Involvement of the cis/trans isomerase Cti in solvent resistance of Pseudomonas putida DOT-T1E

Pseudomonas putida DOT-T1E is a solvent-resistant strain that is able to grow in the presence of high concentrations of toluene. We have cloned and sequenced the cti gene of this strain, which encodes the cis/trans isomerase, termed Cti, that catalyzes the cis-trans isomerization of esterified fatty acids in phospholipids, mainly cis-oleic acid (C(16:1,9)) and cis-vaccenic acid (C(18:1,11)), in response to solvents. To determine the importance of this cis/trans isomerase for solvent resistance a Cti-null mutant was generated and characterized. This mutant showed a longer lag phase when grown with toluene in the vapor phase; however, after the lag phase the growth rate of the mutant strain was similar to that of the wild type. The mutant also showed a significantly lower survival rate when shocked with 0.08% (vol/vol) toluene. In contrast to the wild-type strain, which grew in liquid culture medium at temperatures up to 38.5 degrees C, the Cti-null mutant strain grew significantly slower at temperatures above 37 degrees C. An in-frame fusion of the Cti protein with the periplasmic alkaline phosphatase suggests that this constitutively expressed enzyme is located in the periplasm. Primer extension studies confirmed the constitutive expression of Cti. Southern blot analysis of total DNA from various pseudomonads showed that the cti gene is present in all the tested P. putida strains, including non-solvent-resistant ones, and in some other Pseudomonas species.

A risk factor for early-onset infection in premature newborns: invasion of chorioamniotic tissues by leukocytes

The authors report a prospective study of correlation between histopathological alterations of the placenta, risk factors and early-onset bacterial infections in 224 premature newborns. They used a mathematical model for evaluation and prediction of neonatal bacterial infection according to the localization in chorioamniotic tissues (chorioamniotic plate, amniotic membranes and umbilical cord) invaded by leukocytes. Septicemia, pneumonia or omphalitis were documented in 45 (20%) infected premature newborns and inflammatory lesions in the placenta were observed in all of them. In order of statistical significance, the most important variables for early-onset bacterial neonatal infection were invasion of the chorioamniotic plate, amniotic membranes and umbilical cord tissues by PMNL (P < 0.0000), premature rupture of membranes (P < 0.0000), birthweight lower than 1500 g (P < 0.0000), gestational age under 34 weeks (P < 0.0001), foul smell (P < 0.0038), no antibiotics before delivery (P < 0.0066) and intrapartum fever (P < 0.0087). By logistic stepwise multiple regression analysis, invasion of fetal chorioamniotic plate and of amniotic membranes by leukocytes were the only statistically significant variables. The probability of neonatal infection in premature newborns, when polymorphonuclear neutrophils were present in chorioamniotic plate and in amniotic membranes, was 62.5%, while the probability was 0.5% when these tissues were normal. These data suggest that histological chorioamnionitis has to be considered as an important risk factor for early-onset infection in premature newborns.

The branched-chain dodecylbenzene sulfonate degradation pathway of Pseudomonas aeruginosa W51D involves a novel route for degradation of the surfactant lateral alkyl chain

Pseudomonas aeruginosa W51D is able to grow by using branched-chain dodecylbenzene sulfonates (B-DBS) or the terpenic alcohol citronellol as a sole source of carbon. A mutant derived from this strain (W51M1) is unable to degrade citronellol but still grows on B-DBS, showing that the citronellol degradation route is not the main pathway involved in the degradation of the surfactant alkyl moiety. The structures of the main B-DBS isomers and of some intermediates were identified by gas chromatography-mass spectrometric analysis, and a possible catabolic route is proposed.

Relationship between plasma creatinine concentration and glomerular filtration in preterm newborn infants

Fluid management and dosage regimens of drugs in preterm infants should be based on the glomerular filtration rate. The current methods to determine glomerular filtration rate are invasive, time-consuming, and expensive. In contrast, creatinine clearance can be easy obtained and quickly determined. The purpose of this study was to compare plasma creatinine on the third and seventh day of life in preterm newborn infants, to evaluate the influence of maternal creatinine, and to demonstrate creatinine clearance can be used as a reliable indicator of glomerular filtration rate. We developed a prospective study (1994) including 40 preterm newborns (gestational age < 37 weeks), average = 34 weeks; birth weight (average) = 1840 g, in the first week of life. Inclusion criteria consisted of: absence of renal and urinary tract anomalies; O2 saturation >/= 92%; adequate urine output (>1ml/kg/hr); normal blood pressure; absence of infections and no sympathomimetic amines in use. A blood sample was collected to determine plasma creatinine (enzymatic method) on the third and seventh day of life and creatinine clearance (CrCl) was obtained using the following equation: [formula: see text], k = 0.33 in preterm infant All plasma creatinine determinations showed normal values [third day: 0.78 mg/dl +/- 0.24 (mean +/- SD)and seventh day: 0.67 mg/dl +/- 0.31 - (p>0.05)]. Also all creatinine clearance at third and seventh day of life were normal [third day: 19.5 ml/min +/- 5.2 (mean +/- SD) and seventh day: 23.8 ml/min +/- 7.3 - (p>0,05)]. All preterm infants developed adequate renal function for their respective gestational age. In summary, our results indicate that, for clinical practice, the creatinine clearance, using newborn length, can be used to estimate glomerular filtration rate in preterm newborn infants.

Toluene metabolism by the solvent-tolerant Pseudomonas putida DOT-T1 strain, and its role in solvent impermeabilization

Pseudomonas putida DOT-T1E is a solvent-tolerant strain able to grow with toluene as the sole C-source. Tn5 mutagenesis was carried out and a mutant unable to use toluene as the sole C-source was isolated. DNA was sequenced upstream and downstream of the site where the Tn5 was inserted. Analysis of the DNA revealed 13 open reading frames (ORFs) homologous to the tod genes for the toluene dioxygenase pathway of P. putida F1, which are organized in two operons: todXFC1C2BADEGIH and todST. The Tn5 was inserted at the todH gene. The role of the todXFC1C2BADEGIH operon in toluene metabolism was further confirmed in a todC1 mutant (generated by insertional inactivation), which was unable to use toluene as the sole C-source. Primer extension analysis identified a single promoter upstream from the todX gene. The -10 and -35 regions of this promoter showed no significant homology to known promoters. Expression from the todX promoter occurred in response to toluene, ethylbenzene, styrene, xylenes and other aromatic hydrocarbons. Expression from the todS gene was constitutive. Sensitivity to toluene of the todH and todC1 mutants was similar to that of the wild-type strain. This suggests that toluene metabolism is not involved in toluene tolerance.

Prediction of length of hospital stay in neonatal units for very low birth weight infants

OBJECTIVE

To develop models for estimating the length of hospital stay (LOS) of very low birth weight infants (VLBW), based on perinatal risk factors present during the first week of life and during the entire hospitalization period.

STUDY DESIGN

The files of 155 VLBW were analyzed, and the influence of individual risk factors were initially evaluated by univariate analysis, using multiple-regression. Two mathematical models were built to estimate the LOS.

RESULTS

The first model, using risk factors present during the first 3 days of life, is as follows: LOS = -0.074A + 22.06B + 22.85C - 16.78D - 2.07E + 10.51F + 203.12 (R2 = 0.63). (The letters are added to show what each number represents: A: birth weight; B: occurrence of respiratory distress syndrome; C: endotracheal intubation during resuscitation; D: 1-minute Apgar score; E: gestational age; F: presence of complications during delivery.) The second model, using factors present during the entire hospitalization period, is: LOS = 0.61G + 29.19H + 24.68I + 14.21J + 23.56K + 9.54L + 7.41M + 20.43 (R2 = 0.82). (G: age receiving nutritional support of > or = 120 kcal/kg per day; H: occurrence of systemic candidiasis; I: birth weight < 1000 gm; J: presence of delivery complication; K: occurrence of bronchopulmonary dysplasia; L: birth weight > or = 1000 gm and < or = 1249 gm; M: occurrence of anemia).

CONCLUSION

Both models are applicable for estimating the hospitalization period, and the addition of variables present during the entire hospitalization period improved the accuracy of the model.

The XylS-dependent Pm promoter is transcribed in vivo by RNA polymerase with sigma 32 or sigma 38 depending on the growth phase

The Pm promoter of the TOL plasmid of Pseudomonas putida is expressed at high level along the growth curve. This transcription is dependent on the positive regulator XylS activated by 3-methylbenzoate. The sigma factor sigma 38 is required for expression in early stationary phase and thereafter. To test whether sigma 70 was involved in Pm transcription in exponential phase, we have followed mRNA synthesis in a rpoD thermosensitive strain. No difference in Pm transcription was found between the wild type and the thermosensitive strain at the restrictive temperature of 42 degrees C, indicating that transcription was independent of the sigma factor sigma 70. However, basal levels of mRNA expression from Pm in this strain in exponential phase were more than twofold higher at 42 degrees C, suggesting involvement of sigma 32 in Pm transcription. In a rpoH background, no expression of Pm took place in the exponential phase, whereas it increased during stationary phase, and in a rpoH rpoS double mutant no activity from the Pm promoter was detected along the growth curve. We have shown that the increase in the amount of sigma 32 factor necessary for transcription in exponential phase is provided through induction of the heat shock response by the presence of the effector 3-methylbenzoate, which is also required for activation of the positive regulator XylS. We conclude that activation of Pm transcription is achieved through a switch between two stress-responsive factors, sigma 32 in exponential phase and sigma 38 in stationary phase. In both cases, transcription is dependent on the activator XylS and presents the same transcription start point.

Critical nucleotides in the upstream region of the XylS-dependent TOL meta-cleavage pathway operon promoter as deduced from analysis of mutants

The Pm promoter, dependent on TOL plasmid XylS regulator, which is activated by benzoate effectors, drives transcription of the meta-cleavage pathway for the metabolism of alkylbenzoates. This promoter is unique in that in vivo transcription is mediated by RNA-polymerase with different sigma factors. In vivo footprinting analysis shows that XylS interacted with nucleotides in the -40 to -70 region. In vivo and in vitro methylation of Pm shows extensive methylation of T at position -42 in the bottom strand, suggesting that it represents a key distortion point that may favor XylS/RNA polymerase interactions. Methylation of T-42 was highest in cells bearing XylS and in the presence of an effector. Gs in the -47 to -61 region appeared to be more protected in cells harboring XylS in the presence than in the absence of the effector. Almost 100 mutants in the Pm region between -41 and -78 were generated; transcriptional analysis of these mutants defined the XylS target as two direct repeats with the sequence TGCAN6GGNCA. These motifs cover the -70 to -56 and the -49 to -35 regions. Single point mutations revealed that nucleotides located at -49 to -46 and at -59, -60, -62, and -70 are the most critical for appropriate XylS-Pm interactions.

Is glycosuria a reliable indicator of adequacy of glucose infusion rate in preterm infants?

CONTEXT

Adequacy of glucose infusion may be monitored via the glycosuria levels, as there is a relationship between glycemia and glycosuria regulated by the renal glucose threshold. In the neonatal period, however, this relationship is not so clear.

OBJECTIVE

To evaluate the occurrence of glycosuria in preferm infants submitted to glucose infusion and to verify the relationship between glycosuria and blood glucose level.

DESIGN

Accuracy study.

SETTING

Neonatal intensive care unit of General Maternity Hospital.

PATIENTS

40 Preterm newborns receiving glucose infusion.

PROCEDURES

511 concomitant determinations of glycemia and glycosuria were performed. These 511 pairs were divided into stable and unstable, according to the clinical status of the newborn at the time of data collection, and they were studied in relation to the gestational age, birth weight and glucose infusion rate.

RESULTS

The results revealed a greater frequency of glycosuria in gestational age < or = 30 weeks, birth weight < 1500 g and glucose infusion rate > 6 mg/kg/min. Eight (25.8%) episodes of positive glycosuria occurred in the absence of hyperglycemia, indicating only a moderate concordance between them.

CONCLUSION

Glycosuria alone is an unreliable marker of blood glucose concentration and adequacy of glucose infusion rate. It is therefore necessary to monitor blood glucose levels in infants submitted to continuous glucose infusion.

Prediction of hyperglycemia in preterm newborn infants

Many conditions are associated with hyperglycemia in preterm neonates because they are very susceptible to changes in carbohydrate homeostasis. The purpose of this study was to evaluate the occurrence of hyperglycemia in preterm infants undergoing glucose infusion during the first week of life, and to enumerate the main variables predictive of hyperglycemia. This prospective study (during 1994) included 40 preterm neonates (gestational age < 37 weeks); 511 determinations of glycemic status were made in these infants (average 12.8/infant), classified by gestational age, birth weight, glucose infusion rate and clinical status at the time of determination (based on clinical and laboratory parameters). The clinical status was classified as stable or unstable, as an indication of the stability or instability of the mechanisms governing glucose homeostasis at the time of determination of blood glucose; 59 episodes of hyperglycemia (11.5%) were identified. A case-control study was used (case = hyperglycemia; control = normoglycemia) to derive a model for predicting glycemia. The risk factors considered were gestational age (< or = 31 vs. > 31 weeks), birth weight (< or = 1500 vs. > 1500 g), glucose infusion rate (< or = 6 vs. > 6 mg/kg/min) and clinical status (stable vs. unstable). Multivariate analysis by logistic regression gave the following mathematical model for predicting the probability of hyperglycemia: 1/exp{-3.1437 + 0.5819(GA) + 0.9234(GIR) + 1.0978 (Clinical status)}The main predictive variables in our study, in increasing order of importance, were gestational age, glucose infusion rate and, the clinical status (stable or unstable) of the preterm newborn infant. The probability of hyperglycemia ranged from 4.1% to 36.9%.

Combined physical and genetic map of the Pseudomonas putida KT2440 chromosome

A combined physical and genetic map of the Pseudomonas putida KT2440 genome was constructed from data obtained by pulsed-field gel electrophoresis techniques (PFGE) and Southern hybridization. Circular genome size was estimated at 6.0 Mb by adding the sizes of 19 SwaI, 9 PmeI, 6 PacI, and 6 I-CeuI fragments. A complete physical map was achieved by combining the results of (i) analysis of PFGE of the DNA fragments resulting from digestion of the whole genome with PmeI, SwaI, I-CeuI, and PacI as well as double digestion with combinations of these enzymes and (ii) Southern hybridization analysis of the whole wild-type genome digested with different enzymes and hybridized against a series of probes obtained as cloned genes from different pseudomonads of rRNA group I and Escherichia coli, as P. putida DNA obtained by PCR amplification based on sequences deposited at the GenBank database, and by labeling of macrorestriction fragments of the P. putida genome eluted from agarose gels. As an alternative, 10 random mini-Tn5-Km mutants of P. putida KT2440 were used as a source of DNA, and the band carrying the mini-Tn5 in each mutant was identified after PFGE of a series of complete chromosomal digestions and hybridization with the kanamycin resistance gene of the mini-Tn5 as a probe. We established a circular genome map with an average resolution of 160 kb. Among the 63 genes located on the genetic map were key markers such as oriC, 6 rrn loci (rnnA to -F), recA, ftsZ, rpoS, rpoD, rpoN, and gyrB; auxotrophic markers; and catabolic genes for the metabolism of aromatic compounds. The genetic map of P. putida KT2440 was compared to those of Pseudomonas aeruginosa PAO1 and Pseudomonas fluorescens SBW25. The chromosomal backbone revealed some similarity in gene clustering among the three pseudomonads but differences in physical organization, probably as a result of intraspecific rearrangements.

[Predictive value of the "Clinical Risk Index for Babies" for the risk of neonatal death]

OBJECTIVE

Several indicators, mainly birthweight and gestational age, have been used to predict the mortality risk in neonatal intensive care units. In order to assess the potential value of CRIB in predicting neonatal mortality, the score was used over the first 12 hours of life of the newborns admitted to this unit, during the year of 1996.

METHOD

The inclusion criteria consisted of all infants without inevitably lethal congenital malformations, birthweight below 1,500 g and/or gestational age less than 31 weeks. Newborn children who died within 12 hours after delivery were excluded. The CRIB score covers birth weight, gestational age, the presence of congenital malformations (not inevitably lethal) and three indexes of physiological status during first 12 hours after birth-maximum and minimum appropriate fraction of inspired oxygen and maximum (most acidotic) base excess.

RESULTS

In a prospective cohort, seventy one newborn children were studied. The birthweight (average) was 1,119 +/- 275.6 g, gestational age 30 weeks 4/7 +/- 2 weeks 3/7; male (57%); Apgar 1(0) min. score < or = 3 (36.2%) and Apgar 5 degrees min. score < 5 (5.8%). The mortality rate was 29.6% (gold standard). But mortality rate by birthweight less than 1,000 gr. or gestational age lower than 29 weeks was 60.0% and for the CRIB score above 10 was 100%.

DISCUSSION

The specificity and predictive positive values for CRIB score above 10 were greater than any other two parameters. The area under the receiver operating characteristic (ROC) curve for predicting death was significantly greater for CRIB than for birthweight alone. It was concluded that the CRIB score is a better predictive indicator for mortality than are birthweight and gestational age.

Characterization of cell lysis in Pseudomonas putida induced upon expression of heterologous killing genes

Active biological containment systems are based on the controlled expression of killing genes. These systems are of interest for the Pseudomonadaceae because of the potential applications of these microbes as bioremediation agents and biopesticides. The physiological effects that lead to cell death upon the induction of expression of two different heterologous killing genes in nonpathogenic Pseudomonas putida KT2440 derivatives have been analyzed. P. putida CMC4 and CMC12 carry in their chromosomes a fusion of the PA1-04/03 promoter to the Escherichia coli gef gene and the phiX174 lysis gene E, respectively. Expression of the killing genes is controlled by the LacI protein, whose expression is initiated from the XylS-dependent Pm promoter. Under induced conditions, killing of P. putida CMC12 cells mediated by phiX174 lysis protein E was faster than that observed for P. putida CMC4, for which the Gef protein was the killing agent. In both cases, cell death occurred as a result of impaired respiration, altered membrane permeability, and the release of some cytoplasmic contents to the extracellular medium.

Clinical experience with passive-fixation coradial bipolar endocardial pacing leads. ThinLine Clinical Investigators

Bipolar, transvenous, passive-fixation leads (ThinLine, Sulzer Intermedics Inc., Angleton, TX, USA) incorporating coradial individually coated conductor coils, and a redundant external 55D polyurethane insulation sheath were developed. The diameter of the new leads (< 5 Fr) is in the range of available unipolar leads and is considerably smaller than conventional bipolar pacing leads. From January 9, 1994 to November 12, 1996, 1,536 model 432-04 (523 atrial) and 430-10 (1,013 ventricular) leads were implanted in 1,068 patients at 50 US and 5 Canadian centers to evaluate their safety and efficacy. The study included a general phase, with follow-ups at 1, 3, 6, 12, 18, and 24 months; and a randomized intensive phase with collection of more data and additional 2- and 6-week follow-ups. Capture and sensing thresholds, lead impedance, and handling characteristics were evaluated. Clinical events were monitored and performance was compared to that of two commercially available conventional (coaxial) leads: Sulzer Intermedics models 432-03 (atrial) and 430-07 (ventricular). During a total of 17,530 device months, there were two lead failures, no lead related deaths, 32 explants, 37 complications, and no unexpected adverse device effects. Capture thresholds were lower than those for coaxial controls with identical electrodes, sensing was comparable, lead impedances were within clinically acceptable ranges, and investigators found overall handling characteristics good to excellent. ThinLine coradial bipolar leads are safe and effective for cardiac pacing and sensing.

[Respiratory distress in low birth weight: influence of intrauterine growth retardation]

The aim of this study is to evaluate the influence of intra-uterine growth retardation (IUGR), as well as it's types and severity on the development of respiratory distress among low-birth-weight infants. A total of 673 neonates were studied, the small-for-dates infants (SFD), 40% of total, were divided according to the type of IUGR, in proportionate and disproportionate, and according to the severity, in birth weight below 3rd and between 3rd and 10th percentile. Respiratory distress was more frequent among the appropriate for gestational age (57.3%) compared to the SFD infants (33.7%), (p < 0.0001), and among males (52.6%) compared to females (47.4%) (p = 0.01). There was an inverse relationship between gestational age, as well as birth weight and respiratory distress. It occurred in 90.6% of very-low-birth-weight infants and in 39% of the others, with a predominance among the appropriate for gestational age newborns. Respiratory distress occurred in 80% of neonates below 34 weeks of gestational age and in 26% of the neonates above it (p < 0.0001). Regarding to the small-for-dates infants, respiratory distress occurred more frequently among the disproportionate (42.5%), when compared to proportionate infants (28.1%) (p = 0.03). The severity of IUGR had no influence on these results. The authors concluded that among low birth weight infants, the groups with increased risk for respiratory distress are the appropriate for gestational age and, among small-for-dates and disproportionate infants, those weighing less than 1500 g.

[Immunological behavior (IgG, IgM, IgA) and total complement (CH50) of newborns infants with risk factors for early onset sepsis. Comparative analysis of newborns with and without infection]

Immunological behavior (IgG, IgM, IgA) and total Complement (CH50) of newborns infants with risk factors for early onset sepsis. Comparative analysis between newborns with and without infection. Rev. Hosp. Clín. Fac. Med. S. Paulo, 53(6): 303-310, 1998. The objective of this study was to verify the immunological behavior of the newborn infant in front of an infection. We studied 60 newborn infants that had risk factors for early onset sepsis (premature rupture membranes, clinic amnionitis or tract urinary infection) from de immunological and infection point of view. They were classified into three gestational age groups: < 34 weeks, between 34 and 36 6/7 weeks and > or = 37 weeks. Sepsis diagnosis was done through clinical and laboratorial data and we also included the followings exams: Immunological types (IgG, IgM, IgA) and total complement (CH50) obtained from the newborn at birth and on the fifth day of life. We could verify that 15 newborns (25%) presented early sepsis. There was a statistical association between perinatal asfixia and infection in the group with gestational age < 34 weeks and this same group presented statistical association between infection and death. The serical levels of IgG and CH50 were directly related to the gestational age and there were significant statistical differences between levels of IgG, IgM and total Complement between infected and not infected newborns within the same group os gestional age. We observed that the infection was associated to low levels of IgG and CH50, at birth and on the fifth day, mainly in the group of infected newborns with gestional age < 34 weeks, being this group, therefore, the one that would mostly benefit from an immunological support in front of and infection.

[Hyperglycemia and glucosuria in preterm infants receiving parenteral glucose: influence of birth weight, gestational age and infusion rate]

OBJECTIVE: Morbidity and mortality of premature infants have decreased considerably over the last decades, therefore, adequate nutrition of the premature is a major concern. Enteral feeding is the route of choice, but when it is not possible the parenteral route, which contains glucose as one of its main components, is used. Glucose infusions are not devoid of risk as they facilitate the development of hyperglycemia leading to intracranial hemorrhage, glucosuria and dehydration. The aim of this paper is to relate hyperglycemia and glucosuria to birth weight, gestational age and glucose infusion rate.METHODS: The study was developed at the Nursery of Santa Catarina Hospital (São Paulo). The authors developed a prospective study; 511 concurrent determinations of glycemia and qualitative glucosuria were performed in 40 preterm newborn infants receiving parenteral glucose (mean of 12.8 dosages per newborn).RESULTS: Fifty-nine (11.5%) episodes of hyperglycemia were detected, and their frequency was higher at lower gestational ages (</=34 weeks), lower birth weights (< 1500g) and higher glucose infusion rates (>/= 6 mg/kg/min). Thirty-one (6.1%) episodes of glucosuria were detected, and were more frequent in lower gestational ages (</= 34 weeks), lower birth weights (< 1500g) and higher glucose infusion rates (>/= 6 mg/kg/min).CONCLUSIONS: The frequency of hyperglycemia and glucosuria in preterm newborn infants receiving glucose infusion was higher in lower gestational ages, lower birth weights and higher glucose infusion rates. In preterm newborn infants it is necessary to observe the glucose infusion rate and its respective glycemia, in order to avoid the complications of hyperglycemia.

Influence of carbon source on nitrate removal by nitrate-tolerant Klebsiella oxytoca CECT 4460 in batch and chemostat cultures

The nitrate-tolerant organism Klebsiella oxytoca CECT 4460 tolerates nitrate at concentrations up to 1 M and is used to treat wastewater with high nitrate loads in industrial wastewater treatment plants. We studied the influence of the C source (glycerol or sucrose or both) on the growth rate and the efficiency of nitrate removal under laboratory conditions. With sucrose as the sole C source the maximum specific growth rate was 0.3 h-1, whereas with glycerol it was 0.45 h-1. In batch cultures K. oxytoca cells grown on sucrose or glycerol were able to immediately use sucrose as a sole C source, suggesting that sucrose uptake and metabolism were constitutive. In contrast, glycerol uptake occurred preferentially in glycerol-grown cells. Independent of the preculture conditions, when sucrose and glycerol were added simultaneously to batch cultures, the sucrose was used first, and once the supply of sucrose was exhausted, the glycerol was consumed. Utilization of nitrate as an N source occurred without nitrite or ammonium accumulation when glycerol was used, but nitrite accumulated when sucrose was used. In chemostat cultures K. oxytoca CECT 4460 efficiently removed nitrate without accumulation of nitrate or ammonium when sucrose, glycerol, or mixtures of these two C sources were used. The growth yields and the efficiencies of C and N utilization were determined at different growth rates in chemostat cultures. Regardless of the C source, yield carbon (YC) ranged between 1.3 and 1.0 g (dry weight) per g of sucrose C or glycerol C consumed. Regardless of the specific growth rate and the C source, yield nitrogen (YN) ranged from 17.2 to 12.5 g (dry weight) per g of nitrate N consumed. In contrast to batch cultures, in continuous cultures glycerol and sucrose were utilized simultaneously, although the specific rate of sucrose consumption was higher than the specific rate of glycerol consumption. In continuous cultures double-nutrient-limited growth appeared with respect to the C/N ratio of the feed medium and the dilution rate, so that for a C/N ratio between 10 and 30 and a growth rate of 0.1 h-1 the process led to simultaneous and efficient removal of the C and N sources used. At a growth rate of 0.2 h-1 the zone of double limitation was between 8 and 11. This suggests that the regimen of double limitation is influenced by the C/N ratio and the growth rate. The results of these experiments were validated by pulse assays.

[Propionic acidemia in the neonatal period]

Propionic Acidemia is an inherited disorder of organic acid metabolism characterized by a wide spectrum of clinical and biochemical findings. Many times is present in the neonatal period, when mortality is high and neurologic residua in survivors is severe. The present case concerns to a healthy male newborn who started with a picture of refusing to feed, lethargy and hypothermia at 49 hours of life. He developed a severe neurotoxicity state with metabolic acidosis. The laboratory evaluation showed high levels of 3-hidroxi-propionic, 2-metil-hidroxibutiric and metil-citric in urine, confirming the diagnosis of proprionic acidemia.

Efflux pumps involved in toluene tolerance in Pseudomonas putida DOT-T1E

The basic mechanisms underlying solvent tolerance in Pseudomonas putida DOT-T1E are efflux pumps that remove the solvent from bacterial cell membranes. The solvent-tolerant P. putida DOT-T1E grows in the presence of high concentrations (e.g., 1% [vol/vol]) of toluene and octanol. Growth of P. putida DOT-T1E cells in LB in the presence of toluene supplied via the gas phase has a clear effect on cell survival: the sudden addition of 0.3% (vol/vol) toluene to P. putida DOT-T1E pregrown with toluene in the gas phase resulted in survival of almost 100% of the initial cell number, whereas only 0.01% of cells pregrown in the absence of toluene tolerated exposure to this aromatic hydrocarbon. One class of toluene-sensitive octanol-tolerant mutant was isolated after Tn5-'phoA mutagenesis of wild-type P. putida DOT-T1E cells. The mutant, called P. putida DOT-T1E-18, was extremely sensitive to 0.3% (vol/vol) toluene added when cells were pregrown in the absence of toluene, whereas pregrowth on toluene supplied via the gas phase resulted in survival of about 0.0001% of the initial number. Solvent exclusion was tested with 1,2,4-[14C]trichlorobenzene. The levels of radiochemical accumulated in wild-type cells grown in the absence and in the presence of toluene were not significantly different. In contrast, the mutant was unable to remove 1,2,4-[14C]trichlorobenzene from the cell membranes when grown on Luria-Bertani (LB) medium but was able to remove the aromatic compound when pregrown on LB medium with toluene supplied via the gas phase. The amount of 14C-labeled substrate in whole cells increased in competition assays in which toluene-and xylenes were the unlabeled competitors, whereas this was not the case when benzene was the competitor. This finding suggests that the exclusion system works specifically with certain aromatic substrates. The mutation in P. putida DOT-T1E-18 was cloned, and the knockedout gene was sequenced and found to be homologous to the drug exclusion gene mexB, which belongs to the efflux pump family of the resistant nodulator division type.

Removal of nitrate from industrial wastewaters in a pilot plant by nitrate-tolerant klebsiella oxytoca CECT 4460 and arthrobacter globiformis CECT 4500

Two strains, a gram-negative bacterium Klebsiella oxytoca CECT 4460 and a gram-positive, mycelium-forming bacterium Arthrobacter globiformis CECT 4500, tolerant to up to 1 M nitrate, were isolated from the grounds of a munitions factory. Under strict aerobic conditions and with appropriate C-sources, growth of these bacteria took place when the nitrate concentration in the medium was below 150 mM. Optimal growth conditions regarding the culture medium composition for the biological removal of nitrate were established in batch cultures. Then, the system was scaled up to a 40-L pilot plant and operated under continuous conditions in a factory with direct waste streams from dinitroethylene glycol production after appropriate dilution with nontreated groundwaters. The level of nitrate in the effluent was below 0.5% of the initial N-load. Nitrite and ammonium were undetectable and the level of the C-source in the effluent was below 50 mg per L. On the basis of these results, we conclude that the system worked on site satisfactorily. Copyright 1998 John Wiley & Sons, Inc.

Activation and repression of transcription at the double tandem divergent promoters for the xylR and xylS genes of the TOL plasmid of Pseudomonas putida

The xylR and xylS genes are divergent and control transcription of the TOL plasmid catabolic pathways for toluene metabolism. Four promoters are found in the 300-bp intergenic region: Pr1 and Pr2 are constitutive sigma70-dependent tandem promoters that drive expression of xylR, while expression of the xylS gene is driven from Ps2, a constitutive sigma70-dependent promoter, and by the regulatable sigma54 class Ps1 promoter. In Ps1 the XylR targets (upstream activator sequences [UASs]) overlap the Pr promoters, and two sites for integration host factor (IHF) binding are located at the region from positions -2 to -30 (-2/-30 region) and the -137/-156 region, the latter overlapping the Pr promoters. When the XylR protein binds to the UASs in the absence of effector, it represses expression from Pr promoters. In the XylR-plus background and in the absence of an effector, the level of expression from Ps1 is low, although detectable, whereas Ps2 is active. In this background and in the presence of an effector, XylR increases autorepression. In a sigma54-deficient Pseudomonas putida background, no expression occurred from Ps1 regardless of the presence of an effector. However, in the presence of an effector, the amount of RNA produced from Pr promoters was almost undetectable. This finding suggests that when no transcription occurred at the Ps1 promoter, clearance of XylR from the UASs was almost negligible. In this background, expression from Ps2 was very high regardless of the presence of an effector; this finding suggests that RNA polymerase containing sigma54 modulates expression from the downstream Ps2 sigma70-dependent promoter. In a P. putida IHF-minus background and in the presence of effector, Ps1 expression was the highest found; in contrast, the basal levels of this promoter were the lowest observed. This finding suggests that IHF acts in vivo as a repressor of the sigma54-dependent Ps1 promoter. In an IHF-deficient host background, expression from Ps2 in the presence of effector was negligible. Thus, binding of RNA polymerase containing sigma54 at the upstream promoter may modulate expression from the Ps2 promoter.

Central diabetes insipidus as a complication of neonatal pathology: report of three cases

Three patients, 11, 17 and 41 days old with various degrees of central nervous system (CNS) lesions developed central diabetes insipidus as a complication of hypothalamic damage. Two of the children had congenital CNS malformations including meningomyelocele, hydrocephalus, and prosencephaly, while the third child presented Streptococcus agalactiae meningitis, complicated with CNS hemorrhage and hypertensive dilatation of the lateral ventricles. All of them fulfilled the criteria for central diabetes insipidus, reaching high levels of serum sodium and osmolality, along with hypotonic urine. The responses to intranasal arginine-vasopressin were prompt, normalizing the serum levels of sodium and increasing urinary osmolality, allowing a better metabolic balance, avoiding continuing damage to the already compromised CNS. The neonatologist must be aware of the possibility of this kind of complication even in a normal child with CNS infection. Imaging studies showing hemorrhage in the region of the posterior hypothalamus must be a sign that this type of complication is able to occur.