Cover photograph: Among a library of Escherichia coli transposon mutants, struggling to stay afloat in a tumultuous sea, an E. coli purine auxotroph is rescued by a purine life ring excreted by the solar-powered vessel, Rhodopseudomonas palustris. The image is an analogy for the discovery of unexpected purine cross-feeding from R. palustris to E. coli through transposon sequencing in a mutualistic coculture. (Image by J. B. McKinlay.) (See related article at e00543-20.) (Copyright © 2020 American Society for Microbiology. All Rights Reserved.)