Differential interference contrast micrograph of cyanobacteria Microcystis sp. Surrounding the colony there are rod-shaped bacteria that live in symbiosis with the Microcystis. The Microcystis is covered in a gel-like substance, mucilage, that provide a thriving habitat for the bacteria. The relationship between the bacteria and Microcystis is mutually beneficial. The associated bacterial flora depends on both carbon and energy sourced from the Microcystis, and supply the Microcystis with vitamin B12, which is required for the growth of the colony. The interactions between bacteria and cyanobacteria (blue-green algae) may play a significant part in the formation and development of algal blooms. The occurrence of cyanobacterial mass populations can create a significant water quality problem, especially as many cyanobacterial species are capable of synthesizing a wide range of odours, noxious compounds or potent toxins. Magnification: x450 when printed at 10 centimetres wide at its longest edge.