Even when you don’t have access to a microbiology lab, you can experience and enjoy the microbial world. Although individual cells are invisible, microbes reveal themselves in our daily lives through colors, smells, sounds, textures, and flavors.
In this post, you will learn how to identify bacteria based on the “field mark” of a rainbow metallic sheen that looks like oil contamination. You will be able to appreciate more microbes in your daily life and also no longer be frustrated about “oil contamination” in cases where it’s bacteria doing something completely natural.
Find microbes in your daily life
We usually think about microbes as being invisible. They are all around us, and yet we often can’t see them. But what if we could tell when they are there? What if we could go on a scavenger hunt of sorts to look for them?
We can.
You don’t have to own a microscope to see bacteria or identify them around you.
Field marks for bacteria
A whole book that Betsey Dexter Dyer wrote is about this very concept. Her book, A Field Guide to Bacteria, gives us a tool to help us identify bacteria in the wild, in nature, and all around us using your senses: touch, sight, hearing, smell, and taste. But this post will focus on one identifying feature, a “field mark” for bacteria.
Field mark for bacteria: metallic sheen on water
Have you ever seen what looks like an oil spill? A rainbow on the surface of the water? Or a metallic sheen? It might be metals produced by bacteria, not an oil spill. What a relief, right?
But how can you tell?
You have to touch it. Okay, not with your hand necessarily, but maybe with a stick. If it breaks apart like glass, then it’s a product of bacteria…the metals. If it doesn’t, then it’s an oil spill.
Sometimes you may see rusty-colored water as well. And, in that case, you are seeing mostly iron, not other metals.
Metals change forms in the environment
What is happening when we see that rainbow sheen?
Bacteria living in water or sediments can change the form of metals like iron, manganese, and copper, in the metal cycling process. Some bacteria use iron to help them to produce food. These are iron-oxidizing bacteria.
Bacteria change iron from solid to dissolved and back to solid
Different bacteria participate in changing iron from a solid (ferric Fe3+) to dissolved (ferrous Fe2+) and then back to solid (ferric Fe3+) form.
Rocks and metal pipes contain solid iron.
Bacteria can dissolve solid iron, causing it to go into solution. So, imagine the metal pipe that contains iron.
Certain bacteria produce acids due to fermentation while growing without oxygen, causing the iron to dissolve.
The dissolved iron can then float to the surface of the water.
At this point, two things can cause the iron to become solid again:
- oxygen from the atmosphere can oxidize the iron
- bacteria can oxidize the iron
Oxygen in the atmosphere regularly oxidizes iron and cause it to become solid (ferric Fe3+) again, but bacteria can amplify this process. This same process can occur with other metals.
The solid form of iron (oxidized iron, ferric Fe3+) and other oxidized metals can form the metallic sheen.
Summary
- You can discover microbes in your daily life by looking for “field marks”
- “Signs” or “field marks” for bacteria are especially useful since individual cells are invisible (for most species of bacteria)
- You can use all of your senses to detect field marks for bacteria
- One field mark to look for is a rainbow on water that looks like an oil spill
- The rainbow is a sheen of different metals that bacteria turned into a solid
- Check out the book A Field Guide to Bacteria by Betsey Dexter Dyer to discover more bacterial field marks
Deepen your exploration of the microbial universe!
My ebook, “Joyful Microbiology Activities,” provides 10 engaging, DIY experiments to ignite your curiosity about the unseen world of microbes. Get your copy today!
What is extreme life, and where do we find it?
