Invasive bacterial species can transform microbial communities and may benefit by outcompeting native species of that community by disrupting the roles of that community in the ecosystem. However, these often-non-motile organisms may be dispersal-limited. One possible mechanism for bacterial dispersal is co-invasion with above-ground consumers which feed upon bacteria that perform key ecological roles in terrestrial ecosystems. One such consumer is the terrestrial slug. Due in large part to accidental transport and introduction in conjunction with the transport of live plants, slug invasion is a problem worldwide, including in the United States. In addition to slug-dispersed bacterial interruption of native soil bacterial communities, these dispersed bacteria may also cause concern for human health or agricultural crops. To determine which bacteria may be dispersed by slugs, we performed bacterial microbiome analyses and DNA extractions of 10 Lehmannia valentiana slugs, an invasive slug species in California. Using PCR, we amplified the 16S rRNA region and sequenced with the Illumina MiSeq system. We also exposed sterile microcosm environments to slugs and determined whether slugs disperse bacteria to previously sterile environments.
Slug bacterial microbiomes varied between individuals such that no two slug bacterial microbiomes were identical. However, there was a high degree of overlap between bacterial communities of the specimens. We also found that slugs can disperse ecologically relevant bacteria to a previously sterile environment. For instance, bacteria dispersed in our microcosms from the slugs include Clavibacter, which causes economic damage in tomato and potato, Rhodoccoccus fascians, a plant pathogen which causes leafy gall disease in a variety of plants, Erwinia, a genus containing mostly plant pathogenic species and Pseudomonas viridiflava, which causes crown rot, root rot, and leaf blight on a variety of plant hosts. Prior to this study, little was known about slug bacterial dispersal and information regarding slug bacterial microbiomes, which could provide valuable information for biocontrol studies and address questions regarding possible disturbances to native bacterial soil communities. Moreover, this study provides evidence for the potential of slugs to disperse bacteria. This novel study investigated invasive California slug populations and documented the ability of slugs to transfer bacteria while providing critical information about their bacterial microbiome.