Mycobacterium tuberculosis response to environmental potassium

The purpose of this study was to identify genes that are differentially expressed under conditions of potassium limitation, to elucidate how Mycobacterium tuberculosis (Mtb) senses and responds to ionic changes, and the role of these responses in host colonization. Mtb strain CDC1551 wild type was grown to an OD600 of 0.6 in standing vented T-75 flasks before being subcultured to an OD600 of 0.3 in standing vented T-25 flasks of either standard 7H9, pH 7 or 0 mM K+ 7H9, pH 7 media. Exposure was for 4 hours in a humidified, 37C, 5% CO2 incubator before RNA was extracted. RNA was prepared by removing the rRNA and library prepping with a TruSeq Stranded kit (Illumina) before high-throughput sequencing with an Illumina HiSeq 2500 (High Output v4) (100 bp single end reads, one lane). Two biological samples per condition were sequenced.