Changes in sulfate-reducing bacterial populations during the onset of black band disease

Abstract

Factors that facilitate the onset of black band disease (BBD) of corals remain elusive, though anoxic conditions under the complex microbial mat and production of sulfide are implicated in necrosis of underlying coral tissues. This study investigated the diversity and quantitative shifts of sulfatereducing bacterial (SRB) populations during the onset of BBD using real-time PCR (RT-PCR) and cloning approaches targeting the dissimilatory (bi)sulfite reductase (dsrA) gene. A quantitative-PCR (qPCR) assay targeting the 16S rRNA gene also provided an estimate of total bacteria, and allowed the relative percentage of SRB within the lesions to be determined. Three Montipora sp. coral colonies identified with lesions previously termed cyanobacterial patches (CPs) (comprising microbial communities unlike those of BBD lesions), were tagged and followed through time as CP developed into BBD. The dsrA-targeted qPCR detected few copies of the gene in the CP samples (o65 per ng DNA), though copy numbers increased in BBD lesions (42500 per ng DNA). SRB in CP samples were less than 1% of the bacterial population, though represented up to 7.5% of the BBD population. Clone libraries also demonstrated a shift in the dominant dsrA sequences as lesions shifted from CP into BBD. Results from this study confirm that SRB increase during the onset of BBD, likely increasing sulfide concentrations at the base of the microbial mat and facilitating the pathogenesis of BBD.

Variability in Microbial Community Composition and Function Between Different Niches Within a Coral Reef

“…This is in accordance with previous work that has shown that different coral species harbour different microbial communities [11,19,21,22]. Furthermore, previous work has shown that the microbial communities associated with diseased corals can differ substantially to the communities associated with healthy corals [28,32,[76][77][78]. Although both samples were retrieved from above corals that appeared healthy, without any visible signs of tissue necrosis, colour loss or disease, there remains the possibility that the health status of the two sampled coral niches was different.…”

“…For instance, Vibrio species have been implicated in several coral diseases. Vibrio shiloi and Vibrio coralliilyticus have been shown to be involved in coral bleaching [2,73,74], Vibrio owensii was found to cause Montipora white syndrome [75] and a consortium of Vibrio are believed to be involved in yellow band disease [75][76][77][78][79]. However, while the roles of V. shiloi and V. coralliilyticus in bleaching has been confirmed by several studies [2,73,74], it is still not clear whether other Vibrio species found in association with diseased corals [75][76][77][78][79] are the disease-causing agent, or opportunistic colonisers that most efficiently exploit already compromised corals [70].…”

Mechanisms of direct inhibition of the respiratory sulfate-reduction pathway by (per)chlorate and nitrate

“…Quantitative PCR assay for quantifying dsrA DNA was pooled from four replicate 96-well gradient plates (B800 ml of culture) and Taqman (Life Technologies, Grand Island, NY, USA) quantitative PCR was used to quantify dsrA gene abundance using previous methods with some modifications (Leloup et al, 2007;Bourne et al, 2011;Supplementary Methods).…”

Prevalence, Insidence and Progression Black-band Disease on Scleractinian Coral (Montipora spp) in Shallow Water of Pari Islands

“…Penyakit karang diketahui mempunyai kontribusi yang signifikan terhadap menurunnya kondisi ekosistem terumbu karang (Harvell et al, 2004;Sutherland et al, 2004;Weil et al, 2006). BBD merupakan salah satu jenis penyakit karang bersifat virulen yang ditemui menyerang pada banyak jenis karang scleractinia dan merupakan salah satu penyebab kerusakan pada ekoisistem karang (Frias-lopez et al, 2004;Bourne et al, 2011). BBD hampir dapat dijumpai di seluruh ekosistem karang dunia seperti Indo-pasifik, laut karibia, samudera hindia dan atlantik.…”