N-127. Environmental Persistence of the Elkhorn Coral Pathogen PDL-100 (Serratia marcescens)
The persistence and survival of Serratia marcescens in the marine environment is largely unknown, despite the fact that it is among only 5 identified and confirmed coral pathogens. The environmental strain, PDL-100, which was found to cause white pox disease in the threatened elkhorn coral, Acropora palmata, in 2002 by Patterson et al., is speculated to originate from improperly treated sewage in the Florida Keys, and therefore would need to persist in marine conditions to cause infection or has adapted to the marine environment. This study investigates basic questions related to the fitness of PDL-100 in seawater and coral mucus which may lead to better understanding of the disease dynamics of white pox. Microcosm conditions of natural seawater, mucus from the coral species’ Acropora palmata, Montastraea faveolata, and Siderastrea siderea were used to test the decay rates of PDL-100. We found a significant difference when comparing the survival rate of S. marcescens in these different environments. PDL-100 survival ranged from16 hours in seawater to 96 hours in S. siderea mucus. Persistence was only significantly enhanced in S. siderea mucus (p=0.0009), but survival varied for all coral species. M. faveolata mucus enhanced the survival of PDL-100 up to 48 hours (p=0.0034). Interestingly, survival of PDL-100 was not enhanced in A. palmata mucus; its survival time was only 12 hours, suggesting that other coral species could act as reservoirs for this pathogen on the reef.