Novel Microbial Structures Of The Invasive Hawaiian Sponge Mycale Armata

Invasive species are one of the greatest threats to world's marine ecosystems. As a dominant element of biomass in tropical coral reefs, sponges alone account for about half of introduced marine species in the Hawaiian reef ecosystems. Although marine invertebrate symbionts are well-known to significantly impact on habitat range, ecological behavior, and ecosystems, microbial diversity of invasive marine species is virtually unknown. Mycale armata is intentionally introduced into Hawaii and represents a serious environmental threat to local corals and other marine species because it can overgrow and kill the native coral species. In this study, cultivation- dependent and–independent approaches were applied for studying microbial communities of the sponge M. armata. The members of the microbial community belonged to two domains (bacteria and archaea) and 7 phyla: Proteobacteria (α-,γ-, andδ-Proteobacteria), Firmicutes, Actinobacteria, Bacteroidetes, Crenarchaeota, Cyanobacteria, and one unclassified. The cultured bacteria were representatives of Firmicutes and Proteobacteria (α- andδ-Proteobacteria), but dominated by the Bacillus group of the Low G+C gram-positive groups. Clone sequences of the 16S rRNA library were affiliated with quite diverse phylogenetic groups and were dominated by Proteobacteria (classesα-,γ-, andδ-Proteobacteria), which accounted for 86% of the total clones. Theα-proteobacteria accounted for 75% of the total sequences in the 16S rRNA gene library. Of the microbial groups in M. armata, alphaproteobacteria were, for the first time, reported to be a dominant group in the 16S rRNA gene library of marine sponges. Pathogens Shigella boydii, Candida parapsilosis, Lacazia loboi, and Aspergillus sydowii were recovered from M. armata. To the best of the author's knowledge, this is the first report of pathogens in marine sponges. Coral bleaching has been observed in Kaneohe bay, but no coral disease associated with these pathogens has been reported. DGGE profiles revealed that the microbial structure of M. armata was significantly different from that of the non-invasive sponge Subrites zeteki. Compared to the sequencing of the 16S rRNA gene clone libraries and DGGE sub-clone libraries, this is the first report of the discrepancy among these molecular methods in investigation of sponge-associated microbial consortia. This study revealed a novel, but unique, microbial structure and composition within M. armata and is the first report of microbial diversity of this invasive marine species. Further investigation of the above microbial groups should lead to insight into the underlying mechanism of the invasive nature of M. armata.