Aerobic cultivation of anaerobic rumen protozoa, Entodinium caudatum and Epidinium caudatum

Rumen protozoa, primarily ciliates, are one of the important groups of strictly anaerobic microbes living in the rumen. Despite their ubiquitous occurrence in the rumen and significant contribution to host animals, it is still poorly understood why they live only in the rumen and similar environment. Because rumen protozoa require strict anaerobic conditions to sustain their viability and grow, only a few laboratories equipped with protozoology expertise and anaerobic facilities can grow rumen protozoa in laboratory. Also for the same reason, only a few species have been grown and maintained as laboratory cultures for research. Prompted by a recent study, we hypothesized that anaerobic rumen protozoa could also be cultivated aerobically if antioxidants were included in the media. Indeed, our experiments showed that the cultures of both Entodinium caudatum and Epidinium caudatum, two major rumen protozoal species, could be cultured successfully in aerobic media supplemented with ascorbic acid, glutathione and α-ketoglutarate as antioxidants. Anaerobic fermentation was maintained through the fermentation characteristics and microbial populations were altered to some extent under aerobic conditions. The antioxidants also enhanced the revival of cryopreserved stock cultures of both rumen protozoal species. The results of this study may facilitate and promote future research in which rumen protozoa need to be cultured in laboratory.