Improved Isolation of Uncultured Anaerobic Bacteria using Medium Prepared with Separate Sterilization of Agar and Phosphate

We previously demonstrated that a simple modification in the preparation of agar media, i.e., autoclaving phosphate and agar separately (termed the "PS protocol"), improved the culturability of aerobic microorganisms by reducing the generation of reactive oxygen species. We herein investigated the effects of the PS protocol on the cultivation of anaerobic microorganisms using sludge from a wastewater treatment system as a microbial source. The application of the PS protocol increased colony numbers and the frequency of phylogenetically novel isolates under aerobic, nitrate reduction, and fermentation conditions. The PS protocol is useful for isolating both aerobic and anaerobic microorganisms.