Abstract
The Caribbean spiny lobster, Panulirus argus, is found throughout the Florida Keys and Dry Tortugas. In 1998, lobsters were discovered with small black, necrotic lesions on the carapace some associated with trauma. Since then the number of occurrences of shell disease has increased, a potential problem for the lobster fishery in the southeast. In an effort to determine the etiology of shell disease, bacterial samples were obtained from healthy and diseased lobsters from 28 different locations in the Florida Keys and Dry Tortugas. DNA fingerprinting of the 16s-23s rRNA intergene region (IGR) placed 487 isolates into five major groups of gamma-Proteobacteria, one group of Gram-positive organisms, and individuals of low occurrence were placed in an “Other” group. Sequencing of the 16s rRNA gene and GenBank BLAST analysis identified the genus Erwinia was the second largest group that consisted of 89 isolates. Out of the 89 isolates, 88 were identified as Erwinia cypripedii. The E. cypripedii sequences were aligned with sequences from known strains of marine bacteria; members of the Erwinia, Brenneria, Pectobacterium, Pantoea genera; and other members from the gamma-Proteobacteria group. After performing phylogenetic analyses using the program PAUP*, the lobster isolates were placed into a monophyletic group distinct from, but closely related to, E. cypripedii. Erwinia spp. are normally associated with plants and rotting vegetation, and therefore, not seen in a marine environment especially on the carapace of an invertebrate. Since the isolates showed little diversity by 16S rRNA analysis, two protein coding genes, recombinase A (recA) and recombination-dependent growth C (rdgC), were picked to further analyze the Erwinia isolates. Once again the recA and rdgC gene sequences showed very little diversity among the isolates. Each isolate was also screened for extracellular enzyme production to see if they could break down proteins, lipids, and/or chitin, to establish a possible pathogenic role.
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