Wee Knight Science: Bioremediation by bacterial badasses part I: Why are heavy metals toxic?

We all know that heavy metals like uranium and arsenic, as well as hydrocarbons such as crude oil and plastics are pretty bad for the environment, since they have this weird tendency to kill things. Most people know how oil kills innocent critters: it gets all over their feathers, gills, fur and fins, weighing them down so that they can't use their locomotory method of choice, which often results in them drowning. They probably get eaten sometimes, too, since they're slow, easy prey, and I'm sure that gives some unlucky predator a lingering foul (or fowl, ha) taste and a nasty bout of indigestion.

But how are heavy metals toxic? And what the heck is a heavy metal? Are there metals that aren't heavy? I think those are questions not many folks know the answers to. I didn't, until my junior (senior? It's been a while) year of college.

It all comes down to proteins. Proteins are not, contrary to bodybuilder popular opinion, just a post-workout necessity. Actually, we are all made up of a vast number and diversity of proteins that basically do everything for us. Yes, even plants. Don't be racist, plants are people too. Here are a few examples of cool proteins:

actin keeps your cells in their proper shape, and makes those sexy muscles contract

They look weird, but they're supposed to. That green stuff is actin, and the blue is DNA.

DNA polymerase copies your DNA, in conjunction with DNA helicase, which unzips your genes

Hank Green is my hero. Watch all of his videos.

I'm a little disappointed that I'm already in a relationship and can't use this pickup line on somebody.

trypsin breaks up them food proteins
amylase breaks up them food sugars

rhodopsin eyeballs! I'm actually not 100% sure what this one does, but I do know it's important for seein'.

Pretty. I got this from Petr Novák, Wikipedia - Own work.

I learned what rod and cone cells are from this. I never knew! You should look it up if you don't know already.

Proteins are great. Wouldn't it be sad if they stopped working? Or if something stopped them from working? Like heavy metals?

That's right, sports fans, that huge tangent had a purpose. Coming back around, let's talk about metalloproteins. A lot of super important proteins require metals to function.

Most metalloproteins use lighter metals like sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca). Some use slightly heavier metals like manganese (Mn), cobalt (Co), or zinc (Zn). Heavy metals are elements like silver (Ag), gold (Au), and mercury (Hg). Those metals like proteins, too. They actually like them more than the lighter metals. You can think of heavy metals as bullies. Gold comes up and sees magnesium playing with a DNA polymerase, and he's like "I want to play with that protein!" Since he's bigger, he pushes magnesium in the dirt and takes the polymerase.

Of course, it's not quite that simple, but that's the general idea. You can also imagine that sticking a bigger blob where a smaller one used to be would change the shape of something. Since a protein needs to have a certain shape to work, heavy metals cause problems and basically break whichever protein they attach to.

The title of this post mentions bacteria. Odd, I didn't mention bacteria at all in this article, did I? I guess that will be in part 2!