(I) A few microbial species have found ways to sabotage
the immune system and skew the balance of power in
their favor. (II) For example, Porphyromonas gingivalis,
a mouth-dwelling bacterium, has long been the prime
suspect behind gum disease. (III) Even in small
numbers, they can stop white blood cells from producing
certain chemicals that kill bacteria. (IV) Without these
chemicals to restrict their growth, all the bacterial
populations in the mouth grow explosively, causing
tissue damage known as 'gingivitis'. (V) The standard
care for gingivitis is a professional tooth cleaning and
more flossing.