Use of Tn917 to generate insertion mutations in the group A streptococcus

The Enterococcus faecalis transposon Tn917 is functional in a broad range of bacteria, including both Gram-positive and Gram-negative species. We cloned Tn917-LTV3, a derivative carrying a promoterless lacZ (beta-galactosidase gene), into the thermosensitive shuttle replicon pG+host4 and assayed for chromosomal insertions in group A streptococcus (GAS). Tn917 transposed into the GAS chromosome at a frequency of (2.8 +/- 3.2) x 10(-5) per colony forming unit (cfu). Transposition products were predominantly simple insertions and no target site preference was detectable. Some transcriptional fusions were identified in which the promoterless lacZ of the transposon appeared to be expressed from an external promoter.