Prokaryotic diversity change with lateral progression of bioeroding sponge

Sponge-coral-microbial association has not been well established to understand the sponge invasion over coral. This study defines the microbiome of a newly classified bioeroding sponge Cliona thomasi. Interestingly, 8 genera inclusive of coral pathogens, non-coral pathogens and virulence inducers were found to be sponge specific in comparison to sediment-water. This study also defined the microbial diversity change with lateral progression (peripheral: CIM and CPM, and middle region: CMM) of sponge over coral. Both the microbial richness and abundances were found to be higher at peripheral regions compared to middle region and even showed specificity towards the infestation stage. Interestingly, the abundance of pathogenic and virulence inducers at peripheral regions were found higher than the middle region. These specialized microbial association is indicative of sponge-commensals pathogenicity induction against coral by their invasion directly or through physical intrusion by sponge’s spicules. The associated virulence inducers and even the coral mucus may provide favourable support for them to increase their cell densities to the levels of pathogenicity. Such mechanism of coral health deterioration may opportunistically benefit sponge infestation. This study therefore hypothesize that the specialized microbial cross talks at peripheral regions of sponge may be supportive for their lateral progression over corals.