Extracellular Accumulation of Rhodotorulic Acid in Strains of Microbotryum violaceum

Siderophore accumulation and phytopathogenicity in Microbotryum violaceum

“…Samples for assaying growth and RA accumulation were taken every 1-2 days and cell density determined by hemocytometer count as described previously (Birch and Ruddat, 1998).…”

“…The Fe-perchlorate (hydroxamate) assay of Atkin and Neilands (1968) was used to measure RA levels as described previously (Birch and Ruddat, 1998). The universal chemical assay (UCA) is based on the color change by secreted siderophores.…”

“…The UCA agar contained 50 mL chrome azurol S (Sigma) stock solution (0.061 g/50 mL), 10 mL of 1 mM FeCl 3 -10 mM HCl, and 10 mL 3-(dimethyldodecylammonio)-propanesulfonate (DIDO, Fluka) stock (1.7 mL DIDO diluted with H 2 O to 20 mL). The culture medium contained 200 mL Pipes stock solution per liter (30.24 g in 187.6 mL H 2 O, 12.4 mL of 50% NaOH), histidine (0.1 g/L), and supplemented minimal medium containing 1.5% Noble agar (DIFCO) (Birch and Ruddat, 1998). The pH of the culture medium was adjusted to pH 6.1.…”

“…The pink, haploid sporidial strain, 2.A2+ of M. violaceum was selected for mutagenesis because it produced RA in low-iron medium (Birch and Ruddat, 1998). Approximately, 1600 sporidial colonies from UV-treated sporidia from strain 2.A2 were screened on UCA plates for 3-10 days and 96 putative siderophore mutants were isolated.…”

“…While this appears to be inconsistent with a role of extracellular siderophore production in the pathogenesis of M. violaceum on S. latifolia, the question of correct identification of the fungal strains isolated from Saponaria species must be raised. Birch and Ruddat (1998) examined 23 strains of M. violaceum isolated from eight different Caryophyllacean species, and found that all produced RA. A genetic study of ornithine-cycle mutants of M. violaceum found that crosses among three ornithine-negative mutants apparently inhibited S. latifolia from flowering; many of the infected plants had light green leaves with pronounced ruffles that were interpreted as symptoms of disease (Stevens and Garber, 1987).…”