A History of Iron Metabolism in the Mycobacteria - Iron Acquisition by the Genus Mycobacterium - page 19

Fig. 2.5 Structures of nocobactins from Nocardi species [ 49 , 51 ]. Type a from N. asteroides ,
N. sylvoderifa , N. paraffinae and N. uniformis (now all considered to be equivalent to N. asteroides )
type b from N. brasiliensis and type c from N. caviae and N. phenotolerans . Types b and c are
equivalent in structure to the mycobactins (see Fig. 2.4 ) but type a has its long alkyl chain at R4
and is somewhat equivalent to mycobactins M and N (see Fig. 2.4 ) but also has an unusual oxa-
zoline ring instead of the more usual oxazole ring
M. smegmatis , it was possible to produce cells with 10 % (w/w) of mycobactin, a
truly massive over-production of a siderophore. Richard Hall, one of my very able
graduate students, was also able to achieve good yields of mycobactin by grow-
ing cells on agar plates (though highly purified agar had to be used) but there was
no need to de-ferrinate the culture medium beforehand [ 52 ]. Cells could then be
scraped off just one or two plates and then the mycobactin extracted with etha-
nol in the usual way. Up to 10 mg mycobactin per plate could be attained. It was
then possible to analyze the mycobactins very quickly and easily using both thin
layer chromatography and the newly arrived technique of high-pressure chroma-
tography (HPLC) [ 53 ]. The former technique, with appropriate solvents, separated