The human microbiome, also known as microflora, is comprised of the bacterial colonies of the body. Although bacteria are commonly associated with illness, there are good bacteria known as probiotic bacteria that grow naturally in the microbiome of the human gut. Probiotic bacteria are live microorganisms and consist of approximately 400 different bacterial strains that support life in their host organism. The gut microbiome, also known as intestinal flora, plays a role in normal human development, digestion, body weight, nutrition, and immune system regulation, in addition to influencing various neurological functions. It has been found that environmental factors including antibiotics, illness, stress, and diet can alter an individual's microbiome through their effects on probiotic bacteria situated in the gut microflora.