Fig 1.

Identification of the ald gene whose expression was upregulated in a ΔdevR mutant strain of M. smegmatis grown under hypoxic conditions. (A) Comparative 2D electrophoresis analysis of soluble proteins of the M. smegmatis ΔdevR strain grown under hypoxic (−O₂) or aerobic (+O₂) conditions for 20 h. The spots indicated by the open circles represent three proteins whose synthesis was increased more than 5-fold under hypoxic conditions compared to their levels under aerobic conditions. By means of MALDI-TOF MS, the proteins were identified as MSMEG_2659 (Ald), with a molecular mass of 38 kDa and pI of 5.9, MSMEG_3084 (Gap), with a molecular mass of 32 kDa and pI of 5.2, and MSMEG_2378 (SerA), with a molecular mass of 51 kDa and pI of 4.9. (B) Determination of the transcription levels of ald under hypoxic conditions. The wild-type (WT) and ΔdevR strains were grown either aerobically (+O₂) or under hypoxic conditions (−O₂) for 10, 15, and 20 h. The expression levels of ald and 16S rRNA genes were determined by RT-PCR. The hspX gene, whose expression was known to be induced by DevR under hypoxic conditions, was included in the experiment as a control. The levels of mRNA specific for ald were also determined by qRT-PCR and normalized to those of 16S rRNA. Fold induction of ald expression indicates the level of ald mRNA in hypoxic cultures relative to that in aerobic culture and is given below the RT-PCR results.