'Extreme' genes shed light on origins of photosynthesis
"Knowing how photosynthesis originated and evolved is essential to obtaining the deep understanding required to yield improvements in bioenergy, agriculture and the environment," Touchman says.
Touchman, who is also an adjunct investigator at The Translational Genomics Research Institute (TGen), has chosen his photosynthetic, microbial partners carefully; each bears a unique metabolism, physiology or ecology and differs in fundamental ways from sequenced genomes of any other phototroph. Hidden in these organisms' various genetic codes may be hallmarks: traces of early evolutionary innovations pointing to the origin of oxygen-evolving high-energy photosynthesis.
There are important linkages between Touchman's work on earthbound origins and astrobiology as well. Phototrophic extremophiles are excellent model microbes for studies of interplanetary photosynthetic exchange, Touchman says. That is, exchange that might come about in stellar systems that have terrestrial-type rocky planets that could be capable of exchanging gneiss and rocky material. The arrival of oxygenic photosynthesis via transport of materials by external means, such as meteorites, could profoundly change the direction of biological evolution on a planet's surface.
Transpermia or rocky panspermia is the possibility of the exchange of micro-organisms between planets via impact material. Paul Davies, director of ASU's Beyond Center for Fundamental Concepts in Science, developed some of the thinking upon which Touchman's extraterrestrial pursuits are based: "some microorganisms can survive interplanetary journeys cocooned inside rocks blasted off planets by comet and asteroid impacts. That rocky panspermia is an effective mechanism for spreading life within a planetary system."
"Oxygen is a central biosignature or fingerprint of life sought in the atmospheric spectra of planets beyond our solar system," Touchman says. "Detailed molecular understanding of how photosynthetic microbes can push the boundaries of extreme-environment existence on our own planet will also fill important gaps in our current understanding of extra-terrestrial potential for oxygen-evolving photosynthesis."
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