Exploring the Microbial Community of Shell Disease in Homarus americanus

The American lobster, Homarus americanus is an important commercial fishery in New England, and generated nearly half a billion dollars in revenue in 2012. Outbreaks of shell disease among H. americanus populations have caused a great deal of concern regarding its cause and spread. Although shell disease is not usually lethal, afflicted lobsters have an unattractive appearance and are generally unmarketable. Shell disease is hypothesized to be caused by infectious microorganisms, but no etiological agent has been identified. This project characterizes the microbial communities associated with the formation of shell disease in lobsters and how these communities change during the progression of the disease. Microbial samples were collected on lobsters at the site of a new shell disease location, as well as at 0.5, 1, and 1.5 cm away from the site. Microbial DNA was extracted from each sample, the 16S rRNA gene amplified using PCR, and sequenced using high throughput sequencing. The results showed that microbial communities on diseased lobster shells were significantly different spatially, but not temporally. The diversity of microbes was lowest at the site of shell disease, and increased with distance from the site. This work elucidated the microbial community composition of shell disease, tracked this community throughout the progression of disease, and demonstrated a gradual rather than abrupt demarcation in microbial community between symptomatic and asymptomatic shell.