 At this pH mutualistic flora such as "Staphylococci", "Micrococci", "Corynebacterium" and "Propionibacteria" grow but not transient bacteria such as Gram negative bacteria like "Escherichia" and "Pseudomonas" or Gram positive ones such as "Staphylococcus aureus".Another factor affecting the growth of pathological bacteria is that the antimicrobial substances secreted by the skin are enhanced in acidic conditions.In alkaline conditions, bacteria cease to be attached to the skin and are more readily shed.