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11.
The genome sequence of Leifsonia xyli subsp. xyli, which causes ratoon stunting disease and affects sugarcane worldwide, was determined. The single circular chromosome of Leifsonia xyli subsp. xyli CTCB07 was 2.6 Mb in length with a GC content of 68% and 2,044 predicted open reading frames. The analysis also revealed 307 predicted pseudogenes, which is more than any bacterial plant pathogen sequenced to date. Many of these pseudogenes, if functional, would likely be involved in the degradation of plant heteropolysaccharides, uptake of free sugars, and synthesis of amino acids. Although L. xyli subsp. xyli has only been identified colonizing the xylem vessels of sugarcane, the numbers of predicted regulatory genes and sugar transporters are similar to those in free-living organisms. Some of the predicted pathogenicity genes appear to have been acquired by lateral transfer and include genes for cellulase, pectinase, wilt-inducing protein, lysozyme, and desaturase. The presence of the latter may contribute to stunting, since it is likely involved in the synthesis of abscisic acid, a hormone that arrests growth. Our findings are consistent with the nutritionally fastidious behavior exhibited by L. xyli subsp. xyli and suggest an ongoing adaptation to the restricted ecological niche it inhabits.  相似文献   
12.
Energy metabolism in early life stages of the shrimp Farfantepenaeus paulensis subjected to temperature reduction (26 and 20 °C) was determined using the activities of citrate synthase (CS) and pyruvate kinase (PK). At both temperatures, weight-specific activity of CS decreased throughout the ontogenetic development from protozoea II (PZ II) to postlarva XII–XIV (PL XII–XIV). PK activity reached a pronounced peak in PL V–VI, followed by a further decrease in PL XII–XIV. Temperature reduction produced variation in oxygen consumption rates (QO2), ammonia–N excretion and in enzyme activities. Ammonia–N excretion was higher at 20 °C in mysis III (M III), PL V–VI and PL XII–XIV, resulting in substantially lower O:N ratios in these stages. QO2 was increased in protozoea II (PZ II) and mysis I (M I) at 26 °C, while no difference in QO2 was detected in the subsequent stages at either temperature. This fact coincided with higher CS and PK activities in M III, PL V–VI and PL XII–XIV at 20 °C compared with 26 °C. Regressions between individual enzyme activities and dry weight exhibited slope values of 0.85–0.92 for CS and 1.1–1.2 for PK and temperature reduction was reflected by higher slope values at 20 than at 26 °C for both enzymes. Weight-specific CS activity was positively correlated with QO2 at 20 and 26 °C, and may thus be used as an indicator of aerobic metabolic rate throughout the early stages of F. paulensis. The variation in enzyme activities is discussed in relation to possible metabolic adaptations during specific ontogenetic events of the F. paulensis life cycle. Here, the catalytic efficiency of energy-metabolism enzymes was reflected in ontogenetic shifts in behaviour such as larval settlement and the adoption of a benthic existence in early postlarvae. In most cases, enhanced enzyme activities appeared to counteract negative effects of reduced temperature.  相似文献   
13.
Monoamine oxidase (MAO, type A and B) and semicarbazide-sensitive amine oxidase (SSAO) metabolize biogenic amines, however, the impact of these enzymes in arteries from patients with type 2 diabetes remains poorly understood. We investigated the kinetic parameters of the enzymes to establish putative correlations with noradrenaline (NA) content and patient age in human mesenteric arteries from type 2 diabetic patients. The kinetic parameters were evaluated by radiochemical assay and NA content by high-performance liquid chromatography (HPLC). The activity of MAO-A and SSAO in type 2 diabetic vascular tissues was significantly lower compared to the activity obtained in non-diabetic tissues. In the correlation between MAO-A (K(m)) and NA content, we found a positive correlation for both the diabetic and non-diabetic group, but no correlation was established for patient age. In both groups, MAO-B (V(max)) showed a negative correlation with age. The results show that MAO-A and SSAO activities and NA content of type 2 diabetic tissues are lower compared to the non-diabetic tissues, while MAO-B activity remained unchanged. These remarks suggest that MAO-A and SSAO may play an important role in vascular tissue as well as in the vascular pathophysiology of type 2 diabetes.  相似文献   
14.
Production of polyhydroxyalkanoates (PHA) by mixed cultures has been widely studied in the last decade. Storage of PHA by mixed microbial cultures occurs under transient conditions of carbon or oxygen availability, known respectively as aerobic dynamic feeding and anaerobic/aerobic process. In these processes, PHA-accumulating organisms, which are quite diverse in terms of phenotype, are selected by the dynamic operating conditions imposed to the reactor. The stability of these processes during long-time operation and the similarity of the polymer physical/chemical properties to the one produced by pure cultures were demonstrated. This process could be implemented at industrial scale, providing that some technological aspects are solved. This review summarizes the relevant research carried out with mixed cultures for PHA production, with main focus on the use of wastes or industrial surplus as feedstocks. Basic concepts, regarding the metabolism and microbiology, and technological approaches, with emphasis on the kind of feedstock and reactor operating conditions for culture selection and PHA accumulation, are described. Challenges for the process optimization are also discussed.  相似文献   
15.
Three anthracene derivatives, auxenone, oncocalyxonol and auxemim, were isolated from Auxemma ontocalyx. The structures of these compounds as 1,4,8-trihydroxy-2-methoxy-5-methyl-9,10-anthraquinone, rel-9alpha,11alpha-epoxy-1,4,8alpha,11alpha-tetrahydroxy-2-methoxy-8a beta-methyl-5,6,7,8,8a,9, 10,10a beta-octahydro-10-anthracenone and rel-8alpha,11beta-epoxy-2,11-dimethoxy-8a beta-methyl-5,6,7,8,8a,9-hexahydro-1,4-anthracenedione were determined by analysis of spectral data (1D and 2D NMR, IR, HREIMS and UV).  相似文献   
16.
The kinetics of the enzymatic transesterification between a mixture of triglycerides (oils) and methanol for biodiesel production in a bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/isooctane reversed micellar system, using recombinant cutinase from Fusarium solani pisi as a catalyst, was investigated. In order to describe the results that were obtained, a mechanistic scheme was proposed, based on the literature and on the experimental data. This scheme includes the following reaction steps: the formation of the active enzyme–substrate complex, the addition of an alcohol molecule to the complex followed by the separation of a molecule of the fatty acid alkyl ester and a glycerol moiety, and release of the active enzyme. Enzyme inhibition and deactivation effects due to methanol and glycerol were incorporated in the model. This kinetic model was fitted to the concentration profiles of the fatty acid methyl esters (the components of biodiesel), tri-, di- and monoglycerides, obtained for a 24 h transesterification reaction performed in a stirred batch reactor under different reaction conditions of enzyme and initial substrates concentration.  相似文献   
17.

Introduction

We describe temporal trends in the mortality rates and factors associated with AIDS and non-AIDS related mortality at the Evandro Chagas Clinical Research Institute (IPEC), Oswaldo Cruz Foundation (FIOCRUZ).

Methods

Adult patients enrolling from 1986 through 2009 with a minimum follow up of 60 days were included. Vital status was exhaustively checked using patients’ medical charts, through active contact with individuals and family members and by linkage with the Rio de Janeiro Mortality database using a previously validated algorithm. The CoDe protocol was used to establish the cause of death. Extended Cox proportional hazards models were used for multivariate modeling.

Results

A total of 3530 individuals met the inclusion criteria, out of which 868 (24.6%) deceased; median follow up per patient was 3.9 years (interquartile range 1.7–9.2 years). The dramatic decrease in the overall mortality rates was driven by AIDS-related causes that decreased from 9.19 deaths/100PYs n 1986–1991 to 1.35/100PYs in 2007–2009. Non-AIDS related mortality rates remained stable overtime, at around 1 death/100PYs. Immunodeficiency significantly increased the hazard of both AIDS-related and non-AIDS-related causes of death, while HAART use was strongly associated with a lower hazard of death from either cause.

Conclusions

Our results confirm the remarkable decrease in AIDS-related mortality as the HIV epidemic evolved and alerts to the conditions not traditionally related to HIV/AIDS which are now becoming more frequent, needing careful monitoring.  相似文献   
18.
Dengue is a serious disease transmitted by the mosquito Aedes aegypti during blood meal feeding. It is estimated that the dengue virus is transmitted to millions of individuals each year in tropical and subtropical areas. Dengue control strategies have been based on controlling the vector, Ae. aegypti, using insecticide, but the emergence of resistance poses new challenges. The aim of this study was the identification of specific protease inhibitors of the digestive enzymes from Ae. aegypti larvae, which may serve as a prospective alternative biocontrol method. High affinity protein inhibitors were selected by all of the digestive serine proteases of the 4th instar larval midgut, and the specificity of these inhibitors was characterized. These inhibitors were obtained from a phage library displaying variants of HiTI, a trypsin inhibitor from Haematobia irritans, that are mutated in the reactive loop (P1–P4′). Based on the selected amino acid sequence pattern, seven HiTI inhibitor variants were cloned, expressed and purified. The results indicate that the HiTI variants named T6 (RGGAV) and T128 (WNEGL) were selected by larval trypsin-like (IC50 of 1.1 nM) and chymotrypsin-like enzymes (IC50 of 11.6 nM), respectively. The variants T23 (LLGGL) and T149 (GGVWR) inhibited both larval chymotrypsin-like (IC50 of 4.2 nM and 29.0 nM, respectively) and elastase-like enzymes (IC50 of 1.2 nM for both). Specific inhibitors were successfully obtained for the digestive enzymes of Ae. aegypti larvae by phage display. Our data also strongly suggest the presence of elastase-like enzymes in Ae. aegypti larvae. The HiTI variants T6 and T23 are good candidates for the development as a larvicide to control the vector.  相似文献   
19.
Abstract Two strains of Vibrio anguillarum belonging to O1 and O2 serotypes were examined for their ability to bind hemin and hemoglobin. Whole cells as well as membrane extracts from both strains could clearly bind hemin and hemoglobin constitutively. Hemoglobin binding was completely inhibited by a 100-fold excess of unlabelled hemoglobin and also by hemin, suggesting the existence of specific receptors for heme groups in the cell membranes. Several hemin-binding and hemoglobin-binding bands with similar molecular sizes were detected in polyacrylamide gels as well as in Western blots. Only two of these protein bands in both strains were iron-regulated while the others were independent of the cell iron status. We conclude that both serotypes of V. anguillarum possess heme-binding abilities by means of membrane proteins.  相似文献   
20.

Objective

To investigate the biocatalytic potential of Colletotrichum acutatum and Colletotrichum nymphaeae for monoterpene biotransformation.

Results

C. acutatum and C. nymphaeae used limonene, α-pinene, β-pinene, farnesene, citronellol, linalool, geraniol, perillyl alcohol, and carveol as sole carbon and energy sources. Both species biotransformed limonene and linalool, accumulating limonene-1,2-diol and linalool oxides, respectively. α-Pinene was only biotransformed by C. nymphaeae producing campholenic aldehyde, pinanone and verbenone. The biotransformation of limonene by C. nymphaeae yielded 3.34–4.01 g limonene-1,2-diol l?1, depending on the substrate (R-(+)-limonene, S-(?)-limonene or citrus terpene (an agro-industrial by-product). This is among the highest concentrations already reported for this product.

Conclusions

This is the first report on the biotransformation of these terpenes by Colletotrichum spp. and the biotransformation of limonene to limonene-1,2-diol possibly involves enzymes similar to those found in Grosmannia clavigera.
  相似文献   
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