<i>M.smeg msmeg_6554</i> knockout is incapable of siderophore export which can however be complemented by <i>M.tb irtA</i> as evident from siderophore production by CAS assay.

<p>(A) Block 1, mc²155; 2, mc²155▵6554 on CAS agar plate or 5, in iron depleted; or 8, normal iron replete media. 3, mc²155▵6554 was complemented with pMtb1348; and 6, grown in iron depleted media; or 9, in iron replete media. <i>M.smeg</i> mc²155 strain grown under iron depleted (4) and normal conditions (7) were used as control. The cultures were incubated for 3 days in each case. (B) The graphs indicate the growth pattern of the three strains in iron replete media (1) and iron depleted media (2) in terms of O. D. (A₅₄₀) of the culture monitored from 6 hrs of incubation till 48 hrs. (C) Siderophore concentration in the culture supernatants was measured as a function of CAS reactivity after 1 and 3 days of growth of the wild type mc²155 (M1); mc²155▵6554 (M2); or mc²155▵6554 complemented with <i>M.tb irtA</i> gene (M3) in iron depleted media.