Abstract
Roseofilum reptotaenium is a gliding, filamentous, phycoerythrin-rich cyanobacterium that has been found only in the horizontally migrating, pathogenic microbial mat, black band disease (BBD) on Caribbean corals. R. reptotaenium dominates the BBD mat in terms of biomass and motility, and the filaments form the mat fabric. This cyanobacterium produces the cyanotoxin microcystin, predominately MC-LR, and can tolerate high levels of sulfide produced by sulfate reducing bacteria (SRB) that are also associated with BBD. Laboratory cultures of R. reptotaenium infect coral fragments, suggesting that the cyanobacterium is the primary pathogen of BBD, but since this species cannot grow axenically and Koch’s Postulates cannot be fulfilled, it cannot be proposed as a primary pathogen. However, R. reptotaenium does play several major pathogenic roles in this polymicrobial disease. Here, we provide an overview of the ecology of this coral pathogen and present new information on R. reptotaenium ecophysiology, including roles in the infection process, chemotactic and other motility responses, and the effect of pH on growth and motility. Additionally, we show, using metabolomics, that exposure of the BBD microbial community to the cyanotoxin MC-LR affects community metabolite profiles, in particular those associated with nucleic acid biosynthesis.
Highlights
IntroductionDoes appear to play an important role in a polymicrobial disease that infects and can kill a eukaryotic host
We present additional new information about the biology of Roseofilum reptotaenium to further define the role of this black band disease (BBD) cyanobacterium, and the cyanotoxin that it produces, in the polymicrobial BBD
As the ring progressed to the edges of the coral fragments coral tissue was lysed exposing the underlying coral skeleton (Plates C and D of Figure 3). These results are in agreement with those of use of R. reptotaenium strain 100.1 to infect fragments of the host coral Siderastrea siderea [18]
Summary
Does appear to play an important role in a polymicrobial disease that infects and can kill a eukaryotic host. This is the predominant cyanobacterium associated with black band disease (BBD) of corals. BBD was first observed on scleractinian (stony) corals in the Caribbean in the 1970s [3]. It has since spread worldwide and is globally distributed on tropical and sub-tropical reefs throughout the Pacific and Atlantic Oceans and the Red Sea [4] and has expanded its range throughout the wider
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