A novel culture method with filter paper for isolating aerial microalgae under aerial-phase conditions

Terrestrial microbial mats contain a wide variety of aerial microalgae, including useful drug-resistant and non-drug-resistant algal strains. A method for cultivating aerial microalgae in diverse terrestrial environments is needed to isolate these useful strains. The aim of this study was to develop a novel method for isolating aerial microalgae that does not rely on conventional antibiotics and characterize the isolated strains by screening and species identification. The effectiveness of filter paper as a culture substrate was investigated under aerial conditions; a total of 79 strains of aerial microalgae were successfully isolated from the microbial mat. After screening strains that grew well by altering the nitrogen source, pH, cultivation temperature, and light intensity of the medium, nine promising strains were identified from the isolated strains. Molecular phylogenetic trees suggested that algal strains were aerial microalgae of the genera Coelastrella, Klebsormidium, Tetratostichococcus, and Chloroidium. This simple, filter paper-based isolation method is thus effective for isolating aerial microalgae of various genera.