Bacterial Communities Associated with Porites White Patch Syndrome (PWPS) on Three Western Indian Ocean (WIO) Coral Reefs

Abstract

The scleractinian coral Porites lutea, an important reef-building coral on western Indian Ocean reefs (WIO), is affected by a newly-reported white syndrome (WS) the Porites white patch syndrome (PWPS). Histopathology and culture-independent molecular techniques were used to characterise the microbial communities associated with this emerging disease. Microscopy showed extensive tissue fragmentation generally associated with ovoid basophilic bodies resembling bacterial aggregates. Results of 16S rRNA sequence analysis revealed a high variability between bacterial communities associated with PWPS-infected and healthy tissues in P. lutea, a pattern previously reported in other coral diseases such as black band disease (BBD), white band disease (WBD) and white plague diseases (WPD). Furthermore, substantial variations in bacterial communities were observed at the different sampling locations, suggesting that there is no strong bacterial association in Porites lutea on WIO reefs. Several sequences affiliated with potential pathogens belonging to the Vibrionaceae and Rhodobacteraceae were identified, mainly in PWPS-infected coral tissues. Among them, only two ribotypes affiliated to Shimia marina (NR043300.1) and Vibrio hepatarius (NR025575.1) were consistently found in diseased tissues from the three geographically distant sampling localities. The role of these bacterial species in PWPS needs to be tested experimentally.

Identification of a bacterial pathogen associated with Porites white patch syndrome in the Western Indian Ocean

“…These bacteria were selected for three reasons: (i) they were present only in diseased tissues from the two sites (Mayotte and Reunion Island, this study), and/or (ii) they were highlighted as potential pathogens in our previous study (samples from three geographical locations (Séré et al . ), and/or (iii) have been identified as putative pathogens in previous studies (Austin et al . ; Boyett ; Cervino et al .…”

“…We used the Shimodaira–Hasegawa test (SH‐test) implemented in RAxML (Stamatakis ) to test whether the bacterial isolate haplotype used in ‘phase 2’ formed a monophyletic group with V. hepatarius (the original proposed pathogen see Séré et al . () and compared the likelihood scores of the best tree reconstructed without constraint, vs. the best tree obtained under the monophyly constraint.…”

“…Furthermore, two potential pathogens closely related to Shimia marina and Vibrio hepatarius were encountered in PWPS using nonculture molecular screening methods (Séré et al . ). We have expanded on this initial study with the intention of isolating and identifying a suite of potential pathogens associated with PWPS by combining traditional culture methods, molecular techniques and experimental infection trials.…”

“…Ovoid basophilic bodies (resembling bacterial aggregates) have been reported associated with the disease lesion interface (Séré et al . ) and were more commonly associated with the area of tissue fragmentation, suggesting their potential role in PWPS aetiology. However, they could not be directly linked with the pathology as there was no clear evidence of inflammatory response or tissue lysis associated with these ovoid bodies.…”

“…We attempted to do this in one of the more recently described WS diseases, Porites white patch syndrome (PWPS) (Séré et al . , ), which to date only appears to affect Porites lutea in the Western Indian Ocean (Fig. ).…”