Phosphate depletion: A novel trigger for Mycobacterium tuberculosis persistence

These data represent the global gene expression profile of Mycobacterium tuberculosis after 24 hrs and 72 hrs of inorganic phosphate starvation. Differentially regulated genes appear to include those encoding proteins involved in adaptation to phosphate starvation, namely those involved in phosphate regulation and phosphate assimilation, as well as those involved in the stringent response. To investigate genes involved in phosphate regulation and assimilation, as well as the stringent response, three biological replicates were prepared from log phase cultures in phosphate-replete medium (25mM phosphate),which served as control, and 24 and 72 hrs of phosphate-starved cultures served as sample replicates. After purification of total RNA from above cultures, fluorescent labeled cDNAs were generated and used for dual channel hybridization to perform genome-wide microarray studies. Three slides were used for each time point. Collected microarray data were normalized by global and local normalization. Genes with ≥ 2-fold change in expression in all three hybridizations and q-value ≤0.01 were defined as being significantly differentially regulated. our data showed that genes related to phosphate regulation and assimilation as well as the stringent response were dramatically upregulated.