Rapid detection and quantification methodology for genus Megasphaera as a hydrogen producer in a hydrogen fermentation system

Important issues in the microbiology of biological reactors include bacterial composition and cell counts of bacterial communities. Because oligonucleotide probes targeting a particular phyletic group are available for studying hydrogen fermentation, fluorescence in situ hybridization (FISH) could be an attractive research technique. Although we reported the importance of the Megasphaera spp. for a simple hydrogen fermentation system, fundamental information like population and composition remains unclear. Thus, here, we established the use of Megasphaera-specific oligonucleotide Mega-X for FISH and the optimum conditions for rapid single-cell level identification. The culture isolated from a simple hydrogen fermentation process was identified as Megasphaera elsdenii and was shown to be significantly dominant (30%–58% of the microflora) by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and FISH. The combination of Megasphaera-specific PCR-RFLP and FISH is likely to become an important methodology for understanding the global distribution and behaviour of Megasphaera spp. in the environment.

► Megasphaera is an important microbe in simple hydrogen fermentation systems. ► We established the use of a Megasphaera-specific FISH method that uses FISH probe Mega-X. ► FISH probe Mega-X distinguished between the closely related members of genus Megasphaera. ► In a simple hydrogen fermentation process, M. elsdenii was shown to be dominant. ► PCR-RFLP and FISH for Megasphaera contribute to the understanding of hydrogen fermentation.