Invisible diversity: the many forms of bacteria
The bacteria are incredible.
They were the first form of life to appear on Earth almost 3.8 billion years ago.
They constitute the second most abundant form of life, surpassed only by plants.
And most interesting of all: they exist in practically every environment on our planet, including areas where other forms of life cannot survive. As a result, bacteria exhibit a wide variety of appearance, behavior, and applications, similar to the life forms we see in our everyday lives.
The incredible diversity of bacteria remains underappreciated simply because they are invisible to the naked eye. Here we illustrate how researchers classify these creatures based on their appearance, giving you a glimpse into this microscopic world.
Although bacteria may look similar to other microorganisms such as fungi or plankton, they are completely unique at the microscopic and genetic level.
Bacteria make up one of the three main domains of life. All life shares its earliest ancestor with this group of microbes, along with two other domains: Archaea and Eukarya.
Archaea are very similar to bacteria, but have different contents that make up their cell walls.
Eukarya largely consists of complex, multicellular life, such as fungi, plants, and animals. Bacteria are similar to their unicellular members in that all bacteria are also unicellular. However, while all Eukarya have nuclear membranes that store genetic material, bacteria do not.
Bacteria’s genetic material is free floating in their cell bodies. This affects how their genes are coded, how proteins are synthesized and how they reproduce. For example, bacteria do not reproduce sexually. Instead, they reproduce on their own.
Bacteria go through a process called binary fission, where every single cell splits into two identical cells, and so on. The division is fast. Within minutes, populations can rapidly double, eventually forming a community of genetically identical microbes called a colony.
Colonies can be visible to the human eye and can take on different shapes, textures, sizes, colors and behaviors. You may be familiar with some of them:
Superstars from a small world
The following are some interesting bacterial species, some of which you may be familiar with:
This species is unusually large, measuring 200-700 micrometers in length. They are also incredibly picky, living only in the intestines of a sturgeon, a type of large fish.
D. radiodurans is a bun-shaped species that can withstand 1,500 times more radiation than a human.
Although it is known to occasionally poison food and agricultural areas, not all E.coli species are dangerous.
Down in the depths of a South African gold mine, this species thrives without oxygen, sunlight or friends – it’s the only living species in its ecosystem. It survives by eating minerals in the surrounding rock.
Known for causing stomach ulcers, this spiral-shaped species is also associated with many cancers that affect lymphoid tissue.
Most living things cease to survive at low temperatures, but P. halocryophillus thrives in the permafrost of the High Arctic, where temperatures can drop below -25°C/-12°F.
“Back” to the future
Despite their microscopic size, the contribution of bacteria to our daily lives is enormous. Researchers use them every day to study new environments, create new drug therapies, and even create new materials.
Scientists can profile the diversity of species living in a given habitat by extracting DNA from an environmental sample. Known as metagenomics, this area of genetics typically studies bacterial populations.
In anoxic habitats, bacteria are constantly finding alternative sources of energy. Some have even evolved to eat plastic or metal that has been dumped into the ocean.
The healthcare industry uses bacteria to help create antibiotics, vaccines and other metabolic products. They also play a major role in a new line of self-building materials that include “self-healing” concrete and “living bricks.”
These are just a few of the many examples where bacteria affect our daily lives. Although they are invisible, without them our world would undoubtedly seem a very different place.