The coral-killing invasive sponge, Terpios hoshinota, causes extensive mortality to live corals and is a potential threat to reefs at different geographical locations. However, to date, the invasive mechanism remains largely unknown. In this study, we aimed to understand the bacterial competition between sponge and coral hosted bacteria when sponge outcompetes corals. We analysed the bacterial community of Terpios-invaded coral tissue, and the adjacent healthy tissue of sponge-invaded Favites colonies from Palk bay reef (South East Asia) of the Indian Ocean by using next-generation sequencing. Comparative analysis revealed similar bacterial diversity in both healthy and sponge covered coral tissues. However, relative abundance found to be differed between the groups. Terpios covered coral tissue had higher bacterial abundance than the healthy coral tissue. Bacterial phyla such as Bacteroidetes, Proteobacteria, Firmicutes, Actinobacteria, and Verrucomicrobia live both in sponge covered and healthy coral tissue. Notably, many of the lower abundant bacteria in healthy coral tissue (abundance <1%) became the most abundant in sponge-invaded tissue. In particular, the genus Neisseria, Bacteroides, and members of Pseudoalteromonas predominant in sponge-invaded tissue. Similar bacterial diversity between normal and and sponge-invaded coral tissues suggest that bacteria follow an exploitative competition, which might favoured sponge growth over corals.

杀死珊瑚的侵入性海绵体（Terpios hoshinota）导致活珊瑚大量死亡，并且对不同地理位置的珊瑚礁构成潜在威胁。然而，迄今为止，侵袭性机制仍然很大程度上未知。在这项研究中，我们旨在了解海绵胜过珊瑚时，海绵和珊瑚宿主细菌之间的细菌竞争。我们分析了被Terpios侵袭的珊瑚组织的细菌群落，以及被海绵侵袭的Favites相邻的健康组织通过使用下一代测序技术，从印度洋的帕克湾礁（东南亚）获得了许多菌落。比较分析表明，健康的和海绵覆盖的珊瑚组织中细菌的多样性相似。但是，两组之间的相对丰度有所不同。Terpios覆盖的珊瑚组织比健康的珊瑚组织具有更高的细菌丰度。细菌门例如拟杆菌，变形杆菌，硬毛，放线菌和疣状微生物都生活在海绵覆盖的和健康的珊瑚组织中。值得注意的是，健康珊瑚组织中的许多低丰度细菌（丰度<1％）在海绵侵袭的组织中变得最丰富。特别是属Neisseria，Bacteroides和Pseudoalteromonas的成员主要在海绵组织中。正常和海绵侵害的珊瑚组织之间相似的细菌多样性表明细菌遵循剥削性竞争，这可能比海绵更有利于海绵的生长。