ABSTRACT: The basic experiment is a comparison of gene transcript levels of Streptomyces coelicolor M145 and its wblA deletion mutant at 6 timepoints (24, 36, 48, 60, 72 and 84 hours) encompassing vegetative growth, aerial growth, and sporulation on solid medium. The wblA mutant is morphologically defective, most of its aerial hyphae failing to show any sign of sporulation-directed attributes, and also overproduces some antibiotics. The microarray analysis was aimed to reveal the major transcriptional changes underpinning or associated with this pleiotropic phenotypic change. Using a fairly stringent cut-off, 291 genes were found to be affected, including developmental genes, antibiotic biosynthetic genes, and genes for primary metabolism. Some genes were over-expressed and others under-expressed in the mutant. Although the largest effects were mostly at timepoints corresponding to aerial growth and early sporulation, some genes were most strongly influenced at earlier timepoints. M145 vs wblA deletion mutant. 6 timepoints (24, 36, 48, 60, 72 and 84 hours) encompassing vegetative growth, aerial growth, and sporulation, were analysed. Each timepoint comprised 2 technical replicates each of 3 biological replicates. RNA was isolated from triplicated cultures grown on cellophane overlays on MM + mannitol after 24, 36, 48, 60, 72 and 84 hours of incubation. Samples of the RNA were converted to Cy3-labelled cDNA in vitro, and mixed with Cy5-labelled genomic DNA. Each mixture was hybridised to two glass slide microarrays each carrying oligonucleotide probes corresponding to 99% of the genes in the annotated S. coelicolor genome. Thus RNA from each timepoint was compared to the same batch of genomic DNA and the comparison used to arrive at expression values of genes. These expression values were then used to arrive at differential expression between M145 and the wblA deletion mutant for all genes at all six timepoints.
