BACTERIAL DIVERSITY AND ANTIBIOTIC ACTIVITY IN TEMPERATE AUSTRALIAN MARINE SPONGES

Abstract

The occurrence of permanent sponge-bacterial associations in five temperate marine sponges from Western Australia (Ircinia sp., Chondrilla australiensis, Echinodictyum clathrioides, Tethya ingalli and Coelosphaera sp.) was investigated using culturing techniques, facilitating both bacterial characterisation and subsequent screening for the presence of antimicrobial activity. Based on biochemical tests, most of the 136 bacterial isolates obtained from the sponges and surrounding water column on several occasions were tentatively identified as members of the Vibrionaceae. Fatty acid methyl ester (FAME) analysis indicated that the isolates represented a broad diversity of 32 distinct bacterial groupings. Most bacterial groups (18) were only ever found associated with sponge tissues, whilst others were found only in the water (6) or were present in the water and one or more sponges (8). For only three bacterial groups was there evidence, based on their presence in host tissues on every sampling occasion and absence from the surrounding water, of a permanent relationship with sponge hosts. One of these groups occurred consistently in three of the sponges species studied (C. australiensis, T. ingalli and Coelosphaera sp.), while the other two were consistently associated with only a single sponge species (T. ingalli and Coelosphaera sp.). Crude extracts of Coelosphaera sp. were not inhibitory to Staphylococcus aureus, but a bacterium from this sponge produced a heat labile, non-dialysable inhibitor of S. aureus. Crude extracts of three other sponge species (Ircinia sp., E. clathrioides and T. ingalli) inhibited S. aureus, but culture supernatants of the bacteria from these sponges did not. These results are discussed in terms of their contribution to understanding sponge microbial diversity and the potential for discovery of new pharmacologically active chemicals.