Microbiology is actually a fundamental part of coral biology. Just as humans have beneficial bacteria (on our skin and in our intestines, without which we would not be healthy), so do corals. There may be thousands of species of microorganisms associated with each coral, performing a delicate balance of coordinated services. Some of the ways these microbes can help the coral are by breaking down waste products, recycling nutrients, and fending off other potentially harmful microbes by producing antibiotics or just by occupying the available space.
Deep-sea or cold-water corals live in dark, cold, high-pressure environments. The microbial communities of these corals are adapted to this extreme environment and so are likely to contain interesting bacteria that are new to us. Identifying and characterising those bacteria will not only increase our understanding of microbial diversity, but could also uncover a new source of enzymes or pharmaceuticals.