Sponges have traditionally been viewed as rather unselective filter feeders, and therefore as potential biofilters to remediate microbial water pollution. Here we show that the assumed connection between the ability of sponges to feed on microbes and the potential biotechnological use of such an ability to reduce microbial pollution is more complex than assumed. In a laboratory feeding experiment combined with a transmission electron microscopy study, we assessed the potential of the marine sponge Hymeniacidon perlevis to ingest and digest 3 common pathogenic microbes occurring in coastal waters: 2 bacteria (Escherichia coli and Vibrio anguillarum), and 1 marine yeast Rhodotorula sp. All 3 microbes were ingested by the sponge, but selectively, at different rates and following different cellular mechanisms. Yeast cells were processed very atypically by the sponge. Differences in the ingestion and digestion pathways led to large differences in the effectiveness of the sponge to remove the microbes. While sponge grazing reduced the concentration of E. coli and Rhodotorula sp. to levels far below the initial values, sponges were ineffective in abating concentrations of the most infective bacterium, V. anguillarum. This bacterium, which was digested more slowly than E. coli, proliferated in the experimental flasks at much higher rates than it was grazed. These findings raise the question whether sponges are suitable for bioremediation of microbial pollution, since selective or preferential ingestion of certain bacteria by sponges may end up fueling growth of those grazed less, such as Vibrio spp.
- Microbial pollution
- Yeast digestion