From vampire bacteria and glowing bacteria to magnetic bacteria and electric bacteria, microbes have developed some strange attributes over billions of years of evolution. That’s not even counting the entire class of microbes known as archaea that evolved to survive in some of Earth’s most hostile environments. This week, we’ll be discussing just a fraction of these strange microbes and the unique environments where they thrive.
There are strange microbes in all three of the major domains of life: eukaryotes—the domain of humans, plants, and animals—bacteria, and archaea. The term archaea was first used in the late 1970s to describe microbes that were found in the Yellowstone hot springs. These microbes looked very similar to bacteria, but they were completely genetically and biochemically distinct from any known bacteria, and they were able to thrive in super-hot waters. Most living things cannot survive in very hot environments because their proteins lose stability and breakdown, or denature, as temperatures increase. Some animals, like humans, may be able to withstand a wider range of temperatures because we have specialized systems for thermoregulation—mechanisms like sweating that keep the body at a specific temperature when the external environment is too hot. But microbes don’t have this luxury, so most microbes can’t survive at high temperatures (which is why cooking meat is an effective way to kill off bacteria like salmonella).
Still, some microbes are able to thrive in high temperatures (thermophiles) and other extreme, hostile environments—like highly salty environments (halophiles), highly acidic environments (acidophiles), highly basic environments (alkylophiles), and highly pressurized environments (barophiles). Most of these extremophiles belong to the archaea domain—although not all extremophiles are archaea and not all archaea are extremophiles. While archaea can look very similar to bacteria, there is evidence that they share more genetic similarities with eukaryotes. A lot of the chemical differences between archaea and bacteria contribute directly to their ability to survive in harsh environments. Crucially, many archaea have proteins with specific adaptations that make them more stable in these extreme environments.
While not many bacteria species are extremophiles, some bacteria have picked up other strange traits that may help them survive. In February, we briefly discussed bioluminescence in our Black History Month post on Emmett Chappelle. The bioluminescent bacteria Vibrio fischeri can form symbiotic relationships with a variety of sea creatures. For example, the Hawaiian bobtail squid houses a colony of V. fischeri in a specialized light organ within its mantle. Each night, the squid projects this light downwards, mimicking moonlight and camouflaging the squid from any predators lurking below.
In addition to glowing bacteria, there are also bacteria that can eat and breathe electricity. Bacteria in the genus Geobacter can conduct electrons, passing them from bacterium to bacterium and forming pseudo-wires that pass electrons onto nearby molecules of rust. This conduction allows the bacteria to remove the electrons produced during the production of ATP. Normally, these electrons are passed onto molecules of oxygen and “breathed out” as carbon dioxide, but conductive bacteria have learned to thrive in oxygen-free environments. In addition to electric bacteria, there are magnetotactic bacteria that respond to magnetic fields. These bacteria even respond to the Earth’s magnetic field, allowing them to act like microscopic compasses. These bacteria become magnetic by collecting iron-oxide or iron-sulfide molecules from the environment, packing these molecules into dense magnetic nanoparticles, and aligning the nanoparticles into chains.
Many bacteria can be pathogenic or parasitic to a host organism, but only a couple of bacteria species are considered true predators. Scientists have identified some species of “vampire” bacteria that hunt down other bacteria and suck them dry. These bacterial vampires have a flagellum tail that propels them during their hunt. When they latch onto their prey, they suck out all of the important molecules, leaving an empty husk. Vampire bacteria reproduce directly after “feeding”—in fact, they need to feed off prey before they are able to reproduce. While vampire bacteria may seem pretty scary, they are completely harmless to humans and other multicellular organisms. In fact, vampire bacteria may become useful to humans as a tool to defeat antibiotic-resistant pathogenic bacteria.
So far, we’ve only discussed prokaryotic microbes—both bacteria and archaea are prokaryotes because their DNA isn’t packaged in a nucleus. But eukaryotes, the domain of humans and all plants and animals, also include some pretty interesting microbes, known as protists. For example, the single-celled slime mold Physarum polycephalum grows out in a maze of veins in search of food. These unique protists actually have several nuclei in charge of “making decisions” for the cell, and they leave behind chemical information in their slime trails that helps them find the fastest route to food without retracing their steps. Scientists have even found evidence that these mold cells can learn over time and pass on information to other mold cells via fusion. Another weird protist is a group of free-swimming algae called warnowiids. This strange, single-cell alga contains a structure called an ocelloid that mimics all of the components of a human eye. Scientists still aren’t sure how much these pseudo-eyes can actually “see” and what their true purpose may be.
This blog post represents just a tiny fraction of the weird and wonderful world of microbes. Comment below with your favorite weird microbe, and we might cover it in a future post! Also check out last month’s post on the delta variant and principles of viral evolution. Comment or email us at contact@anyonecanscience.com to let us know what you think of this week’s post. And subscribe below for weekly science emails!
