gene fusions to the ptsmpel locus of escherichia coli we have constructed gene fusions between ptsmpel and lacz these fusions affect both phenotypes assigned to the ptsmpel locus at 40 min namely no growth on mannose or glucosamine and inhibition of the penetration of bacteriophage lambda dna as well as that of other lambdoid phages such as hy2 since the lacz gene fusions are insertion mutations that abolish target gene function by disrupting the linear contiguity of the gene it would appear that ptsm and pel are either the same gene or two genes within the same operon several size classes of these ptsmpellacz fusions have been isolated and the corresponding hybrid proteins are associated with the cytoplasmic membrane of escherichia coli this is consistent with the proposal that ptsmpel codes for enzyme ii of the phosphotransferase transport system pts specific for mannose glucosamine fructose and glucose however we have also identified tn10 insertion mutations that confer a man phenotype but have no effect on the pel phenotype complementation analysis indicates that the tn10 insertions and the lacz gene fusions are in different genes both of these genes are involved in mannose uptake this suggests that the locus at 40 min can be subdivided into two genes whose products are required for mannose uptake and that only one of these is involved in the penetration of lambda dna