Antibacterial Activity of Marine and Black Band Disease Cyanobacteria against Coral-Associated Bacteria

Miroslav Gantar,Aaron W Miller,Dina Stanić,Laurie L Richardson,Longin T Kaczmarsky

doi:10.3390/md9102089

Abstract

Black band disease (BBD) of corals is a cyanobacteria-dominated polymicrobial disease that contains diverse populations of heterotrophic bacteria. It is one of the most destructive of coral diseases and is found globally on tropical and sub-tropical reefs. We assessed ten strains of BBD cyanobacteria, and ten strains of cyanobacteria isolated from other marine sources, for their antibacterial effect on growth of heterotrophic bacteria isolated from BBD, from the surface mucopolysaccharide layer (SML) of healthy corals, and three known bacterial coral pathogens. Assays were conducted using two methods: co-cultivation of cyanobacterial and bacterial isolates, and exposure of test bacteria to (hydrophilic and lipophilic) cyanobacterial cell extracts. During co-cultivation, 15 of the 20 cyanobacterial strains tested had antibacterial activity against at least one of the test bacterial strains. Inhibition was significantly higher for BBD cyanobacteria when compared to other marine cyanobacteria. Lipophilic extracts were more active than co-cultivation (extracts of 18 of the 20 strains were active) while hydrophilic extracts had very limited activity. In some cases co-cultivation resulted in stimulation of BBD and SML bacterial growth. Our results suggest that BBD cyanobacteria are involved in structuring the complex polymicrobial BBD microbial community by production of antimicrobial compounds.

Highlights

Black band disease (BBD) of corals is known to contribute to the degradation of coral reefs in the wider Caribbean [1], the Indo-Pacific [2], including the Great Barrier Reef [3], and the Red Sea [4]
Seven BBD cyanobacteria were active against both BBD and surface mucopolysaccharide layer (SML) bacteria, while only three of the other marine cyanobacteria were active against both groups
Our results indicate that both pathogenic (BBD) and non-pathogenic marine cyanobacteria can affect the growth of coral-associated bacteria, and that while most of this activity is manifested as inhibition of growth, growth stimulation occurs

Summary

Introduction

Black band disease (BBD) of corals is known to contribute to the degradation of coral reefs in the wider Caribbean [1], the Indo-Pacific [2], including the Great Barrier Reef [3], and the Red Sea [4]. BBD is a dark, well-defined cyanobacterial mat that forms a band, which moves across the coral surface, degrading coral tissue and leaving behind bare coral skeleton. It is a polymicrobial disease dominated by non-heterocystous filamentous cyanobacteria and contains populations of sulfate-reducing bacteria, sulfide-oxidizing bacteria, and heterotrophic bacteria.

Results

Discussion

Conclusion