This is even more appropriate to Mars and Titan research.
Use of a microbe in an anaerobic system for electrical generation and indirectly for sustained growth or reproduction of the microbes over time in the process. A medium is still present with bound organics, but
"When the medium was replaced with an anaerobic buffer lacking nutrients required for growth, acetate-dependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks. This represents the first report of microbial electricity production solely by cells attached to an electrode."
The link at reply #4 gives a non-natural enzyme process synthetic pathway, whereas this article shows growth in an anaerobic system with successful progression of energy production by natural microbial processes or attendant chemical progressions inherent in the system. No description of the sunlight or temperature range potential for the system.
Where on Mars would we find acetates for fueling microbes?