Relation between bacterial activity in the surface microlayer and estuarine hydrodynamics

Bacterial communities of the surface microlayer (SML) of the estuary Ria de Aveiro (Portugal) were characterized in terms of abundance and activity during a 2-year survey at two sites with distinct hydrodynamic properties (marine and brackish water zones). The hydrodynamic conditions were simulated using a bidimensional numerical model and related to the microbiological observations. The pattern of variation of bacterial biomass productivity (BBP) was distinct between the two sampling sites. At the outer site, BBP was significantly lower at the SML, whereas at the inner site, it was significantly enhanced at the SML. Although the total bacterial abundance was similar in the SML and underlying water (UW), the fraction of cells attached to particles was significantly higher at the SML (two to three times). The integration of microbiological results with environmental and hydrological variables shows that strong currents in the marine zone promote the vertical mixing, inhibiting the establishment of an SML bacterial community distinct from that of UW. In contrast, in the brackish water zone, lower current velocities provide conditions for enhancing the bacterial activity in the enriched SML. Estuarine dynamics influence the distribution and activity of microorganisms at the SML and in the water column, with anticipated impacts for the carbon cycle in the estuarine environment.     

Short-term effects of amoxicillin on bacterial communities in manured soil

Antibiotic-resistant bacteria, nutrients and antibiotics that enter the soil by means of manure may enhance the proportion of bacteria displaying antibiotic resistance among soil bacteria and may affect bacterial community structure and function. To investigate the effect of manure and amoxicillin added to manure on soil bacterial communities, microcosm experiments were performed with two soil types and the following treatments: (1) nontreated, (2) manure-treated, (3) treated with manure supplemented with 10 mg amoxicillin kg(-1) soil and (4) treated with manure supplemented with 100 mg amoxicillin kg(-1) soil, with four replicates per treatment. Manure significantly increased the total CFU count and the amoxicillin-resistant CFU count of both soil types. However, only the soil with a history of manure treatment showed a significant increase in the relative number of amoxicillin-resistant bacteria as a result of amoxicillin amendment. The majority of plasmids exogenously isolated from soil originated from soil treated with amoxicillin-supplemented manure. All 16 characterized plasmids carried the bla-TEM gene, and 10 of them belonged to the IncN group. The bla-TEM gene was detected in DNA directly extracted from soil by dot-blot hybridization of PCR amplicons and showed an increased abundance in soil samples treated with manure. Molecular fingerprint analysis of 16S rRNA gene fragments amplified from soil DNA revealed significant effects of manure and amoxicillin on the bacterial community of both soils.     

Membrane cholesterol in the regulation of aminophospholipid asymmetry and phagocytosis in oxidized erythrocytes

Cholesterol is known to affect several membrane functions, including membrane susceptibility to oxidative stress. In order to gain a better understanding of the relationship between cholesterol contents, structural integrity, and degree of survival in oxidatively stressed erythrocytes, here we analyzed the transbilayer phospholipid distribution, the morphology, and the degree of clearance observed in cholesterol-modified (enriched or depleted) and unmodified (control) erythrocytes exposed to tert-butylhydroperoxide. We report that the modification of cholesterol contents in erythrocytes promotes the externalization of phosphatidylserine (PS) to the membrane surface, which is consistent with a concomitant inhibition of aminophospholipid translocase (APLT) and an increased uptake of modified erythrocytes by macrophages. Moreover, cholesterol depletion modifies the transbilayer aminophospholipid distribution induced by oxidative stress to a great extent, significantly increasing PS externalization, which is associated with the strongest decrease in APLT activity. The loss of normal PS asymmetry is positively correlated with enhanced phagocytosis, and an increase in echinocyte forms is observed in all oxidized erythrocytes. We envisage that PS externalization could be due, at least in part, to the decrease in APLT activity induced by oxidative stress, the activity of which is also dependent on membrane cholesterol contents.     

Mutations, clinical findings and survival estimates in South American patients with X-linked adrenoleukodystrophy

In this study, we analyzed the ABCD1 gene in X-linked adrenoleukodystrophy (X-ALD) patients and relatives from 38 unrelated families from South America, as well as phenotypic proportions, survival estimates, and the potential effect of geographical origin in clinical characteristics.

Methods

X- ALD patients from Brazil, Argentina and Uruguay were invited to participate in molecular studies to determine their genetic status, characterize the mutations and improve the genetic counseling of their families. All samples were screened by SSCP analysis of PCR fragments, followed by automated DNA sequencing to establish the specific mutation in each family. Age at onset and at death, male phenotypes, genetic status of women, and the effect of family and of latitude of origin were also studied.

Results

We identified thirty-six different mutations (twelve novel). This population had an important allelic heterogeneity, as only p.Arg518Gln was repeatedly found (three families). Four cases carried de novo mutations. Intra-familiar phenotype variability was observed in all families. Out of 87 affected males identified, 65% had the cerebral phenotype (CALD). The mean (95% CI) ages at onset and at death of the CALD were 10.9 (9.1–12.7) and 24.7 (19.8–29.6) years. No association was found between phenotypic manifestations and latitude of origin. One index-case was a girl with CALD who carried an ABCD1 mutation, and had completely skewed X inactivation.

Conclusions

This study extends the spectrum of mutations in X-ALD, confirms the high rates of de novo mutations and the absence of common mutations, and suggests a possible high frequency of cerebral forms in our population.     

Structure and properties of the 5a,6-anhydrotetracycline-platinum(II) dichloride complex: a theoretical ab initio study

Ab initio structural parameters, relative energies and spectroscopic properties are reported for the 5a,6-anhydrotetracycline-platinum(II) dichloride complex. Distinct coordination modes were analyzed in gas phase and aqueous medium indicating the tricarbonylmethane moiety (O3-Oam-O1) as the most probable Pt(II) complexation sites, supporting experimental proposals. The theoretical (1)H NMR analysis in conjunction with the observed data suggests that the Pt(II) might be bound to the O3-Oam preferentially, even though this site was found slightly unfavorable, based on energetic grounds, relative to O1-Oam. The aquation reaction, which is an important activation step in the action mechanism of cisplatin like molecules, was also investigated showing rate constants (0.5-1 x 10(-5) M(-1) s(-1)) of the same order of magnitude as those for the parent cisplatin compound. This is an important result stressing the importance of tetracyclines-Pt(II) complexes as lead compounds for the development of new platinum based antitumor drugs.     

Sapling survival and growth of coniferous and broad‐leaved trees in successional highland habitats in Mexico

Abstract. We assessed survival and growth of transplanted saplings of understory broad‐leaved trees (Oreopanax xalapensis, Rapaneajuergensenii, Rhamnus sharpii and Tern‐stroemia lineata) and canopy conifers (Abies guatemalensis, Pinus ayacahuite and P. pseudostrobus) into Grassland (GR), Mid‐Successional Oak Forest (MS), and Old‐Growth Oak Forest (OF) stands in the central highlands of Chiapas, Mexico. A total of 727 plants were monitored over eight years. The results suggest habitat preferences of the studied species that should be considered for their conservation oriented management. Conifers had highest survival and growth in GR, while broad‐leaved trees survived better under sparse canopy in MS, but grew tallest in full light. Saplings of all species in dense canopy sites in OF were smaller, and the survival of conifers was lower. An integrated response index (IRI) calculated for each species with survival and relative growth rates showed similar trends. Re‐introduction of the endangered A. guatemalensis is possible in open habitats if fire, trampling and grazing are suppressed. Open habitats in current man‐made landscapes in the highlands of Chiapas may limit the establishment of understory trees requiring partial shade. Inclusion of such species in restoration programs has not been usual so far; yet, local and global interest in native species for such programs is increasing. Information on the response of these kind of species in contrasting habitats may help to incorporate them in the management of high‐diversity forests that may follow pine plantations.     

Dynamics of Fungal Communities in Bulk and Maize Rhizosphere Soil in the Tropics

The fungal population dynamics in soil and in the rhizospheres of two maize cultivars grown in tropical soils were studied by a cultivation-independent analysis of directly extracted DNA to provide baseline data. Soil and rhizosphere samples were taken from six plots 20, 40, and 90 days after planting in two consecutive years. A 1.65-kb fragment of the 18S ribosomal DNA (rDNA) amplified from the total community DNA was analyzed by denaturing gradient gel electrophoresis (DGGE) and by cloning and sequencing. A rhizosphere effect was observed for fungal populations at all stages of plant development. In addition, pronounced changes in the composition of fungal communities during plant growth development were found by DGGE. Similar types of fingerprints were observed in two consecutive growth periods. No major differences were detected in the fungal patterns of the two cultivars. Direct cloning of 18S rDNA fragments amplified from soil or rhizosphere DNA resulted in 75 clones matching 12 dominant DGGE bands. The clones were characterized by their HinfI restriction patterns, and 39 different clones representing each group of restriction patterns were sequenced. The cloning and sequencing approach provided information on the phylogeny of dominant amplifiable fungal populations and allowed us to determine a number of fungal phylotypes that contribute to each of the dominant DGGE bands. Based on the sequence similarity of the 18S rDNA fragment with existing fungal isolates in the database, it was shown that the rhizospheres of young maize plants seemed to select the Ascomycetes order Pleosporales, while different members of the Ascomycetes and basidiomycetic yeast were detected in the rhizospheres of senescent maize plants.     

Structural and dynamics analysis of matrix metalloproteinases MMP-2 complexed with chemically modified tetracyclines (CMTs)

Matrix metalloproteinases (MMPs) play a critical role in physiological processes and pathological conditions such tumor invasion and metastasis. In recent years, a number of MMP inhibitors have been proposed, including the chemically modified tetracyclines (CMTs), which have been evaluated in preclinical cancer models showing promising results. This work provides insights into the structure and dynamics of the MMP-2 catalytic domain complexed with seven CMT (CMT-n), based on the analysis of molecular dynamics trajectories in solution. The comparative analysis of various relevant molecular aspects of the different complexes of MMP-2 and CMT-n derivatives was performed aiming to elucidate the effect of ligands on the enzyme structure. These include the radial distribution function of the water molecules around the catalytic zinc, the solvent accessible surface area for the inhibitors and the root-mean-square fluctuation for all amino acid residues. The results help to understand the differences in the binding modes of related compounds and, therefore, add to further design of novel tetracycline-based inhibitors for MMP enzymes.