In a symbiotic host system, collagen degradation could benefit the bacteria, but would be harmful for the eukaryotic host. Using a polyphasic approach, we investigated the presence of

collagenolytic activity in the bacterial community hosted by the marine sponge Cymbastela concentrica. Functional screening for collagenase activity using metagenomic library clones (227 Mbp) and cultured isolates of sponge’s bacterial community, as well as bioinformatic analysis of metagenomic shotgun-sequencing data (106 679 predicted genes) were used. The results show that the abundant members of the bacterial community contain very few genes encoding for collagenolytic enzymes, while some low-abundance learn more sponge isolates possess collagenolytic activities. These findings indicate that collagen is not a preferred nutrient source for the majority of the members of the bacterial community associated with healthy C. concentrica, and that some low-abundance bacteria have collagenase activities that have the potential to harm the sponge through tissue degradation. Collagen is the major component of extracellular matrices of all metazoan life and represents an important protein conferring integrity and the physical form of eukaryotic organisms

(Harrington, 1996; Exposito et al., 2008). Sponges are among the oldest Metazoa and often contain collagen, which is either dispersed as AC220 thin fibrils or organized as bundles, termed spongin, in the intercellular matrix (Simpson, 1984; Brusca & Brusca, 1990). The expression of collagen is known to be essential for the development and structural integrity of sponges (Garrone et al., 1975; Shimizu & Yochizato, 1993; Krasko et al., 2000). Sponges harbour specific bacterial communities in different

cellular compartments, often for an extended period of time, and hence close associations between the microorganisms and the sponge host have been established (Taylor et al., 2007). Collagen is an essential and abundant part of the internal mesohyl structure of most sponges Liothyronine Sodium (and in particular the Demospongia), where many microorganisms reside. As a rich source of nitrogen and carbon, collagen could provide nutrients for the sponge-associated microorganisms, and this may potentially have implications for the structural integrity of the host. A few cases of sponge diseases have been attributed to the presence of bacterial pathogens (Gaino & Pronzato, 1989; Webster et al., 2002; Mukherjee et al., 2009) and collagenolytic enzymes have been speculated to lead to tissue necrosis in sponges. Generally, bacterial collagenases, including the well-characterized enzymes from Clostridium sp. (Matsushita et al., 1994) and Vibrio sp. (Yu & Lee, 1999; Vaitkevicius et al., 2008), have been linked to pathogenicity and are regarded as virulence factors in human disease.