Factors affecting the attachment of rhizospheric bacteria to bean and soybean roots

The plant rhizosphere is an important soil ecological environment for plant-microorganism interactions, which include colonization by a variety of microorganisms in and around the roots that may result in symbiotic, endophytic, associative, or parasitic relationships within the plant, depending on the type of microorganisms, soil nutrient status, and soil environment. Rhizosphere competence may be attributable to the differences in the extent of bacterial attachment to the root surface. We present results of the effect of various factors on the attachment to bean (Phaseolus vulgaris) and soybean (Glycine max) roots of some bacterial species of agronomic importance, such as Rhizobium tropici, Rhizobium etli, Ensifer fredii (homotypic synonym Sinorhizobium fredii), and Azospirillum brasilense; as well as the attachment capability of the plant growth promoting rhizobacteria Pseudomonas fluorescens and Chryseobacterium balustinum. Additionally, we have studied various bacterial traits, such as autoaggregation and flagella movements, which have been postulated to be important properties for bacterial adhesion to surfaces. The lack of mutual incompatibility between rhizobial strains and C. balustinum has been demonstrated in coinoculation assays.     

In vitro penetration of fresh and vitrified swine oocytes by homologous spermatozoa using different incubation systems

The present study consisted of two experiments. In the first one, ejaculates from four boars were used to compare in vitro penetration (IVP) rates of fresh and vitrified swine oocytes by homologous spermatozoa in four treatments: fresh oocytes in conventional incubation (CO2 incubator) (FC), vitrified oocytes in conventional incubation (VC), fresh oocytes in submarine (bag) incubation (FS) and vitrified oocytes in submarine incubation (VS). The IVP rates for FC, VC, FS and VS were 46.5, 44.3, 36.9 and 33.1%, respectively. Analysis through Chi-square tests identified no differences in IVP rates between FC and VC and between FS and VS (P > 0.05), but IVP rate for FC was greater (P < 0.05) than those for both FS and VS. Besides IVP rate for VC did not differ (P > 0.05) from those for FC and FS, but it was greater than that for VS (P < 0.05). Logistic regression analysis identified differential effects of treatments dependant on individual boars. The second experiment evaluated the influence of semen storage period on the semen quality of the two boars associated with greater IVP rate in the first experiment. Semen quality was estimated by IVP rate using the VC treatment and by the following methods: sperm motility, sperm morphology, hypoosmotic swelling test (HOST) and thermal stress test (TST). According to analysis using Chi-square tests, IVP rate did not differ (P > 0.05), for the first boar, between 0 (100.0%) and 24 h of semen storage (98.1%) nor after 48 and 72 h (66.0 and 59.3%, respectively), but IVP rates were greater during the 0-24 h period compared with the 48-72 h period (P < 0.05). For the second boar, IVP rate at 0 h (50.6%) was greater (P < 0.05) than at 24, 48 and 72 h of semen storage (34.3, 28.3 and 24.0%, respectively), with no further differences observed after 24 h (P > 0.05). Logistic regression analysis identified that the effect of storage on IVP rate was influenced by the effect of individual boars. No differences in semen quality during the storage period were identified by conventional methods of semen evaluation, for either boar (P > 0.05) using analysis of variance with repeated measures. These results indicate that IVP test can be used to estimate boar fertility, even when vitrified oocytes are used (if using conventional CO2 incubators) or using an alternative submarine incubation system (if using fresh oocytes). The IVP test was the only method of semen evaluation that identified the reduction in semen quality up to 72 h of storage.     

Functional evaluation of serine 252 of Saccharomyces cerevisiae phosphoenolpyruvate carboxykinase

Saccharomyces cerevisiae phosphoenolpyruvate (PEP) carboxykinase mutant Ser252Ala, affecting the conserved Walker A serine residue, was characterized to elucidate the role of this serine residue. The substitution did not result in changes in the protein structure, as indicated by circular dichroism, intrinsic fluorescence spectroscopy, and gel-exclusion chromatography. Kinetic analysis of the mutated enzyme in both directions of the main reaction and in the two secondary reactions showed an approximately 50-fold increase in apparent K(m) for oxaloacetate with minor alterations in the other kinetic parameters. These results show that the hydroxyl group of serine 252 is required for proper oxaloacetate interaction.     

Initial characterization of a recombinant kynureninase from Trypanosoma cruzi identified from an EST database

Kynureninase has been described in bacteria, fungi and animals as an enzyme involved in the catabolic degradation pathway of l-tryptophan. This pyridoxal 5′-phosphate (PLP)-dependent enzyme catalyzes the hydrolytic cleavage of l-kynurenine and 3-hydroxy-l-kynurenine to yield l-alanine and either anthranilic or 3-hydroxyanthranilic acid, respectively. We identified a putative kynureninase gene from a Trypanosoma cruzi project aiming at the structural and functional characterization of more than 100 proteins differentially expressed during metacyclogenesis. This gene encodes a protein similar in size and sequence to kynureninases from other sources. This open reading frame was cloned and the recombinant enzyme was overexpressed. Recombinant T. cruzi kynureninase was purified to homogeneity and its identity was confirmed by mass spectrometry. The apparent molecular mass of the native T. cruzi kynureninase was estimated by gel filtration, suggesting that the protein is a homodimer. Circular dichroism spectrum indicated a mixture of α-helix and β-sheet structure, expected for an aminotransferase fold. l-kynurenine, preferentially hydrolyzed by prokaryotic inducible kynureninases, and 3-hydroxy-l-kynurenine, the preferred substrate in fungi and vertebrates, are both catabolized equally well by T. cruzi kynureninase. Further experimental assays will be performed to fully understand the importance of this enzyme for T. cruzi metabolism.     

Structural insights into IKKβ inhibition by natural products staurosporine and quercetin

This Letter describes the results of two combined approaches: homology modeling and molecular docking studies, in order to propose the molecular basis of IKKβ inhibition by staurosporine and quercetin as ATP-competitive inhibitors. The results provides a rationale and structural frameworks for designing potent ATP binding-site inhibitors of IKKβ, which is an attractive drug target for inflammatory diseases and has been found to be responsible for some of the already observed pharmacological effects for marketed drugs.     

Binary and ternary inclusion complexes of finasteride in HPβCD and polymers: Preparation and characterization

The aim of this study was to determine whether inclusion complexes between 2-hydroxypropyl-β-cyclodextrin (HPβCD) and finasteride (FIN) are formed, and to characterize these. Equimolar FIN/HPβCD solid systems in the presence or absence of 0.1% (w/v) of polyvinylpyrrolidone K30 (PVP K30) or 0.3% of chitosan were prepared by coevaporation and freeze-drying methods. The systems were characterized by phase solubility, NMR, DSC, and XRD analysis. The results suggest that true binary and ternary inclusion complexes were formed.     

Low natural repopulation of marginal coral communities under the influence of upwelling

The study of coral repopulation in marginal communities may provide a useful analog for understanding the dynamics of coral reefs subjected to deleterious environmental changes. Repopulation of scleractinian reef corals may strongly impact the community structure on tropical reefs; however, the extent of this process on coral communities influenced by upwelling is unknown, especially in the Caribbean. In this study, the potential for natural repopulation of coral communities subjected to wind-driven upwelling was evaluated at three sites on the island of Cubagua, Venezuela. Coral spawning behavior was recorded and both larval settlement and juvenile abundance were estimated. Upwelling did not appear to affect coral spawning behavior, since at this locality spawning occurred at dates and times similar to those reported for well-developed reefs in the Caribbean. Also, juveniles produced by brooding corals were six times more abundant than those of broadcasting species, similar to patterns on other Caribbean reefs that are not under the influence of upwelling. By contrast, mean larval settlement (4 settlers m⁻²) and juvenile abundance (0.1 juveniles m⁻²) in Cubagua were both lower than those elsewhere in the Caribbean and on Pacific reefs. Thus, the potential for repopulation of these marginal communities seems lower than for well-developed coral reefs in other regions. These results suggest that more fully developed coral reefs also may have reduced repopulation potential, as they become influenced by suboptimal environmental conditions. Handling editor: I. Nagelkerken     

Predicting the distribution of the crested tinamous, Eudromia spp. (Aves, Tinamiformes)

A bioclimatic analysis of the crested tinamous was conducted to explore climatic factors underpinning the distribution of both Eudromia elegans and E. formosa and to evaluate its potential application in paleontological studies. The study utilized records throughout the entire known range of Eudromia spp. in southern South America. Relationships between 20 environmental parameters and the presence of Eudromia species were established, mapping and characterizing their spatial distribution in a geographic information system using BIOCLIM and MAXENT algorithms. The MAXENT prediction map shows a more homogeneous pattern while BIOCLIM showed a patchier pattern. The models applied here generated maps that adjust to the well-known previous distributions of both species. Nevertheless, for Eudromia elegans, the distribution predicted by MAXENT includes areas where it is actually considered absent, and the BIOCLIM prediction does not include some areas where it is presumed present. Eudromia formosa were found in warmer and wetter sites than E. elegans. Low precipitation areas were identified as suitable for Eudromia elegans. Strong differences between the climatic profiles for both Eudromia spp distributions occurred, with the precipitation the most important influence. E. formosa tolerates the highest maximum temperatures, whereas E. elegans supports the lowest temperatures.     

Effect of tamoxifen and retinoic acid on bradykinin induced proliferation in MCF‐7 cells

Chemopreventive approaches for the treatment of breast cancer have been validated clinically and with in vitro studies. The combined action of tamoxifen/all‐trans retinoic acid was advantageous in MCF‐7 cells, reducing cell proliferation, Bcl‐2 and c‐Myc protein levels and increasing E‐Cadherin protein levels and Gap junctional Intercellular Communication. We further investigated their combined effect in the presence of bradykinin, a pro‐inflammatory agent, previously reported to contribute to the proliferation of breast cancer cells. Bradykinin increased MCF‐7 cell proliferation, c‐Myc levels and ERK1/2 activity. The co‐incubation of bradykinin‐MCF‐7 cells with tamoxifen/all‐trans retinoic acid reduced cell proliferation, ERK1/2 activity, as well as Bcl‐2, c‐Myc, and bradykinin receptor‐2 levels, without altering the enhanced E‐cadherin levels induced by tamoxifen/all‐trans retinoic acid. We showed that the anti‐tumoral effect of tamoxifen/all‐trans retinoic acid is beneficial in MCF‐7 breast cancer cells grown in a bradykinin‐pro‐mitogenic environment, an effect that might be, at least in part, through the MAPK pathway and B2‐bradykinin receptor inhibition. J. Cell. Biochem. 106: 473–481, 2009. © 2008 Wiley‐Liss, Inc.