Probiotic bioaugmentation of an anti-Bd bacteria, Janthinobacterium lividum, on the amphibian, Notophthalmus viridescens: Transmission efficacy and persistence of the probiotic on the host and non-target effects of probiotic addition on ecosystem components

Amphibians worldwide are threatened by the fungal disease chytridiomycosis, caused by the skin pathogen Batrachochytrium dendrobatidis. Mutualistic skin bacteria are a critical element in amphibians’ defenses against chytridiomycosis. Probiotic bioaugmentation of beneficial, anti-Bd bacteria on amphibians is a potential conservation strategies. Outdoor experimental ponds were used to investigate transmission efficacy and persistence of the anti-Bd bacteria, Janthinobacterium lividum, on the amphibian, Notophthalmus viridescens. More specifically, this research investigated whether a short-term individual bath, environmental bioaugmentation, or both are necessary to afford transmission and persistence of J. lividum on N. viridescens. Additionally, this research investigated the effectiveness of these different probiotic bioaugmentation methods in ameliorating Bd infection in N. viridescens. Lastly, this research investigated the non-target effects of J. lividum on leaf decomposition, periphyton production, and zooplankton. Bd introduction into the experimental ponds was successful, and infection of newts occurred as expected; however, morbidity effects associated with Bd did not occur, and no probiotic treatment reduce Bd prevalence or increase proportional change in Bd loads below the levels found in the Bd only treatment. Interestingly, the bath+water (combination of individual bath of the amphibian and environmental bioaugmentation) treatment did reduce morbidity and Bd prevalence in comparison to the bath only treatment and water only treatment. This was likely associated with the transmission efficacy and persistence of J. lividum on the newts being greater in the bath+water treatment. These results suggest that the ideal treatment method to afford probiotic establishment and persistence on the host may be the combination of a probiotic bath and environmental bioaugmentation. Furthermore, alternations to leaf decomposition, periphyton production, or zooplankton community structure were observed as a result probiotic treatments. Therefore, probiotic conservation strategies may be unlikely to harm other organisms and disrupt ecosystem processes; however, additional studies are required before treatment of natural environments is conducted. Developing an understanding of the transmission and persistence of probiotic bacteria is crucial for determining how to administer them to amphibians effectively and efficiently. Probiotic bioaugmentation is a new conservation frontier that requires continued research in order to develop effective and efficient methods for combating the amphibian fungal disease chytridiomycosis.