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Estudio de los procesos de metanogénesis y sulfato reducción en tapetes microbianos de ambientes hipersalinos
Get PDF"En ambientes hipersalinos, la metanogénesis ocurre típicamente a partir de compuestos
metilados, principalmente trimetilamina y metanol, los cuales han sido denominados como
sustratos “no competitivos”. En el presente trabajo, a través de incubaciones de
microcosmos, se evaluó la competencia por diferentes sustratos entre arqueobacterias
metanogénicas y bacterias sulfato reductoras, en tapetes microbianos de ambientes
hipersalinos de Guerrero Negro, Baja California Sur, México. Los sustratos que más
estimularon la sulfato reducción fueron el acetato y el lactato, con tasas respiratorias
máximas de 5.88 y 2.57 mmol por gramo de sedimento por día (mmol/gsed –d) cada uno,
mientras que, los sustratos preferentes para la metanogénesis, fueron la trimetilamina y el
metanol, con tasas respiratorias de 1.09 y 0.92 mmol/gsed –d, respectivamente. Se
encontró que tanto la trimetilamina como el metanol, son sustratos potenciales para la
sulfato reducción en estos ecosistemas. Por otro lado, en las incubaciones donde el
sulfato fue retirado, se detectó actividad metanogénica acetoclástica, la cual no había sido
previamente reportada en ecosistemas hipersalinos. El presente estudio aporta nueva
información sobre el uso de sustratos por arqueobacterias metanogénicas y bacterias
sulfato reductoras en ambientes hipersalinos y sobre la compartición de sustratos por
ambos grupos microbianos, sugiriendo abrir de nuevo la discusión si realmente existen
sustratos exclusivos para la metanogénesis en estos ecosistemas.""Methanogenesis in hypersaline environments typically occurs from methylated
compounds, mainly trimethylamine and methanol, which have been called as "noncompetitive"
substrates. In this work, through microcosm incubations, competition of
different substrates was evaluated between methanogenic archaea and sulfate-reducing
bacteria in hypersaline microbial mats from Guerrero Negro, Baja California Sur, Mexico.
Acetate and lactate promoted sulfate reduction with maximal respiratory rates of 5.88 and
2.57 mmol per gram of sediment per day (mmol/gsed-d). Preferred substrates for
methanogenesis were trimethylamine and methanol, with respiratory rates of 1.09 and
0.92 mmol/gsed-d, respectively. We found that both trimethylamine and methanol, are
potential substrates for sulfate reduction in these ecosystems. Furthermore, in incubations
where sulfate was removed, acetoclastic methanogenic activity was detected, which had
not previously been reported in hypersaline ecosystems. This study provides new
information on the use of substrates by methanogenic archaea and sulfate-reducing
bacteria in hypersaline environments and sharing substrates by both microbial groups,
suggesting reopen the discussion if there really exist “non-competitive” substrates for
methanogenesis in these ecosystems.
Paths of water entry and structures involved in the breaking of seed dormancy of Lupinus
Get PDF"Physical dormancy is the water impermeability of the seed coat caused by one or more palisade cell layer(s) called macrosclereids. The specialised structure for water entry sites is the water gap, which serves as a detector of environmental cues for germination. In Fabaceae, the water gap is the lens, although another seed structure for water entry could exist. In this study, we identified the initial site of water entry, observed the hydration of a cushion-like structure near the radicle, described the anatomy of the water gap, and analysed the association of anatomical seed traits with the initial site of water entry and the imbibition velocity of six species of Lupinus from the state of Jalisco, Mexico. Dye tracking with a toluidine blue solution was used to identify the initial site of water entry. The anatomical description was performed using conventional microtechnique and a light microscope. The entry of the toluidine solution into seeds of L. montanus was observed after 6 h, followed by L. exaltatus and L. mexicanus after 18 h and L. elegans, L. reflexus and L. rotundiflorus after 48 h. The site of water entry was the lens in L. elegans, L. exaltatus, L. reflexus and L. rotundiflorus and the micropyle in L. mexicanus and L. montanus. The cushion-like structure was responsible for water accumulation in embryo imbibition. Significant differences among anatomical seed traits such as thickness in the hilar region, the counter-palisade layer, cushion-like structure, epidermis, hypodermis, and innermost parenchyma layer were found among the species.
Maximal unstable dissipative interval to preserve multi-scroll attractors via multi-saturated functions
Get PDF"In this paper, we present families of piecewise linear systems which are controlled by a continuous piecewise monoparametric control function for the generation of monoparametric families of multi-scroll attractors. Thus, the maximum range of values that the parameter set can take in order to preserve the useful dynamics for generating of multi-scroll attractors is found and it will be called maximal robust dynamics interval. This class of dynamical systems is the result of combining two or more unstable “one-spiral” trajectories. We give necessary and sufficient conditions in order to preserve multi-scroll attractors in terms of a parameter, i.e., a family of multi-scroll attractors is generated by means of a family of switching systems with multiple monoparametric companion matrices. Lastly, we provide an example to show how the developed theory works.
HPV genotype distribution and anomalous association of HPV33 to cervical neoplastic lesions in San Luis Potosí, Mexico
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Background: The association of human papillomavirus (HPV) types to neoplastic lesions increase as a function of their oncogenicity and the duration of the infection since lesion severity progresses from low-grade to high-grade and cancer. In an outbreak, the prevalence of the HPV type involved would increase and the proportion of the associated low-grade lesions would predominate over severe lesions. In this study, the prevalence of HPV types and their association to neoplastic lesions was determined in women subjected to colposcopy in San Luis Potosi, Mexico.
Methods: DNA from high-risk (HR) and low-risk (LR) HPV types was identified by E6 nested multiplex PCR in cervical scrapes from 700 women with normal cytology, atypical squamous cells of undetermined significance (ASCUS), low-grade squamous intraepithelial lesions (LSIL), high-grade squamous intraepithelial lesions (HSIL) or invasive cervical cancer (CC).
Results: Overall HPV-DNA prevalence was 67.7 %, that of HR-HPV was 63.1 %, and that of LR-HPV was 21.3 %. The highest prevalence (78.2 %) occurred in the 15-24 year group, whereas that of single infections was 52 % and that of multiple infections (i.e., by 2-6 HPV types) was 48 %. The most prevalent HR types were HPV33 (33.1 %), HPV16 (16.6 %), HPV18 and HPV51 (6.7 % each). HR-HPV prevalence was 29.6 % in normal cytology, 26.7 % in ASCUS, 63.3 % in LSIL, 68.2 % in HSIL, and 90.5 % in CC. Three prevalence trends for HR-HPV types were found in neoplastic lesions of increasing severity: increasing (LSIL CC) for HPV33.
Conclusions: Two-thirds of the women subjected to colposcopy from 2007 to 2010 in San Luis Potosi have HPV infections which predominate in the 15-24 years group. Around half of the infections are by one viral type and the rest by 2-6 types. HPV33 is the most prevalent type, followed by HPV16. Overall HR-HPV prevalence increases with the severity of neoplastic lesions. HPV33 prevalence is highest in LSIL and its U-shaped trend with progressing neoplastic lesions differs from the growing/asymptotic trends of other HR-HPV types. An ongoing or recent HPV33 outbreak is consistent with its high prevalence and anomalous association to LSIL.
Metodología para el análisis de información geofísica de pozos implementando herramientas FOSS: caso de estudio Complejo Volcánico de Colima
Get PDF"En la actual era de la información las herramientas de software libre y de código abierto FOSS por sus siglas en inglés, son implementadas en gran variedad de disciplinas incluyendo servicios, en la industria, en tecnología y por supuesto en la ciencia (Ebart, 2008), debido a las ventajas de popularidad, fiabilidad, rendimiento, escalabilidad, seguridad y coste total de propiedad que tiene sobre los software especializados
(Wheeler, 2007). La toma de datos geofísicos en pozos es una práctica estándar en el proceso para la autorización de perforación y el aprovechamiento de agua subterránea. Estos datos se reportan con un mínimo de procesamiento en los informes y su interpretación se limita a la identificación de unidades geológicas principales. Este estudio pretende implementar una metodología para dar estructura, para
almacenar, para analizar y visualizar información geofísica de pozos con la finalidad de facilitar la interpretación y entendimiento de diversos contextos geológicos utilizando software libre y de código abierto.
La metodología se aplica en un área de interés delimitada en una franja circular con centro en el volcán Nevado de Colima localizado en la parte occidental del Cinturón Volcánico Transmexicano. La franja tiene un ancho entre 25 y 30 km aproximadamente y se extiende media circunferencia desde la parte norte del volcán hacia su lado suroeste. Este trabajo se basa en el análisis de 63 registros geofísicos (rayos gamma natural, resistividades y potencial espontáneo) de 40 pozos dispersos en la zona de estudio, con una densidad de información promedio de 40 sitios en un área total de 1500 km2. Se cuenta con una distribución suficientemente uniforme que justifica su procesamiento e interpretación de manera espacial.
La elaboración de mapas a partir de los datos geofísicos para las superficies escogidas respecto a la geometría del edificio volcánico en el sistema de información geográfica GRASS permitió describir la distribución de valores en tres dimensiones. Con base en el conjunto de mapas elaborados se presenta un modelo geofísico de los primeros 300 metros de profundidad con respecto a la superficie con tres perfiles de
corte. El procesamiento espectral de los datos utilizando filtros tipo pasa-bajos permite identificar las diferentes unidades principales en función de la dirección de los perfiles. Con base en las características físicas de los materiales geológicos de la zona se propone la clasificación de las unidades en materiales sedimentario y/o volcaniclástico. Espesores típicos de las unidades principales en los diferentes perfiles
fueron del orden de magnitud de decenas de metros. La continuidad de unidades específicas a lo largo de direcciones radiales as´ı como circulares se infirió aplicando criterios estadísticos multivariables. Dentro de dichas unidades principales al combinar el filtrado espectral y el análisis numérico de los datos se vuelve posible identificar y describir tendencias lineales, patrones y variaciones de diferentes ´ordenes de magnitud en los valores geofísicos; as´ı como interpretar en términos de paquetes sedimentarios, intercalaciones
de materiales volcánicos, geometría de unidades acuíferas, entre otros. Los resultados obtenidos en el presente estudio sugieren que el procesamiento avanzado y la re-interpretación de datos geofísicos de pozos levantados de manera rutinaria para fines hidrogeológicos-administrativos puede conducir a un mejor
entendimiento de ambientes geológicos diversos tal como se ilustró en el presente estudio para el caso de la región cercana al Complejo Volcánico de Colima.""In the current information era, tools the free software and open (FOSS) are implemented in a variety of disciplines including; services, industry, technology and science (Ebart, , 2008). Thid mainly, due to the advantages that it represent, like popularity, reliability, performance, scalability, security and total cost of ownership, compared to that with that on the specialized software (Wheeler, 2007 ). Geophysical surveys logs in water wells are a standard practice for the authorization process of the drilling and exploitation of underground water. These data are reported with a minimum of processing, and interpretation reports are limited to identifying main geological units and/or physical properties of rocks. This study aims to implement a methodology for structuring, storage, analyze and interpret of geophysical data for wells applicable to understand different geological units, all using free and open source software. The study area comprises a sector of the Colima Volcanic Complex (CVC) and it is delimited by a circular fringe, centered at the summit of the Nevado de Colima volcano in the western part of The Trans-Mexican Volcanic Belt, the fringe 25 by 30 km wide, approximately, extending north from the volcano to the southwest side. This work is based on the analysis of 63 well logs (natural gamma ray, resistivity and spontaneous potential) of 40 wells scattered throughout the study area, with an average density of information of 40 sites on a total area of 1500 km2. It has a sufficiently uniform distribution that justifies its processing and interpretation on a spatial way. The mapping of geophysical data in the geographic information system GIS was performed for selected surfaces relatives to the geometry of the volcano, and this allowed me to describe the distribution of values in three dimensions. Based on the set of maps developed, models of the first 300 meters depth with respect to the surface with three surface profiles are presented. The spectral data processing using low-pass filters allow the identification of different major units as a function of the direction on the profiles. Based on the physical characteristics of geological materials from the area, a classification of the units is proposed as sedimentary and / or volcaniclastic material. Typical thicknesses of major units in the different profiles were defined in the order of tens meters.
Análisis estructural y funcional de la proteína Clp de Xanthomonas axonopodis pv. citri
Get PDFTesis (Maestría en Ciencias en Biología Molecular)"Clp (Crp-like protein) es un regulador de la expresión de factores de virulencia en la bacteria gram negativa Xanthomonas axonopodis pv. citri, fitopatógeno causante del cáncer de los cítricos y de gran importancia económica. Este factor de transcripción pertenece a la familia CRP/FNR presentando 45% de identidad de secuencia con CAP (por sus siglas del inglés Catabolite Activator Protein), sin embargo es único en su clase por dos cuestiones. En primer lugar es capaz de unirse al ADN sin necesidad de unirse a su ligando, y esta unión a ligando solo provoca su inhibición. Además el ligando que une es c-di-GMP, a diferencia de la mayoría de los integrantes de la familia que unen AMPc como es el caso de CAP. Nuestro objetivo es resolver la estructura tridimensional del complejo Clp-ADN. Para esto se expresó Clp en la cepa BL21 (DE3) Star de Echerichia Coli, induciendo la expresión de la proteína con 0.4 mM de IPTG a 28 ⁰C durante 16 horas tras un choque frio de 2 horas. La purificación se realizó mediante tres pasos cromatográficos, IMAC, intercambio iónico y por último exclusión molecular. El proceso tuvo un rendimiento final de 0.6 mg/litro de cultivo. La proteína Clp recombinante obtenida presentó actividad biológica evaluada por un ensayo de movilidad monitoreado mediante exclusión molecular, mostrándose que el tiempo de retención del complejo Clp-ADN disminuye (10 mL = 197242 Da) con respecto al ADN solo (11.8 ml = 65493 Da). Por análisis de Thermofluor se observó que el cloruro de sodio, el glicerol, el cloruro de litio y el ácido glutámico aumentaron la estabilidad térmica de Clp.""The Crp-like protein (Clp) is a global regulator of the expression of virulence factors in gram negative bacteria Xanthomonas axonopodis pv. citri. phytopathogen that causes citrus cancer, which is economically important. This factor belongs to the CRP / FNR family and presents 45% of sequence similarity with Catabolite Activator Protein (CAP). However it is unique in its class for two reasons: first, it is able to bind DNA without binding to its ligand, and the ligand binding causes inhibition. Furthermore, the binding ligand is c-di-GMP, unlike most family members, such as CAP, that bind cAMP. Our goal is to solve the threedimensional structure of Clp-DNA complex. Clp was expressed in the BL21 (DE3) Star Escherichia coli strain, inducing protein expression with IPTG 0.4 mM at 28 ⁰C for 16 hours after a cold shock for 2 hours. Purification was performed by three chromatographic steps, IMAC, ion exchange and lastly molecular exclusion. The process had a final yield of 0.6 mg / liter of culture. Recombinant Clp obtained presented biological activity evaluated by size-exclusion mobility shift assay, showing that the retention time of the Clp-DNA complex decreases (10mL = 197,242 Da) compared to DNA alone (11.8ml=65,493Da). Sodium chloride, glycerol, lithium chloride and glutamic acid increased the thermal stability of Clp.
Influence of human activities on some medium and large-sized mammals’ richness and abundance in the Lacandon Rainforest
Get PDF"We evaluated the influence of six human activities (related variables) on the richness and abundance of large and medium-sized mammals in the southern portion of the Lacandon Rainforest, including protected and non-protected areas. The human activities measured have different influences on mammal richness and abundance. Our results show that some human activities (human density and anthropogenic land cover, and agriculture/cattle ranching) had no effect on large and medium-sized mammal populations, but community-based protection, such as medium levels of tourism and hunting, had a negative influence on richness and abundance. Those variables negatively influencing the mammal community were reported in one of the study sites. Data indicate both an opportunity for applied integral conservation actions that involve people and their activities, as well as an opportunity to support biodiversity conservation in agricultural landscapes by integrating human activities with protected areas and conservation.
Analog electronic implementation of a class of hybrid dissipative dynamical system
Get PDF"An analog electronic implementation by means of operational amplifiers of a class of hybrid dissipative systems in R3R3 is presented. The switching systems have two unstable hyperbolic focus-saddle equilibria with the same stability index, a positive real eigenvalue and a pair of complex conjugated eigenvalues with negative real part. The analog circuit generates signals that oscillate in an attractor located between the two unstable equilibria, and may present saturation states at the moment of energizing it, i.e. if the initial voltage on the capacitors do not belong to the basin of attraction the circuit will end on a saturation state.
Butterfly conservation within cities: a landscape scale approach integrating natural habitats and abandoned fields in central Mexico
Get PDF"Growing urbanization and the expansion of the agricultural frontier in tropical ecosystems have generated patchy landscapes composed of remnants of natural habitats and abandoned fields. This scenario offers an opportunity to develop urban reserves in order to preserve local fauna in expanding cities. We propose that if native animals are able to use these two habitat types, reserves composed of a mixture of natural habitats and abandoned fields would contain more diversity than reserves composed only of natural habitats. However, to be useful for conservation, these reserves must harbor specialized organisms that depend on natural habitats. To test this proposal, we focused on diurnal butterflies inhabiting an urban reserve located within the city of Puebla (Mexico), which contains relics of oak forests and abandoned fields. Butterfly assemblages were sampled and compared in the different habitat types of the reserve. The data were then pooled and analyzed for the reserve as a whole. These analyses discriminated between habitat generalist and forest specialist butterflies. Our results indicated that the different habitat types of the reserve harbor different forest specialist butterflies, which in turn enhanced the diversity of forest-dwelling butterflies at the landscape scale. This suggests that the inclusion of abandoned fields together with natural habitats in the design of urban protected areas could help to preserve at least part of the regional biodiversity.
Improved predictions of the geographic distribution of invasive plants using climatic niche models
Get PDF"Climatic niche models for invasive plants are usually constructed with occurrence records taken from literature and collections. Because these data neither discriminate among life-cycle stages of plants (adult or juvenile) nor the origin of individuals (naturally established or man-planted), the resulting models may mispredict the distribution ranges of these species. We propose that more accurate predictions could be obtained by modelling climatic niches with data of naturally established individuals, particularly with occurrence records of juvenile plants because this would restrict the predictions of models to those sites where climatic conditions allow the recruitment of the species. To test this proposal, we focused on the Peruvian peppertree (Schinus molle), a South American species that has largely invaded Mexico. Three climatic niche models were constructed for this species using high-resolution dataset gathered in the field. The first model included all occurrence records, irrespective of the life-cycle stage or origin of peppertrees (generalized niche model). The second model only included occurrence records of naturally established mature individuals (adult niche model), while the third model was constructed with occurrence records of naturally established juvenile plants (regeneration niche model). When models were compared, the generalized climatic niche model predicted the presence of peppertrees in sites located farther beyond the climatic thresholds that naturally established individuals can tolerate, suggesting that human activities influence the distribution of this invasive species. The adult and regeneration climatic niche models concurred in their predictions about the distribution of peppertrees, suggesting that naturally established adult trees only occur in sites where climatic conditions allow the recruitment of juvenile stages. These results support the proposal that climatic niches of invasive plants should be modelled with data of naturally established individuals because this improves the accuracy of predictions about their distribution ranges.