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Un mecanismo de transferencia de electrones extracelular basado en flavina en diversas bacterias Gram positivas
Samuel H Light1, Lin Su2,3, Rafael Rivera-Lugo1
1Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
Nature
|September 14, 2018
Resumen
Listeria monocytogenes utiliza un nuevo sistema de transferencia de electrones extracelular (EET) basado en flavina para el crecimiento y la supervivencia. Este mecanismo, distinto de las vías conocidas, implica genes y flavinas específicos, que afectan a las comunidades microbianas.
Área de la Ciencia:
- Microbiología y Fisiología Microbiana
- Sistemas bioelectroquímicos
- Genética y Biología Molecular
Sus antecedentes:
- La transferencia extracelular de electrones (EET) es crucial para los procesos bioelectroquímicos microbianos, sin embargo, los mecanismos más allá de los sistemas basados en el hemo son poco conocidos.
- Las bacterias que respiran minerales suelen emplear vías complejas de transferencia de electrones basadas en el hemo.
- La existencia y la base mecanicista de vías alternativas de EET siguen siendo en gran medida inexploradas.
Objetivo del estudio:
- Para aclarar el mecanismo de transferencia extracelular de electrones en el patógeno Listeria monocytogenes transmitido por los alimentos.
- Identificar la base genética y los componentes clave de un nuevo sistema de EET basado en flavina.
- Investigar el papel fisiológico y la prevalencia de este mecanismo EET en las comunidades microbianas.
Principales métodos:
- Examen genético avanzado para identificar mutantes de L. monocytogenes con actividad reducida de la ferrreductaza extracelular.
- Identificación y caracterización de un locus de ocho genes responsable de la EET.
- Ensayos bioquímicos y análisis genéticos para determinar las funciones de genes y moléculas específicas (NADH deshidrogenasa, pool de quinona, flavoproteínas, lanzaderas de flavina).
Principales resultados:
- Se identificó un nuevo locus de ocho genes que codifica una deshidrogenasa NADH especializada y facilita la EET basada en flavina en L. monocytogenes.
- Este sistema canaliza los electrones a un grupo de quinonas distinto y utiliza flavoproteínas extracelulares y lanzaderas de flavina para la transferencia de electrones a aceptores como el hierro o los electrodos.
- La activación de EET apoya el crecimiento en fuentes de carbono no fermentables, y los mutantes de EET muestran defectos competitivos en el intestino del ratón; los ortólogos están muy extendidos en Firmicutes.
Conclusiones:
- L. monocytogenes emplea un mecanismo EET dependiente de flavina único, distinto de los sistemas basados en el hemo, que permite la transferencia de electrones a aceptores externos.
- Este sistema EET basado en flavina es esencial para la utilización de ciertas fuentes de carbono y confiere una ventaja competitiva en entornos asociados al huésped.
- Los genes y el mecanismo EET identificados prevalecen en todo el filo Firmicutes, lo que sugiere una amplia relevancia ecológica y patógena para las bacterias electrogénicas.
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