Cultivation of Bacteria from Marine Sponges

Abstract

Sponges (phylum Porifera) are among the oldest of the multicellular animals (Metazoans). Sponges have been the focus of much recent interest due to the fact that they harbour a diverse range of symbiotic microorganisms. These symbiotic microorganisms are essential for the host s function and interaction with the environment. Our understanding of sponge-bacteria association is limited due to our inability to cultivate most sponge-associated microorganisms. In recent years many new approaches have been developed for culturing marine bacteria. These include the use of a variety of growth conditions, such as temperature, oxygen levels, different atmospheric pressures and novel culture media. These approaches have largely been neglected when it came to the cultivation of sponge-associated bacteria. This thesis focuses on the cultivation of sponge-associated bacteria from the marine sponges Cymbastela concentrica, Tedania sp. and Scopalina sp. using agar plate cultures and floating filter cultures. A variety of low- and high-nutrient media were used, including media amended with sponge extracts. A total of 202 isolates were identified from the three sponge species. Most of the cultivated bacteria were isolated from agar plate cultures, with highest number of isolates from the sponge Tedania sp. Media that were rich in nutrients were more successful and resulted in higher diversity of morphotypes and genetically distinct isolates as compared to low-nutrient media. Media with and without addition of sponge extract showed no difference between number and type of isolated bacteria. Isolated bacteria were classified into 16 genera, with Pseudovibrio being the most dominant genus. Most of the isolated Pseudovibrio sp., Ruegeria sp., Aquimarina sp., and Vibrio sp., have close matches with microorganisms isolated previously from marine sponges. The results presented in this thesis highlight the use of multiple cultivation methods to improve cultivability of sponge-associated bacteria.