The research group of Takuro Nunoura, Senior Researcher of the Marine Life Science and Engineering Research and Development Center, Ocean Research and Development Organization, is a TCA cycle in which bacteria derived from the hydrothermal activity area of the Southern Okinawa Trough are indispensable for the biosynthesis of life-critical compounds such as amino acids. It was discovered for the first time that it has the most primitive form of the circuit (citric acid cycle).
There has been long debate as to whether the birth form of life on Earth was an autotroph that self-fixes carbon or a heterotroph that uses organic matter.For many organisms, the TCA cycle is an essential metabolic mechanism for survival, but there are several forms of the TCA cycle, and there have been various debates about the appearance of the primitive TCA cycle before and after the birth of life.
Now, the research group has shown that the thermophilic sulfur trioxide-reducing bacterium Themosulfidibacter takaii has the most primitive form of the TCA cycle. As a result of a multidimensional omics analysis that comprehensively looks at DNA, RNA, proteins, and metabolites, the concentration of intermediate metabolites supplied is determined even though the bacterium uses the exact same group of enzymes under different growth conditions. Correspondingly, it was clarified that the reaction direction of the TCA cycle was flexibly switched.The flexible nature of this TCA circuit is that organisms born in hydrothermal environments with sufficient chemical energy have an autotrophic and mixed nutritional lifestyle, depending on the carbonic acid and organic matter present and their amount. It suggests that it was changed flexibly.In other words, it is thought that life was born not as an organism specializing in heterotrophic or autotrophic nutrition, but as an entity that flexibly adapts to given environmental conditions.
Paper information:[Science] A primordial and reversible TCA cycle in a facultatively chemolithoautotrophic thermophile
