a 4.6-kilobase (kb) EcoRI-NdeI fragment which contained the 1.7-kb pfoA gene and an upstream 2.9-kb region. An E. coli strain transformed by this plasmid produced 20-fold more perfringolysin O than a strain containing only the 1.7-kb pfoA gene. The stimulatory effect of the upstream region on in vivo expression of the pfoA gene was further analyzed by using a set of deletion mutants. Stimulation was still observed with a 3.9-kb fragment, but stimulation was not observed with fragments that were 3.6 kb or less long, indicating that the upstream region between 3.9 and 1.7 kb was involved in activation of pfoA gene expression. Nucleotide sequencing showed that this region contained one open reading frame (pfoR) coding for 343 amino acids. The deduced amino acid sequence of pfoR possesses several motifs that are characteristic of DNA-binding proteins. When a region coding for a helix-turn-helix, one of the most important motifs of DNA-binding proteins, was deleted within pfoR, stimulation was completely abolished. These results indicate that pfoR positively controls expression of the pfoA gene.
Collapse
|
91
|
Genthner FJ, Upadhyay J, Campbell RP, Genthner BR. Anomalies in the enumeration of starved bacteria on culture media containing nalidic acid and tetracycline. MICROBIAL ECOLOGY 1990; 20:283-288. [PMID: 24193980 DOI: 10.1007/bf02543883] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/1990] [Revised: 08/02/1990] [Indexed: 06/02/2023]
Abstract
Culturable counts of antibiotic resistant, genetically engineeredPseudomonas fluorescens were determined on antibiotic-containing plate count agar during starvation in water. Prior to starvation, colony counts obtained on all media separated into two groups. The mean of the colony counts on plate count agar with or without tetracycline (4.9 × 10(6) ml(-1)) was significantly higher than the mean colony counts on plate count agar containing either nalidixic acid or nalidixic acid plus tetraclycline (2.5×10(6) ml(-1)). After 20 days of starvation the highest mean colony counts continued to be obtained on plate count agar (7.2 × 10(6) ml(-1)) with slightly, but significantly, lower counts obtained on plate count agar containing either nalidixic acid (5.6 × 10(6) ml(-1)) or tetraclycline (1.5×10(6) ml(-1)). A combination of nalidixic acid and tetracycline in plate count agar, however, dramatically reduced colony counts (8.3 × 10(2) ml(-1)) after this starvation period. The addition of catalase to plate count agar containing nalidixic acid and tetracycline negated the effect caused by this combination of antibiotics. When colony counts obtained over the entire 20 day incubation were considered, the addition of MgSO4 to plate count agar containing nalidixic acid and tetracycline resulted in a significant increase in colony counts. Other combinations of antibiotics, nalidixic acid+carbenicillin, nalidixic acid+kanamycin, streptomycin+tetracycline, streptomycin+carbenicillin, rifampicin+tetracycline, rifampicin+carbenicillin, and rifampicin+kanamycin, did not inhibit colony formation of starved cells. Antibiotic resistant strains ofP. putida andEscherichia coli also displayed sensitivity to the combination of nalidixic acid and tetracycline in plate count agar after starvation.
Collapse
Affiliation(s)
- F J Genthner
- Microbial Ecology and Biotechnology Branch, 32561, Gulf Breeze, Florida, USA
| | | | | | | |
Collapse
|
92
|
Sarwar M, Akhtar M. Cloning of aminoglycoside phosphotransferase (APH) gene from antibiotic-producing strain of Bacillus circulans into a high-expression vector, pKK223-3. Purification, properties and location of the enzyme. Biochem J 1990; 268:671-7. [PMID: 2163618 PMCID: PMC1131492 DOI: 10.1042/bj2680671] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The aminoglycoside phosphotransferase gene from a butirosin-producing strain of Bacillus circulans was cloned in a high-expression vector (pKK223-3) to give the recombinant plasmid pMS5. Escherichia coli harbouring the plasmid, E. coli JM103[pMS5], was characterized, and several features of the expression of the phosphotransferase were studied. The phosphotransferase activity was best expressed in a medium lacking glucose, and the highest levels of the enzyme were found between 12 and 24 h of growth. The induction of the phosphotransferase expression with isopropyl beta-D-thiogalactopyranoside (inducer) was found to be undesirable as the overproduction of the enzyme led to the killing of the bacteria. The subcellular location of the phosphotransferase, and also the site in vivo of the phosphorylation of neomycin, was found to be in the cytoplasm. The phosphotransferase was purified to homogeneity in good yield (17 mg of purified protein/3 litres of culture) and was shown to be a monomer of Mr 30,000-32,000. The N-terminal amino acid sequence was in agreement with that predicted from the gene sequence and confirmed the absence of any signal sequence. The regiospecificity of the phosphotransferase reaction was studied by m.s. and by 1H-, 13C- and 31P-n.m.r. using ribostamycin as the substrate, and it was found that the antibiotic was phosphorylated at the 3'-hydroxy group.
Collapse
Affiliation(s)
- M Sarwar
- Department of Biochemistry, University of Southampton, U.K
| | | |
Collapse
|
93
|
Zscheck KK, Murray BE. Evidence for a staphylococcal-like mercury resistance gene in Enterococcus faecalis. Antimicrob Agents Chemother 1990; 34:1287-9. [PMID: 2118329 PMCID: PMC171805 DOI: 10.1128/aac.34.6.1287] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We investigated mercury resistance (Hgr) in 52 clinical isolates of Enterococcus faecalis from two different geographical regions. Eleven of the 52 strains were resistant to HgCl2, and plasmids from these enterococci hybridized with a staphylococcal mercury resistance gene probe. Hgr from 5 of the 11 transferred at frequencies ranging from approximately 2 X 10(-7) to 2 X 10(-3).
Collapse
Affiliation(s)
- K K Zscheck
- Program in Infectious Diseases and Clinical Microbiology, University of Texas Medical School, Houston 77030
| | | |
Collapse
|
94
|
Karkaria CE, Chen CM, Rosen BP. Mutagenesis of a nucleotide-binding site of an anion-translocating ATPase. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39005-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
|
95
|
Simkiss K, Watkins B. The influence of gut microorganisms on zinc uptake in Helix aspersa. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 1990; 66:263-271. [PMID: 15092239 DOI: 10.1016/0269-7491(90)90006-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/1989] [Revised: 04/20/1990] [Accepted: 04/27/1990] [Indexed: 05/24/2023]
Abstract
An artificial diet was prepared that enabled the snail Helix aspersa to be fed food containing varying amounts of metals, antibiotics or bacteria. By this means it is possible to show that the body burden of zinc was significantly correlated with the dietary intake. The snail was, however, able to detect high concentrations of the metal and reduced its intake of such contaminated food. The bacterial population of the alimentary tract modified the amount of zinc absorbed from the diet. It appears, therefore, that biological monitoring programmes, based upon bioaccumulation measurements, should take these influences into account.
Collapse
Affiliation(s)
- K Simkiss
- Department of Pure and Applied Zoology, University of Reading, PO Box 228, Reading RG6 2AJ, UK
| | | |
Collapse
|
96
|
Nakamura K, Sakamoto M, Uchiyama H, Yagi O. Organomercurial-volatilizing bacteria in the mercury-polluted sediment of Minamata Bay, Japan. Appl Environ Microbiol 1990; 56:304-5. [PMID: 2310185 PMCID: PMC183330 DOI: 10.1128/aem.56.1.304-305.1990] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A total of 4,604 bacterial strains isolated from the sediments of Minamata Bay and nearby low-level-mercury stations (control stations) were screened for the ability to volatilize mercury from inorganic and organic mercurial compounds. The strains that volatilize mercury from several kinds of organomercurials were found only in the sediments of Minamata Bay.
Collapse
Affiliation(s)
- K Nakamura
- Department of Basic Medical Science, National Institute for Minamata Disease, Kumamoto, Japan
| | | | | | | |
Collapse
|
97
|
Nücken EJ, Henschke RB, Schmidt FR. Nucleotide-sequence of insertion element IS15 delta IV from plasmid pBP11. DNA SEQUENCE : THE JOURNAL OF DNA SEQUENCING AND MAPPING 1990; 1:85-8. [PMID: 1966776 DOI: 10.3109/10425179009041351] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The nucleotide sequence of an insertion element in R-factor R1767 derivative pBP11 was determined. It is almost overall identical with IS15 delta, IS26 and IS46. Like IS46 it flanks one end of the sul-bla determinant and is involved in amplification of the resistance cassette. The significance for this process of a palindrome comprising part of IS15 delta IV is discussed.
Collapse
Affiliation(s)
- E J Nücken
- Institut für Bodenbiologie, Bundesforschungsanstalt für Landwirtschaft, Braunschweig, FRG
| | | | | |
Collapse
|
98
|
|
99
|
Sox TE, Olson CA. Binding and killing of bacteria by bismuth subsalicylate. Antimicrob Agents Chemother 1989; 33:2075-82. [PMID: 2694949 PMCID: PMC172824 DOI: 10.1128/aac.33.12.2075] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Bismuth subsalicylate (BSS) is a compound without significant aqueous solubility that is widely used for the treatment of gastrointestinal disorders. BSS was able to bind bacteria of diverse species, and these bound bacteria were subsequently killed. A 4-log10 reduction of viable bacteria occurred within 4 h after a 10 mM aqueous suspension of BSS was inoculated with 2 x 10(6) Escherichia coli cells per ml. Binding and killing were dependent on the levels of inoculated bacteria, and significant binding but little killing of the exposed bacteria occurred at an inoculum level of 2 x 10(9) E. coli per ml. Intracellular ATP decreased rapidly after exposure of E. coli to 10 mM BSS and, after 30 min, was only 1% of the original level. Extracellular ATP increased after exposure to BSS, but the accumulation of extracellular ATP was not sufficient to account for the loss of intracellular ATP. The killing of bacteria exposed to BSS may have been due to cessation of ATP synthesis or a loss of membrane integrity. Bactericidal activity of BSS was also investigated in a simulated gastric juice at pH 3. Killing of E. coli at this pH was much more rapid than at pH 7 and was apparently due to salicylate released by the conversion of BSS to bismuth oxychloride. It is proposed that the binding and killing observed for BSS contribute to the efficacy of this compound against gastrointestinal infections such as traveler's diarrhea.
Collapse
Affiliation(s)
- T E Sox
- Sharon Woods Technical Center, Procter and Gamble Company, Cincinnati, Ohio 45241
| | | |
Collapse
|
100
|
Flatau GN, Clément RL, Mahdyoun F, Leblanc G, Gauthier MJ. Role of transmembrane electrical potential on cadmium fixation by a marine pseudomonad. Res Microbiol 1989; 140:553-62. [PMID: 2623367 DOI: 10.1016/0923-2508(89)90087-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The role of cellular energy, and mainly that of electrical transmembrane potential, in cadmium fixation by a marine pseudomonad suspended in a mineral medium was investigated by studying the effects of ionophores. Although fixation of cadmium by cells was generally less when respiratory activity was inhibited, it was not affected by a reduction of the transmembrane electrical potential delta psi in mureinoplasts. These observations strongly suggest that cadmium fixation in this isolate was not the result of a delta psi-dependent active transport.
Collapse
Affiliation(s)
- G N Flatau
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unité 303 Mer et Santé, Nice, France
| | | | | | | | | |
Collapse
|