Microbial disease causation in marine invertebrates: problems, practices, and future prospects

Diseases of marine organisms appear to be increasing world-wide, but the causes of many of these remain a mystery. Here we outline steps that we have taken to identify various pathogens of marine invertebrates. These methods, however, rely on the successful cultivation of marine pathogens in the laboratory. Although Koch's postulates were established to generate evidence that a microorganism is the cause of an infectious disease, the limitations of these postulates in detecting microbes that are resistant to cultivation renders the sole use of them impossible in some situations. We, therefore, discuss some sensitive and comprehensive methods for detecting human-associated pathogens that can be adapted and applied to marine systems. A set of nucleic acid sequence-based approaches For establishing microbial disease causation in marine invertebrates is outlined that can be used in collaboration with traditional culture-based and histopathological methods to build a compelling case for microbial disease causation. In addition to providing potential evidence of causation, these same methods can add greatly to the current database of knowledge dealing with marine microbial communities and will ultimately enhance our understanding of emerging diseases in marine systems.