Creation of deletions in cassette array of Vibrio rotiferianus DAT722. Genetic features of the integron are labelled in the figure (A). The numbers below each cassette indicates its position in the array relative to attI. The white (group 1) and grey cassettes (group 2) indicate the two groups of paralogous cassettes described in the Materials and Methods section. Not all cassettes are shown with gaps of missing cassettes marked with a ~ symbol. A 1834 bp DNA fragment consisting of, in order, a portion of the white paralogous cassette sequence (448 bp), the aphA1 gene from pLOW2 (964 bp) and a portion of the grey paralogous sequence (410 bp) was cloned into the suicide vector pCVD442 to create pMAQ1081 (B). Plasmid pMAQ1081 was conjugated into Vibrio sp. DAT722-Sm resulting in a single crossover at cassette 61 creating strain MD7 (C). Counterselection of MD7 with sucrose medium resulted in isolation of deletion mutants that had undergone a second crossover with cassette 15, creating mutant d16-60 and deletion of cassettes 16 to 60 (C, i), with cassette 7 resulting in mutants d8-60a, d8-60b and d8-60c and deletion of cassettes 8 to 60 (C, ii).