PROCESSOS OXIDATIVOS AVANÇADOS NO TRATAMENTO DE ÁGUAS RESIDUÁRIAS: POSSIBILIDADES MECANÍSTICAS NA DEGRADAÇÃO DE POLUENTES

Este trabalho teve como finalidade apresentar estudos mecanísticos dos principais Processos Oxidativos Avançados (POAs) e alguns resultados, demonstrando a eficiência da tecnologia no tratamento de águas residuárias. Os POAs são técnicas capazes de gerar o radical hidroxila in situ, o que atribui uma enorme eficácia na degradação de diversos compostos recalcitrantes aos métodos convencionais. Tal efeito vem em razão dessa espécie química possuir elevado potencial de oxidação, sendo capaz de degradar matérias orgânicas como compostos organonitrogenados, organohalogenados e oxidar metais tóxicos, possibilitando a remoção dessa classe de poluente por filtração ou precipitação. O estudo mostra alguns resultados do emprego dos processos fotocatalíticos, eletroquímicos e fotoeletroquímicos no tratamento de águas residuárias reconhecidamente resistentes às principais tecnologias de tratamentos convencionais, proporcionando excelentes resultados na descoloração de percolado de aterro sanitário, efluentes têxteis e efluente da primeira extração alcalina (E1) da produção de papel e celulose. Os POAs podem oferecer opções viáveis para remediar problemas ambientais, reduzindo consideravelmente a poluição, além da grande versatilidade de adaptação aos tratamentos de várias efluentes aquosos.

ESTUDOS DA TOXICIDADE DO ALUMÍNIO EM VALORES DE pH 7,0 E 7,5 PARA BRASSICA OLERACEA L. E RAPHANUS SATIVUS L

A toxicidade do alumínio tem sido verificada somente em valores de pH abaixo de 5,5 devido a solubilidade dos íons Al3+ que ocorre em meio ácido. Este trabalho teve o objetivo de estudar a toxicidade do alumínio em valores de pH 7,0 para a espécie Raphanus sativus L. (rabanete) e 7,5 para a Brassica oleracea L. (couve) com a finalidade de verificar se em tais valores de pH o alumínio não apresentava efeitos deletérios observáveis. Foi utilizada uma metodologia em que o meio de cultivo continha sementes como organismos testes e um rígido controle dos valores de pH. Os ensaios toxicológicos empregavam concentrações otimizadas de macro e micronutrientes necessários ao desenvolvimento das plântulas. Com o estudo foi possível verificar elevada Toxicidades Aguda e Crônica dos íons Al3+ em valores de pH 7,0 e 7,5 para as plantas estudadas, comprovando que os efeitos tóxicos do alumínio podem ser verificados também em meio de cultivo com valores de pH neutro e ligeiramente básico.

ESTUDO DA TOXICIDADE DO GLIFOSATO NA GERMINAÇÃO DE COUVE E RABANETE

O presente trabalho teve como objetivo avaliar os efeitos tóxicos do glifosato (N-(fosfonometil)-glicina), um herbicida muito utilizado na agricultura brasileira, como agente estressor, através de uma metodologia de avaliação de toxicidade crônica e aguda nas sementes de couve (Brassica oleracea L.) e rabanete (Raphanus sativus L.). A metodologia escolhida possibilitou a análise dos parâmetros CENO (Concentração de Efeito Não Observável), CEO (Concentração de Efeito Observável) e CE50 (Concentração Efetiva) para cada uma das espécies. Tratando-se do rabanete, foi observado que o CENO aparecia em 1 mg.L-1 de agente estressor, o CEO em 2 mg.L-1 e o CE50 em aproximadamente 7 mg.L-1. Para a couve, observou-se o aparecimento do CENO em 16 mg.L-1, o CEO em 18 mg.L-1 e o CE50 entre 14 e 15 mg.L-1. Foi possível ter, através do estudo, um alto controle do valor de pH (7,0 para o rabanete e 7,5 para a couve), elevada sensibilidade e baixo custo se comparado a outros testes de toxicidade.

ESTUDO DA TOXICIDADE DA UREIA NA GERMINAÇÃO DE RABANETE E COUVE

A ureia é amplamente utilizada como fertilizante no meio agrícola. Contudo, em determinadas concentrações ela pode apresentar significativa toxicidade. O presente trabalho teve como objetivo avaliar o comportamento da ureia como agente estressor na germinação de sementes de Raphanus sativus L. (rabanete) e Brassica oleracea L. (couve), encontrando o CENO (Concentração de Efeito Não Observável), CEO (Concentração de Efeito Observável) e CE50 (Concentração Efetiva) para cada uma das espécies. Os experimentos foram realizados através da preparação de um meio de cultivo constituído de soluções contendo macro e micronutrientes em concentrações otimizadas e ágar dissolvido, além de diferentes concentrações de ureia adicionadas. Para controlar os valores de pH do meio de cultivo, foram utilizados dois tipos de soluções tampão: pH 7,0 para estudos com o rabanete e pH 7,5 para a couve. Em relação ao rabanete, observou-se que o CENO aparecia em 20 mg.L-1 de agente estressor, o CEO em 30,0 mg.L-1 e o CE50 em 183,0 mg.L-1. Para a couve, observou-se o aparecimento do CENO em 1,0 mg.L-1, o CEO em 2,0 mg.L-1 e o CE50 em, aproximadamente, 418,0 mg.L-1. Com esses dados, pode-se notar que a couve apresentou maior sensibilidade nas avaliações de toxicidade crônica (CENO/CEO) e o rabanete, maior sensibilidade nas avaliações de toxicidade aguda (CE50).

[Training in laparoscopy and appendicitis]

BACKGROUND

In order to improve laparoscopic skills, appendectomy is the most common procedure because of its high frequency and low difficulty. In spite of that, during the learning curve (each surgeon´s first 35 interventions) the incidence of complications may increase, so improvement in training means a bigger risk for some patients.

METHODS

We retrospectively reviewed major complications (intra-abdominal abscess, intestinal occlusion, hemorrhage) of 1,710 appendectomies performed at our service between 1997 and 2013. We divided them in three groups: open appendectomy (OA, n= 1,258), laparoscopic appendectomy during the learning curve (LDC, n= 154) and laparoscopic appendectomy after the learning curve (LAC, n= 298). In addition, we distinguish between simple appendicitis (n= 1,233) and peritonitis (n= 477).

RESULTS

In the OA group we detected110/1,258 major complications (8.7%), 28/154 major complications (18.2%) in the LDC group and 19/298 (6.4%) in the LAC group (p<0.05 LDC vs OA and LAC). In the simple appendicitis group, we found 13/889 major complications (1.5%) in OA, 3/115 (2.6%) in LDC group and 2/229 (0.9%) in LAC group (p= ns LDC vs OA and LAC). In the peritonitis group, 97/369 (26.3%) major complications were found in OA group, 25/39 (64%) in LDC group and 17/69 (24.6%) in LAC group (p<0.05 LDC vs OA and LAC).

CONCLUSIONS

Educational purpose laparoscopic appendectomy must be used in simple appendicitis cases.

[Biodegradable catheters for fistula prevention in hypospadias. Experimental preliminary study]

INTRODUCTION

Continuous technical innovations are not enough to resolve the high incidence of fistula after hypospadias repair. A urethral catheter-tutor made of reabsorbable polymeric biomaterial (RPB) which could be left in situ long enough could reduce the complications.

TARGET

To investigate in an animal model differents RPB to be used in urology.

METHODOLOGY

CRL Wistar rats, males, divided into 5 equal groups according to the used polymers: polylactide; lactic-coprolactone copolymer; lactic-glycolic copolymer; simulated; control silicones. Three individuals were sacrificed per group at 4th, 10th and 16th week. In all animals (exceptuating the simulated group), biomaterial was fixed to the bladder wall bylaparotomy. Animals remained in individual housing and kept under daily control of hematuria during the first 15 days and weekly weight and urine control for pH and lactate. After being slaughtered, remaining polymer was collected for chemical analysis and bladder tissue for hystologic study.

RESULTS

There was no mortality, hematuria nor other clinical signs. The bladder wall showed a mild foreign body reaction. The values of lactate and pH in urine did not reach toxic levels. Lactic-glycolic was totally reabsorbed by the 10th week and had the lowest degree of calcification. Polylactide and lactic-coprolactone remained intact.

CONCLUSION

The model of urinary bladder has proven useful for studying the degradation of bioresorbable polymers. The analyzed polymers have spent long time to be reabsorbed, so we will have to study new others.

In situ X-ray data collection from highly sensitive crystals of Pseudomonas putida PtxS in complex with DNA

Pseudomonas putida PtxS is a member of the LacI protein family of transcriptional regulators involved in glucose metabolism. All genes involved in this pathway are clustered into two operons, kgu and gad. PtxS controls the expression of the kgu and gad operons as well as its own transcription. The PtxS operator is a perfect palindrome, 5'-TGAAACCGGTTTCA-3', which is present in all three promoters. Crystallization of native PtxS failed, and PtxS-DNA crystals were finally produced by the counter-diffusion technique. A portion of the capillary used for crystal growth was attached to the end of a SPINE standard cap and directly flash-cooled in liquid nitrogen for diffraction tests. A full data set was collected with a beam size of 10×10 µm. The crystal belonged to the trigonal space group P3, with unit-cell parameters a=b=213.71, c=71.57 Å. Only unhandled crystals grown in capillaries of 0.1 mm inner diameter diffracted X-rays to 1.92 Å resolution.

Crystallization and crystallographic analysis of the ligand-binding domain of the Pseudomonas putida chemoreceptor McpS in complex with malate and succinate

Methyl-accepting chemotaxis proteins (MCPs) are transmembrane proteins that sense changes in environmental signals, generating a chemotactic response and regulating other cellular processes. MCPs are composed of two main domains: a ligand-binding domain (LBD) and a cytosolic signalling domain (CSD). Here, the crystallization of the LBD of the chemoreceptor McpS (McpS-LBD) is reported. McpS-LBD is responsible for sensing most of the TCA-cycle intermediates in the soil bacterium Pseudomonas putida KT2440. McpS-LBD was expressed, purified and crystallized in complex with two of its natural ligands (malate and succinate). Crystals were obtained by both the counter-diffusion and the hanging-drop vapour-diffusion techniques after pre-incubation of McpS-LBD with the ligands. The crystals were isomorphous and belonged to space group C2, with two molecules per asymmetric unit. Diffraction data were collected at the ESRF synchrotron X-ray source to resolutions of 1.8 and 1.9 Å for the malate and succinate complexes, respectively.

Sustained Photoproduction of Ammonia from Dinitrogen and Water by the Nitrogen-Fixing Cyanobacterium Anabaena sp. Strain ATCC 33047

Conditions have been developed that lengthen the time during which photosynthetic dinitrogen fixation by filaments of the cyanobacterium Anabaena sp. strain ATCC 33047 proceeds freely, whereas the subsequent conversion of ammonia into organic nitrogen remains blocked, with the resulting ammonia released to the outer medium. When l-methionine-dl-sulfoximine was added every 20 h, maximal rates of ammonia production (25 to 30 mumol/mg of chlorophyll per h) were maintained for about 50 h. After this time, ammonia production ceased due to a deficiency of glutamine and other nitrogenous compounds in the filaments, conditions which finally led to cell lysis. The effective ammonia production period could be further extended to about 7 days by adding a small amount of glutamine at the end of a 40-h production period or by allowing the cells to recover for 8 h in the absence of l-methionine-dl-sulfoximine after every 40-h period in the presence of the inhibitor. A more prolonged steady production of ammonia, lasting for longer than 2 weeks, was achieved by alternating treatments with the glutamine synthetase inhibitors l-methionine-dl-sulfoximine and phosphinothricin, provided that 8-h recovery periods in the absence of either compound were also alternated throughout. The biochemically manipulated cyanobacterial filaments thus represent a system that is relatively stable with time for the conversion of light energy into chemical energy, with the net generation of a valuable fuel and fertilizer through the photoreduction of dinitrogen to ammonia.

Nitroaromatics Are Substrates for the TOL Plasmid Upper-Pathway Enzymes

Expression of the xylMA genes encoding for toluene monoxygenase from the lactose promoter in a broad-host-range plasmid allows the oxidation of toluene and m- and p-nitrotoluene to their corresponding benzyl alcohols and benzaldehydes in Pseudomonas putida and Escherichia coli. Benzyl alcohols accumulate until reaching a concentration of about 80 muM, while benzaldehydes accumulate steadily with time for at least 24 h. TOL-encoded benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase recognize m- and p-nitro-substituted compounds as substrates. In contrast, the XylR protein, which regulates the TOL plasmid-encoded upper-pathway operon, does not recognize nitro-substituted toluenes as effectors.

Cross validation with the mood disorder questionnaire (MDQ) of an instrument for the detection of hypomania in Spanish: the 32 item hypomania symptom check list (HCL-32)

BACKGROUND

The detection and diagnosis of present or past hypomanic episodes is of key importance for the differential diagnosis between depressive disorders and type II bipolar disorder. However, there are few instruments available to satisfactorily screen for the latter condition. The Hypomania Symptom Checklist-32 (HCL-32) is a self-applied questionnaire with 32 hypomania items and 8 severity and functional impact items which is being developed in several European countries for this purpose. Our aim was to develop and validate the psychometric properties of the HCL-32 scale in Spain in patients with bipolar disorder and to compare its properties with other instruments available for the detection of bipolar II disorder.

METHODS

Patients were selected from 15 psychiatric outpatient departments, diagnosed with type I or type II bipolar disorder (BDI and BDII) and unipolar major depression (MD) according to DSM-IV-TR criteria. A control group of healthy subjects (HS) was likewise assessed. The patient selection criteria included a well-established diagnosis and a stable disorder and pharmacological treatment. The HCL-32 was administered to 237 subjects distributed among the above groups, on two occasions four weeks apart. We analysed the internal consistency, test-retest reliability and discriminative capacity of the HCL-32.

RESULTS

The internal consistency of the Spanish version of the HCL-32, evaluated by Cronbach's alpha, was 0.94. Mean of affirmative questions by group were 21.2 (SD 5.8) for BDI, 19.3 (SD 6.2) for BDII, 8.6 (SD 6.6) for MD and 6.6 (SD 6.1) for HS, with statistically significant differences between them (Kruskal-Wallis test, p<0.001). Concurrent validity using the diagnosis variable was 0.72. Test-retest reliability was 0.90. We analysed the best cut-off point by means of a ROC curve analysis; for 14 affirmative responses, a sensitivity of 0.85 95%CI (0.78, 0.91) and specificity of 0.79, 95%CI (0.72, 0.87) were obtained. The positive and negative probability ratios were 4.1 and 5.3 (1/0.19 respectively). HCL-32 shows a dual factor structure of items, one as an energy-activity factor and another one as a factor involving items related to disinhibition and problems with self-control and attention.

LIMITATIONS

The sample size of bipolar patients (particularly type BDII) should be increased in further studies.

CONCLUSIONS

The Spanish version of the HCL-32 has good psychometric properties and sufficient sensitivity and specificity, detecting 8 out of every 10 patients with BD. The HCL-32 is a useful screening tool of patients with bipolar disorder in clinical settings. In its present form it adequately discriminates between bipolar and unipolar or healthy subjects, but not between BD I and BII.

Hyperhomocysteinemia in patients with mild chronic renal failure

BACKGROUND

The aim of this study was to evaluate the prevalence of high plasma levels of homocysteine in patients with mild renal failure.

METHODS

Forty-six chronic renal failure patients (25 males and 21 females, mean age 55.6+/-14.4 years) were recruited for the study. Mean plasma creatinine was 2.1+/-1.0 mg/dl and mean creatinine clearance was 50.6+/-26.3 ml/min. Patients with severe renal failure were excluded. Patients were compared with a control group with normal renal function (n=35, 22 men and 13 women, mean age 50.0+/-11.5 years). Plasma homocysteine values were measured in both groups at baseline and after an oral overload of methionine.

RESULTS

Baseline homocysteine levels of patients were higher than those of controls (16.5+/-7.3 vs. 10.4+/-4.2 micromol/l, p<0.0001). Some 34 patients and 4 controls had increased plasma homocysteine levels at baseline. After the oral overload, 4 more patients had abnormally increased homocysteine levels, meaning that 83% of the patients with chronic renal failure had hyperhomocysteinemia.

CONCLUSIONS

Hyperhomocysteinemia is a very common finding among patients with mild renal failure. The need for vitamin supplementation should be evaluated in the first stage of chronic renal failure.

A strain of Arthrobacter that tolerates high concentrations of nitrate

A gram-positive strain identified as Arthrobacter globiformis CECT 4500, tolerant to up to 1 M nitrate, was isolated from the grounds of a munitions factory. Under strict aerobic conditions, this bacterium used a wide variety of C-sources to obtain the energy required for growth, which took place when the nitrate concentration in the medium was below 150 mM. Cells of this bacterium growing in the absence of nitrate were seen as individual cells or forming pairs, whereas cells grown in the presence of nitrate formed short filaments. With ethylene glycol as the C-source, optimal conditions for the full nitrate removal by Arthrobacter were established under laboratory conditions with wastewaters from the synthesis of dinitroethylene glycol.

Inhibition of growth and induction of apoptosis in human breast cancer by transfection of gef gene

The gef gene has cell-killing functions in Escherichia coli. To evaluate the feasibility of using this gene as a new strategy for cancer therapy, we transfected it in MCF-7 cells derived from breast cancer (MCF-7TG). The gef gene was cloned in a pMAMneo vector under the control of a mouse mammary tumour virus promoter, inducible by dexamethasone (Dex), and was transfected with liposomes. After selection and induction, expression of the gef gene was confirmed by reverse transcription-polymerase chain reactions (RT-PCR) and Western blot. Cell viability was determined with a haemocytometre and the sulphorodamine B colorimetric assay, and the cell cycle was studied by propidium iodide (PI) staining. Annexin V-FITC and PI assays were used to evaluate apoptosis, which was confirmed by electron microscopy. In comparison with MCF-7 parental cells and MCF-7 cells transfected with an empty vector, MCF-7TG cells induced with Dex showed a significant decrease in proliferation rate, which was associated with evidence of apoptosis. Morphological findings confirmed apoptosis and showed a typical pattern of mitochondrial dilation. Furthermore, the cell cycle was characterised by premature progression from G(1) to S phase and G(2) delay. Our results show that the gef gene was able to decrease proliferation in a breast cancer cell line, and induce apoptosis. These findings suggest that the gef gene is a potential candidate for tumour therapy.

Analysis of polyethylene thickness of tibial components in total knee replacement

BACKGROUND

Excessive wear of the polyethylene bearing surfaces of tibial components has become an important factor in early failure of total knee arthroplasty. Inadequate thickness of the polyethylene insert is one cause of excessive wear, and various minimum thicknesses have been recommended in order to reduce contact stresses within the polyethylene. However, the true thicknesses of modular polyethylene tibial inserts typically are not stated accurately by the manufacturers in their product information. The purpose of this study was to determine whether the information about the thickness of tibial inserts supplied by the manufacturers is adequate.

METHODS

Five of the thinnest available polyethylene tibial inserts from five different manufacturers were selected. The minimum thickness of each was measured with use of a Sigma electronic micrometer comparator to an accuracy of +/-0.005 mm.

RESULTS

The stated thicknesses of the polyethylene tibial inserts were 8, 9, and 10 mm, values that differed markedly from the actual minimum thicknesses, which ranged from 5.5722 to 6.2048 mm (mean values).

CONCLUSION

The thickness of polyethylene tibial inserts has been implicated as a potential cause of excessive wear and early failure of total knee replacements. This paper highlights the fact that the information supplied by the manufacturers is inaccurate and potentially misleading; in one case, the true thickness was much less than the recommended minimum thickness. We recommend that the minimum thickness of the tibial components as well as the combined thickness of the polyethylene insert and the metal tibial tray be specified in the product information and on the packaged insert.

Expression of a Pseudomonas putida aminotransferase involved in lysine catabolism is induced in the rhizosphere

Using a transposon carrying a promoterless lux operon to generate transcriptional fusions by insertional mutagenesis, we have identified a Pseudomonas putida gene with increased expression in the presence of corn root exudates. Expression of the transcriptional fusion, induced by the amino acid lysine, was detected in P. putida in the rhizosphere of plants as well as in response to seed exudates. The mutant was unable to grow on lysine or delta-aminovalerate as carbon sources, which indicates that the affected function is involved in the pathway for lysine catabolism. However, the mutant strain grew with glutaric acid, the product of delta-aminovalerate metabolism via glutaric acid semialdehyde, as a C source. The translated sequence of the interrupted gene showed high levels of similarity with aminotransferases. These sets of data suggest that the product of this gene has delta-aminovalerate aminotransferase activity. This is the first direct genetic evidence correlating a DNA sequence with such activity in Pseudomonadaceae.

Lipoma of the liver associated with hepatocellular carcinoma and polycystic liver disease

BACKGROUND/AIMS

We report on a patient with lipoma of the liver associated with hepatocellular carcinoma (HCC) and polycystic liver disease.

METHODS

Clinical features of a patient with lipoma, HCC and polycystic liver disease are presented. A right liver lobectomy was performed.

RESULTS

Histological examination revealed a poorly differentiated multicentric HCC, as well as bile duct cysts and an encapsulated tumor of adipose tissue. The postoperative course was uncomplicated. The patient died 4 years after surgery with local recurrence of HCC.

CONCLUSION

We find the report to be of interest because of the unusual nature of this association and the low prevalence of lipoma of the liver. The association of liver polycystic disease with other types of tumor is discussed and the literature dealing with lipomas of the liver reviewed.

Residues 137 and 153 of XylS influence contacts with the C-terminal domain of the RNA polymerase alpha subunit

XylS and XylS1 are transcriptional regulators that stimulate transcription from the Pm promoter for the meta-cleavage pathway operon for alkylbenzoate degradation. These regulators that differ in five amino acids interact with alpha-CTD domain of RNA polymerase. These interactions take place preferentially through residues 291 in XylS and 289 in XylS1. Substitution at position 137 and 153 in XylS influence the interactions with alpha-CTD because single and double mutants in these positions turned preferential interactions to residue 289.

A WbpL mutant of Pseudomonas putida DOT-T1E strain, which lacks the O-antigenic side chain of lipopolysaccharides, is tolerant to organic solvent shocks

Lipopolysaccharides (LPS) are major components of the outer membrane of gram-negative bacteria and are considered a defense barrier. To determine if LPS play a role in resistance to solvents in the solvent-tolerant Pseudomonas putida DOT-T1E strain, we have generated mutants unable to synthesize the O-antigen side chain of LPS. The wbpL gene, encoding the enzyme that begins the synthesis of the O-antigen side chain of LPS of the solvent-tolerant strain, was cloned, sequenced, and knocked out in vitro with a cassette encoding kanamycin resistance, and a mutant called WbpL0 of the DOT-T1E strain was generated in vivo by site-directed mutagenesis. The WbpL mutant was compared with the wild-type strain with regard to tolerance to a number of toxic compounds, including chelating agents, organic acids, detergents, and aromatic hydrocarbons. It was found that the mutant was as tolerant as the wild-type strain to organic acids and aromatic hydrocarbons and more sensitive to ethylenediaminetetraacetic acid and deoxycholate.

Involvement of the TonB system in tolerance to solvents and drugs in Pseudomonas putida DOT-T1E

Pseudomonas putida DOT-T1E is able to grow with glucose as the carbon source in liquid medium with 1% (vol/vol) toluene or 17 g of (123 mM) p-hydroxybenzoate (4HBA) per liter. After random mini-Tn5'phoA-Km mutagenesis, we isolated the mutant DOT-T1E-PhoA5, which was more sensitive than the wild type to 4HBA (growth was prevented at 6 g/liter) and toluene (the mutant did not withstand sudden toluene shock). Susceptibility to toluene and 4HBA resulted from the reduced efflux of these compounds from the cell, as revealed by accumulation assays with (14)C-labeled substrates. The mutant was also more susceptible to a number of antibiotics, and its growth in iron-deficient minimal medium was inhibited in the presence of ethylenediamine-di(o-hydroxyphenylacetic acid (EDDHA). Cloning the mutation in the PhoA5 strain and sequencing the region adjacent showed that the mini-Tn5 transposor interrupted the exbD gene, which forms part of the exbBD tonB operon. Complementation by the exbBD and tonB genes cloned in pJB3-Tc restored the wild-type characteristics to the PhoA5 strain.

Physiological characterization of Pseudomonas putida DOT-T1E tolerance to p-hydroxybenzoate

Pseudomonas putida DOT-T1E was isolated as a toluene-tolerant strain. We show that it is also able to grow on high concentrations (up to 17 g/liter [123 mM]) of p-hydroxybenzoate (4HBA). Tolerance to this aromatic carboxylic acid (up to 30 g/liter [217 mM]) is improved by preexposing the cells to low 4HBA concentrations; the adaptation process is caused by the substrate itself rather than by products resulting from its metabolism. The mechanisms of 4HBA tolerance seem to involve increased rigidity of the cell membrane as a result of a decrease in the cis/trans ratio of unsaturated fatty acids. In addition, energy-dependent efflux systems seem to operate in the exclusion of 4HBA from the cell membranes.

Biological degradation of 2,4,6-trinitrotoluene

Nitroaromatic compounds are xenobiotics that have found multiple applications in the synthesis of foams, pharmaceuticals, pesticides, and explosives. These compounds are toxic and recalcitrant and are degraded relatively slowly in the environment by microorganisms. 2,4,6-Trinitrotoluene (TNT) is the most widely used nitroaromatic compound. Certain strains of Pseudomonas and fungi can use TNT as a nitrogen source through the removal of nitrogen as nitrite from TNT under aerobic conditions and the further reduction of the released nitrite to ammonium, which is incorporated into carbon skeletons. Phanerochaete chrysosporium and other fungi mineralize TNT under ligninolytic conditions by converting it into reduced TNT intermediates, which are excreted to the external milieu, where they are substrates for ligninolytic enzymes. Most if not all aerobic microorganisms reduce TNT to the corresponding amino derivatives via the formation of nitroso and hydroxylamine intermediates. Condensation of the latter compounds yields highly recalcitrant azoxytetranitrotoluenes. Anaerobic microorganisms can also degrade TNT through different pathways. One pathway, found in Desulfovibrio and Clostridium, involves reduction of TNT to triaminotoluene; subsequent steps are still not known. Some Clostridium species may reduce TNT to hydroxylaminodinitrotoluenes, which are then further metabolized. Another pathway has been described in Pseudomonas sp. strain JLR11 and involves nitrite release and further reduction to ammonium, with almost 85% of the N-TNT incorporated as organic N in the cells. It was recently reported that in this strain TNT can serve as a final electron acceptor in respiratory chains and that the reduction of TNT is coupled to ATP synthesis. In this review we also discuss a number of biotechnological applications of bacteria and fungi, including slurry reactors, composting, and land farming, to remove TNT from polluted soils. These treatments have been designed to achieve mineralization or reduction of TNT and immobilization of its amino derivatives on humic material. These approaches are highly efficient in removing TNT, and increasing amounts of research into the potential usefulness of phytoremediation, rhizophytoremediation, and transgenic plants with bacterial genes for TNT removal are being done.

Dual system to reinforce biological containment of recombinant bacteria designed for rhizoremediation

Active biological containment (ABC) systems have been designed to control at will the survival or death of a bacterial population. These systems are based on the use of a killing gene, e.g., a porin-inducing protein such as the one encoded by the Escherichia coli gef gene, and a regulatory circuit that controls expression of the killing gene in response to the presence or absence of environmental signals. An ABC system for recombinant microorganisms that degrade a model pollutant was designed on the basis of the Pseudomonas putida TOL plasmid meta-cleavage regulatory circuit. The system consists of a fusion of the Pm promoter to lacI, whose expression is controlled by XylS with 3-methylbenzoate, and a fusion of a synthetic P(lac) promoter to gef. In the presence of the model pollutant, bacterial cells survived and degraded the target compound, whereas in the absence of the aromatic carboxylic acid cell death was induced. The system had two main drawbacks: (i) the slow death of the bacterial cells in soil versus the fast killing rate in liquid cultures in laboratory assays, and (ii) the appearance of mutants, at a rate of about 10(-8) per cell and generation, that did not die after the pollutant had been exhausted. We reinforced the ABC system by including it in a Deltaasd P. putida background. A P. putida Deltaasd mutant is viable only in complex medium supplemented with diaminopimelic acid, methionine, lysine, and threonine. We constructed a P. putida Deltaasd strain, called MCR7, with a Pm::asd fusion in the host chromosome. This strain was viable in the presence of 3-methylbenzoate because synthesis of the essential metabolites was achieved through XylS-dependent induction. In the P. putida MCR7 strain, an ABC system (Pm::lacI, xylS, P(lac)::gef) was incorporated into the host chromosome to yield strain MCR8. The number of MCR8 mutants that escaped killing was below our detection limit (<10(-9) mutants per cell and generation). The MCR8 strain survived and colonized rhizosphere soil with 3-methylbenzoate at a level similar to that of the wild-type strain. However, it disappeared in less than 20 to 25 days in soils without the pollutant, whereas an asd(+), biologically contained counterpart such as P. putida CMC4 was still detectable in soils after 100 days.

Three efflux pumps are required to provide efficient tolerance to toluene in Pseudomonas putida DOT-T1E

In Pseudomonas putida DOT-T1E multidrug efflux pumps of the resistance-nodulation-division family make a major contribution to solvent resistance. Two pumps have been identified: TtgABC, expressed constitutively, and TtgDEF, induced by aromatic hydrocarbons. A double mutant lacking both efflux pumps was able to survive a sudden toluene shock if and only if preinduced with small amounts of toluene supplied via the gas phase. In this article we report the identification and characterization in this strain of a third efflux pump, named TtgGHI. The ttgGHI genes form an operon that is expressed constitutively at high levels from a single promoter. In the presence of toluene the operon is expressed at an even higher level from two promoters, the constitutive one and a previously unreported one that is inducible and that partially overlaps the constitutive promoter. By site-directed mutagenesis we constructed a single ttgH mutant which was shown to be unable to survive sudden 0.3% (vol/vol) toluene shocks regardless of the preculture conditions. The mutation was transferred to single and double mutants to construct mutant strains in which two or all three pumps are knocked out. Survival analysis of induced and noninduced cells revealed that the TtgABC and TtgGHI pumps extruded toluene, styrene, m-xylene, ethylbenzene, and propylbenzene, whereas the TtgDEF pump removed only toluene and styrene. The triple mutant was hypersensitive to toluene, as shown by its inability to grow with toluene supplied via the vapor phase.

Mutations in genes involved in the flagellar export apparatus of the solvent-tolerant Pseudomonas putida DOT-T1E strain impair motility and lead to hypersensitivity to toluene shocks

Pseudomonas putida DOT-T1E is a solvent-tolerant strain able to grow in the presence of 1% (vol/vol) toluene in the culture medium. Random mutagenesis with mini-Tn5-'phoA-Km allowed us to isolate a mutant strain (DOT-T1E-42) that formed blue colonies on Luria-Bertani medium supplemented with 5-bromo-4-chloro-3-indolylphosphate and that, in contrast to the wild-type strain, was unable to tolerate toluene shocks (0.3%, vol/vol). The mutant strain exhibited patterns of tolerance or sensitivity to a number of antibiotics, detergents, and chelating agents similar to those of the wild-type strain. The mutation in this strain therefore seemed to specifically affect toluene tolerance. Cloning and sequencing of the mutation revealed that the mini-Tn5-'phoA-Km was inserted within the fliP gene, which is part of the fliLMNOPQRflhBA cluster, a set of genes that encode flagellar structure components. FliP is involved in the export of flagellar proteins, and in fact, the P. putida fliP mutant was nonmotile. The finding that, after replacing the mutant allele with the wild-type one, the strain recovered the wild-type pattern of toluene tolerance and motility unequivocally assigned FliP a function in solvent resistance. An flhB knockout mutant, another gene component of the flagellar export apparatus, was also nonmotile and hypersensitive to toluene. In contrast, a nonpolar mutation at the fliL gene, which encodes a cytoplasmic membrane protein associated with the flagellar basal body, yielded a nonmotile yet toluene-resistant strain. The results are discussed regarding a possible role of the flagellar export apparatus in the transport of one or more proteins necessary for toluene tolerance in P. putida DOT-T1E to the periplasm.

The methionine biosynthetic pathway from homoserine in Pseudomonas putida involves the metW, metX, metZ, metH and metE gene products

Biosynthesis of methionine from homoserine in Pseudomonas putida takes place in three steps. The first step is the acylation of homoserine to yield an acyl-L-homoserine. This reaction is catalyzed by the products of the metXW genes and is equivalent to the first step in enterobacteria, gram-positive bacteria and fungi, except that in these microorganisms the reaction is catalyzed by a single polypeptide (the product of the metA gene in Escherichia coli and the met5 gene product in Neurospora crassa). In Pseudomonas putida, as in gram-positive bacteria and certain fungi, the second and third steps are a direct sulfhydrylation that converts the O-acyl-L-homoserine into homocysteine and further methylation to yield methionine. The latter reaction can be mediated by either of the two methionine synthetases present in the cells.

Degradation of o-methoxybenzoate by a two-member consortium made up of a gram-positive Arthrobacter strain and a gram-negative Pantotea strain

Aromatic carboxylic acids substituted with methoxylated groups are among the most abundant products in "alpechin", the wastes resulting from pressing olives to obtain olive oil. Degradation of o-methoxybenzoate by an stable consortium made of a gram positive bacterium, Arthrobacter oxydans, and gram negative one, Pantotea agglomerans, was shown to mineralize this compound efficiently. The concerted action of both microorganisms was needed for the two first steps in the process, namely, the conversion of o-methoxybenzoate into salycilate, and the hydroxylation of the latter to gentisate. Gentisate was further degraded by the Arthrobacter strain.

Responses of Gram-negative bacteria to certain environmental stressors

Bacteria in nature are exposed to variations in temperature, and are affected by the availability of nutrients and water and the presence of toxic molecules. Their reactions to these changes require a series of rapid adaptive responses. Although transcriptional regulation is of primary importance in these responses, translational regulation and even activation of 'silenced' enzymes are critical for survival in changing environments. Bacteria have developed a series of mechanisms at the membrane structure level to cope with high concentrations of solvents. In addition, solvent-tolerant strains express highly effective efflux pumps to remove solvents from the cytoplasm. Desiccation tolerance is based on the synthesis and accumulation of osmoprotectants together with changes in fatty acid composition to preserve membrane structure. Both cold shock and heat shock responses are mainly regulated at a post-transcriptional level, translation efficiency in the case of cold shock and mRNA half-life and sigma32 stability in the case of heat shock.

Interactions of the XylS regulators with the C-terminal domain of the RNA polymerase alpha subunit influence the expression level from the cognate Pm promoter

The Pseudomonas putida meta-cleavage operon encodes the enzymes for the catabolism of alkylbenzoates. Activation of meta-operon transcription is mediated by the XylS protein which, upon activation by effectors, binds two sites between -70 and -35 with respect to the main transcription initiation point at the Pm promoter. Two naturally occurring regulators, XylS and XylS1, that differ by only five amino acids, have been analyzed with regard to potential interactions of these positive regulators with the C-terminal domain of the alpha subunit of RNA polymerase (alpha-CTD). For these studies we expressed a derivative of alpha deprived of the entire C-terminal domain (alpha-Delta235) and found that expression from Pm with XylS or XylS1 was significantly decreased. To discern whether alpha-CTD activation depended on interactions with DNA and/or XylS proteins we tested a large collection of alanine substitutions within alpha-CTD. Most substitutions that had an effect on XylS and XylS1-dependent transcription were located in or adjacent to helix 1 and 4, which are known to be involved in alpha-CTD interactions with DNA. Two alanine substitutions in helix 3 (residues 287 and 291) identified a putative region of alpha-CTD/XylS regulator interactions.

Global and cognate regulators control the expression of the organic solvent efflux pumps TtgABC and TtgDEF of Pseudomonas putida

Pseudomonas putida DOT-T1E grows on a water-toluene double liquid phase. Toluene tolerance in this microorganism is mainly achieved by at least two efflux pumps that belong to the RND family. The TtgDEF efflux pump is induced by toluene, whereas the other efflux pump, called TtgABC, is expressed at a high level in cells not exposed to toluene and at a lower level in cells grown with toluene. The ttgR gene is adjacent to the ttgABC operon and is transcribed divergently from ttgA. The expression level of ttgR was fourfold higher in cells growing in the presence of toluene than in its absence. In a TtgR-deficient background, expression from the ttgA promoter increased about 20-fold, suggesting that TtgR represses expression from the ttgA promoter. In this mutant, background expression of the ttgR gene was also much higher than in the wild-type background; however, its level of expression increased in the presence of toluene. In a ttgR mutant background, expression from the ttgD promoter followed the same pattern of expression as in the wild type. Analysis of a P. putida pTn5cat mutant that exhibited increased sensitivity to a sudden toluene shock, regardless of whether or not it was previously exposed to low toluene concentrations, revealed that pTn5cat had interrupted an lrp-like gene. The ttgR gene was expressed at very high levels in this mutant, with concomitant repression of expression of the ttgABC operon. The second ttgDEF efflux pump was expressed at low levels in this mutant strain, suggesting that the Lrp-like protein is a global regulatory protein involved in the solvent-tolerant response of this strain.

A bioluminescent derivative of Pseudomonas putida KT2440 for deliberate release into the environment

Recombinant derivatives of Pseudomonas putida strain KT2440 are of potential interest as microbial inoculants to be deliberately released for agricultural applications. To facilitate tracking of this strain and its derivatives after introduction into the environment, a mini-Tn5-'luxAB transposon was introduced into the chromosome of P. putida KT2440, yielding strain P. putida S1B1. Sequencing of the DNA region located upstream of the 'luxAB genes and similarity search with the P. putida KT2440 genome sequence, localized the transposon within a 3021-bp open reading frame (ORF), whose translated sequence showed significant similarity with the hypothetical YdiJ proteins from Escherichia coli and Haemophilus influenzae. A second ORF adjacent to and divergent from the ydiJ sequence was also found and showed significant homology with various LysR-type transcriptional activator proteins from several bacteria. Disruption of the ydiJ locus in P. putida S1B1 did not affect the survival of the strain in unvegetated or vegetated soils. Bioluminescent detection of P. putida S1B1 cells enriched in selective media directly from soil allowed detection of culturable cells in soil samples over a period of at least 8 months. The addition of the luxAB biomarker facilitates tracking in the root system of several plant species grown under sterile and non-sterile conditions. The correlation of the bioluminescent phenotype with the growth activity of P. putida S1B1 cells colonizing the root system of barley and corn plants was estimated by monitoring ribosomal contents using quantitative hybridization with fluorescence-labeled ribosomal RNA probes. A correlation between inoculum density, light output, and ribosomal contents was found for P. putida cells colonizing the root system of barley seedlings grown under sterile conditions. Although ribosomal contents, and therefore growth activity, of P. putida S1B1 cells extracted from the rhizosphere of corn plants grown in non-sterile soil were similar to those found in starved cells, the luminescent system permitted non-destructive in situ detection of the strain in the upper root system.

Transcription activation by a variety of AraC/XylS family activators does not depend on the class II-specific activation determinant in the N-terminal domain of the RNA polymerase alpha subunit

The N-terminal domain of the RNA polymerase alpha subunit (alpha-NTD) was tested for a role in transcription activation by a variety of AraC/XylS family members. Based on substitutions at residues 162 to 165 and an extensive genetic screen we conclude that alpha-NTD is not an activation target for these activators.

Control of expression of divergent Pseudomonas putida put promoters for proline catabolism

Pseudomonas putida KT2440 uses proline as the sole C and N source. Utilization of this amino acid involves its uptake, which is mediated by the PutP protein, and its conversion into glutamate, mediated by the PutA protein. Sequence analysis revealed that the putA and putP genes are transcribed divergently. Expression from the putP and putA genes was analyzed at the mRNA level in different host backgrounds in the absence and presence of proline. Expression from the put promoters was induced by proline. The transcription initiation points of the putP and putA genes were precisely mapped via primer extension, and sequence analysis of the upstream DNA region showed well-separated promoters for these two genes. The PutA protein acts as a repressor of put gene expression in P. putida because expression from the put promoters is constitutive in a host background with a knockout putA gene. This regulatory activity is independent of the catabolic activity of PutA, because we show that a point mutation (Glu896-->Lys) that prevents catalytic activity allowed the protein to retain its regulatory activity. Expression from the put promoters in the presence of proline in a putA-proficient background requires a positive regulatory protein, still unidentified, whose expression seems to be sigma(54) dependent because the put genes were not expressed in a sigma(54)-deficient background. Expression of the putA and putP genes was equally high in the presence of proline in sigma(38)- and ihf-deficient P. putida backgrounds.

[Pyogenic and non-pyogenic vertebral osteomyelitis: descriptive and comparative study of a series of 40 cases]

BACKGROUND

To describe the features of vertebral osteomyelitis (VO) in our area, and to compare pyogenic VO (PVO) and non-pyogenic VO (NPVO).

METHODS

Retrospective study of patients with VO diagnosed in our hospital between january 1992 and december 1998.

RESULTS

We identify 40 patients with VO: 17 (42.5%) with tuberculous VO, 12 (30%) with PVO, 10 (25%) with brucellar VO and 1 (2.5%) with a VO caused by Candida albicans. The mean age was 52.9 years, and 75% of patients were male. Only a 20% of cases had a known immunosuppression. Fever/febricule was present in 55% of patients and vertebral pain in 95%. The more frequent locations were lumbar (67.5%) and dorsal (27.5%). One or more paravertebral or epidural abscesses were present in 67.5% of cases and spinal cord compression was present in 27.5%. An elevated erythrocyte sedimentation rate (ESR) was present in 40% and leukocytosis in 27.5%. Sequelae after complete treatment occurred in 40% of patients, with residual vertebral pain in 37.5%. There was a shorter clinical course and a higher frequency of fever/febricule and leukocytosis in PVO than in NPVO.

CONCLUSIONS

In our area the more frequent etiology of VO is tuberculosis. VO occurs predominantly in males older than 50 years, without known immunosuppression, and almost exclusively with lumbar or dorsal locations. The absence of fever/febricule, leukocytosis or elevated ESR do not exclude the diagnosis of VO. Sequelae after complete treatment are relatively frequent, fundamentally residual vertebral pain. There are some differences in the features between PVO and NPVO, which may aid in the differential diagnosis of both entities.

Mutations in each of the tol genes of Pseudomonas putida reveal that they are critical for maintenance of outer membrane stability

The outer membrane of gram-negative bacteria functions as a permeability barrier that protects cells against a large number of antibacterial agents. OprL protein of Pseudomonas putida has been shown to be crucial to maintain the stability of this cell component (J. J. Rodríguez-Herva, M.-I. Ramos-González, and J. L. Ramos. J. Bacteriol. 178:1699-1706, 1996). In the present study we cloned and mutagenized the orf1, tolQ, tolR, tolA, and tolB genes from P. putida KT2440, which were located upstream of the oprL gene. Polar and nonpolar mutations of the P. putida tolQ, tolR, tolA, and tolB genes were generated in vitro by using the omega-Km(r) interposon, which carries two transcriptional stop signals, or a promoterless xylE cassette, lacking any transcriptional stop signal, respectively. The mutant constructs were used to inactivate, by reverse genetics procedures, the corresponding chromosomal copies of the genes. The phenotype of each mutant strain was analyzed and compared with those of the wild-type strain and the previously characterized P. putida oprL::xylE mutant. All mutant strains exhibited a similar phenotype: altered cell morphology, bleb formation at the cell surface, release of periplasmic and outer membrane proteins to the extracellular medium, increased sensitivity to a variety of compounds (i.e., EDTA, sodium dodecyl sulfate, deoxycholate, and some antibiotics), filament formation, and severely reduced cell motility. Altogether, these results demonstrate the importance of the Tol-OprL system for the maintenance of outer membrane integrity in P. putida and suggest a possible role of these proteins in assembling outer membrane components.

Mutational analysis of the highly conserved C-terminal residues of the XylS protein, a member of the AraC family of transcriptional regulators

The XylS protein of the TOL plasmid of Pseudomonas putida belongs to the so-called AraC/XylS family of regulators, that includes more than 100 different bacterial proteins. A conserved stretch of about 100 amino acids is present at the C-terminal end. This conserved region is believed to contain seven alpha-helices, including two helix-turn-helix (HTH) DNA binding motifs (alpha(2)-T-alpha(3) and alpha(5)-Talpha-(6)), connected by a linker alpha-helix (alpha(4)), and two flanking alpha-helices (alpha(1) and alpha(7)). The second HTH motif is the region with the highest homology in the proteins of the family, with certain residues showing almost 90% identity. We have constructed XylS single mutants in the most conserved residues and have analysed their ability to stimulate transcription from its cognate promoter, Pm, fused to 'lacZ. The analysis revealed that mutations in the alpha(5)-helix conserved residues had little effect on the XylS transcriptional activity, whereas the distribution of polarity in the alpha(6)-helix was important for the activity. The strongest effect of the mutations was observed in conserved residues located outside the DNA binding domain, namely, Gly-290 in the turn between the two helices, Pro-309 located downstream of alpha(6), and Leu-313, in the small last helix alpha(7), that seems to play an important role in the activation of RNA-polymerase. Our analysis shows that conservation of amino acids in the family reflects structural requirements rather than functionality in specific DNA interactions.

Retrotransfer of DNA in the rhizosphere

Retrotransfer of DNA refers to the phenomenon by which a plasmid travels from a host strain to a recipient one and returns to the original host, bringing with it DNA from the recipient. The resultant host strain with DNA from the recipient is called a retrotransconjugant. The retrotransfer phenomenon mediated by the TOL plasmid pWW0 and other plasmids has been documented on plates under optimal laboratory culture conditions, but never under natural conditions. In this work, we show that retrotransfer mediated by the IncP9 TOL pWW0 plasmid occurs in the rhizosphere, a niche in which the continuous supply of nutrients via root exudates allows cells to reach a high density. This suggests that this unusual sexual fertilization may be of great importance in lateral gene transfer. We also show that retrotransfer of DNA seems to require co-integration of the plasmid and the host chromosome and subsequent resolution, because a TOL plasmid with a mutation in the tnpR gene, encoding the resolvase of the Tn4653 of the TOL plasmid, was self-transferred between Pseudomonas strains, but unable to mobilize chromosome.

Genetic analysis of functions involved in adhesion of Pseudomonas putida to seeds

Many agricultural uses of bacteria require the establishment of efficient bacterial populations in the rhizosphere, for which colonization of plant seeds often constitutes a critical first step. Pseudomonas putida KT2440 is a strain that colonizes the rhizosphere of a number of agronomically important plants at high population densities. To identify the functions involved in initial seed colonization by P. putida KT2440, we subjected this strain to transposon mutagenesis and screened for mutants defective in attachment to corn seeds. Eight different mutants were isolated and characterized. While all of them showed reduced attachment to seeds, only two had strong defects in their adhesion to abiotic surfaces (glass and different plastics). Sequences of the loci affected in all eight mutants were obtained. None of the isolated genes had previously been described in P. putida, although four of them showed clear similarities with genes of known functions in other organisms. They corresponded to putative surface and membrane proteins, including a calcium-binding protein, a hemolysin, a peptide transporter, and a potential multidrug efflux pump. One other showed limited similarities with surface proteins, while the remaining three presented no obvious similarities with known genes, indicating that this study has disclosed novel functions.

Middle-term results of a cementless threaded self-tapping acetabular cup

Various designs of acetabular cup are available for cementless fixation in patients undergoing total hip arthroplasty. Conflicting results have been reported in the literature about the middle to long-term outcomes with the use of these cups. We present our experience of a design of self-tapping threaded acetabular cup with metal backing (the ACSYS acetabular cup). This is a study of 41 hips with average follow up of 6.43 years. Functional grading of the hips was very satisfactory and none of the patients needed revision for aseptic loosening. No case of significant cup migration or osteolysis was noted. The paper also reviews the literature.

Respiration of 2,4,6-trinitrotoluene by Pseudomonas sp. strain JLR11

Under anoxic conditions Pseudomonas sp. strain JLR11 can use 2,4, 6-trinitrotoluene (TNT) as the sole N source, releasing nitrite from the aromatic ring and subsequently reducing it to ammonium and incorporating it into C skeletons. This study shows that TNT can also be used as a terminal electron acceptor in respiratory chains under anoxic conditions by Pseudomonas sp. strain JLR11. TNT-dependent proton translocation coupled to the reduction of TNT to aminonitrotoluenes has been observed in TNT-grown cells. This extrusion did not occur in nitrate-grown cells or in anaerobic TNT-grown cells treated with cyanide, a respiratory chain inhibitor. We have shown that in a membrane fraction prepared from Pseudomonas sp. strain JLR11 grown on TNT under anaerobic conditions, the synthesis of ATP was coupled to the oxidation of molecular hydrogen and to the reduction of TNT. This phosphorylation was uncoupled by gramicidin. Respiration by Pseudomonas sp. strain JLR11 is potentially useful for the biotreatment of TNT in polluted waters and soils, particularly in phytorhizoremediation, in which bacterial cells are transported to the deepest root zones, which are poor in oxygen.

A set of genes encoding a second toluene efflux system in Pseudomonas putida DOT-T1E is linked to the tod genes for toluene metabolism

Sequence analysis in Pseudomonas putida DOT-T1E revealed a second toluene efflux system for toluene metabolism encoded by the ttgDEF genes, which are adjacent to the tod genes. The ttgDEF genes were expressed in response to the presence of aromatic hydrocarbons such as toluene and styrene in the culture medium. To characterize the contribution of the TtgDEF system to toluene tolerance in P. putida, site-directed mutagenesis was used to knock out the gene in the wild-type DOT-T1E strain and in a mutant derivative, DOT-T1E-18. This mutant carried a Tn5 insertion in the ttgABC gene cluster, which encodes a toluene efflux pump that is synthesized constitutively. For site-directed mutagenesis, a cassette to knock out the ttgD gene and encoding resistance to tellurite was constructed in vitro and transferred to the corresponding host chromosome via the suicide plasmid pKNG101. Successful replacement of the wild-type sequences with the mutant cassette was confirmed by Southern hybridization. A single ttgD mutant, DOT-T1E-1, and a double mutant with knock outs in the ttgD and ttgA genes, DOT-T1E-82, were obtained and characterized for toluene tolerance. This was assayed by the sudden addition of toluene (0.3% [vol/vol]) to the liquid culture medium of cells growing on Luria-Bertani (LB) medium (noninduced) or on LB medium with toluene supplied via the gas phase (induced). Induced cells of the single ttgD mutant were more sensitive to sudden toluene shock than were the wild-type cells; however, noninduced wild-type and ttgD mutant cells were equally tolerant to toluene shock. Noninduced cells of the double DOT-T1E-82 mutant did not survive upon sudden toluene shock; however, they still remained viable upon sudden toluene shock if they had been previously induced. These results are discussed in the context of the use of multiple efflux pumps involved in solvent tolerance in P. putida DOT-T1E.

Proline catabolism by Pseudomonas putida: cloning, characterization, and expression of the put genes in the presence of root exudates

Pseudomonas putida KT2442 is a root-colonizing strain which can use proline, one of the major components in root exudates, as its sole carbon and nitrogen source. A P. putida mutant unable to grow with proline as the sole carbon and nitrogen source was isolated after random mini-Tn5-Km mutagenesis. The mini-Tn5 insertion was located at the putA gene, which is adjacent to and divergent from the putP gene. The putA gene codes for a protein of 1,315 amino acid residues which is homologous to the PutA protein of Escherichia coli, Salmonella enterica serovar Typhimurium, Rhodobacter capsulatus, and several Rhizobium strains. The central part of P. putida PutA showed homology to the proline dehydrogenase of Saccharomyces cerevisiae and Drosophila melanogaster, whereas the C-terminal end was homologous to the pyrroline-5-carboxylate dehydrogenase of S. cerevisiae and a number of aldehyde dehydrogenases. This suggests that in P. putida, both enzymatic steps for proline conversion to glutamic acid are catalyzed by a single polypeptide. The putP gene was homologous to the putP genes of several prokaryotic microorganisms, and its gene product is an integral inner-membrane protein involved in the uptake of proline. The expression of both genes was induced by proline added in the culture medium and was regulated by PutA. In a P. putida putA-deficient background, expression of both putA and putP genes was maximal and proline independent. Corn root exudates collected during 7 days also strongly induced the P. putida put genes, as determined by using fusions of the put promoters to 'lacZ. The induction ratio for the putA promoter (about 20-fold) was 6-fold higher than the induction ratio for the putP promoter.

Cell envelope mutants of Pseudomonas putida: physiological characterization and analysis of their ability to survive in soil

To generate mutants with altered lipopolysaccharides (LPS) of the wild-type Pseudomonas putida KT2442, we used the mini-Tn5luxAB-Km transposon. A mutant was found among luminescent colonies and selected as a negative clone in enzyme-linked immunosorbent assay (ELISA) with monoclonal antibody (mAb) 7.3B, which recognizes the O-antigen of P. putida LPS. The DNA region of the LPS mutant interrupted by the minitransposon insertion was cloned and sequenced. Comparison of the deduced amino acid sequence with protein sequence databases showed similarity to the O-antigen polymerase (Wzy) of Salmonella enterica (muenchen). The wild-type gene was rescued by polymerase chain reaction (PCR), cloned into a broad-host-range plasmid and used to carry out complementation assays. The cloned gene was able to restore the wild-type phenotype of the P. putida wzy mutant. We constructed an isogenic mutant of the luminescent wzy mutant to which an oprL mutation was transferred by homologous recombination with an oprL::xylE cassette. The wzy mutants of P. putida were more sensitive to SDS, deoxycholate and EDTA than the corresponding parental strains. We analysed the ability of wzy, oprL and wzy oprL mutants of P. putida to colonize soil. In comparison with the wild-type strain, the ability of single mutants to colonize soil decreased; this characteristic was more evident for the double mutant, especially at high temperatures.