Generated by In Vitro Transposon Mutagenesis†

We screened for transposon-generated mutants of Synechocystis sp. strain PCC 6803 that exhibited aberrant phototactic movement. Of the 300 mutants generated, about 50 have been partially characterized; several contained transposons in genes encoding chemotaxis-related proteins, while others mapped to novel genes. These novel genes and their possible roles in motility are discussed. Cyanobacteria such as Synechocystis sp. strain PCC 6803 exhibit surface-dependent phototactic motility which requires type IV pili (2, 4). To identify structural and regulatory com-ponents important for motility, we screened for mutants with aberrant phototactic movement (i.e., nonmotile or negatively phototactic under conditions in which wild-type cells show positive phototaxis). A Synechocystis genomic library was constructed that con-tained approximately 105 clones with an average insert size of 6 to 8 kbp (3). The library of clones was used for in vitro transposon mutagenesis, and mutagenized clones were use