AME 24:9-16 (2001)  -  doi:10.3354/ame024009

Antimicrobial activity of the reef sponge Amphimedon viridis from the Red Sea: evidence for selective toxicity

Dovi Kelman1,2,*, Yoel Kashman3, Eugene Rosenberg4, Micha Ilan1, Ilan Ifrach1, Yossi Loya1,2

1Department of Zoology, George S. Wise Faculty of Life Sciences,
2National Center for High Throughput Screening (HTS) of Novel Bioactive Compounds,
3School of Chemistry, and
4Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel

ABSTRACT: Living benthic marine organisms such as sponges and corals are frequently colonized by bacteria that may be pathogenic to them. One of the means by which they are able to combat microbial attack is by chemical defense. We tested the activity of crude organic extracts of 11 dominant Red Sea reef sponges against a panel of bacteria isolated from their natural environment. Amphimedon viridis (Keller) exhibited the highest antimicrobial activity. Bioassay-directed fractionation resulted in the isolation of an active fraction that contained a purified mixture of halitoxin and amphitoxin, which are highly bioactive pyridinium alkaloids. These compounds showed selective activity against specific bacteria rather than being of a broad spectrum. They were highly active against 8 strains of bacteria isolated from the seawater surrounding these sponges, whereas 6 different bacterial strains associated with the sponge A. viridis were resistant to these compounds. This selective toxicity may be important in enabling certain bacteria to live in close association with their sponge host while it maintains a chemical defense against microbial pathogenesis.

KEY WORDS: Antimicrobial activity · Chemical defense · Sponges · Marine bacteria · Amphimedon · Halitoxin · Secondary metabolites · Red Sea

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