Bioaugmentation against chytrid: Is it becoming a reality?

Bioaugmentation, according to Wikipedia, is “the introduction of a group of natural microbial strains or a genetically engineered variant to treat contaminated soil or water”. As was mentioned in an earlier post, bioaugmentation is one of the suggested solutions to protecting frogs from succumbing to chytridiomycosis. Before it can be employed, however, several questions need to be answered, the first of which is: Will bioaugmentation even work? A recent study has just answered this question through an experiment using redback salamanders (Plethodon cinereus), the species from which Janthinobacterium lividum (a bacteria known to inhibit Bd) was isolated.

In the experiment, soil was used as a medium to transfer the bacteria (J. lividum) to the skin of the salamanders. After the redback salamanders had been exposed to this protective bacteria, those in the experimental groups were exposed to Bd. It was found that not only was J. lividum successfully transferred to the salamander’s skin, but it also served as protection against the amphibian chytrid fungus. This suggests that soil may be a viable transfer medium for wild amphibians.

Encouraging as this information seems, the issue is more complex than it may at first appear. Soil is itself an extremely complex and variable micro environment, with different organisms colonizing it in different areas. The pH and composition of soil also varies over time and space, affecting the ability of chytrid-inhibiting bacteria such as J. lividum to colonize it. In addition, while it may temporarily colonize the soil, the bacteria may be removed over time or lose effectiveness. And then there is always the danger of introducing something novel into the environment, even if for the purposes of protecting frogs from disease. There have been plenty of cases where invasive species were introduced with good intentions, only for them to wind up running rampant. The best example of this is Kudzu, a fast-growing vine that was spread throughout the U.S. during the Great Depression to help prevent soil erosion. It has now virtually taken over the southeastern United States, out-competing native plants and sometimes blanketing entire fields. This illustrates the care that must be taken to consider all the possible variables and outcomes before using bioaugmentation of a potentially invasive organism.

I believe that we still have many more steps to take before bacteria can be applied to the environment in any sort of mass scale as protection against chytrid. More experiments using bioaugmentation in the laboratory and in controlled field settings should be performed before even considering distributing J. lividum or other inhibitory bacteria in the environment. However, if after rigorous testing, it is still found to be a plausible method, bioaugmentation may yet be the solution (or, more likely, one of many solutions) to fighting chytridiomycosis.

Frog: 3, Fungus: 3

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