By Robert Hazen, George Mason University
All organisms obtain and use energy. All organisms reproduce, with variations. All organisms also grow and develop. And, all organisms respond to changes in their external environment. All living things have to adopt a strategy to compete for resources and survive variations in the environment.
Single-celled Organisms
Different kinds of organisms adopt different strategies to survive. The one-celled organisms might seem to be the simplest group in terms of survival strategies; but actually, it turns out they’re by far the most diverse.
Single-celled organisms live under different extreme conditions and have developed a huge variety of metabolic strategies to gain energy to survive. Single-celled organisms are found at any place where there’s liquid water: under the Arctic ice, near boiling point in hot springs, in salt lakes, and even deep underground in solid rock, where there’s only a small amount of water circulating. We also find single-celled organisms in the deepest part of the ocean, in places where hot volcanic waters are circulating through rocks. Microbes, then, are incredibly diverse in their ability to survive almost any kind of water-rich environment.
Different Strategies of Microbes
Microbes get their energy from an equally wide variety of sources. Some microbes are photosynthetic; they obtain light from the Sun. Many microbes consume biomolecules from other living things. Almost like animals, they bring in molecules with which to build their structures, with which to get energy.
But there are hosts of microbes that get energy from the oxidation or the reduction of rocks. In effect, these microbes eat rocks; they live on rock surfaces. For example, there are bacteria that oxidize hydrogen to make water. They can oxidize iron to make iron oxides; oxidize methane, to make CO2 plus water; or they can oxidize sulfur compounds, to make a whole variety of horrible-smelling things. All of these types of bacteria transfer electrons to oxygen, in the process of oxidation.
Many microbes use the opposite strategy; they survive by reducing compounds. They reduce iron oxides, or sulfur, or carbon, or other compounds; and in these cases, electrons are transferred from the oxygen to other groups of atoms. Any time you can get energy, either by moving an electron to or from oxygen or any other pair of atoms, you’re going to find a microbe that’s likely to exploit that pathway.
Most microbes live as isolated single cells, but some have developed the ability to organize into amazing colonies, into structures. For example, slime mold, where you actually can have 3D structures of stalks and spikes and so forth; somehow these individual bacteria are communicating in a colonial way that we don’t exactly understand.
This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium.
Strategies of Fungi
The kingdom of fungi includes mold, mushrooms, and yeast: all kinds of organisms that in some ways resemble plants, in terms of their self-structure and their growth patterns, but they’re non-photosynthetic.
Fungi adopt a remarkable variety of strategies to survive. Some fungi, like yeast, are single-celled organisms. They form bacteria-like colonies; they reproduce primarily asexually, by the production of spores, by normal cell division. Other fungi, including the molds, consist of myriad intertwined filaments; these grow as fluffy masses.
Mold begins as single-celled spores that can travel easily through the air, but when they land on a food source, these filaments start growing cell by cell, adding cells onto the end of each filament, and they get longer and longer.
Lichens and Mushrooms
Then there are lichens that have a remarkable cooperative lifestyle. They include fungi filaments that are intertwined with photosynthetic algae. There are single-celled organisms living with the fungi. The fungi provide essential minerals and also a protective anchored habitat with those filaments; the algae provide an energy source for the fungi, so there’s this symbiosis between the two types. When you see a lichen, you’re actually seeing two species or more that are intertwined with each other.
Mushrooms are the only type of fungi that rely primarily on sexual reproduction. They consist of innumerable filaments that are completely intertwined with each other and form that mass: the solid mass of the mushroom. That distinctive umbrella shape of many mushrooms, and the textured undersides of the mushroom caps, facilitate the release and the transfer and the spread of spores.
Significance of Fungi
Fungi may seem simple and insignificant, perhaps not worthy of much serious notice, but they play many important roles in nature. For example, they help to decompose dead organisms. They convert rocks into soils. Through the process of fermentation, fungi facilitate the production of cheese, soy sauce, alcoholic beverages—many of the things we consume. Of course, many mushrooms are edible, and part of people’s diets.
Fungi assist in the manufacture of many industrial products as well, including soaps, and plastics. Then there’s penicillin and the antibiotics developed from fungi. Penicillin has saved countless lives, and the discovery of penicillin is a fascinating example of a chance discovery. It was the British bacteriologist, Sir Alexander Fleming who was growing cultures of the often-dangerous bacterium Staphylococcus in his laboratory. He grew these in dishes with a nutrient; he set them out, and let the bacterium grow. But he noticed that one of the dishes that he had been working with was contaminated by the common mold penicillium.
Fleming realized that the mold must be producing a chemical that actually kills off bacteria, and he said, that could be an important discovery. Shortly thereafter, methods were developed to manufacture large quantities of this chemical substance called penicillin, and the drug was put into mass production in 1943. That was in time to save countless lives during World War II, and, of course, subsequently, with the widespread adoption of these antibacterial agents.
Common Questions about the Survival Strategies of Microbes
Single-celled organisms are found at any place where there’s liquid water: under the Arctic ice, near boiling point in hot springs, in salt lakes, in the deepest part of the ocean, in places where hot volcanic waters are circulating through rocks.
Some microbes are photosynthetic; they obtain light from the Sun. Many microbes consume biomolecules from other living things. Hosts of microbes get energy from the oxidation or the reduction of rocks. Many microbes use the opposite strategy; they survive by reducing compounds.
Fungi help to decompose dead organisms. They convert rocks into soils. Through the process of fermentation, fungi facilitate the production of cheese, soy sauce, alcoholic beverages, etc. Soaps, plastics, penicillin, and antibiotics are also developed from fungi.
