Tipología de prestadores de servicios agropecuarios y forestales especializados para las zonas tropicales en méxico

Presently, rural extension work in Mexico has developed under a vertical strategy, where technology transference is the main objective without taking into account the participation of producers; thus, it is necessary for professional service providers (PSP) to develop the human and social capital of people with a sustainable management of the natural resources available. With the objective of characterizing the professional service providers from the project of training for specialized technicians in tropical agriculture, livestock production and forestry for the development of tropical zones in Mexico, in the bilateral agreement signed between Mexico and Brazil, a survey was performed and analyzed, under three sections: general data, expectations and perspectives, which helped to identify the main characteristics of extension workers and the limitations they face to adequately carry out the activities of rural extension work in Mexico. The PSP indicated that inadequate public policies for the agricultural-livestock sector are the main factor that limits the service of the extension worker, as well as the discrepancy in salaries they earn, under the premise that a continuous improvement is necessary in the service of rural extension work in Mexico, in order to achieve the development of skills among them to be able to transmit them to peers and agricultural and livestock producers

Identificación de hongos y micotoxinas asociadas a granos de café en Chiapas, Mexico

Objective: To identify the mycobiota associated to coffee beans (Coffea sp.) collected in the state of Chiapas, Mexico, as well as the incidence and levels of contamination by total aflatoxins and ochratoxin A.Design/methodology/approach: To obtain representative samples of coffee beans, visits were made to the main producing and storage areas in seven regions of Chiapas, from March 2006 to December 2007. From each sample, 100 grains were taken, sterilized and sown in PDA medium. The isolated fungi were identified at genus or species level. The identification of mycotoxins was performed by ELISA and the Ridasoft Win Software version 1.45 was used for their quantification.Results: Twenty-five genera/species of fungi were identified, with Aspergillus being the prevalent genus, followed by Penicillium, Fusarium, Curvularia, Rhizopus, Helminthosporium and Pestalotia. A. niger, A. flavus, A. ochraceus and A. clavatum were identified. There was a difference in the incidence of fungi between grain type and sampling regions. Regarding mycotoxins, there were differences according to type of grain and origin of the sample. Total aflatoxins were not found at high levels, but high levels were found for ochratoxin A.Study limitations/implications: Total aflatoxins in coffee do not show levels of risk to health, but ochratoxin A is present in risky levels for human health.Findings/conclusions: The incidence of fungi and contamination with mycotoxins is variable, depending on the type of coffee bean, region and year of sampling

A novel role for RecA under non-stress: promotion of swarming motility in Escherichia coli K-12

BACKGROUND: Bacterial motility is a crucial factor in the colonization of natural environments. Escherichia coli has two flagella-driven motility types: swimming and swarming. Swimming motility consists of individual cell movement in liquid medium or soft semisolid agar, whereas swarming is a coordinated cellular behaviour leading to a collective movement on semisolid surfaces. It is known that swimming motility can be influenced by several types of environmental stress. In nature, environmentally induced DNA damage (e.g. UV irradiation) is one of the most common types of stress. One of the key proteins involved in the response to DNA damage is RecA, a multifunctional protein required for maintaining genome integrity and the generation of genetic variation. RESULTS: The ability of E. coli cells to develop swarming migration on semisolid surfaces was suppressed in the absence of RecA. However, swimming motility was not affected. The swarming defect of a ΔrecA strain was fully complemented by a plasmid-borne recA gene. Although the ΔrecA cells grown on semisolidsurfaces exhibited flagellar production, they also presented impaired individual movement as well as a fully inactive collective swarming migration. Both the comparative analysis of gene expression profiles in wild-type and ΔrecA cells grown on a semisolid surface and the motility of lexA1 [Ind-] mutant cells demonstrated that the RecA effect on swarming does not require induction of the SOS response. By using a RecA-GFP fusion protein we were able to segregate the effect of RecA on swarming from its other functions. This protein fusion failed to regulate the induction of the SOS response, the recombinational DNA repair of UV-treated cells and the genetic recombination, however, it was efficient in rescuing the swarming motility defect of the ΔrecA mutant. The RecA-GFP protein retains a residual ssDNA-dependent ATPase activity but does not perform DNA strand exchange. CONCLUSION: The experimental evidence presented in this work supports a novel role for RecA: the promotion of swarming motility. The defective swarming migration of ΔrecA cells does not appear to be associated with defective flagellar production; rather, it seems to be associated with an abnormal flagellar propulsion function. Our results strongly suggest that the RecA effect on swarming motility does not require an extensive canonical RecA nucleofilament formation. RecA is the first reported cellular factor specifically affecting swarming but not swimming motility in E. coli. The integration of two apparently disconnected biologically important processes, such as the maintenance of genome integrity and motility in a unique protein, may have important evolutive consequences

Negative Autoregulation by Fas Stabilizes Adult Erythropoiesis and Accelerates Its Stress Response

Erythropoiesis maintains a stable hematocrit and tissue oxygenation in the basal state, while mounting a stress response that accelerates red cell production in anemia, blood loss or high altitude. Thus, tissue hypoxia increases secretion of the hormone erythropoietin (Epo), stimulating an increase in erythroid progenitors and erythropoietic rate. Several cell divisions must elapse, however, before Epo-responsive progenitors mature into red cells. This inherent delay is expected to reduce the stability of erythropoiesis and to slow its response to stress. Here we identify a mechanism that helps to offset these effects. We recently showed that splenic early erythroblasts, ‘EryA’, negatively regulate their own survival by co-expressing the death receptor Fas, and its ligand, FasL. Here we studied mice mutant for either Fas or FasL, bred onto an immune-deficient background, in order to avoid an autoimmune syndrome associated with Fas deficiency. Mutant mice had a higher hematocrit, lower serum Epo, and an increased number of splenic erythroid progenitors, suggesting that Fas negatively regulates erythropoiesis at the level of the whole animal. In addition, Fas-mediated autoregulation stabilizes the size of the splenic early erythroblast pool, since mutant mice had a significantly more variable EryA pool than matched control mice. Unexpectedly, in spite of the loss of a negative regulator, the expansion of EryA and ProE progenitors in response to high Epo in vivo, as well as the increase in erythropoietic rate in mice injected with Epo or placed in a hypoxic environment, lagged significantly in the mutant mice. This suggests that Fas-mediated autoregulation accelerates the erythropoietic response to stress. Therefore, Fas-mediated negative autoregulation within splenic erythropoietic tissue optimizes key dynamic features in the operation of the erythropoietic network as a whole, helping to maintain erythroid homeostasis in the basal state, while accelerating the stress response

SOS Response Induces Persistence to Fluoroquinolones in Escherichia coli

Bacteria can survive antibiotic treatment without acquiring heritable antibiotic resistance. We investigated persistence to the fluoroquinolone ciprofloxacin in Escherichia coli. Our data show that a majority of persisters to ciprofloxacin were formed upon exposure to the antibiotic, in a manner dependent on the SOS gene network. These findings reveal an active and inducible mechanism of persister formation mediated by the SOS response, challenging the prevailing view that persisters are pre-existing and formed purely by stochastic means. SOS-induced persistence is a novel mechanism by which cells can counteract DNA damage and promote survival to fluoroquinolones. This unique survival mechanism may be an important factor influencing the outcome of antibiotic therapy in vivo