Seminar Details

Sponge-associated bacteria: Towards culturing the uncultured




Adi Lavi - Dept. of Zoology, Tel Aviv University


Most sponges (phylum Porifera) contain rich bacterial community within their bodies and therefore are considered holobionts. The essence of symbiotic relationship between the sponge and its associated microorganisms is not fully understood. The Red-Sea coral-reef sponge Theonella swinhoei, contains many natural products. Some of these compounds inhibit cancer cells growth, while others are active against bacteria and fungi. The source of most of these compounds are the symbiotic bacteria within the sponge, while the source of others is yet unknown. To this day, only a small subset of all symbiotic bacteria from sponges were cultured in the laboratory. The most common culturing conditions are aimed at isolating marine bacteria, but do not resemble the natural habitat of sponge-associated bacteria. The hypothesis of the current study was that in order to expand the pool of culturable sponge--associated bacteria, and which could be used as a source for natural products, the physical conditions within the sponge should be studied and defined. Using this information, new culturing conditions were designed, allowing isolation of many sponge-associated bacteria. Several isolates were identified as producers of anti-bacterial and anti-fungi compounds. As part of this study the dissolved-oxygen (DO) concentration was measured inside the sponge body in-natura for 24-48 hours. Results show that the inner environment of the sponge is constantly sub-saturated. Moreover, it was found that DO concentration changes temporally and spatially in the sponge. DO levels may even reach anoxia while the sponge is actively pumping water through its body. These results suggest the sponge can alter its activity levels, as reflected by its oxygen uptake. In order to calculate the sponge pumping rate, used as a proxy for assessing its activity level, the volume of sponge had to be measured. For this matter a new method was developed, allowing measurement of surface area and volume of undisturbed sessile marine organisms in their natural habitat, using Structure From Motion 3D modeling. Moreover, the method allows tracking growth rates and assessing changes in surface texture of the organism. The combined knowledge from this study would allows to design culturing environments well adapted to isolate novel sponge-associated bacteria, and therefore assist in finding new useful natural compounds.

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