Antagonistic and Synergistic Co-Culture Activity of the Bat Microbiome

Abstract

Throughout North America, the emerging disease White-nose Syndrome (WNS) has decimated bat species (Cheng et al. 2016). The causative agent of WNS is the pathogenic fungus Pseudogymnoascus destructans. This fungus invades epidermal tissue and disrupts the physiological processes of hibernation, which leads to dehydration and starvation. Treatment options for WNS include antifungal volatiles, UV light, and antifungal bacteria from the bat microbiome. The bat microbiome is a complex mixture of different bacteria that can be assigned into two categories, the core (resident) and non-core (transient). To determine potential antagonistic or synergistic interactions with members of the microbiome we performed co-culture assays using the bacteria Staphylococcus aureus and Pseudomonas aeruginosa. An isolate was considered bioactive if it produced a zone of inhibition when singularly challenged against S. aureus or P. aeruginosa. In co-culture, if only one isolate was bioactive we assumed antagonism or synergism depending on previous single challenge activity, while if both isolates were active we assumed synergism. For S. aureus, 7/10 core and 7/10 non-core isolates produced activity in single culture, while one co-culture produced synergistic activity and 2/10 core and 3/10 non-core combinations were antagonistic. For P. aeruginosa, 3/10 core and 1/10 non-core isolates produced activity in single culture, while six co-culture combinations produced synergistic activity and 4/10 core and 5/10 non-core combinations were synergistic. The differences in assay activity between the non-core and core isolates with S. aureus and P. aeruginosa indicate probable antagonistic and synergistic activity in the bat microbiome that is likely species specific.