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Sulfide, microcystin, and the etiology of black band disease.

ABSTRACT: Black band disease (BBD) consists of a cyanobacterial-dominated, sulfide-rich microbial mat that migrates across coral colonies, degrading coral tissue. The mat contains diverse bacteria that include photoautotrophs (cyanobacteria), sulfate-reducers, sulfide-oxidizers, and organoheterotrophs. BBD sulfate-reducers contribute to BBD pathobiology by production of sulfide, which causes coral tissue lysis and death, and the cyanotoxin microcystin is produced by BBD cyanobacteria. Here we used a model system of coral fragments to investigate the roles of sulfide and microcystin in BBD by exposure to the metabolic inhibitors sodium molybdate and 3-(3', 4'-dichlorophenyl)-1, 1-dimethylurea (DCMU), which inhibit sulfate reduction and oxygenic photosynthesis, respectively. Exposure of BBD inocula to sodium molybdate prior to inoculation prevented infection of healthy fragments but did not prevent continued band migration and coral tissue lysis by active BBD infections. Exposure to DCMU did not inhibit either the initiation of BBD or continued migration of active BBD. Exposure of healthy coral fragments to sulfide, purified microcystin, and a combination of both revealed that both microcystin and sulfide are toxic to coral and act synergistically. Measurement of growth of bacteria isolated from BBD and the healthy coral surface mucopolysaccharide layer (SML) during exposure to microcystin revealed that growth of relatively more BBD than SML isolates was stimulated, although effects were not uniform and the majority exhibited no effect. Our results indicate that sulfide is required for initiation of BBD, both microcystin and sulfide are involved in BBD pathobiology, and microcystin may structure the BBD bacterial community.

SUBMITTER: Richardson LL

PROVIDER: S-EPMC3518071 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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Sulfide, microcystin, and the etiology of black band disease.

Richardson Laurie L LL Miller Aaron W AW Broderick Emily E Kaczmarsky Longin L Gantar Miroslav M Stanić Dina D Sekar Raju R

Diseases of aquatic organisms 20091101 1-2

Black band disease (BBD) consists of a cyanobacterial-dominated, sulfide-rich microbial mat that migrates across coral colonies, degrading coral tissue. The mat contains diverse bacteria that include photoautotrophs (cyanobacteria), sulfate-reducers, sulfide-oxidizers, and organoheterotrophs. BBD sulfate-reducers contribute to BBD pathobiology by production of sulfide, which causes coral tissue lysis and death, and the cyanotoxin microcystin is produced by BBD cyanobacteria. Here we used a model ...[more]

PMID: 20095243

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Project description:BackgroundTransmission mechanisms of black-band disease (BBD) in coral reefs are poorly understood, although this disease is considered to be one of the most widespread and destructive coral infectious diseases. The major objective of this study was to assess transmission mechanisms of BBD in the field based on the spatio-temporal patterns of the disease.Methodology/principal findings3,175 susceptible and infected corals were mapped over an area of 10x10 m in Eilat (northern Gulf of Aqaba, Red Sea) and the distribution of the disease was examined monthly throughout almost two full disease cycles (June 2006-December 2007). Spatial and spatio-temporal analyses were applied to infer the transmission pattern of the disease and to calculate key epidemiological parameters such as (basic reproduction number). We show that the prevalence of the disease is strongly associated with high water temperature. When water temperatures rise and disease prevalence increases, infected corals exhibit aggregated distributions on small spatial scales of up to 1.9 m. Additionally, newly-infected corals clearly appear in proximity to existing infected corals and in a few cases in direct contact with them. We also present and test a model of water-borne infection, indicating that the likelihood of a susceptible coral becoming infected is defined by its spatial location and by the relative spatial distribution of nearby infected corals found in the site.Conclusions/significanceOur results provide evidence that local transmission, but not necessarily by direct contact, is likely to be an important factor in the spread of the disease over the tested spatial scale. In the absence of potential disease vectors with limited mobility (e.g., snails, fireworms) in the studied site, water-borne infection is likely to be a significant transmission mechanism of BBD. Our suggested model of water-borne transmission supports this hypothesis. The spatio-temporal analysis also points out that infected corals surviving a disease season appear to play a major role in the re-introduction of the disease to the coral community in the following season.

Dataset Information

Sulfide, microcystin, and the etiology of black band disease.

Publications

Sulfide, microcystin, and the etiology of black band disease.

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