Cytochrome c6 is an important molecule in cyanobacteria that helps transfer electrons in photosynthesis. A study looked at a mutant cyanobacterium lacking cytochrome c6 and found that its photosystem I activity was not greatly affected when grown without copper. However, when grown in a low carbon environment with ammonium as a nitrogen source, the mutant had growth issues. The mutant showed increased expression of proteins involved in photosystem I function, which may help protect it from damage.