Circumvention of the Mycobactin Requirement of Mycobacterium paratuberculosis

Abstract

Circumvention of the mycobactin requirement of Mycobacterium paratuberculosis. J. Bacteriol. 89:762-767. 1965.-The mycobactin growth requirement of Mycobacterium paratuberculosis was circumvented on glucosecontaining synthetic medium with an initial pH of 5.5. Mycobactin was required during the first transfer on the synthetic medium. Subsequent transfers have grown in the absence of mycobactin. The growth of mycobactin-"independent" strains of M. paratuberculosis on the synthetic medium was found to be stimulated by low concentrations of mycobactin. The circumvention of the mycobactin requirement appears to depend upon the properties of the medium and not upon having created conditions which promote endogenous mycobactin synthesis. Investigation of the glucose-containing synlthetic medium showed that: (i) growth stimulatory compounds were formed during autoclaving, and (ii) compared with neutrality a pH of 5.5 gave markedly increased pellicle yields. It was suggested that the growth-stimulatory compounds formed during autoclaving may in part be responsible for the circumvention of the mycobactin requirement.

Mycobactins: iron-chelating growth factors from mycobacteria.

“…Dependent strains of this organism, in contrast to other mycobacteria, seem to have a true genetic defect, being unable to produce mycobactin. When they were grown without added mycobactin, even in medium of low iron content which should stimulate mycobactin production, no trace of mycobactin-like material was found by biological assay or by tests for hydroxylamine (50). The extreme dependence on exogenous mycobactin and the high specificity of the mycobactins to the mycobacteria present problems in explaining the florid growth of M. paratuberculosis in intestinal tissue in Johne's disease.…”

“…Although M. paratuberculosis has this highly specific requirement of mycobactin for growth, Morrison has found conditions under which various strains of the organism will grow at least slowly without supplementation by mycobactin. These involve the use of unusually acid conditions, preferably around pH 5.0, and growth in a simple glucose-containing medium which has been autoclaved at pH 5.5 (34,50). The autoclave treatment produces unidentified compounds having absorption maxima at 230 and 290 nm.…”

Iron-binding compounds of Mycobacterium avium, M. intracellulare, M. scrofulaceum, and mycobactin-dependent M. paratuberculosis and M. avium

“…The presence of the exochelins also explains how the mycobactin requirement of M. paratuberculosis can be circumvented by using a medium of low pH if ferric ammonium citrate is added (9). At the low pH sufficient iron must be able to gain access to the cell, probably by simple diffusion, to allow growth to be initiated.…”

Antibody reactivities of Mycobacterium paratuberculosis infected sheep as analyzed by enzyme-linked immunosorbent assay and Western blotting

“…The antigens used in ELISA and Western blotting were prepared from a clinical isolate of M. ptb and a M. phlei culture both grown as pellicules on Watson and Reid's synthetic medium [11]. Bacteria were harvested by centrifugation (10000 x g, 20 min) and washed twice with 0.15 M phosphate buffered saline (PBS), pH 7.5.…”