Anaerobic infections are caused by anaerobic bacteria. Anaerobic bacteria do not grow on solid media in room air (0.04% carbon dioxide and 21% oxygen); facultative anaerobic bacteria can grow in the presence as well as in the absence of air.Microaerophilic bacteria do not grow at all aerobically or grow poorly, but grow better under 10% carbon dioxide or anaerobically.naerobic bacteria do not grow on solid media in room air (0.04% carbon dioxide and 21% oxygen); facultative anaerobic bacteria can grow in the presence as well as in the absence of air.