Characterisation of the bacterial and fungal communities associated with different lesion sizes of Dark Spot Syndrome occurring in the Coral Stephanocoenia intersepta

摘要

The number and prevalence of coral diseases/syndromes are increasing worldwide. Dark Spot Syndrome (DSS) afflictsudnumerous coral species and is widespread throughout the Caribbean, yet there are no known causal agents. In this studyudwe aimed to characterise the microbial communities (bacteria and fungi) associated with DSS lesions affecting the coraludStephanocoenia intersepta using nonculture molecular techniques. Bacterial diversity of healthy tissues (H), those in advanceudof the lesion interface (apparently healthy AH), and three sizes of disease lesions (small, medium, and large) variedudsignificantly (ANOSIM R = 0.052 p,0.001), apart from the medium and large lesions, which were similar in their communityudprofile. Four bacteria fitted into the pattern expected from potential pathogens; namely absent from H, increasing inudabundance within AH, and dominant in the lesions themselves. These included ribotypes related to Corynebacteriumud(KC190237), Acinetobacter (KC190251), Parvularculaceae (KC19027), and Oscillatoria (KC190271). Furthermore, two Vibrioudspecies, a genus including many proposed coral pathogens, dominated the disease lesion and were absent from H and AHudtissues, making them candidates as potential pathogens for DSS. In contrast, other members of bacteria from the sameudgenus, such as V. harveyii were present throughout all sample types, supporting previous studies where potential coraludpathogens exist in healthy tissues. Fungal diversity varied significantly as well, however the main difference betweenuddiseased and healthy tissues was the dominance of one ribotype, closely related to the plant pathogen, Rhytisma acerinum,uda known causal agent of tar spot on tree leaves. As the corals’ symbiotic algae have been shown to turn to a darkerudpigmented state in DSS (giving rise to the syndromes name), the two most likely pathogens are R. acerinum and theudbacterium Oscillatoria, which has been identified as the causal agent of the colouration in Black Band Disease, anotherudwidespread coral disease.