Impact of Alliaria petiolata, a non-native plant species, on soil microbial diversity

Background/Question/Methods The flora of America is in danger due to competition from nonnative, invasive plants. These plants commandeer the space and nutrients of the native species. One such invasive species is garlic mustard (Alliaria petiolata), a European import that is a member of the Brassicaceae family. The climate conditions in the US and the lack of natural herbivores favor the growth of garlic mustard. One hypothesis explaining how invasive species can gain an advantage is that the invader selectively alters the soil microbial diversity. Such a change may favor the growth of the invasive while retarding native species growth. The goal of this study is to identify the microbes associated with garlic mustard. DNA was isolated from soil in the rhizosphere of A. petiolata and from non-invaded soil. The 16s rDNA signature sequences were amplified as a first step toward detecting the different microbial species. The amplified sequences were ligated to cloning vector DNA and transformed into Escherichia coli. Bioinformatic analysis of the cloned inserts sequences with the Ribosomal Database Project II afforded a snapshot of the associated bacteria. Results/Conclusions Twenty-one sequences derived from non-invaded soil (NGM) and twenty-nine sequences from soil invaded by A. petiolata (GM) were analyzed. The results were notable in that 30% of the GM soil sequences grouped with the phylum Verrucomicrobia. Members of this phylum appeared to be absent in non-invaded soil. Results from the ClustalW analysis of the nine Verrucomicrobia sequences suggest that each sequence was derived from a separate organism with a unique sequence. Verrucomicrobiae appear to be widely distributed in soils but little is known of their physiology. These results suggest that garlic mustard plays a role in selectively altering the soil bacterial diversity.