Sequence data suggest that H.chejuensis is a versatile microorganism well suited to the marine lifestyle. The large genome contains a plethora of regulatory genes, transporter-encoding genes and those for secreted hydrolytic enzymes. The large genome size and a number of functionally redundant genes may play roles in diverse environmental conditions. Many of the niche-specific genes are situated in GIs. In addition, the presence of a list of potential virulence genes allows us to speculate that it may occupy a unique ecological position as what might be a ‘predator’ of microalgae.
The algicidal pigment, whose identity as prodigiosin was unveiled from gene mining and structural analyses, was shown to be highly effective against C.polykrikoides, a major red-tide microalga. Prodigiosin, a red pigment known for centuries, is a cytotoxic compound showing a broad range of activity (37). This tripyrrole alkaloid also induces apoptosis in human cancer cells (38). However, its activity against dinoflagellates has not been explored before. Pigments produced by marine bacteria may function as protective agents against solar radiation or protozoan grazing (39). Though the biological roles of prodigiosins in the producing organisms have not been defined, we infer that prodigiosin, as well as toxins, TTSS-delivered proteins and other virulence effectors, contributes to the pathogenic lifestyle of H.chejuensis.
Considering that clay dispersal has been the only practical management strategy (6,7), our work opens a possibility that biological control of harmful algal blooms with a microbe antagonistic to the causative organisms or its products might be feasible. Specifically, use of H.chejuensis or its bioactive substances may provide a promising alternative for controlling algal blooms caused by C.polykrikoides. The genome information gained through our study would function as a guide to understanding the bacteria–algae interactions and utilizing it for devising more rationale-based control measures. Finally, our work illustrates an example of accelerated discovery process through genomics and provides a research model in marine bioprospecting.
Sequence data, annotations and detailed information of the genome are also accessible through the Genome Encyclopedia of Microbes (GEM), http://www.gem.re.kr/.
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