Identification of genes essential for Moraxella catarrhalis growth under iron-limiting conditions using Genomic Array Footprinting (GAF): Expression analysis of directed gene deletion mutants.

Iron-sequestration by the human host is a first line defense against respiratory pathogens like Moraxella catarrhalis, which consequently experiences a period of iron-starvation during colonization and infection. We determined the genetic requirements for M. catarrhalis growth during iron-starvation using the high-throughput genome-wide screening technology genomic array footprinting (GAF). To further characterize the functional consequences of the gene deletions (GAF identified genes), we determined transcriptome profiles of the wild-type and directed mutant strains during exponential growth in BHI medium. The results described in this study are further discussed in Stefan P.W. de Vries, Peter Burghout, Jeroen D. Langereis, Aldert Zomer, Peter W.M. Hermans, Hester J. Bootsma: Genetic requirements for Moraxella catarrhalis growth under iron-limiting conditions, Molecular Microbiology. M. catarrhalis BBH18 directed mutants (n = 3) and their parental wild-type BBH18 strain (n = 4) were expanded to mid-log phase (OD620nm, 1.2 to 1.4) and RNA was isolated as previously described (de Vries et al., 2010 J Bacteriol 192: 3574-3583). Total RNA was labeled according to standard Nimblegen gene expression array protocols and hybridized to 4x72K custom design Nimblegen arrays for read-out.