Breast milk bacteria. Coloured scanning electron micrograph (SEM) from a culture of breast milk. Several recent studies have found that breast milk contains a healthy dose of commensal bacteria; all the staphylococci, streptococci, and lactic acid bacteria that are found in the infant gut. Recent research has found that 30 percent of babies gut bacteria seem to come from the mothers breast milk and that another 10 percent can be traced to skin around the mothers nipple. After birth, beneficial bacteria from the mother and environment colonize the infants intestine, helping digest food and training the babys immune system to recognize bacterial allies and enemies. Magnification: x5000 when printed at 10 centimetres wide