Differences in soil bacterial diversity after treatment with benzyl isothiocyanate, an allelopathic secondary metabolite derivative of Alliaria petiolata (garlic mustard)

The species, Alliaria petiolata (garlic mustard), has overtaken the understory of North American forests for over a century, but how the plant has become invasively successful is not well understood. There is some indication that the secretion and breakdown of its allelopathic metabolic compounds, known as glucosinolates, contribute to its success. Benzyl isothiocyanate, an end product of garlic mustard glucosinolate breakdown, has been found in previous studies to inhibit seed germination and the growth of certain mycorrhizal fungi species. Soil bacterial communities, in addition to fungi, play an important role in the surrounding abiotic and biotic environment. This study aims to better understand the effect garlic mustard and benzyl isothiocyanate might have on the surrounding bacterial communities. Soil samples were collected from two locations, one where garlic mustard was present and one where the plant was not present. The samples collected from each location were divided into a treatment group with benzyl isothiocyanate and a control group. Bacterial DNA extracted from each of the four experimental groups was amplified and sequenced at the V3-V4 16S rRNA region. Alpha and beta diversity, as well as OTU abundance were analyzed using QIIME2 software and two-way statistical analyses. Significant differences in bacterial diversity were only observed for experimental groups based on location from where the soil samples were derived. Except for one bacteria taxon, there were no significant differences in bacterial diversity or abundance observed between treatment groups. A significant difference of an interaction between treatment and location of the experimental groups was not found. More studies of the effects garlic mustard’s glucosinolate derivates have on the microbial environment need to be conducted