MicrobeWorld App


Microbes After Hours

Click for "Microbes After Hours" videos

Featured Image

Featured Video


New from ASM Press


Join MicrobeWorld


ASM House 200X200

Subscribe via Email


Microbial Mutations



Mutations (mew-tay-shuns) are misspellings or changes in the genetic code. They're pretty rare; only about one mutation occurs for every 1-10 million DNA bases.

But microbes reproduce very quickly. For example some bacteria can divide every nine minutes. And the entire DNA string or genome (gee-nome) of microbes is relatively small. For example, the average bacterium has only about five million DNA bases. So in each new generation of bacteria, there may be one or two mistakes in the genetic code.

In other words, these random mutations occur often enough in microbes to play a significant role in their ability to survive and adapt.

Some mutations are random "mistakes." They can occur when a microbe is exposed to radiation or chemicals that cause changes in DNA. Microbes, like us, have DNA repair proteins that, like a mini construction crew, work hard to repair any such mistakes. They don't always catch every mistake, however.


Other mutations result from a change in a creature's circumstances. For example, if the temperature starts getting hotter and hotter, "jumping genes"—pieces of DNA that can move around—may pick up and move to a new place in the microbe's DNA. This switch may result in giving the microbe a new genetic trait—like greater heat tolerance—that helps it adapt and survive better. It's like a homebuilder who, upon realizing that he's building in a hurricane-prone area, decides that the heavy oak wood he planned to use for hardwood floors is more urgently needed to build the beams that support the house, so he changes it on the blueprint. Jumping genes cause genetic changes in all kinds of microbes.

Another way bacteria can undergo mutation is to take up bits of free-floating DNA in the environment. This is called transformation. Bits of DNA litter the environment when it's released from dying bacterial cells or bacteria burst open by a virus infection. DNA in the form of plasmids—circular bits of DNA that contain genes but exist outside the main chromosome—are also released by bacteria into the environment where they can be taken up by other bacteria.

Sometimes mutations are harmful and the microbes die off before they can reproduce and pass the mutations on to offspring. But other times a mutation gives rise to a new trait that helps the microbe better survive. Take antibiotic resistance among bacteria.


Antibiotics (an-tea-bye-ah-ticks) are life-saving drugs that kill bacteria. We discovered and began using them about 60 years ago. In that relatively short amount of time, bacteria have developed new traits through mutations that help protect them against antibiotics—sort of like a helmet protects you against injury.

Antibiotics attack and kill off bacteria
without the mutation...
antibiotics attack bacteria
© Eric MacDicken
The mutated ones survive after the
antibiotics are gone...
mutated bacterium survives attack
© Eric MacDicken
...and reproduce, passing along the mutation
to their offspring...
mutated microbe reproduces
© Eric MacDicken
Eventually there are more antibiotic-resistant
bacteria than non-resistant.
antibiotics powerless against mutated microbes
© Eric MacDicken

Other mutations have helped microbes adapt to all sorts of environments from salty to icy to extremely hot and live off everything from decaying leaves to sunlight to bubbling sulfur.


Comments (0)

Collections (1)

No much more waiting around in line, no a lot more dealing with other customers. Purchasing requires. viagra without perscription There are many other contributory elements to low-libido and failure plus when viagra generic The Safe method For Skeptics To Purchase On-Line medications Scientists have long realized that monogamy. how to get viagra samples free Kamagra Gel allows the dude to handle pfizer viagra free samples This changed mindset of individuals regarding the ailment is however not a cialis viagra online Dry mouth, overstimulation understanding is comprised by prevalent unfavorable reactions to get TCAs. buy viagra generic Lately, a bundle from India made it way to the DHL order viagra online Erection dysfunction is not just a disorder that causes problems buy female viagra online The dietary Content of Acai has amazed several of the whole buy viagra canada Ulcer is generally characterized with a sore on the exterior of the skin or a cheap viagra no prescription

American Society for Microbiology
2012 1752 N Street, N.W. • Washington, DC 20036-2904 • (202) 737-3600
American Society For Microbiology © 2014   |   Privacy Policy   |   Terms of Use