Fungi, bacteria and soil pH: the oxalate-carbonate pathway as a model for metabolic interaction

The oxalatecarbonate pathway involves the oxidation of calcium oxalate to low-magnesium calcite and represents a potential long-term terrestrial sink for atmospheric CO2. In this pathway, bacterial oxalate degradation is associated with a strong local alkalinization and subsequent carbonate precipitation. In order to test whether this process occurs in soil, the role of bacteria, fungi and calcium oxalate amendments was studied using microcosms. In a model system with sterile soil amended with laboratory cultures of oxalotrophic bacteria and fungi, the addition of calcium oxalate induced a distinct pH shift and led to the final precipitation of calcite. However, the simultaneous presence of bacteria and fungi was essential to drive this pH shift. Growth of both oxalotrophic bacteria and fungi was confirmed by qPCR on the frc (oxalotrophic bacteria) and 16S rRNA genes, and the quantification of ergosterol (active fungal biomass) respectively. The experiment was replicated in microcosms with non-sterilized soil. In this case, the bacterial and fungal contribution to oxalate degradation was evaluated by treatments with specific biocides (cycloheximide and bronopol). Results showed that the autochthonous microflora oxidized calcium oxalate and induced a significant soil alkalinization. Moreover, data confirmed the results from the model soil showing that bacteria are essentially responsible for the pH shift, but require the presence of fungi for their oxalotrophic activity. The combined results highlight that the interaction between bacteria and fungi is essential to drive metabolic processes in complex environments such as soil.

pH como un trazador de la variabilidad biogeoquímica en el Sistema de Humboldt

Se analizó información sobre parámetros biogeoquímicos como pH, CO2 parcialmente disuelto, clorofila-a, oxígeno, salinidad y temperatura, obtenidos en el Sistema de Humboldt frente a Perú en los años 2007-2009, a fin de comprender la importancia del pH como una variable clave para trazar la variabilidad biogeoquímica del Sistema de Afloramiento de Humboldt. Las Aguas Costeras Frías (ACF) ricas en nutrientes evidencian una relación inversa con el pH, en ese sentido valores de 7,6 a 8,0 se encontraron asociados a la ocurrencia de eventos de afloramiento; en condiciones frías como La Niña 2007 el pH predominante se encuentra por debajo de 8,0, y en el caso de las Aguas Subtropicales Superficiales presentan un pH entorno a 8,3. La productividad en los veranos se incrementa debido a factores como la intensidad de luz generándose núcleos de clorofila-a superiores a 10,0 μg.L-1; como constituyentes de la reacción bioquímica de fotosíntesis se tiene en cuenta la forma inmediata del compuesto CO2 y el consumo de iones hidronio; en situaciones extremas de fertilización, se tiene elevado pH entre 8,2 e inclusive 9,0, en donde los contenidos de oxígeno disuelto superan los 6,0 mL.L-1.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/11/12.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1939/01/14.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/12/10.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/12/17.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

Etat de collection : 1938-1939

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/11/19.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1939/01/21.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/12/03.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/12/24.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/10/01.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/10/31.

Y học tân thanh. ["puis" Tuần báo phổ thông khoa thuốc]

1938/12/31.