Detection of cell viability in cultures of hyperthermophiles

Fluorescent dyes were assessed with regard to their ability to discriminate between viable and non-viable cells of hyperthermophilic archaea and bacteria. Using bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC4(3)), a membrane potential-sensitive probe, a safe and rapid discrimination of viable cells was possible by fluorescence microscopy. Single viable individuals, identified by DiBAC4(3), were selectively isolated from mixtures of viable and dead cells by the use of a laser microscope (`optical tweezers') and grown in pure culture.