Substrate uptake in extremely halophilic microbial communities revealed by microautoradiography and fluorescence in situ hybridization.

The combination of fluorescence in situ hybridization and microautoradiography (FISH-MAR approach) was applied to brine samples of a solar saltern crystallizer pond from Mallorca (Spain) where the simultaneous occurrence of Salinibacter spp. and the conspicuous square Archaea had been detected. Radioactively labeled bicarbonate, acetate, glycerol, and an amino acid mixture were tested as substrates for the microbial populations inhabiting such brines. The results indicated that hitherto uncultured 'square Archaea' do actively incorporate amino acids and acetate. However, Salinibacter spp. only showed amino acid incorporation in pure culture, but no evidence of such activity in their natural environment could be demonstrated. No glycerol incorporation was observed for any component of the microbial community.