To gain insight into the species richness and phylogeny of the microbial communities associated with sponges in mangroves, we performed an extensive phylogenetic analysis, based on terminal restriction fragment length polymorphism profiling and 16S ribosomal RNA gene sequences, of the 4 sponge species Aplysina fulva, Haliclona hogarthi, Tedania ignis and Ircinia strobilina as well as of ambient seawater. The sponge-associated bacterial communities contained 13 phyla, including Poribacteria and an unclassified group not found in the ambient seawater community, 98% of which comprised Proteobacteria, Cyanobacteria and Bacteroidetes. Although the sponges themselves were phylogenetically distant and bacterial community variation within the host species was observed, microbial phyla such as Proteobacteria, Acidobacteria, Chloroflexi and the unclassified group were consistently observed as the dominant populations within the communities. The sponge-associated bacterial communities resident in the Caribbean Sea mangroves are phylogenetically similar but significantly distinct from communities found in other biogeographical sites such as the deep-water environments of the Caribbean Sea, the South China Sea and Australia. The interspecific variation within the host species and the distinct biogeographical characteristics that the sponge-associated bacteria exhibited indicate that the acquisition, establishment and formation of functional sponge-associated bacterial communities may initially be the product of both vertical and horizontal transmission, and is then shaped by the internal environment created by the sponge species and certain external environmental factors.
KEY WORDS: Sponge · Bacterial diversity · Community composition · 16S rRNA · T-RFLP · MangroveResale or republication not permitted without written consent of the publisher Aquat Microb Ecol 62: 231-240, 2011 multiply and gradually establish themselves within the sponge mesohyl (Taylor et al. 2007a,b). The establishment of this relationship relies on mutual recognition between the sponge and its microbial partners, and also on physical competition among the microbial communities themselves (Wilkinson 1984, Müller & Müller 2003, Müller et al. 2004). In accordance with this hypothesis, sponges inhabiting the same ecological niche tend to harbor similar microbial communities. The vertical transmission of specific microbes from parent to progeny in sponges is another mechanism that has been reported recently (Usher et al. 2001, Enticknap et al. 2006, Schmitt et al. 2007, Sharp et al. 2007, Lee et al. 2009). In this scenario, a sponge is colonized by an ancestral strain, and the microbes then evolve to become specific to that sponge, thereby exhibiting spatial and temporal stability. Thus, there may be consistent communities of sponge-associated bacteria not altered by changes of environment (Hentschel et al. 2002, Lee et al. 2006.Recent surveys contradict the existence of a general uniform sponge-associated microbial community regardless of sponge ...