passages: PMC-2861602-sec-09__text
passages: sec
passages: Discussion
  This is the first study to employ such a large number of replicated samples in order to assess the bacterial communities of healthy and diseased corals, and the first culture-independent assessment of bacterial communities on Acroporid WS corals on the GBR. Despite the potential of not capturing rare or very low abundance bacterial ribotypes, the DGGE analysis used in this study indicated similar results of captured bacterial ribotypes and tentative bacterial species replacement in unhealthy corals to that of less replicated studies using other non-culture based techniques (e.g. [3], [54], [69]; Figure 4). The results from this research reinforce, with statistically relevant data, that corals harbour bacterial communities different to the water column [7], [9], [42], corroborate findings that corals associate only with certain specific bacterial groups, and that these coral-associated bacterial communities are 'host' species-specific [2]. The data presented here highlight a cluster of bacterial ribotypes frequently associated with corals, and the distribution of these bacterial ribotypes on healthy and diseased corals, which allows for further targeted research into a tentative link between these common coral associates and coral health. This study indicates that coral bacterial community assessments require a number of replicates per coral species and site to accurately describe the diversity present across the population and in order to draw inferences on health-related changes in the community composition. In addition, the comparisons of healthy and diseased Acropora hyacinthus samples showed that bacterial communities can change dramatically in diseased individuals. The DGGE profiles observed for corals displaying signs of White Syndrome comprised a range of bacterial ribotypes not generally found on healthy corals, including close relatives of bacteria previously found on Black Band Diseased corals. However the community profiles across the samples taken from diseased coral colonies were inconsistent and not indicative of a single bacterial causative agent.
  
  