Bacteria exists in many shapes and sizes. There are the round (cocci), the long (rods) and the coiled (spiroquetes). Outside of these three basic classifications, there exist even more unique types of bacteria. They are versatile and adaptable to a range of environments. There are even some types that exist under pretty wacky conditions. These particular organisms are called extremophiles.

The term “extremophile” derives from the Greek words philos, which means to love or lover of, and the word “extreme”. Hence extremophiles are organisms that live in extreme environments and have been found living in extreme conditions on Earth. Temperatures as little as -15°C to as high as 121°C, from pH values 0.0 to 12.8, high levels of pressure, high salt concentrations up to 30% [wt/vol] NaCl, and very arid conditions.

Let’s take a look at some of these amazing lifeforms and check out how exactly they manage to live in the world’s most undesirable environments.

Acidophilic Bacteria

Image Source

Acidoplhiles are organisms that grow at very acidic pH values, less than 3.0. The bacteria Ferroplasma acidiphilum, a pleomorphic microbe (an archaeobacteria), is found in the mines of Iron Mountain, California in mine drainage systems. Such resilent mine water cells often contain iron, copper and zinc. They survive by oxidizing iron and releasing hydrogen as a waste product. Researchers have discovered that Ferroplasma acidiphilum not only extracts energy from iron, but also uses it as an element for most of its cellular proteins. It’s possible that the microorganism has a primordial characteristic from the earliest days, when conditions on Earth were similar to this mine water.

Image Source

Researchers that have studied the proteins of Ferroplasma have made an amazing discovery: Almost all of the proteins of the bacteria contain atoms of iron. The iron atoms in those proteins are used as anchors that hold together the loose protein chains.

Psychrophilic Bacteria

Image Source

Psychrophiles are organisms which exhibit optimum growth at temperatures 15°C or lower. The recent discovery of cold-tolerant microorganisms gives us an idea of how tough the environmental conditions are that they are able to survive. Psychrophilic bacteria belongs to the Proteobacteria group. Many species have been collected from cold environments including Arthrobacter sp., Psychrobacter sp., and members of the genera Halomonas, Pseudomonas, Hyphomonas, and Sphingomonas

Image Source

For example, the genus Psychrobacter is aerobic, non-motile, Gram-negative coccobacilli, often found in pairs. Psychrobacter species can reproduce at temperatures ranging from -10°C to 40°C and have been isolated primarily from low temperature marine environments including Antarctic sea ice. Bacteria proteins are responsible for these microbes ability to live and reproduce in cold environments. Growth and survival of low temperatures is also relevant to food storage and processing, general mechanisms of bacterial survival, and stress responses of microorganisms. Also, understanding the adaptations that Psychrobacter has made to inhabit permafrost will enable hypothesis about potential microbial life in extraterrestrial cold environments.

Thermophilic Bacteria

Image Source

Thermophile refers to bacteria that develops at relatively high temperatures, between 45°C and 80°C. Thermophiles are classified into obligate and facultative thermophiles (moderate thermophiles). Hyperthermophiles are extreme thermophiles for which the optimal growth temperatures are above 80°C. First thermophiles were found living in the hot streams of Yellowstone, and after that, prokaryotes have been detected growing around black smokers and hydrothermal vents in the deep sea at temperatures as high as 120°C. Some of the organisms found at those temperatures are Bacillus flavothermus (60°C), Thermus aquaticus (70°C – 72°C), Methanococcus jannaschii (85°C), Sulfolobus acidocaldarius (75°C – 85°C), Pyrodictium (105°C).

Sea Vent (Source)

The most remarkable discovery was made by Thomas Brock, when in the 60s he found that Thermus aquaticus, an archaea organism at Yellowstone National Park’s hot springs and is capable of resisting high temperatures. Scientists have since dedicated their efforts to study this microbe’s proteins and apply their discoveries to today’s molecular biology. They found that the Thermus aquaticus’ polymerase enzyme is capable of duplicating DNA at high temperatures, so it is used now for the Polymerase Chain Reaction (PCR) technique to replicate DNA, and further similar studies (like the Human Genome project).

Yellowstone National Park (Source)

Many other organisms are found in the hot springs of Yellowstone National Park and those microorganisms are responsible for the vibrant colors of the springs. Because thermophiles are ancient, and because they prefer the steamy conditions that were typical of the early times on Earth, many scientists think they could help us understand evolution.

Halophilic Bacteria

Image Source

Salt (NaCL) is the only solute found in a wide concentration range in nature. The microorganisms are named based on their growth response to salt. Microorganisms that require or tolerate some salt for growth are halophiles. Extreme halophiles (require between 15% and 30% NaCl for growth), all of which are archaea, inhabit water that is up to 10 times more saline than ordinary seawater, such as the ones found at the Great Salt Lake in Utah, Owens Lake in California, and the Dead Sea.

Image Source

Vibrio vulnificus is a Gram-negative, motile curved bacterium found in marine environments. The bacterium grow best in warm seawater and is part of a group of vibrios that are “moderate halophiles”. Vibrios (like Vibrio cholerae) are frequently isolated from oysters and other shellfish. V. vulnificus causes disease in individuals who eat contaminated seafood (usually raw or undercooked oysters) or have an open wound that is exposed to seawater, but it causes only a little infection.

Deinococcus Radiodurans

i

Image Source

Radiobiologists have long believed that ionizing radiation, like gamma rays, kills cells by splitting DNA. Deinococcus radiodurans can survive tough conditions, lack of nutrients, and, most important, a thousand times more radiation than a person can. The bacterium’s name means “strange berry that withstands radiation”. The red, spherical bacterium was discovered accidentally nearly fifty years ago in a can of meat that spoiled despite it was sterilized with radiation.

“The organism can put its genome back together with absolute fidelity,” says Claire M. Fraser, of The Institute for Genome Research (TIGR) in Rockville, Maryland. This characteristic is what makes D. radiodurans so great, because even when radiation shatters DNA, it can be repaired by the bacterium proteins. Additionally, the microbe has between four and ten copies of its DNA, rather than the usual single copy. The additional genomes may allow the bacterium to recover at least one complete copy of its genome after exposure to radiation.