Evidencia existente sobre la influencia de la ingesta de prebióticos sobre el riesgo de cáncer colorrectal

El cáncer colorrectal es uno de los cánceres más comunes a nivel mundial. Entre el riesgo a desarrollarlo y la microbiota intestinal existe una relación compleja que puede ser modificada por la alimentación. El efecto de los prebióticos sobre la composición y la actividad de la microbiota colónica pueden producir cambios beneficiosos en la flora alterada de los pacientes con cáncer de colon. De todos los prebióticos, se sospecha que la inulina HP y el sinergil (30% oligofructosa y 70% de inulina) son los que mantienen una relación más estrecha con la neoplasia. Este fenómeno podría ser explicado por la longitud de las cadenas de los fructanos. Los estudios realizados en animales observan que la administración de prebióticos reduce el número y la multiplicidad de focos de criptas aberrantes, reduce el número y la vida media de los tumores, inhibe el crecimiento de éstos y potencia el efecto de diferentes fármacos quimioterapéuticos. Los resultados obtenidos en roedores que pretenden simular la predisposición genética no son homogéneos. Algunos de los estudios realizados en humanos, mayoritariamente sanos, observan cambios en la composición de la microbiota, en el perfil de los ácidos biliares y en los ácidos grasos de cadena corta, pero los resultados obtenidos difieren entre los diferentes estudios y no obtienen resultados concluyentes.

Avaliação da qualidade microbiológica de frutos minimamente processados comercializados em supermercados de Fortaleza

O processamento mínimo tem sido descrito como a manipulação, o preparo, embalagem e a distribuição de produtos agrícolas, através de procedimentos como seleção, limpeza, lavagem, descascamento e corte, que não afetem suas características organolépticas, agregando valor aos mesmos. Vários fatores limitam o consumo destes produtos, os quais estão envolvidos na sua vida útil, tais como: aumento da respiração e da produção de etileno, escurecimento enzimático, descoloração da superfície, perda de água e, sobretudo, alterações microbiológicas. No presente trabalho, o enfoque foi dado a este ultimo fator. Foram analisadas 20 amostras de goiaba, manga, melão japonês, mamão formosa e abacaxi minimamente processados e comercializados em supermercados da cidade de Fortaleza-CE, considerando-se a quantificação de coliformes totais, fecais, bolores e leveduras, e detecção de bactérias potencialmente patogênicas, tais como Salmonella sp e Staphylococcus coagulase positivo. Através dos resultados deste trabalho, permitiu-se sugerir a necessidade de controle de qualidade, observando as boas práticas de fabricação, para posterior implementação de um sistema preventivo de APPCC, análise de perigos e pontos críticos de controle, para se assegurar um produto saudável e seguro para o consumidor.

Micromorphological characterization and lithification of microbial mats from the Ebro Delta (Spain)

The structural organization of microbial mats from the Ebro Delta (Spain) and their accretion and partial lithification processes were explored using scanning electron microscopy in back-scattered electron mode and low-temperature scanning electron microscopy. Two differentiated zones were distinguished in a transverse section of a fragment taken from the mat at a depth of 2.5 mm. The first consisted of an upper layer in which the dominant microorganisms, Microcoleus spp., actively grew in an embedded slack matrix of exopolysaccharides. Microcoleus filaments were oriented parallel to the surface and to each other, with filaments below arranged perpendicularly to one another but without crossing. Most of the minerals present were allochthonous grains of calcium phosphate biocorroded by cyanobacteria. The second zone was below a depth of 1 mm and made up of accretion layers with large deposits of calcium carbonate and smaller amounts of calcium phosphate of biological origin. The predominance of a particular type of mineral precipitation with a characteristic external shape and/or texture within a zone, e.g., sponge-like deposits of calcium phosphate, appears to depend on the taxa of the prevailing microorganisms

Quorum-sensing regulates biofilm formation in Vibrio scophthalmi

Background: In a previous study, we demonstrated that Vibrio scophthalmi, the most abundant Vibrio species among the marine aerobic or facultatively anaerobic bacteria inhabiting the intestinal tract of healthy cultured turbot (Scophthalmus maximus), contains at least two quorum-sensing circuits involving two types of signal molecules (a 3-hydroxy-dodecanoyl-homoserine lactone and the universal autoinducer 2 encoded by luxS). The purpose of this study was to investigate the functions regulated by these quorum sensing circuits in this vibrio by constructing mutants for the genes involved in these circuits. Results. The presence of a homologue to the Vibrio harveyi luxR gene encoding a main transcriptional regulator, whose expression is modulated by quorumsensing signal molecules in other vibrios, was detected and sequenced. The V. scophthalmi LuxR protein displayed a maximum amino acid identity of 82% with SmcR, the LuxR homologue found in Vibrio vulnificus. luxR and luxS null mutants were constructed and their phenotype analysed. Both mutants displayed reduced biofilm formation in vitro as well as differences in membrane protein expression by mass-spectrometry analysis. Additionally, a recombinant strain of V. scophthalmi carrying the lactonase AiiA from Bacillus cereus, which causes hydrolysis of acyl homoserine lactones, was included in the study. Conclusions: V. scophthalmi shares two quorum sensing circuits, including the main transcriptional regulator luxR, with some pathogenic vibrios such as V. harveyi and V. anguillarum. However, contrary to these pathogenic vibrios no virulence factors (such as protease production) were found to be quorum sensing regulated in this bacterium. Noteworthy, biofilm formation was altered in luxS and luxR mutants. In these mutants a different expression profile of membrane proteins were observed with respect to the wild type strain suggesting that quorum sensing could play a role in the regulation of the adhesion mechanisms of this bacterium.

Vida immortal

Poques coses han captivat tan poderosament la imaginació humana com la idea de viure eternament. Però tots sabem que els éssers vius, més tard o més d'hora, moren.

Minimal requirements for parameters to be used for the development of predictive models for microbial source tracking. The example of the pair somatic coliphages and phages infecting Bacteroides

Several methods and approaches for measuring parameters to determine fecal sources of pollution in water have been developed in recent years. No single microbial or chemical parameter has proved sufficient to determine the source of fecal pollution. Combinations of parameters involving at least one discriminating indicator and one universal fecal indicator offer the most promising solutions for qualitative and quantitative analyses. The universal (nondiscriminating) fecal indicator provides quantitative information regarding the fecal load. The discriminating indicator contributes to the identification of a specific source. The relative values of the parameters derived from both kinds of indicators could provide information regarding the contribution to the total fecal load from each origin. It is also essential that both parameters characteristically persist in the environment for similar periods. Numerical analysis, such as inductive learning methods, could be used to select the most suitable and the lowest number of parameters to develop predictive models. These combinations of parameters provide information on factors affecting the models, such as dilution, specific types of animal source, persistence of microbial tracers, and complex mixtures from different sources. The combined use of the enumeration of somatic coliphages and the enumeration of Bacteroides-phages using different host specific strains (one from humans and another from pigs), both selected using the suggested approach, provides a feasible model for quantitative and qualitative analyses of fecal source identification.

Potential impact of environmental bacteriophages in spreading antibiotic resistance genes

The idea that bacteriophage transduction plays a role in the horizontal transfer of antibiotic resistance genes is gaining momentum. Such transduction might be vital in horizontal transfer from environmental to human body-associated biomes and here we review many lines of evidence supporting this notion. It is well accepted that bacteriophages are the most abundant entities in most environments, where they have been shown to be quite persistent. This fact, together with the ability of many phages to infect bacteria belonging to different taxa, makes them suitable vehicles for gene transfer. Metagenomic studies confirm that substantial percentages of the bacteriophage particles present in most environments contain bacterial genes, including mobile genetic elements and antibiotic resistance genes. When specific genes of resistance to antibiotics are detected by real-time PCR in the bacteriophage populations of different environments, only tenfold lower numbers of these genes are observed, compared with those found in the corresponding bacterial populations. In addition, the antibiotic resistance genes from these bacteriophages are functional and generate resistance to the bacteria when these genes are transfected. Finally, reports about the transduction of antibiotic resistance genes are on the increase.

On the origin of the selectivity of plasmidic H-NS towards horizontally acquired DNA: Linking H-NS oligomerization and cooperative DNA binding

The nucleoid-associated protein H-NS is a global modulator of the expression of genes associated with adaptation to environmental changes. A variant of H-NS expressed in the R27 plasmid was previously shown to selectively modulate the expression of horizontally acquired genes, with minimal effects on core genes that are repressed by the chromosomal form of H-NS. Both H-NS proteins are formed by an oligomerization domain and a DNA-binding domain, which are connected by a linker that is highly flexible in the absence of DNA. We studied DNA binding by means of oligomer-forming chimeric proteins in which domains of the chromosomal and plasmidic variants are exchanged, as well as in monomeric truncated forms containing the DNA-binding domain and variable portions of the linker. Point mutations in the linker were also examined in full-length and truncated H-NS constructs. These experiments show that the linker region contributes to DNA binding affinity and that it is a main component of the distinct DNA binding properties of chromosomal and plasmidic H-NS. We propose that interactions between the linker and DNA limit the flexibility of the connection between H- NS oligomerization and DNA binding and provide an allosteric indirect readout mechanism to detect long- range distortions of DNA, thus enabling discrimination between core and horizontally acquired DNA.

Evidencia existente sobre la influencia de la ingesta de prebióticos sobre el riesgo de cáncer colorrectal

El cáncer colorrectal es uno de los cánceres más comunes a nivel mundial. Entre el riesgo a desarrollarlo y la microbiota intestinal existe una relación compleja que puede ser modificada por la alimentación. El efecto de los prebióticos sobre la composición y la actividad de la microbiota colónica pueden producir cambios beneficiosos en la flora alterada de los pacientes con cáncer de colon. De todos los prebióticos, se sospecha que la inulina HP y el sinergil (30% oligofructosa y 70% de inulina) son los que mantienen una relación más estrecha con la neoplasia. Este fenómeno podría ser explicado por la longitud de las cadenas de los fructanos. Los estudios realizados en animales observan que la administración de prebióticos reduce el número y la multiplicidad de focos de criptas aberrantes, reduce el número y la vida media de los tumores, inhibe el crecimiento de éstos y potencia el efecto de diferentes fármacos quimioterapéuticos. Los resultados obtenidos en roedores que pretenden simular la predisposición genética no son homogéneos. Algunos de los estudios realizados en humanos, mayoritariamente sanos, observan cambios en la composición de la microbiota, en el perfil de los ácidos biliares y en los ácidos grasos de cadena corta, pero los resultados obtenidos difieren entre los diferentes estudios y no obtienen resultados concluyentes.

Eficàcia d'un biopreparat de microorganismes nadius de muntanya sobre el nematode Meloidogyne javanica en cultiu de tomàquet

Es va determinar l’efecte nematicida d’un biopreparat fet a partir de material de mantell de bosc autòcton, tècnica coneguda com a Activació de Microorganismes de Muntanya, sobre una població de Meloidogyne javanica, en cultiu de tomàquet cv. Durinta, en condicions de semicamp i sota hivernacle. Es van realitzar 5 aplicacions de biopreparat actiu (MMactivat) i el mateix biopreparat esterilitzat en autoclau (MMautoclavat) en un volum d’1L de sorra de riera autoclavada a raó de 8,4 mL per planta. La primera aplicació es va fer just desprès de trasplantar el conreu i una setmana abans d’inocular 1 J2·cm-3 de sòl, i els quatre tractaments restants amb cadència setmanal. Paral·lelament, es va determinar les unitats formadores de colònia de fongs i bacteris del biopreparat actiu i esterilitzat, així com la presència de coliformes fecals. Al final de l’assaig, desprès que el nematode completés una generació, es va avaluar el pes sec aeri i el pes fresc de les arrels, el nombre d’ous per planta, i la freqüència d’aïllament de fongs endòfits d’arrel i tija de tomaquera. El pH del biopreparat era de 3,7. Les mostres contenien nivells superiors a 107 UFC ml-1 tant de fongs com de bactèries. No es va detectar la presència de coliformes totals obtenint un valor < 3 NMP/mL amb p≤0,05. No es van aïllar colònies de bacteris termodúrics ni de Pseudomonas aureginosa ni P. fluorescens que poguessin actuar com a organismes de control biològic. El biopreparat no va mostrar cap efecte sobre el desenvolupament aeri i radicular de la planta. La producció d’ous en les plantes tractades amb el biopreparat actiu i esterilitzat va ser un 63% i un 67% menor que en el testimoni sense tractar. Es van detectar fongs endòfits en arrel i tija de tomaquera en la majoria de les mostres sense atendre a cap tractament, inclòs el control sense tractar.

The awr gene family encodes a novel class of Ralstonia solanacearum type III effectors displaying virulence and avirulence activities

We present here the characterization of a new gene family, awr, found in all sequenced Ralstonia solanacearum strains and in other bacterial pathogens. We demonstrate that the five paralogues in strain GMI1000 encode type III-secreted effectors and that deletion of all awr genes severely impairs its capacity to multiply in natural host plants. Complementation studies show that the AWR (alanine-tryptophanarginine tryad) effectors display some functional redundancy, although AWR2 is the major contributor to virulence. In contrast, the strain devoid of all awr genes (¿awr1-5) exhibits enhanced pathogenicity on Arabidopsis plants. A gain-of-function approach expressing AWR in Pseudomonas syringae pv. tomato DC3000 proves that this is likely due to effector recognition, because AWR5 and AWR4 restrict growth of this bacterium in Arabidopsis. Transient overexpression of AWR in nonhost tobacco species caused macroscopic cell death to varying extents, which, in the case of AWR5, shows characteristics of a typical hypersensitive response. Our work demonstrates that AWR, which show no similarity to any protein with known function, can specify either virulence or avirulence in the interaction of R. solanacearum with its plant hosts.

Oligonucleotide cyclization: The thiol-maleimide reaction revisited

A novel method to synthesize cyclic oligonucleotides (5- to 26-mer) using the thiol-maleimide reaction is described. The target molecules were obtained after subsequent removal of thiol and maleimide protecting groups from 5′-maleimido-3′-thiol-derivatized linear precursors. Retro-Diels-Alder conditions deprotecting the maleimide simultaneously promoted cyclization cleanly and in high yield.

Estudi dels efectes de les plantes ornamentals en la qualitat ambiental de l'aire urbà : anàlisi ecològic i aerobiològic a Tiana

Pollen allergy has a remarkable clinical impact all over Europe, and there are evidences that the prevalence of allergic respiratory induced reactions by pollen in Europe has been increasing in recent decades. The presence of potentially allergenic ornamental species in the town of Tiana, representing 41% of total species recorded. Approximately 28% of these species are Platanus acerifolia. This study attempts to relate the effect it has on the people’s health, the presence of certain urban ornamental plants by identifying and locating the ornamental trees in the town.

Outer membrane vesicles from cold-adapted antarctic bacteria

Many Gram-negative, cold-adapted bacteria from the Antarctic environment produce large amounts of extracellular matter with potential biotechnological applications. Transmission electron microscopy (TEM) analysis after high-pressure freezing and freeze substitution (HPF-FS) showed that this extracellular matter is structurally complex, appearing around cells as a netlike mesh, and composed of an exopolymeric substance (EPS) containing large numbers of outer membrane vesicles (OMVs). Isolation, purification and protein profiling via 1D SDS-PAGE confirmed the outer membrane origin of these Antarctic bacteria OMVs. In an initial attempt to elucidate the role of OMVs in cold-adapted strains of Gram-negative bacteria, a proteomic analysis demonstrated that they were highly enriched in outer membrane proteins and periplasmic proteins associated with nutrient processing and transport, suggesting that the OMVs may be involved in nutrient sensing and bacterial survival. OMVs from Gram-negative bacteria are known to play a role in lateral DNA transfer, but the presence of DNA in these vesicles has remained difficult to explain. A structural study of Shewanella vesiculosa M7T using TEM and Cryo-TEM revealed that this Antarctic Gram-negative bacterium naturally releases conventional one-bilayer OMVs, together with a more complex type of OMV, previously undescribed, which on formation drags along inner membrane and cytoplasmic content and can therefore also entrap DNA.