Abstract
Kitasatosporia setae KM-6054T produces both filamentous mycelia and submerged spores (SS) in the submerged culture with shaking. SS were not produced in a chemically defined medium, MMT, but were produced when the medium was added with yeast extract or casamino acids. In MMT supplemented with casamino acids (MMT-CA), SS began to elongate within 1 hour incubation and grew up to form long filamentous mycelia after 6 hours. Spore chains were produced at the tips of the hyphal branches after 10 hours, and then short spore chains were fragmented to yield SS after 15 hours.
In feeding experiments, the strain produced SS in MMT when casamino acids were added within 4 hours after inoculation, but not when added after 6 hours. In MMT-CA, additional feeding of casamino acids did not influence the initiation time of SS formation.
In a nutritional shift-down experiment, the strain formed SS when casamino acids were removed from MMT-CA after 8 hours of cultivation, but not when removed within 6 hours. The strain starts to form cells committing SS already after about 8 hours under nutrient rich condition. Cells that commit SS formation started to be formed within about 8 hours incubation under nutrient-rich conditions. It seems thus likely that the SS formation of K. setae KM-6054T is not regulated with nutritional starvation, but by a clock mechanism.
