RESUMO
Because nanomaterials have been increasingly developed and used in many technology and industry sectors over the last 20 years, an increasing number of workers is likely to be exposed to airborne nanoparticles. In addition, the question of the nanomaterial characteristics that should be assessed in epidemiological studies remains open. Thus, assessing occupational exposure to airborne nanoparticles will not only rely on mass concentration and chemical composition. Rather, key parameters, such as particle size, have to be included in measurement strategies. We previously proposed a methodology to estimate the Count Median Diameter (CMD) of an aerosol based on the simultaneous size-integrated measurement of two particle concentrations, lung-deposited surface area, and number, thanks to field-portable, commercially available aerosol instruments (Nanoparticle Surface Area Monitor/Condensation Particle Counter combination). In addition to previous work, this study investigates the case of various polydisperse metal oxides, organic oil, and salt particles with CMDs ranging from 16-410 nm. Once corrected, the CMDs derived from the NSAM/CPC agree within ±20% with regard to the reference electrical mobility equivalent diameter, regardless of aerosol composition, morphology, or geometric standard deviation (GSD). Furthermore, the field-applicability of the method was tested through 6 sets of experimental data stemming from workplace measurement campaigns where different materials were produced and handled (TiO2, SiO2, Ag, Multi-Walled Carbon Nanotubes-MWCNT), covering a range of CMDs between 40 and 190 nm. All situations considered, the approach based on the combination of a NSAM and a CPC leads to a satisfying estimation of particle CMD, within ±20% compared to reference CMD.
Assuntos
Poluentes Ocupacionais do Ar/análise , Nanopartículas/análise , Exposição Ocupacional/análise , Aerossóis/análise , Monitoramento Ambiental/métodos , Tamanho da Partícula , Local de TrabalhoRESUMO
Worldwide biodiversity assessments have mainly focused on species richness but little is known about the diversity of species roles, i.e. functional diversity, while this is a key facet to understanding the consequences of global changes on the ecosystem services to human societies. Here, we report the world pattern of functional diversity of freshwater fish using a database encompassing morphological characteristics of more than 9,000 species. The Neotropical realm hosts more than 75% of global functional diversity while other realms each host less than 25%. This discrepancy is mediated by high functional uniqueness in some diversified Neotropical fish orders. Surprisingly, functional diversity patterns were weakly related to functional vulnerability. In the Neotropics the loss of threatened species will cause a limited loss of functional diversity (<10%) whereas in the Nearctic and Palearctic realms, decline of the functional diversity will reach 43% and 33%, respectively, conferring a high functional vulnerability to these realms. Conservation of the Neotropical fish diversity is a key target to maintain world fish functional diversity, but this should not hide the pressing need to conserve the vulnerable fish faunas of the rest of the world, in which functional diversity is to a large extent supported by threatened species.
Assuntos
Biodiversidade , Clima , Ecossistema , Peixes/crescimento & desenvolvimento , Animais , Conservação dos Recursos Naturais/métodos , Conservação dos Recursos Naturais/estatística & dados numéricos , Bases de Dados Factuais/estatística & dados numéricos , Espécies em Perigo de Extinção , Extinção Biológica , Peixes/anatomia & histologia , Peixes/classificação , Água Doce , Geografia , HumanosRESUMO
Fabry disease (FD) is an X-linked genetic disorder caused by the deficient activity of lysosomal α-galactosidase (α-Gal). While males are usually severely affected, clinical presentation in female patients may be more variable ranging from asymptomatic to, occasionally, as severely affected as male patients. The aim of this study was to evaluate the existence of skewed X-chromosome inactivation (XCI) in females with FD, its concordance between tissues, and its contribution to the phenotype. Fifty-six females with FD were enrolled. Clinical and biological work-up included two global scores [Mainz Severity Score Index (MSSI) and DS3], cardiac magnetic resonance imaging, measured glomerular filtration rate, and measurement of α-Gal activity. XCI was analyzed in four tissues using DNA methylation studies. Skewed XCI was found in 29% of the study population. A correlation was found in XCI patterns between blood and the other analyzed tissues although some punctual variability was detected. Significant differences in residual α-Gal levels, severity scores, progression of cardiomyopathy and deterioration of kidney function, depending on the direction and degree of skewing of XCI were evidenced. XCI significantly impacts the phenotype and natural history of FD in females.
Assuntos
Doença de Fabry/diagnóstico , Doença de Fabry/genética , Inativação do Cromossomo X , Adulto , Idoso , Ativação Enzimática , Doença de Fabry/metabolismo , Feminino , Doenças Genéticas Ligadas ao Cromossomo X/diagnóstico , Doenças Genéticas Ligadas ao Cromossomo X/genética , Heterozigoto , Humanos , Testes de Função Renal , Pessoa de Meia-Idade , Mutação , Fenótipo , Regiões Promotoras Genéticas , RNA Longo não Codificante/genética , Índice de Gravidade de Doença , Remodelação Ventricular , Adulto Jovem , alfa-Galactosidase/genética , alfa-Galactosidase/metabolismoRESUMO
Venous thromboembolic disease during pregnancy is an important cause of obstetric morbidity and mortality. Suggestive clinical signs lead systematically physicians to evocate this diagnosis. Unfortunately, the incidence of events remains low, reducing the ability to perform well-designed research and to give adequate recommendations. The discovery in term pregnancy of an iliofemoral venous thrombosis raises the question of obstetrical care, mainly considering potentially embolic risk. Through a case report and based on a thinking about the few medical publications in this field, we suggest that the placing of temporary inferior vena cava filter in presence of an extensive deep venous thrombosis at term pregnancy could be debatable.
Assuntos
Veia Ilíaca , Complicações Cardiovasculares na Gravidez/terapia , Nascimento a Termo , Trombose Venosa/terapia , Doença Aguda , Anticoagulantes/uso terapêutico , Feminino , Heparina/uso terapêutico , Humanos , Veia Ilíaca/diagnóstico por imagem , Gravidez , Complicações Cardiovasculares na Gravidez/diagnóstico por imagem , Nascimento a Termo/fisiologia , Ultrassonografia Doppler , Ultrassonografia Pré-Natal , Trombose Venosa/diagnóstico por imagem , Trombose Venosa/etiologia , Adulto JovemRESUMO
We report the case of a 15 year old male who presented complaining of neck pain and upper extremity radicular symptoms one day post trampoline trauma. He was diagnosed with a nondisplaced vertical or "slit fracture" at C5 and C6. It is believed that the mechanism of injury, trampoline trauma, allowed this unusual fracture. A review of the literature provides some insight regarding speed of force and fracture displacement that may have relevance in this particular case. A review of the literature failed to find a previous report of such an event
Assuntos
Vértebras Cervicais/lesões , Cervicalgia/diagnóstico , Fraturas da Coluna Vertebral/diagnóstico , Extremidade Superior/lesões , Adolescente , Traumatismos em Atletas/diagnóstico , Vértebras Cervicais/diagnóstico por imagem , Humanos , Hipestesia/diagnóstico , Masculino , Radiografia , Fraturas da Coluna Vertebral/diagnóstico por imagem , Extremidade Superior/diagnóstico por imagemRESUMO
Alcohol is by far the most frequent addiction across industrial countries. Associated with unrest, rejection and other negative counter-attitudes, alcohol dependence often confines the patient to isolation. The objective of this article is to describe potential obstacles to access to health care, the strategies enabling this access and finally different programs and therapeutic modalities of a long-term treatment. This article focuses on these issues in term of level of intervention.
Assuntos
Alcoolismo/psicologia , Alcoolismo/terapia , Isolamento Social , Assistência Ambulatorial , Hospitalização , Humanos , PsicoterapiaRESUMO
We report a case of extreme, largely unilateral dilatation of Virchow-Robin spaces. Fluid-attenuated inversion-recovery images revealed high-signal foci adjacent to the dilated spaces, possibly due to chronic ischaemia.
Assuntos
Encefalopatias/diagnóstico , Imageamento por Ressonância Magnética , Idoso , Córtex Cerebral/irrigação sanguínea , Córtex Cerebral/patologia , Dilatação Patológica , Feminino , Humanos , Isquemia/patologiaRESUMO
The small regulatory RNA SsrA has both tRNA and mRNA activities. It charges alanine and interacts with stalled ribosomes, allowing for translation to resume on the SsrA mRNA moiety. Hence, unfinished peptides carry a short amino acid tag, which serves as a signal for degradation by energy-dependent proteases. In SsrA-defective Escherichia coli strains, thermoinducible mutants of the transposable bacteriophage Mu (Mucts) are no longer induced at high temperature. Here we show that truncated forms of the key regulator of Mu lysogeny, the repressor Repc, accumulate in the absence of SsrA. These forms resemble C-terminally truncated dominant Mu repressor mutants previously isolated from Mucts, which are no longer thermoinducible and bind operator DNA with a high affinity even at high temperature. Using various ssrA alleles, we demonstrate the importance of SsrA charging on the ribosome for controlling Mu prophage repression. Our results thus substantiate the previous observation that trans-translation is not the only function of the SsrA. The alternative function of SsrA appears to influence the stability of Mu lysogens by controlling the translation of the C-terminal domain of the repressor protein, which modulates the affinity of the protein for DNA and its susceptibility to proteolytic degradation.
Assuntos
Bacteriófago mu/genética , RNA Bacteriano/genética , Alanina/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , Mapeamento Cromossômico , Escherichia coli/genética , Escherichia coli/metabolismo , Escherichia coli/virologia , Genes Bacterianos , Genoma Viral , Dados de Sequência Molecular , Mutação , Fenótipo , Plasmídeos/genética , RNA Bacteriano/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismoRESUMO
CONTEXT: Data on the efficacy and safety of ipriflavone for prevention of postmenopausal bone loss are conflicting. OBJECTIVES: To investigate the effect of oral ipriflavone on prevention of postmenopausal bone loss and to assess the safety profile of long-term treatment with ipriflavone in postmenopausal osteoporotic women. DESIGN AND SETTING: Prospective, randomized, double-blind, placebo-controlled, 4-year study conducted in 4 centers in Belgium, Denmark, and Italy from August 1994 to July 1998. PARTICIPANTS: Four hundred seventy-four postmenopausal white women, aged 45 to 75 years, with bone mineral densities (BMDs) of less than 0.86 g/cm(2). INTERVENTIONS: Patients were randomly assigned to receive ipriflavone, 200 mg 3 times per day (n = 234), or placebo (n = 240); all received 500 mg/d of calcium. MAIN OUTCOME MEASURES: Efficacy measures included spine, hip, and forearm BMD and biochemical markers of bone resorption (urinary hydroxyproline corrected for creatinine and urinary CrossLaps [Osteometer Biotech, Herlev, Denmark] corrected for creatinine), assessed every 6 months. Laboratory safety measures and adverse events were recorded every 3 months. RESULTS: Based on intent-to-treat analysis, after 36 months of treatment, the annual percentage change from baseline in BMD of the lumbar spine for ipriflavone vs placebo (0.1% [95% confidence interval (CI), -7.9% to 8.1%] vs 0.8% [95% CI, -9.1% to 10.7%]; P =.14), or in any of the other sites measured, did not differ significantly between groups. The response in biochemical markers was also similar between groups (eg, for hydroxyproline corrected for creatinine, 20.13 mg/g [95% CI, 18.85-21.41 mg/g] vs 20.67 mg/g [95% CI, 19.41-21.92 mg/g]; P =.96); urinary CrossLaps corrected for creatinine, 268 mg/mol (95% CI, 249-288 mg/mol) vs 268 mg/mol (95% CI, 254-282 mg/mol); P =.81. The number of women with new vertebral fracture was identical or nearly so in the 2 groups at all time points. Lymphocyte concentrations decreased significantly (500/microL (0.5 x 10(9)/L]) in women treated with ipriflavone. Thirty-one women (13.2%) in the ipriflavone group developed subclinical lymphocytopenia, of whom 29 developed it during ipriflavone treatment. Of these, 15 (52%) of 29 had recovered spontaneously by 1 year and 22 (81%) of 29 by 2 years. CONCLUSIONS: Our data indicate that ipriflavone does not prevent bone loss or affect biochemical markers of bone metabolism. Additionally, ipriflavone induces lymphocytopenia in a significant number of women.
Assuntos
Isoflavonas/uso terapêutico , Osteoporose Pós-Menopausa/tratamento farmacológico , Idoso , Análise de Variância , Biomarcadores , Densidade Óssea , Remodelação Óssea , Método Duplo-Cego , Feminino , Humanos , Isoflavonas/efeitos adversos , Isoflavonas/metabolismo , Linfopenia/induzido quimicamente , Pessoa de Meia-Idade , Osteoporose Pós-Menopausa/metabolismo , Osteoporose Pós-Menopausa/prevenção & controle , Estudos Prospectivos , Fraturas da Coluna Vertebral/epidemiologiaRESUMO
Tn4371, a 55-kb transposable element involved in the degradation and biphenyl or 4-chlorobiphenyl identified in Ralstonia eutropha A5, displays a modular structure including a phage-like integrase gene (int), a Pseudomonas-like (chloro)biphenyl catabolic gene cluster (bph), and RP4- and Ti-plasmid-like transfer genes (trb) (C. Merlin, D. Springael, and A. Toussaint, Plasmid 41:40-54, 1999). Southern blot hybridization was used to examine the presence of different regions of Tn4371 in a collection of (chloro)biphenyl-degrading bacteria originating from different habitats and belonging to different bacterial genera. Tn4371-related sequences were never detected on endogenous plasmids. Although the gene probes containing only bph sequences hybridized to genomic DNA from most strains tested, a limited selection of strains, all beta-proteobacteria, displayed hybridization patterns similar to the Tn4371 bph cluster. Homology between Tn4371 and DNA of two of those strains, originating from the same area as strain A5, extended outside the catabolic genes and covered the putative transfer region of Tn4371. On the other hand, none of the (chloro)biphenyl degraders hybridized with the outer left part of Tn4371 containing the int gene. The bph catabolic determinant of the two strains displaying homology to the Tn4371 transfer genes and a third strain isolated from the A5 area could be mobilized to a R. eutropha recipient, after insertion into an endogenous or introduced IncP1 plasmid. The mobilized DNA of those strains included all Tn4371 homologous sequences previously identified in their genome. Our observations show that the bph genes present on Tn4371 are highly conserved between different (chloro)biphenyl-degrading hosts, isolated globally but belonging mainly to the beta-proteobacteria. On the other hand, Tn4371-related mobile elements carrying bph genes are apparently only found in isolates from the environment that provided the Tn4371-bearing isolate A5.
Assuntos
Bactérias/genética , Bactérias/metabolismo , Compostos de Bifenilo/metabolismo , Elementos de DNA Transponíveis/genética , Bifenilos Policlorados/metabolismo , Biodegradação Ambiental , Conjugação Genética , Meios de Cultura , Cupriavidus necator/genética , Cupriavidus necator/metabolismo , Sondas de DNA , Hibridização de Ácido Nucleico , Plasmídeos/genéticaRESUMO
The formation of araB-lacZ coding sequence fusions in Escherichia coli is a particular type of chromosomal rearrangement induced by Mucts62, a thermoinducible mutant of mutator phage Mu. Fusion formation is controlled by the host physiology. It only occurs after aerobic carbon starvation and requires the phage-encoded transposase pA, suggesting that these growth conditions trigger induction of the Mucts62 prophage. Here, we show that thermal induction of the prophage accelerated araB-lacZ fusion formation, confirming that derepression is a rate-limiting step in the fusion process. Nonetheless, starvation conditions remained essential to complete fusions, suggesting additional levels of physiological regulation. Using a transcriptional fusion indicator system in which the Mu early lytic promoter is fused to the reporter E. coli lacZ gene, we confirmed that the Mucts62 prophage was derepressed in stationary phase (S derepression) at low temperature. S derepression did not apply to prophages that expressed the Mu wild-type repressor. It depended upon the host ClpXP and Lon ATP-dependent proteases and the RpoS stationary phase-specific sigma factor, but not upon Crp. None of these four functions was required for thermal induction. Crp was required for fusion formation, but only when the Mucts62 prophage encoded the transposition/replication activating protein pB. Finally, we found that thermally induced cultures did not return to the repressed state when shifted back to low temperature and, hence, remained activated for accelerated fusion formation upon starvation. The maintenance of the derepressed state required the ClpXP and Lon host proteases and the prophage Ner-regulatory protein. These observations illustrate how the cts62 mutation in Mu repressor provides the prophage with a new way to respond to growth phase-specific regulatory signals and endows the host cell with a new potential for adaptation through the controlled use of the phage transposition machinery.
Assuntos
Bacteriófago mu/genética , Bacteriófago mu/fisiologia , Proteínas de Escherichia coli , Escherichia coli/genética , Escherichia coli/virologia , Protease La , Recombinação Genética , Proteases Dependentes de ATP , Adenosina Trifosfatases/metabolismo , Proteínas de Bactérias/metabolismo , Bacteriófago mu/metabolismo , Proteínas de Transporte , Proteína Receptora de AMP Cíclico/metabolismo , Endopeptidase Clp , Escherichia coli/metabolismo , Genes Bacterianos , Proteínas de Choque Térmico/metabolismo , Óperon Lac , Lisogenia , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Serina Endopeptidases/metabolismo , Fator sigma/metabolismo , Ativação ViralRESUMO
Tn4371 is a 55-kb catabolic transposon originally isolated from Ralstonia eutropha A5 that encodes enzymes catalyzing the complete degradation of biphenyl. Unlike previously described transposons encoding similar genes for aromatic compound degradation. Tn4371 carries a phage-like degradation, Tn4371 integrase gene and RP4/Ti-like transfer genes. Tn4371 transposition involves an excision/integration process and, consistent with this site-specific recombination mechanism, the ends of the element are transiently covalently bound. Transposition is targeted to a limited number of sites on the CH34 chromosome and pMOL30 plasmid as well as on RP4. One of these sites consists of a 5'-TTTTTCAT-3' sequence which is also present between the covalently joined ends of the transposon. Conjugative transfer of Tn4371 could not yet be demonstrated although the functionality of its transfer machinery could be established through the identification of a second transposable element, Tn-bph, which contains the right half of Tn4371, including the bph catabolic gene cluster and the identified transfer genes. Tn-bph transfers by conjugation and integrates in a new host genome independently of the larger element. Tn4371 thus appears as composite transposon combining an enteric phage-like integration system, RP4/Ti-like conjugation genes, and Pseudomonas-like catabolic genes.
Assuntos
Elementos de DNA Transponíveis/fisiologia , Técnicas de Transferência de Genes , Integrases/genética , Sequência de Aminoácidos , Sequência de Bases , Cupriavidus necator/genética , Escherichia coli/genética , Dados de Sequência Molecular , Plasmídeos/genética , Pseudomonas/metabolismo , Análise de Sequência de DNARESUMO
Tn4371, a 55-kb catabolic transposon originally isolated from Ralstonia eutropha A5, carries genes for the degradation of biphenyl/4-chlorobiphenyl, which are clustered on a 13-kb DNA segment located in the middle of the element. DNA sequencing revealed that two potential regulatory genes, bphR and bphS, border this region. Transcriptional fusion experiments using bphC as a reporter gene, Northern hybridization and primer extension analysis led to the conclusion that the transposon-encoded genes bphEFGA1A2A3BCD form an operon transcribed from a sigma70 promoter, pE. Transcription from pE was not influenced by deletion of the bphR gene of Tn4371, which should encode a LysR-like regulator. The bphS gene product negatively regulated pE, and displayed significant similarity to GntR-like regulators. This is the first reported example of a GntR-like regulator involved in the control of an aromatic degradation pathway.
Assuntos
Proteínas de Bactérias , Compostos de Bifenilo/metabolismo , Elementos de DNA Transponíveis , Proteínas de Ligação a DNA/genética , Proteínas de Escherichia coli , Genes Reguladores , Proteínas Repressoras/genética , Fatores de Transcrição , Sequência de Aminoácidos , Sequência de Bases , Northern Blotting , Primers do DNA , DNA Bacteriano , Regulação Bacteriana da Expressão Gênica , Dados de Sequência Molecular , Família Multigênica , Óperon , Regiões Promotoras Genéticas , Proteínas Repressoras/química , Homologia de Sequência de AminoácidosRESUMO
Like several other Escherichia coli bacteriophages, transposable phage Mu does not develop normally in groE hosts (M. Pato, M. Banerjee, L. Desmet, and A. Toussaint, J. Bacteriol. 169:5504-5509, 1987). We show here that lysates obtained upon induction of groE Mu lysogens contain free inactive tails and empty heads. GroEL and GroES are thus essential for the correct assembly of both Mu heads and Mu tails. Evidence is presented that groE mutations inhibit processing of the phage head protein gpH as well as the formation of a 25S complex suspected to be an early Mu head assembly intermediate.
Assuntos
Bacteriófago mu/fisiologia , Chaperonina 10/fisiologia , Chaperonina 60/fisiologia , Escherichia coli/virologia , Proteínas Virais/metabolismo , Montagem de Vírus , Bacteriófago mu/metabolismo , Chaperonina 10/genética , Chaperonina 60/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Lisogenia , Morfogênese , MutaçãoRESUMO
In bacteria lysogenic for bacteriophage Mu, the phage repressor binds to a tripartite operator region, O1,O2,O3, to repress the lytic promoter pE, located in O2, and negatively autoregulate its own synthesis at the pCM promoter located in O3. We isolated and characterized operator mutations which lead to derepression of pE. Their location in the first and third repressor-consensus-binding sequences in O2 confirms the importance of these sites for repressor/operator interactions.
Assuntos
Bacteriófago mu/genética , Regiões Operadoras Genéticas/genética , Mutação Puntual/genética , Sequência de Bases , Clonagem Molecular , Sequência Consenso , DNA Viral/metabolismo , Regulação Viral da Expressão Gênica , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Ligação Proteica , Proteínas Repressoras/metabolismo , Deleção de SequênciaAssuntos
Falso Aneurisma/diagnóstico por imagem , Aneurisma Cardíaco/diagnóstico por imagem , Ruptura Cardíaca Pós-Infarto/diagnóstico por imagem , Idoso , Falso Aneurisma/etiologia , Diagnóstico Diferencial , Feminino , Aneurisma Cardíaco/etiologia , Ruptura Cardíaca Pós-Infarto/etiologia , Ventrículos do Coração , Humanos , Radiografia , Fatores de RiscoRESUMO
Tn4371 is a 55 kb transposon which encodes enzymes for the degradation of biphenyl and 4-chlorobiphenyl compounds into benzoate and 4-chlorobenzoate derivatives. We constructed a cosmid library of Tn4371 DNA. The bph genes involved in biphenyl/4-chlorobiphenyl degradation were found to be clustered in the middle of the transposon. Sequencing revealed an organisation of the bph genes similar to that previously found in Pseudomonas sp. KKS102, i.e. the bphEGF genes are located upstream of bphA1A2A3 and bphA4 is separated from bphA1A2A3 by bphBCD. Consensus sequences for sigma54-associated RNA polymerase were found upstream of bphA1 and bphEGF. Plasmid RP4::Tn4371 was transferred into a mutant of Alcaligenes eutrophus H16 lacking sigma54. In contrast to wild-type H16 exconjugants, the sigma54 mutant exconjugants could not grow on biphenyl, indicating the dependence of Tn4371 bph gene expression on sigma54. The Tn4371-encoded bph pathway was activated when biphenyl and various biphenyl-like compounds were present in the growth medium. Preliminary observations indicate the presence of a region outside the catabolic genes downstream of bphA4 which is involved in mediating at least the basal expression of BphC.
Assuntos
Compostos de Bifenilo/metabolismo , Elementos de DNA Transponíveis , Proteínas de Ligação a DNA , Genes Bacterianos , Família Multigênica , Alcaligenes/genética , Alcaligenes/metabolismo , Biodegradação Ambiental , Cosmídeos , RNA Polimerases Dirigidas por DNA/metabolismo , Regulação Bacteriana da Expressão Gênica , Biblioteca Gênica , Dados de Sequência Molecular , Regiões Promotoras Genéticas , RNA Polimerase Sigma 54 , Fator sigma/metabolismoRESUMO
Alcaligenes eutrophus CH34 used benzoate as a sole source of carbon and energy, degrading it through the 3-oxoadipate pathway. All the enzymes required for this degradation were shown to be encoded by chromosomal genes. Catechol 1,2-dioxygenase activity was induced by benzoate, catechol, 4-chlorocatechol, and muconate. The enzyme is most likely a homodimer, with an apparent molecular weight of 76,000 +/- 500. According to several criteria, its properties are intermediate between those of catechol 1,2-dioxygenases (CatA) and chlorocatechol 1,2-dioxygenases (ClcA). The determined Km for catechol is the lowest among known catechol and chlorocatechol dioxygenases. Similar Km values were found for para-substituted catechols, although the catalytic constants were much lower. The catechol 1,2-dioxygenase from strain CH34 is unique in its property to transform tetrachlorocatechol; however, excess substrate led to a marked reversible inhibition. Some meta- and multi-substituted catechols behaved similarly. The determined Km (or Ki) values for para- or meta-substituted catechols suggest that the presence of an electron-withdrawing substituent at one of these positions results in a higher affinity of the enzyme for the ligand. Results of studies of recognition by the enzyme of various nonmetabolised aromatic compounds are also discussed.