The effect of ampicillin plus streptomycin on growth and photosynthesis of two halotolerant chlorophyte algae

Abstract

Streptomycin and ampicillin are antibiotics commonly used to eliminate prokaryotes from the cultures of eukaryotic algae. We studied the effects of 25 mg l−1 streptomycin plus 50 mg l−1 ampicillin on the growth and photosynthesis of two broadly halotolerant algae, Picochlorum oklahomensis and Dunaliella sp. (Chlorophyceae). We measured growth rate, oxygen evolution, chlorophyll fluorescence kinetics, and pigment content in low (150 μmol photons m−2 s−1) and high (600 μmol photons m−2 s−1) light grown batch cultures. Our results show only a minor effect of the antibiotics on P. oklahomensis, and none on Dunaliella sp., so this combination of antibiotics is suitable for maintenance of stock cultures for physiological experiments. We also show that these antibiotics can be used in turbidostat cultures of P. oklahomensis, which otherwise tend to succumb to bacteria.