Sequence analysis
The DNA insert from the βLR16 metagenomic clone was 5,169 base pairs. Sequence analysis
further supported the phenotypic results, showing that the metagenomic DNA insert from
βLR16 did not encode a predicted β-lactamase gene (Fig. 1). In silico open reading frame
(ORF) analysis suggested two ORFs that share homology to known genes, and loss-of-phenotype
transposon mutants mapped to these two putative genes (Fig. 1). The location of the lossof-
phenotype transposon insertions suggested that either both genes were required for
resistance, or that mutations in the upstream metallopeptidase gene were polar on the downstream
response regulator gene (Fig. 1).