Sponge-Microbe Interactions

Sponges are amongst the oldest creatures on our planet and have evolved over 650 million years ago. Today, more than 8,600 sponge species are formally described with the majority of them inhabiting marine ecosystems. Sponges are attached to the bottom of the seafloor where they continuously pump enormous amounts of seawater through their body in order to filter out small particles from the water, which they feed on. The remarkable filtration capacity of sponges helps to recycle otherwise lost nutrients in marine ecosystems and hence sponges are an important constituent of the marine food web. Furthermore, sponges are known to produce a vast range of chemical substances that find application in medicine and biotechnology. The secret to their evolutionary, ecological and biotechnological success of sponges is their intimate relationship with microbes. Sponges harbour a myriad of microbes in their tissue. The symbiotic microbes can contribute up to 35% of the weight of the sponge and these microbes can be extremely diverse (from a few microbial species up to hundreds of different microbial species in one single sponge). The microbial symbionts play an important role in the health of sponges, however, until today the mechanistic interaction between the sponge and its microbial symbionts remains very poorly understood. In this project, we will tackle key questions of the sponge-microbe symbiosis using a novel combination of state-of-the-art molecular methodologies and cutting edge microscopy techniques. This project aims, for example, to shed light on how microbial symbionts are transferred between the sponges and their offspring, and to investigate the functions of the microbial symbionts in the first days of a baby sponge. Furthermore, this project will also examine how nutrients are shared among the sponge host and its microbial symbionts, and how sponge diseases can disrupt the nutrient flow between them. The coral reef sponge Ianthella basta, often referred to as elephant ear sponge, will be used as model species as it is the ideal sponge for the task. This sponge species is commonly found in coral reefs throughout the Indo-Pacific Ocean, it has a very simple fan-shaped body, it can be kept for extended periods of time in an aquaria system, and last but not least it lives in a symbiotic association with only three microbial species. The sponges will be collected at the Great Barrier Reef in collaboration with Dr. Nicole Webster (Australian Institute of Marine Science) and shipped to Austria, where they will be analysed at the Division of Microbial Ecology at the newly founded Centre for Microbiology and Environmental Systems Science (University of Vienna).

Did you know that marine sponges, those fascinating creatures of the ocean, play a crucial role in the balance of carbon and nitrogen in their ecosystems? They achieve this with the help of tiny partners called ammonia-oxidizing archaea, or AOA for short. However, we've only scratched the surface of understanding how these AOA function and interact within sponge communities. In our FWF-funded project, we delved into the world of sponge-associated AOA and made some exciting discoveries. We identified novel but distinct groups of these microbes, each with its own unique traits and roles. First up, we found a brand-new group of AOA, which we have named "Nitrosokoinonia". These little microbes are like the recycling champions of the sponge world, breaking down waste products of the sponge, such as ammonium and urea, and turning them into energy. They even get a helping hand from other bacteria, called nitrite-oxidising bacteria - short NOB, which further recycle the waste of AOA to help detoxify the tissue of their sponge host. Then, we looked closely at another AOA symbiont called "Nitrosospongia ianthellae" which exclusively occurs in the tropical Elephantear sponge (Ianthella basta). This symbiont lives in a close relationship with another bacteria in the tissue of its sponge host. Together, they team up to break down taurine, a common compound found in sponges. Lastly, we found a very unusual AOA with incredibly tiny genomes, but don't let their size fool you-they are still hard at work. These little microbes are experts at gaining energy by converting ammonium into nitrite and therefore fixing carbon, helping the sponge host to get rid of any ammonium in its tissue. Overall, our research shows how amazing the world of sponge-associated AOA is. By understanding their roles and relationships, we gain valuable insights into how these very important animals function.