O-linked protein glycosylation in bacteria: snapshots and current perspectives

•Bacterial O-linked protein glycosylation systems of biological significance are being encountered with increasing frequency.•Significant advances have been in elucidating the structures and functions of dedicated glycosyltransferases functioning within the cytoplasm.•Studies of O-linking oligosaccharyltransferases targeting extracytoplasmic proteins remain complicated by the associations of the enzymes, glycan donors and protein targets with the membrane.