Phosphate uptake by the yeast, Rhodotorula rubra, and the green alga, Selenastrum capricornutum Printz, after phosphate additions to steady-state continuous cultures

Abstract

We examined phosphate (Pi) uptake by two well-characterized microorganisms: a green alga (Selenastrum capricornutum) and a heterotrophic yeast (Rhodotorula rubra). Phosphate uptake was measured in dual- and single-species continuous cultures after perturbation of a phosphorus (P)-limited steady-state culture by additions of varying concentrations of Pi. We found that, under these conditions, both organisms had very high transport rates for Pi. The yeast was able to attain higher internal P concentrations than predicted from either steady-state or from P-starved batch culture data. Because the yeast was able to sequester and store Pi more efficiently than the alga under dilute Pi continuous culture conditions, co-existence of the two organisms was ultimately controlled by the concentration of carbon available for growth of the yeast.