Search

En México existen escasos estudios que describen a los cuerpos acuáticos empleados para la agricultura y el rol que tiene el agua de riego como fuente de inóculo, persistencia y dispersión de parásitos fitopatógenos, tal es el caso de los oomycetes que habitan ambientes acuáticos con capacidad de infectar un amplio rango de hospedantes cultivados. Debido a la falta de información sobre qué géneros y especies de oomycetes están presentes en el agua, su identificación es de suma importancia para gestionar alternativas de manejo y control de estos para la producción agrícola en la región. Con el objetivo de determinar qué oomycetes se aíslan en aguas superficiales empleadas para la irrigación en el Valle de Culiacán, Sinaloa, en el periodo comprendido de septiembre de 2018 a enero de 2019, en diferentes redes hídricas agrícolas (presas, estanques, ríos y canales), se colocaron trampas flotantes elaboradas con bolsas de polipropileno y dos frutos de pera que sirvieron como cebo. Se obtuvieron aislados de oomycetes, los cuales se identificaron en base a sus características morfológicas y secuencias de ADN (con los iniciadores ITS 4/6, COX y NADH), también se realizaron pruebas de patogenicidad en plantas y frutos de las familias de solanáceas y cucurbitáceas. Se aislaron e identificaron los organismos: Phytophthora parsiana, P. virginiana, P. lagoariana, P. capsici y P. hydropathica. Todas las especies de Phytophthora resultaron patogénicas, tuvieron capacidad de infectar plantas y frutos, causando síntomas de marchitez y pudrición en las hortalizas inoculadas.

Bee pollen is a favorable microhabitat for many microorganisms and its dissemination via commercialization must be of important consideration. Here the data presented describe the characterization ...

The potential presence of spore-forming bacteria related to the Bacillus cereus group in Mexican chili powder elaborated from Capsicum annuum L. is of commercial and clinical interest, because chili powder is an essential spice in the Mexican diet and in diets around the globe. To facilitate detection and isolation of members of this group of spore-forming bacteria from Mexican chili powder samples, we identified colonies that grew on agar medium selective for Bacillus cereus sensu lato, supplemented with polymyxin B (10 µg/mL) and ampicillin (10 to 100 µg/mL). The presumptive B. cereus (s.l.) isolates were tested using a tRNACys-PCR-based approach and the results identified species related phylogenetically to B. cereus, B. thuringiensis, and B. toyonensis. Their toxigenic potential was assessed by serological tests to detect enterotoxins (Nhe and Hbl) and by PCR targeting the hemolysin BL (hbl) component C (hblC) and non-hemolytic enterotoxin component A (nheA). The antibiotic profiles of the isolates showed a high resistance to β-lactams (100% of the isolates), trimethoprim-sulfamethoxazole (100%), tetracycline (90%), erythromycin (77%), clindamycin (74%), and chloramphenicol (42%). Our results indicate the presence of B. cereus s.l. with toxigenic characteristics in Mexican chili powder. Because of the potential for these organisms to cause disease through their production of various toxins, and resistance to antibiotics, we recommend that a microbiological risk assessment must be considered in the Mexican regulatory requirements.

In Bacillus subtilis, the tRNA(Cys) lacks an encoded CCA 3′ end. To gain insight into the role of CCAase and RNases in tRNA(Cys) processing, several mutant strains were generated. Northern blot and RT-PCR results suggest that enzymes other than CCAase can participate in CCA addition at the 3′ end of the immature tRNA(Cys). ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s42770-019-00075-5) contains supplementary material, which is available to authorized users.

Background: In spore-forming bacteria, the molecular mechanisms of accumulation of transfer RNA (tRNA) during sporulation must be a priority as tRNAs play an essential role in protein synthesis during spore germination and outgrowth. However, tRNA processing has not been extensively studied in these conditions, and knowledge of these mechanisms is important to understand long-term stress survival. Methods:To gain further insight into tRNA processing during spore germination and outgrowth, the expression of the single copy tRNA Cys gene was analyzed in the presence and absence of 1.2 M NaCl in Bacillus subtilis using RNA-Seq data obtained from the Gene Expression Omnibus (GEO) database. The CLC Genomics work bench 12.0.2 (CLC Bio, Aarhus, Denmark, https://www.qiagenbioinformatics.com/) was used to analyze reads from the tRNA Cys gene. Results:The results show that spores store different populations of tRNA Cys-related molecules. One such population, representing 60% of total tRNA Cys, was composed of tRNA Cys fragments. Half of these fragments (3´-tRF) possessed CC, CCA or incorrect additions at the 3´end. tRNA Cys with correct CCA addition at the 3´end represented 23% of total tRNA Cys, while with CC addition represented 9% of the total and with incorrect addition represented 7%. While an accumulation of tRNA Cys precursors was induced by upregulation of the rrnD operon under the control of σ A -dependent promoters under both conditions investigated, salt stress produced only a modest effect on tRNA Cys expression and the accumulation of tRNA Cys related species. Conclusions:The results demonstrate that tRNA Cys molecules resident in spores undergo dynamic processing to produce functional molecules that may play an essential role during protein synthesis.

Traditional mining activities are usually correlated with high levels of soil pollution, which is a major environmental concern. Extensive mining activities have taken place in the San Joaquin region in the State of Queretaro, Mexico resulting in high levels of mercury soil pollution (up to 1532 ± 300 mg/kg). We isolated mercury-resistant fungal strains from the San Joaquin region soils and identified them through morphologic characteristics and ITS rDNA region sequence analysis. We determined that fungi isolated belong to the genus Trichoderma. All the isolates selected showed the ability to catalyze the volatilization of Hg. For air sampling, an active sampling device was constructed and using acid KMnO4 as an absorbent, the concentration of mercury in solution was determined through the cold vapor atomic absorption method. The results show mercury volatilization from the fungal species assay, with a maximum of 213.04 ± 32.6 μg/m3 while mycelium accumulation ranged from less than 17.5 ± 2.9 to 20.0 ± 3.4 μg/g. The fungal isolates were also evaluated for their ability to reduce mercury uptake in Arabidopsis thaliana. These observations suggest the utility of Trichoderma for the mobilization of mercury in those contaminated soils.

American foulbrood (AFB) caused by Paenibacillus larvae is the most destructive honeybee bacterial disease and its dissemination via commercial bee pollen is an important mechanism for the spread of this bacterium. Because Mexico imports bee pollen from several countries, we developed a tRNA(Cys)-PCR strategy and complemented that strategy with MALDI-TOF MS and amplicon-16S rRNA gene analysis to evaluate the presence of P. larvae in pollen samples. P. larvae was not detected when the tRNA(Cys)-PCR approach was applied to spore-forming bacterial colonies obtained from three different locations and this result was validated by bacterial identification via MALDI-TOF MS. The genera identified in the latter analysis were Bacillus (fourteen species) and Paenibacillus (six) species. However, amplicon-16S rRNA gene analysis for taxonomic composition revealed a low presence of Paenibacillaceae with 0.3 to 16.2% of relative abundance in the commercial pollen samples analyzed. Within this family, P. larvae accounted for 0.01% of the bacterial species present in one sample. Our results indicate that the tRNA(Cys)-PCR, combined with other molecular tools, will be a useful approach for identifying P. larvae in pollen samples and will assist in controlling the spread of the pathogen.

Bee pollen is a highly nutritive natural foodstuff. Because of its use as a comestible, the association of bacteria with bee pollen is commercially and biologically important. We report here the bacterial diversity of seven bee pollen samples (five from Europe, one from Chile, and one from Mexico) based on 16S rRNA gene amplicon metagenome sequencing.

Bee pollen is a valuable natural product and by its nutritional composition is important for the development of insects of agricultural interest. In this work, we determined whether gamma irradiation can minimize the risk of microbial contamination of commercial bee pollen used for the mass rearing of bumblebees. Bee pollen samples were treated with target doses of 0, 2, 5, 7 and 9 kGy of gamma radiation emitted by a 60Co source and then analyzed for microbial content. Neither fungi nor coliform bacteria were detected in samples irradiated at 5 kGy or higher. Yeasts and aerobic bacteria were not detected in the samples irradiated at 7 kGy or higher (

Oxidative stress occurs when cells are exposed to elevated levels of reactive oxygen species that can damage biological molecules. One bacterial response to oxidative stress involves disulfide bond formation either between protein thiols or between protein thiols and low-molecular-weight (LMW) thiols. Bacillithiol was recently identified as a major low-molecular-weight thiol in Bacillus subtilis and related Firmicutes. Four genes (bshA, bshB1, bshB2, and bshC) are involved in bacillithiol biosynthesis. The bshA and bshB1 genes are part of a seven-gene operon (ypjD), which includes the essential gene cca, encoding CCA-tRNA nucleotidyltransferase. The inclusion of cca in the operon containing bacillithiol biosynthetic genes suggests that the integrity of the 3′ terminus of tRNAs may also be important in oxidative stress. The addition of the 3′ terminal CCA sequence by CCA-tRNA nucleotidyltransferase to give rise to a mature tRNA and functional molecules ready for aminoacylation plays an essential role during translation and expression of the genetic code. Any defects in these processes, such as the accumulation of shorter and defective tRNAs under oxidative stress, might exert a deleterious effect on cells. This review summarizes the physiological link between tRNACys regulation and oxidative stress in Bacillus.

Oxidative stress occurs when cells are exposed to elevated levels of reactive oxygen species that can damage biological molecules. One bacterial response to oxidative stress involves disulfide bond formation either between protein thiols or between protein thiols and low-molecular-weight (LMW) thiols. Bacillithiol was recently identified as a major low-molecular-weight thiol in Bacillus subtilis and related Firmicutes. Four genes (bshA, bshB1, bshB2, and bshC) are involved in bacillithiol biosynthesis. The bshA and bshB1 genes are part of a seven-gene operon (ypjD), which includes the essential gene cca, encoding CCA-tRNA nucleotidyltransferase. The inclusion of cca in the operon containing bacillithiol biosynthetic genes suggests that the integrity of the 3′ terminus of tRNAs may also be important in oxidative stress. The addition of the 3′ terminal CCA sequence by CCA-tRNA nucleotidyltransferase to give rise to a mature tRNA and functional molecules ready for aminoacylation plays an essential role during translation and expression of the genetic code. Any defects in these processes, such as the accumulation of shorter and defective tRNAs under oxidative stress, might exert a deleterious effect on cells. This review summarizes the physiological link between tRNACys regulation and oxidative stress in Bacillus.

We report here the first draft assembly for the genome of Acinetobacter idrijaensis strain MII, isolated from the Idrija mercury mine area (Slovenia). This strain shows a strikingly high tolerance to mercury, and the genome sequence shows genes involved in the mechanisms for heavy metal tolerance pathways and multidrug efflux pumps.

El tizón de fuego causado por Erwinia amylovora (Ea), es una de las enfermedades más severas del manzano, debido a que origina la muerte de yemas florales y en ocasiones del árbol completo. Un método para su manejo es el uso de antibióticos. Sin embargo, el uso inapropiado de éstos puede inducir resistencia en las bacterias. En este trabajo se evaluó el aceite esencial de orégano (Lippia berlandieri) (carvacrol 80%) durante los años 2005 y 2006, como una alternativa orgánica para el manejo de Ea. La concentración mínima bactericida (CMB) encontrada in vitro fue de 0.055 a 0.073% (p/v). Se evaluó una concentración de 0.11% (p/v) en campo y se determinó su efecto en la reducción del daño ocasionado por Ea; estos resultados se compararon con los obtenidos con Agry- MR MR MR Mycin 100 , Cuprimicin 100 y Agry-Gent Plus 800 . Durante ambos años, los tratamientos no presentaron diferencias significativas con respecto al testigo. El momento de la aplicación se basó en la detección de poblaciones epifíticas mediante la impresión de estigmas en medio semi-selectivo, temperatura y humedad con valores de 5%, 16.7°C y 78%, respectivamente para 2005. Por otra parte en el ciclo 2006 estos mismos parámetros fueron de 96%, 15.2°C y 70%, respectivamente. La identificación y resistencia de Ea a estreptomicina, se determinó utilizando medios semi-selectivos, los resultados fueron confirmados por reacción en cadena de la polimerasa (PCR). Se detectó y aisló una cepa de Ea resistente a estreptomicina. Éste es el primer reporte mediante técnicas moleculares de una cepa de Ea resistente a estreptomicina en la zona manzanera de Chihuahua, México.

RNA processing is an essential pathway in the regulation of genetic expression in the cell. In this work, Bacillus subtilis was used to understand the effects of mercury on the mechanism of tRNA metabolism. The CVAAS (cold vapor atomic absorption spectroscopy) method revealed that from the addition of HgCl2 (0.75 μg ml(-1)) during the bacterial exponential phase, ca. 48% of the added mercury was taken up by the cells. This led to an immediate reduction in the rate of cell division. During this response, we observed accumulation of species shorter than mature tRNA(Cys) over a 10 h period. We did not observe this accumulation for another five tRNAs analyzed. tRNA processing is largely dependent on RNase R and PNPase in B. subtilis. Thus, when the exonuclease PNPase was absent, we found that the shorter tRNA(Cys) species increased and mature tRNA(Cys) decreased after mercury addition, but this proportion changed during the time analyzed. However, in the absence of RNase R and PNPase the accumulation of the shorter tRNA(Cys) was more pronounced and the mature form was not recovered. In the single rnr mutant strain the shorter tRNA(Cys) was not observed. All together, we provide in vivo evidence that PNPase and RNase R are indispensable in controlling tRNA(Cys) quality in the presence of mercury.

Multidrug-resistant microorganisms are of great concern to public health. Genetic mobile elements, such as plasmids, are among the most relevant mechanisms by which bacteria achieve this resistance. We obtained an Escherichia coli strain CM6, isolated from cattle presenting severe diarrheic symptoms in the State of Querétaro, Mexico. It was found to contain a 70 kb plasmid (pMEX01) with a high similarity to the pHK01-like plasmids that were previously identified and described in Hong Kong. Analysis of the pMEX01 sequence revealed the presence of a blaCTX-M-14 gene, which is responsible for conferring resistance to multiple β-lactam antibiotics. Several genes putatively involved in the conjugative transfer were also identified on the plasmid. The strain CM6 is of high epidemiological concern because it not only displays resistance to multiple β-lactam antibiotics but also to other kinds of antibiotics.