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PubMedDate not supplied

[Fluorene cometabolism by Rhodococcus rhodochrous and Pseudomonas fluorescens].

The transformation of fluorene by Rhodococcus rhodochrous strain 172 grown on sucrose and Pseudomonas fluorescens strain 26K grown on glycerol was studied as a function of the substrate concentration and the growth phase. Under certain cultivation conditions, fluorene was completely consumed from the medium. The specific transformation rate of fluorene was considerably higher when it was transformed in the presence of the cosubstrates than when it served as the sole carbon source. An approach to the evaluation of the specific transformation rate of fluorene during batch cultivations is proposed.

Biodegradation, Environmental↗

PubMed1992

Mechanistic and structural studies on Rhodococcus ATCC 39484 nitrilase.

Rhodococcus ATCC 39484 produced a nitrilase when induced with isovaleronitrile. The enzyme was obtainable pure in milligram amounts, had a subunit Mr of 40 kDa, and demonstrated a substrate-induced activation related to aggregation of subunits to form a 560-kDa complex. The enzyme had a broad substrate specificity, had a pH optimum of 7.5, was stable up to 40 degrees C, and had one disulfide bridge and two free cysteine residues, one of which appeared to be catalytically essential. The N-terminal sequence was determined and found to have 78.3% homology, in a 23-residue overlap, with Klebsiella ozaenae nitrilase. The enzyme was inhibited competitively by benzylamine and benzaldehyde and irreversibly by benzyl bromide. However, benzyl bromide was shown to be nonspecific, causing multiple alkylation. Acid quenching of enzyme-substrate mixtures allowed for the detection of covalent enzyme-substrate complexes using mass spectrometry. The covalent intermediate is suggested to be either a thioimidate or an acylenzyme and a reaction mechanism consistent with this observation and also the inhibitor results is proposed. The rate of breakdown of the covalent intermediates was found to be rate limiting even for substrates with undetectable rates of hydrolysis or those with very slow rates of intermediate formation. For phenylacetonitrile, a poor substrate, in addition to acid, approximately 2% of the product was the corresponding amide. This result suggests that a tetrahedral intermediate is formed which, for selected substrates, can break down anomalously to produce amide in place of the normal acid product. Under the conditions used in this study all other substrates tested were converted to acid.

Amino Acid Sequence↗

PubMed1992

Rhodococcus equi cavitary pneumonia in HIV-infected patients: an unsuspected opportunistic pathogen.

Two patients seropositive for human immunodeficiency virus (HIV) and with no previous acquired immunodeficiency syndrome-defining conditions developed cavitary pneumonia and pleural disease caused by Rhodococcus equi. R. equi was isolated from these patients' sputum and lung biopsy specimens, respectively, but the microorganism was initially considered to be a contaminant (patient 1) or misidentified as a nontuberculous mycobacterium (patient 2). The R. equi infection was fatal in one patient, who died after 4 months without specific antimicrobial therapy; the second patient was unresponsive to combination therapy with various antimicrobial agents. R. equi may cause life-threatening infections in HIV-infected patients. Microbiology laboratories should be cognizant of the need to exclude R. equi as a cause of infection in highly immunosuppressed patients.

AIDS-Related Opportunistic Infections↗

PubMedDate not supplied

Rhodococcus equi peritonitis in continuous ambulatory peritoneal dialysis.

The human Rhodococcus equi (R. equi) infection is now emerging, although extrapulmonary manifestation and isolation from patients without human immunodeficiency virus (HIV) infection remains unusual. Considerable effort is required to correctly identify and diagnose this facultative pathogen in patients with peritonitis in end-stage renal failure (ESRF) on continuous ambulatory peritoneal dialysis (CAPD). In the six cases of R. equi CAPD peritonitis reported in this series, diagnoses were made, on average, after 15 days and prolonged antibiotic therapy with morbidity in two patients. A diagnosis of R. equi should be considered in patients with suspected diphtheroid or Nocardia CAPD peritonitis, even with no history of animal contact. This study is the largest series on R. equi CAPD peritonitis and highlights the impact of this disease.

Actinomycetales Infections↗

PubMedDate not supplied

[Fluorene degradation by bacteria of the genus Rhodococcus].

Of the four investigated Rhodococcus strains (R. rhodochrous 172, R. opacus 4a and 557, and R. rhodnii 135), the first three strains were found to be able to completely transform fluorene when it was present in the medium as the sole source of carbon at a concentration of 12-25 mg/l. At a fluorene concentration of 50-100 mg/l in the medium, the rhodococci transformed 50% of the substrate in 14 days. The addition of casamino acids and sucrose (1-5 g/l) stimulated fluorene transformation, so that R. rhodochrous 172 could completely transform it in 2-5 days. Nine intermediates of fluorene transformation were isolated, purified, and structurally characterized. It was found that R. rhodnii 135 and R. opacus strains 4a and 557 hydroxylated fluorene with the formation of 2-hydroxyfluorene and 2,7-dihydroxyfluorene. R. rhodochrous 172 transformed fluorene via two independent pathways to a greater degree than did the other rhodococci studied.

Amino Acids↗

PubMedDate not supplied

[Rhodococcus equi infections in AIDS: personal cases].

We report on the occurrence of an uncommon pathogen, Rhodococcus equi (R.e.) in HIV infection. In the period february 1990-July 1991 we performed the diagnosis of R.e. infection (lung, lung-central nervous system) in two infected patients, aged 27 and 31 years, both males, drug addicts, classified as CDC IV. In the first of them an cavitating right bronchopneumonia (bpm) was diagnosed as of tuberculous origin, on the ground of the microscopic demonstration of an acid-fast, gram-positive strain in b.a.l.. A standard antituberculous regimen was uneffective and R.e. was eventually isolated in three blood culture taken shortly before the exitus and at post-mortem examination of the lungs. In the second patient a subclavian right bpm developed without microbiological evidence of any common pathogen. A third-generation cephalosporin course was only partially successful (clinical amelioration, incomplete clearing of radiological findings). After 3 months the patient relapsed and an aseptic meningitis developed. Cultures of blood and csf yielded a R.e. strain; post-mortem examination revealed a diffuse, cavitating bpm. Our personal experience underlines the difficulty in recognizing R.e. infections in compromised host, because of similarity to other entities (i.e. tuberculosis) and the absence of pathognomonic hints.

AIDS-Related Opportunistic Infections↗

PubMedDate not supplied

[Degradation of 2,4-dinitrophenol by free and immobilized cells of Rhodococcus erythropolis HL PM-1].

Degradation of 2,4-dinitrophenol (2,4-DNP) by the cells of Rhodococcus erythropolis HL PM-1 was studied. The enzymes involved in 2,4-DNP degradation were inducible, and their resynthesis took place during the process. Cell immobilization by embedding into agar gels decreased the degrader activity. Maximum rates of 2,4-DNP degradation by free and immobilized cells were 10.0 and 5.4 nmol/min per mg cells, respectively. The concentration dependence of 2,4-DNP degradation was typical of substrate inhibition kinetics. The immobilized cells were used in a model reactor designed for 2,4-DNP biodegradation. Its maximum capacity was 0.45 nmol/min per mg cells at a volumetric flow rate of 20 h-1. The reactor operated for 14 days without losing capacity; its half-lifetime equaled 16 days.

2,4-Dinitrophenol↗

PubMed2003

Comparison of yeast (Candida maltosa) and bacterial (Rhodococcus erythropolis) phenol hydroxylase activity and its properties in the phenolic compounds biodegradation.

Aromatic contaminants of the environment, to which belongs phenol and its derivatives, are toxic and in most of the cases hard to degrade. Removal of these pollutants by biological, gentle and effective way, depends on specific environmental conditions in the locality and on the biodegradation potential of the used microbial population. Closer characterization of the biodegradation and enzyme mechanisms is therefore an essential assumption of the successful implementation of microbes. This paper is focused on comparison of the biodegradation activity between the soil yeast Candida maltosa and bacteria Rhodococcus erythropolis towards various aromatics connected with determination of the first enzyme of the phenol biodegradation pathway: phenol hydroxylase (PH). The effect of substrate type, substrate concentration, growth phase of the microorganisms and presence of humic acids in the cultivation medium, on phenol biodegradation and PH activity are discussed.

Air Pollutants↗

PubMed1992

[Lung abscess caused by Rhodococcus (Corynebacterium) equi in HIV infection. Two cases].

Rhodococcus (Corynebacterium) equi is a well-known Gram positive bacillus which is usually pathogenic in farm animals but rarely causes diseases in humans. Only 30 cases of human infection have been reported in the literature. R. equi has recently been added to the list of opportunistic agents in severe HIV infection. Its most common manifestation in immunocompromised is a slowly progressive pneumonia which may cavitate. R. equi pulmonary infections are difficult to treat: they usually require prolonged parenteral antibiotic therapy and often need surgical treatment. Two cases of cavitary pneumonia in patients with severe HIV infection are reported here. In one case the disease was associated with pulmonary Kaposi sarcoma and pneumocystis pneumonia; the other case was the first opportunistic infection in the course of HIV infection.

Acquired Immunodeficiency Syndrome↗

PubMed2004

Molecular cloning and identification of a novel oxygenase gene specifically induced during the growth of Rhodococcus sp. strain T104 on limonene.

Rhodococcus sp. strain T104 is able to utilize both limonene and biphenyl as growth substrates. Furthermore, T104 possesses separate pathways for the degradation of limonene and biphenyl. Previously, we found that a gene(s) involved in limonene degradation was also related to indigo-producing ability. To further corroborate this observation, we have cloned and sequenced a 8,842-bp genomic DNA region with four open reading frames, including one for indole oxygenase, which converts indole to indigo (a blue pigment), The reverse transcription PCR data demonstrated that the identified indole oxygenase gene is specifically induced by limonene, thereby implicating this gene in the degradation of limonene by T104.

Cloning, Molecular↗

PubMedDate not supplied

[Utilization of H2O2 as the oxygen source by bacteria of the genera Pseudomonas and Rhodococcus].

The growth of bacteria of the genera Pseudomonas and Rhodococcus in the presence of hydrogen peroxide as the sole source of oxygen was studied. The toxic effect of H2O2 in the concentration range of 100-200 microg/ml was shown to extend the lag phase by 2 to 3 days. Apart from the peroxide toxicity, the bacterial growth was inhibited by the toxic effect of dissolved oxygen in concentrations over 100 microg O2/ml; in the presence of a liquid hydrocarbon phase, this effect was alleviated. Under decreased partial pressure of oxygen in the presence of hydrocarbons (12-15 vol %), the culture growth was initiated at high initial concentrations of H2O2 (300 microg/ml). When hydrogen peroxide concentrations exceeded 320 microg/ml, no growth occurred, no matter how much hydrocarbon was added.

Biotechnology↗

PubMed2005

Identification of two-component regulatory genes involved in o-xylene degradation by Rhodococcus sp. strain DK17.

Putative genes for a two-component signal transduction system (akbS and akbT) were detected near the alkylbenzene-degrading operon of Rhodococcus sp. DK17. Sequence analysis indicates that AkbS possesses potential ATP-binding and histidine autophosphorylation sites in the N- and C-terminal regions, respectively, and that AkbT has a typical response regulator domain. Mutant analysis combined with RT-PCR experiments further shows that AkbS is required to induce the expression of o-xylene dioxygenase in DK17.

Amino Acid Motifs↗

PubMed1992

[Rhodococcus equi in HIV infected patients: 2 new cases].

We reported two HIV infected patients with bacteremia and pneumonia due to Rhodococcus equi. None of them had suffer any opportunistic infection before this episode. Clinical presentation includes respiratory tract symptoms of subacute onset and fever. The X-ray examination in both cases revealed pneumonia and lung abscess in upper lobes as well as lung infiltrates in other lobes. The microorganism was isolated in lung fine needle aspiration, bronchoalveolar lavage and blood cultures in both cases. One patient died and the other was under antibiotic treatment 5 months after discharge. The therapeutic options in this infection must include the use of at least two different antibiotics to which the microorganism is sensitive, and for a prolonged period of time. Surgical treatment should be considered if the evolution is poor.

Actinomycetales Infections↗

PubMed2005

Changes in structure of lymphatic organs in foals died due to Rhodococcus equi infection.

The aim of this study was to investigate the structure of lymphatic organs in foals which died due to Rhodococcus equi infection. The material for this study consisted of 9 foals, of both genders, various breeds, 6-14 weeks old. The routine histopathological examination and immunocytochemical reaction for cytokeratine-3 receptors revealed the disturbances in the thymus epithelial cells development. This was manifested by a complete lack of cells expressing cytokeratine-3 receptors, as well as absence of normal thymocytes differentiation. The supposed thymus epithelial cells were very few, expressing faint reaction of cytokeratine-3 receptors. The relative deficiencies in the lymphatic tissue development in peripheral lymphatic organs were observed. It was concluded, that the observed pathological changes may indicate the inherited, not described yet gene failure, which was responsible for the thymus epithelial cells developmental disturbances, and was expressed with various intensity in examined foals. The causes of the fatal course of rhodococcosis in foals were primary disturbances in the immune competence.

Actinomycetales Infections↗

PubMedDate not supplied

[The role of intercellular contacts in the initiation of growth and in the development of a transiently nonculturable state by the cultures of Rhodococcus rhodochrous grown in poor media].

It was found that the growth of Rhodococcus rhodochrous cells in modified Saton's medium strongly depends on the rate of culture agitation in the flask: an agitation at 250 rpm in flasks with baffles stops cell multiplication, whereas slight agitation leads to pronounced culture growth. The growth retardation phenomenon was reversible and did not manifest itself in exponential-phase cultures or when the cells were grown in a rich medium; furthermore, it was not connected with the degree of culture aeration. When agitated at a moderate rate, the bacterial cells formed aggregates in the lag phase, which broke up into single cells in the exponential phase. The inhibitory effect of vigorous agitation was removed by the addition to the medium of the supernatant (SN) of a log-phase culture grown in the same medium with moderate agitation. Vigorous agitation is thought to interfere with the cell contacts, whose establishment is necessary for the development of an R. rhodochrous culture in a poor medium, which occurs in the form of (micro) cryptic growth. When grown in modified Saton's medium, R. rhodochrous cells were capable of transition, in the prolonged stationary phase, to a resting and transiently nonculturable state. Such cells could be resuscitated by incubation in a liquid medium with the addition of the supernatant or the Rpf secreted protein. The formation of transiently nonculturable cells was only possible under the conditions of a considerable agitation rate (250-300 rpm), which prevented secondary (cryptic) growth of the culture. This circumstance indicates the importance of intercellular contacts not only for the initiation of growth but also for the transition of the bacteria to a dormant state.

Adaptation, Physiological↗

PubMedDate not supplied

[Heterogeneity of Rhodococcus opacus 1CP as a response to stress induced by chlorophenols].

Dissociation of Rhodococcus opacus 1CP during culturing in different media (containing phenol and its monochlorinated derivatives as the sole source of carbon and energy) was studied. Three variants of strain 1CP (S1, S2, and R) differing in the morphology of cells and colonies, lipid composition, and manner of growth on phenol and monochlorophenols were isolated. It was shown that 2- and 4-chlorophenols were most actively degraded by the smooth (S) forms of the culture, and that the rough (R) form predominated when the culture was grown in a rich medium. The S forms differed from the R forms of the strain by an increased content of cardiolipin, fatty acids, and phosphatidylethanolamine.

Acetates↗

PubMed2005

[Biodegradation of di-n-butyl phthalate by mangrove microorganism Rhodococcus ruber 1K].

A di-n-butyl phthalate (DBP)degrading bacterium Rhodococcus ruber was isolated from mangrove soil, and its degrading characteristics were studied. The results showed that the bacterium could grow well on the substrate with DBP as the sole source of carbon and energy, and the DBP of 50 mg x L(-1) could be completely degraded after 48 h. Under aerobic condition, the tentative pathway proposed for DBP degradation was through monoester initially, then phthalic acid, and finally CO2 and H2O.

Biodegradation, Environmental↗

PubMed2003

[Study on the degradation pathway of biphenyl by Rhodococcus pyridinovorans R04].

Metabolites of Rhodococcus pyridinovorans R04 from biphenyl were analyzed by GC-MS. The results demonstrated that biphenyl was degraded via a route of 2,3-dihydro-2,3-dihydroxybiphenyl and 2,3-dihydroxybiphenyl. 4-Benzoylbutyric acid and 1-phenylethanone were also found in the GC-MS analysis, which indicated there were other pathways beside the main route.

Bacterial Proteins↗