<prompt> The protective bacterium in the normal vagina is:PeptostreptococcusLactobacillusGardenella vaginalisE. coli  <response>: Vagina has inhabitant bacteria called as Doderleins bacteria which is a lactobaccilli, and converts the glycogen present in vaginal epithelium into lactic acid.Thus, pH of the vagina is acidicThe pH of the vagina in an adult woman is 4 -5.5 with an average of 4.5.The pH of vagina varies with age for further details see preceding text. 