Spore-forming properties and enhanced oxygen tolerance of butyrate-producing Anaerostipes spp

Butyrate producing bacteria are promising candidates for next-generation probiotics. However, they are extremely sensitive to oxygen, which is a significant obstacle to their inclusion in food matrices in a viable form. The present study characterized the spore-forming properties and stress tolerance of human gut butyrate-producing Anaerostipes spp. Spore formation properties in six species of Anaerostipes spp. were studied by in vitro and in silico tests. Spores were observed from the cells of three species using microscopic analyses, while the remaining three did not form spores under the tested conditions. Spore-forming properties were confirmed by an ethanol treatment. The spores of Anaerostipes caccae were tolerant to oxygen and survived for 15 weeks under atmospheric conditions. Spores tolerated heat stress at 70 °C, but not at 80 °C. An in silico analysis of the conservation of potential sporulation signature genes revealed that the majority of human gut butyrate-producing bacteria were classified as potential spore formers. Comparative genomics revealed that three spore-forming Anaerostipes spp. specifically possessed the spore formation-related genes of bkdR, sodA, and splB, which may be key genes for different sporulation properties in Anaerostipes spp. The present study demonstrated the enhanced stress tolerance of butyrate producing Anaerostipes spp. for future probiotic application. Presence of specific gene(s) are possibly keys for sporulation in Anaerostipes spp. •Three Anaerostipes spp. tested formed spores, but other 3 did not.•The spores of A. caccae were tolerant to oxygen and survived for 15 weeks.•Bile salts are essential for germination of spores in Anaerostipes spp.•All three sporulating Anaerostipes spp. had conserved putative spore formation genes.