Australian Subtropical White Syndrome (ASWS) is an infectious, temperature dependent disease of the subtropical coral
Turbinaria mesenterina involving a hitherto unknown transmissible causative agent. This report describes significant
changes in the coral associated bacterial community as the disease progresses from the apparently healthy tissue of ASWS
affected coral colonies, to areas of the colony affected by ASWS lesions, to the dead coral skeleton exposed by ASWS. In an
effort to better understand the potential roles of bacteria in the formation of disease lesions, the effect of antibacterials on
the rate of lesion progression was tested, and both culture based and culture independent techniques were used to
investigate the bacterial communities associated with colonies of T. mesenterina. Culture-independent analysis was
performed using the Oligonucleotide Fingerprinting of Ribosomal Genes (OFRG) technique, which allowed a library of 8094
cloned bacterial 16S ribosomal genes to be analysed. Interestingly, the bacterial communities associated with both healthy
and disease affected corals were very diverse and ASWS associated communities were not characterized by a single
dominant organism. Treatment with antibacterials had a significant effect on the rate of progress of disease lesions
(p = 0.006), suggesting that bacteria may play direct roles as the causative agents of ASWS. A number of potential
aetiological agents of ASWS were identified in both the culture-based and culture-independent studies. In the cultureindependent study an Alphaproteobacterium closely related to Roseovarius crassostreae, the apparent aetiological agent of
juvenile oyster disease, was found to be significantly associated with disease lesions. In the culture-based study Vibrio
harveyiwas consistently associated with ASWS affected coral colonies and was not isolated from any healthy colonies. The
differing results of the culture based and culture-independent studies highlight the importance of using both approaches in
the investigation of microbial communities