How to identify an unknown bacterial species? The thousands of species of bacteria are differentiated by many factors, including morphology(shape), chemical composition (often detected by staining reactions) nutritional requirements biochemical activities, and source of energy(sunlight or chemicals)The thousands of species of bacteria are differentiated by many factors, including morphology (shape), chemical composition (often detected by staining reactions), nutritional requirements, biochemical activities, and source of energy (sunlight or chemicals). How to identify an unknown bacterial species ?