Abstract Soil ecosystem provides fundamental services as bio-geochemical cycle regulation. Nitrogen cycle is managed by the microbiota that it harbors and depends on the stability of the ecosystem to cope abiotic disturbances such as metal and metalloid contamination. High concentrations of nickel (Ni) and zinc (Zn) in agricultural soils are frequently related to the application of conventional farming practices, composting, irrigation and biosolids deposit, as well as wastewater polluted from the mining and thermoelectric industry. To better understand the effects of this kind of abiotic disturbance a microcosm, this study was performed with agricultural soil from the Coast of Hermosillo, Sonora, Mexico and contaminated with Ni (II) and Zn (II) salphen complexes to evaluate their effect on the system, regarding the nitrogen cycle fluxes over time. The results obtained by spectrophotometric analyzes of the inorganic nitrogen pool, atomic absorption and pH revealed that the soil system functioning based on the nitrogen cycle was recovered 240 days after disturbances with M-salphen. This suggest the potential use of NiSB15 as a promoter to increase nitrate concentration at 60 days in conjunction with NiSA15 to increase ammonium concentration in agricultural soils contaminated with heavy metals.

Resumen El suelo proporciona servicios ecosistémicos fundamentales como la regulación del ciclo del nitrógeno, el cual, es dirigido por la microbiota que éste alberga y su estabilidad depende de perturbaciones bióticas o abióticas, como la contaminación por metales. Altas concentraciones de níquel (Ni) y zinc (Zn) en suelos agrícolas están relacionadas con prácticas agrícolas convencionales, composta, biosólidos, así como el riego con agua contaminada proveniente de la industria minera y termoeléctrica, principalmente. Con el objetivo de estudiar los efectos de dicha perturbación abiótica, se realizó un estudio a nivel microcosmos con suelo agrícola proveniente de la Costa de Hermosillo, Sonora, México, perturbado con compuestos M-salfen de Ni(II) y Zn(II), para evaluar su efecto en el funcionamiento del ciclo del nitrógeno a lo largo del tiempo. Los resultados obtenidos de los análisis espectrofotométricos de la reserva de nitrógeno inorgánico, de absorción atómica y de pH revelaron la recuperación de la funcionalidad del ciclo del nitrógeno en 240 días posteriores a las perturbaciones con M-salfen aplicadas, sugiriendo que, la utilización de NiSB15 promueve el incremento de la concentración de nitrato a los 60 días y, en conjunción con NiSA15 aumenta la concentración de amonio en suelos agrícolas contaminados con metales pesados.

ABSTRACT Chaetoceros muelleri is one of the most widely used microalgae species in aquaculture in northwestern Mexico as food for fish and crustaceans. Its importance is due to its fast growth, nutritional quality and lipid accumulation under nutrient-limiting conditions. However, the biochemical and molecular mechanisms of uptake of phosphorus (P) limiting conditions for this species is still unknown. This study aimed to analyze the growth and biochemical composition of C muelleri in response to different phosphorus concentrations. Four treatments under different phosphorus conditions were used: control (72 μM P), excess (144 μM P) and two treatments with phosphorus limitation, limited A (18 μM P) and limited B (7 μM P). The highest cell concentration was observed in control and excess of P (>3.4×106 cells mL−1). The highest dry mass concentration and chlorophyll-a content were found in control medium (72 μM P) whereas the highest total lipid (4.42%) was found in the lowest P-concentration medium (7 μM P). No significant differences were found in the total protein content, but we did find differences between the treatments with phosphorus limitation (7 and 18 μM P).

RESUMO: Plantas pertencentes ao gênero Jatropha têm despertado interesse devido ao seu alto teor de óleo que poderia ser usado para produzir biodiesel. Também é amplamente relatado que os principais ácidos graxos das oleaginosas da Jatropha são os ácidos oléico e linoleico. No entanto, existem poucos estudos relacionados a espécies nativas de pinhão-manso do noroeste do México que estão adaptados a condições áridas, e a expressão de genes envolvidos na síntese de ácidos graxos para essas espécies ainda é desconhecida. Portanto, o objetivo deste estudo foi analisar a expressão de cinco genes, ACP1, KASII, D9SD, FAD2-1 e FAD2-2, que estão envolvidos na síntese de ácidos oleico e linoleico em sementes selvagens maduras de Jatropha cinerea, espécies nativas do Deserto de Sonora, usando RT-PCR semi-quantitativa. Sementes de J. cinerea foram coletadas aleatoriamente em Bahía de Kino, Sonora (México), região caracterizada por ambientes agressivos como solos salinos e mudanças extremas de temperatura, e sementes de J. curcas maduras de uma variedade não-tóxica de Veracruz, México, usado como referência. Análise RT-PCR de três repetições biológicas foram consideradas para garantir dados consistentes. Nossa análise mostrou uma maior expressão dos genes KASII e FAD2-1 em sementes de J. cinerea comparado a J. curcas, enquanto a expressão de ACP1, D9SD e FAD2-2 foi maior em J. curcas. Além disso, as sequências dos genes Actin e FAD2-1 obtidas são as primeiras relatadas para J. cinerea, fornecendo, assim, informações para o desenvolvimento de novos estudos.

ABSTRACT: Plants belonging to genus Jatropha has arisen interest because of its high oil content that could be used to produce biodiesel. It is also widely reported that the main fatty acids in Jatropha oilseed are oleic and linoleic acids. However, there are scarce studies related to native species of Jatropha from Northwestern Mexico which are adapted to arid conditions, and the expression of genes involved in fatty acid synthesis for these species is still unknown. Therefore, the aim of this study was to analyze the expression of five genes, ACP1, KASII, D9SD, FAD2-1 and FAD2-2, which are involved in the oleic and linoleic acids synthesis in mature wild-seeds of Jatropha cinerea, a native species from Sonoran Desert, using semi-quantitative RT-PCR. The J. cinerea seeds were randomly collected in Bahía de Kino, Sonora (México) which is a region characterized by its harsh environments such as saline soils and extreme temperature changes and J. curcas mature seeds from a non-toxic variety from Veracruz, Mexico were used as a reference. The RT-PCR analysis of three biological replicates were considered to ensure data consistent. Our analysis showed a higher expression of KASII and FAD2-1 genes in J. cinerea seeds compared to J. curcas, meanwhile the expression of ACP1, D9SD and FAD2-2 were higher in J. curcas. Furthermore, Actin and FAD2-1 genes sequences here obtained are the first reported for J. cinerea, thus providing information to develop further studies.