White coating appears on surface of tongue.

Sour, bitter, or metallic taste.

High levels of Postnasal Drip or mucous in the throat. (This doesn't cause the problem, but makes it worse, because these bacteria prefer to break down proteins (which have high levels of sulphur content). Mucous is high in proteins.

Dryness in the mouth, extreme morning breath, or evidence of thicker saliva. (Saliva naturally contains oxygen. The drier your mouth or the thicker your saliva, the lower your oxygen level in your mouth. Therefore, you create an anaerobic environment, perfect for these bacteria.)

An increase in bad breath, following foods, mouthwashes, during the menstrual cycle or other hormonal therapies (estrogen, progesterone, etc.). Essentially humans are walking chemistry labs: food, alcohol, hormones, etc