Microbes Enriched in Seawater after Addition of Coral Mucus

We investigated which microbial taxa in coastal Red Sea water were stimulated by addition of mucus from the coral Fungia sp. Decreases in the concentration and C/N ratio of particulate organic material during short-term incubations (50 h) were paralleled by a steep rise in the number of Gammaproteobacteria, particularly Alteromonadaceae, followed by Vibrionaceae. Two almost identical genotypes affiliated with Alteromonas macleodii accounted for up to >85% of all Alteromonadaceae (45% of the total cells) in the mucus-amended enrichments but were rare in unamended control incubations and in ambient seawater. A. macleodii-like bacteria might thus be important in the transfer of organic carbon from coral mucus to the pelagic microbial food webs of coral reefs.