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Un ciclo de TCA primordial y reversible en un termófilo facultativamente quimioautotrófico
Takuro Nunoura1, Yoshito Chikaraishi2,3,4, Rikihisa Izaki5
1Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. takuron@jamstec.go.jp.
Science (New York, N.Y.)
|February 9, 2018
Resumen
Este estudio revela un nuevo ciclo de ácido tricarboxílico reversible en *Thermosulfidibacter takaii*. Esta antigua vía de fijación de carbono utiliza citrato sintasa, desafiando los modelos anteriores del ciclo reductor de TCA.
Área de la Ciencia:
- Microbiología
- La bioquímica
- Astrobiología
Sus antecedentes:
- El ciclo del ácido tricarboxílico reductor (rTCA) es una antigua vía fundamental de fijación de carbono crucial para la vida en la Tierra.
- Comprender la evolución y los mecanismos de fijación de carbono es clave para comprender la vida temprana y la vida extraterrestre potencial.
Objetivo del estudio:
- Para investigar las vías de fijación de carbono en la bacteria quimiolitotrófica de ramificación profunda * Thermosulfidibacter takaii * ABI70S6 T .
- Para aclarar los mecanismos y la importancia evolutiva del ciclo del ácido tricarboxílico (TCA) en este organismo.
Principales métodos:
- Análisis genómico para identificar genes metabólicos.
- Ensayos enzimáticos para determinar la función y la regulación de las enzimas.
- Perfiles metabólicos para analizar los intermediarios metabólicos bajo diferentes condiciones de crecimiento.
Principales resultados:
- Descubrimiento de un ciclo de TCA reversible previamente desconocido en *Thermosulfidibacter takaii*.
- Demostrar que la dirección del ciclo TCA está controlada por la fuente de carbono disponible.
- Identificación de la citrato sintasa (CS) como la enzima clave que impulsa el ciclo de rTCA en condiciones quimio-autotróficas, evitando la escisión del citrato dependiente del ATP.
Conclusiones:
- El ciclo rTCA en *Thermosulfidibacter takaii* funciona en sentido inverso a través de la citrato sintasa, que difiere de los modelos convencionales.
- Este mecanismo de CS reversible puede representar una forma ancestral del ciclo rTCA.
- Los hallazgos sugieren un posible origen facultativo de la vida.
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