Have you ever wondered what microbes are? Are they... animals? Bacteria? Consumers? Thanks to Google, we know you have! We found the most commonly searched microbial questions, from A to Z, and put them to Rob DeSalle and Susan Perkins, curators of the Museum's new exhibition about the human microbiome.
What Are Microbes?
Microbes are organisms that are too small to be seen without using a microscope, so they include things like bacteria, archaea, and single cell eukaryotes — cells that have a nucleus, like an amoeba or a paramecium. Sometimes we call viruses microbes too.
Microbes come in a huge variety of shapes — everything from rods to spheres, even corkscrew shapes. They’re all about the same size, with some a little bigger than others and smaller than others. They don’t have much of a color unless we apply a stain to them, which we sometimes do to see them under the microscope.
Microbes A to Z
With a tip of our hat to geologist Miles Traer at Stanford for the inspiration, here are our lightning-round answers to the internet’s burning questions about the wild world of microbes:
ARE MICROBES BACTERIA?
No, not exclusively. Bacteria are microbes, but not all microbes are bacteria.
ARE MICROBES DANGEROUS?
Not as dangerous as we used to think.
The grand majority of microbes are either not in contact with us or, if they are in contact with us, they’re actually mutualistic, which means that we gain a benefit from them, they gain a benefit from us. Or they’re simply neutral.
They’re dangerous when we make them dangerous. We make them dangerous through antibiotic overuse. Antibiotics change the makeup of the microbial ecology in the gut, especially, and that change in microbial makeup triggers a bunch of secondary reactions and interactions.
WERE MICROBES FIRST TO EVOLVE?
Yes, three and a half billion years ago—and they’ll be the last. Microbes will have the planet to themselves again.
Steven Jay Gould once said we should forget about the Age of Dinosaurs, forget about the Age of Man—we’ve always lived in the Age of Bacteria.
DO MICROBES HAVE DNA?
Yes.They play by the same genetic rules that we play by. They play by the same molecular rules that we play by, in general. The only thing that they have that’s different with respect to their DNA is that they can pick up stray pieces of DNA a lot better than we can.
It’s really clear from looking at DNA sequences that we share ancestry with these microbes. That we’re all related to archaea, bacteria, all the eukaryotes, we’re all related to each other through a common ancestor and we can show that quite clearly with DNA sequences.
DO MICROBES JUMP?
They’re pretty good at moving. There’s this really cool microbe Bdellovibrio, which is probably the fastest living thing on the planet, relative to its size. It’s got a flagellim, and it swims really fast, and it hits its target cell and embeds its head into the target cell, and then gets in.
It can go 60 micrometers per second, which is probably 600 times its length.
CAN MICROBES LIVE ON MARS?
If they could get there, yes. All they need is nitrogen, water, and sulfur. We have bacteria on our planet that live solely on sulfur products.
ARE MICROBES NAMED?
There’s only 8,000 or 9,000 bacteria have valid scientific names. In other words, 8,000 or 9,000 bacteria have gone through the process of being vetted by the nomenclatural commission, and this is sad because they have very strict rules about how and when you can name something.
You have to have a culture of it, which eliminates 99 percent of all the bacterial and archaea on the planet.
ARE MICROBES PARASITES?
Some. Malaria is caused by parasitic protozoans. Toxoplasma is a microbe that wants to be in the brain of a mouse, and when it’s in the brain of a mouse it makes the mouse less fearful. That way the mouse gets eaten by a cat, and the parasite completes its life cycle. So, it finishes its life cycle in the gut of a cat. The spores come out in the poop of the cat, the mouse picks them up. The cycle starts again.
ARE MICROBES RESISTANT TO ANTIBIOTICS?
More and more. When you take antibiotics you’re not creating antibiotic resistance. You are selecting for existing antibiotic resistance. So, when Gloria Dominguez-Bello sampled Amerindian people in Brazil who had never been to a doctor, never taken any medication, they found antibiotic resistant genes in their microbiomes. How did that happen? Because they were there all the time.
ARE MICROBES THE SAME AS BACTERIA?
No. Bacteria are microbes, but not all microbes are bacteria.
ARE MICROBES VIRUSES?
Not all. Microbes include bacteria, archaea, single-celled eukaryotes, things like amoeba and cilates and malaria.
ARE MICROBES XEROPHILIC?
Some microbes don’t need water. There are microbes in every desert, there are microbes in salt flats. They can survive in really, really dry places.
ARE MICROBES ZOONOTIC?
Zoonotic means from animals, and yes, they are passed between humans and animals. If you sample microbiomes of people who live in the same house, if you have a dog, everyone in the house has more microbiomes in common because everyone is loving on the dog.