Enterococcus faecium DPC3675 is a derivative of E. faecium DPC1146 which contains a single copy of the conjugative transposon Tn916. Although the transposon is observed to be oriented in one direction in individual colonies, DNA extracted from cultures grown from these colonies contains the transposon in both orientations, as determined by PCR analysis and sequencing of the transposon/chromosome junctions. Therefore, Tn916 possesses a hitherto unreported ability to invert within a particular insertion site during growth in broth. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.