Ingenious Little Bugs
Posted on Monday, December 19th, 2011
It even sounds gross.
But saliva is also kind of amazing stuff.
And in more important ways than that.
one of the functions of saliva is to wash debris from your teeth. If you don’t produce enough, your teeth become more vulnerable to decay. This is the case with habitual mouth breathers, for instance, and those who take prescription medications, many of which include dry mouth as a “side effect.” Similarly, the flow of fluids within your teeth normally repels pathogenic (disease-causing) microbes. Everything changes, however, when you eat a lot of sugar, white flour products and other refined, fermentable carbohydrates. As conditions in the mouth grow more acidic, the flow actually reverses. Pathogens and their toxic byproducts are pulled into the tooth.
Your spit also serves as a source of calcium and phosphate, which help remineralize your teeth, strengthening tooth enamel. But it also contains enzymes, proteins and antimicrobial compounds that help fight infection, which may well be why we instinctively “lick our wounds” when hurt.
But why then, you may be thinking, are our mouths so perpetually germy?
Well, just as our bodies have their defenses – saliva, the immune system, the excretory system and so on – so do other living things, including microbes. They do some pretty amazing things, too.
For instance, one recent study of P. gingivalis found that this bacterium actually “hacks” into the cells of the subgingival crevice and “reprograms them to create living conditions more to its microbial liking.”
As more immune cells are co-opted to follow the wrong program, the usually benign bacterial residents of the subgingival crevice — not P. gingivalis, as long suspected — opportunistically rise up in number, altering their community dynamics and prompting them to infect the tooth’s supportive structures, or periodontium.
* * *
“As the other bacteria attack, and immune cells counterattack, progressively damaging the integrity of the tooth in the process, P. gingivalis sits in the shadows and feasts on the inflammatory spoils,” said George Hajishengallis, D.D.S., Ph.D., a researcher at the University of Louisville School of Dentistry and a co-lead author on the study. “This is one ingenious little bug.”
What’s more, as a different study suggests, it does this in disguise!
The capsule of Porphyromonas gingivalis, the bacterium that causes gum disease, provides stealth, boosting the bacterium’s virulence, according to a paper published in the November Infection and Immunity. Call it a sugar coating, if you will, for in fact, the capsule is made from sugar molecules, which do not ordinarily elicit immunity. Thus it hides the bacterium’s proteins within, preventing immune response.
In the study, the researchers, led by Janina P. Lewis of Virginia Commonwealth University, Richmond, compared the ability of normal, and mutant bacteria that were missing the capsule, to activate the immune system, to enter eukaryotic cells (the kind that are present in multicellular organisms), to cause disease, and to survive in mice. “The mutant bacteria activated the host to a greater extent, and thus, were more easily killed by eukaryotic cells,” says Lewis. “Thus, the capsule protects the bacteria and allows them to survive unnoticed in our bodies.”
Capsules also protect both bacteria and fungi, including P. gingivalis, as per this report, from being engulfed by the immune system’s phagocytes (phago=eat; cyto=cell) and from being identified by dendritic cells as dangerous, thus marking them for destruction by antibodies. Conversely, in the study, mutant, non-encapsulated P. gingivalis were rapidly engorged by immune cells, and killed.
Pretty sneaky…and why you need to brush and floss daily, breaking up those microbial colonies and distracting them from their dirty work.
Image by Mr. Greenjeans, via Flickr