Making delicious foods
The yeast Saccharomyces cerevisiae has been used for millennia because it ferments sugars and makes carbon dioxide, which causes bread to rise.
The lactic acid bacteria, such as Lactobacillus and Bifidobacteria, are used in making fermented milk products. Buttermilk, sour cream, cheese, and yogurt are made by letting these bacteria ferment milk to different degrees.
Microorganisms are also responsible for the pickling process. Species ofLactobacillus are happy in very acidic conditions, so they’re almost always there at the final stages of pickling.
Soy sauce is a fermentation product of soybean and wheat paste. The lactic acid bacteria and fungi such as Aspergillus produce the distinctive taste of soy sauce.
Leguminous plants, such as soybeans, peas, clover, alfalfa, and beans, form intimate associations with nitrogen-fixing bacteria like Rhizobium. The bacteria essentially move into the root cells and form little homes for themselves callednodules.
Brewing beer, liquor, and wine
Along with bread-making, the yeast Saccharomyces cerevisiae is probably best known for its use in making alcoholic beverages. This process involves mixing a sugar source — barley for beer, fruit juice for wine, or rice or potato starch for spirits — with yeast and water.
The yeast first consumes the sugars aerobically until the oxygen runs out; then it ferments the sugars anaerobically, producing ethanol and carbon dioxide as waste.
Killing insect pests
The bacterium Bacillus thuringiensis (also known as Bt) produces a toxin that is specific to certain types of insects, many of which are pests encountered by gardeners and farmers.
Another group of insect pathogens uses small worms callednematodes to get inside of their insect host. Members of the bacterial genera Photorhabdus and Xenorhabdus hitch a ride inside soil-dwelling nematodes without harming them. .
Microorganisms are an important part of wastewater treatment during a few different steps of the process. After the sewage has been physically filtered to remove solid waste, called primary treatment, microbes break down the insoluble organic matter during secondary treatment.
Microorganisms in sewage treatment plants also convert nitrate in the wastewater to nitrogen gas that is lost to the air. This process, calleddenitrification, is important because water with a high nitrate content can stimulate huge blooms of algae that foul lakes, rivers, and streams.
Contributing to medicine
Microbes have evolved over the last 3.5 billion years to compete with one another mostly through chemical means. It’s not surprising, then, that the vast majority of the thousands of antibiotics known to us are made by microorganisms.
Because of this long history of competition and survival in the face of these chemicals, bacteria are naturally suited to develop antibiotic resistance. This means that despite having such an impressive arsenal of antibiotics, we’re still struggling to control the growth of many strains of bacteria that have become resistant to them.
Setting up your aquarium
In nature, fish live in complex environments filled with plants, insects, and microorganisms. Because of their biological complexity, natural habitats are good at absorbing and recycling fish waste, such as ammonia.
To stop this buildup of ammonia from happening, aquarium owners have to do two things:Encourage the establishment in the tank of ammonia-oxidizing bacteria and archaea that live in the filter and the tank sediment and convert ammonia to less harmful products in a process called nitrification.
Making and breaking down biodegradable plastics
Most of the plastic used today is synthetically made from petroleum and is extremely resistant to degradation. The best kind of biodegradable plastics are the ones made by bacteria because they can also be broken down by bacteria.
Turning over compostable waste
The ability of the compost pile in your backyard or in your municipal waste treatment center to turn kitchen and yard waste into what looks like dirt depends directly on microorganisms.
Maintaining a balance
The complex microbial communities on and in the human body can sometimes get out of balance. Probiotics have been designed to administer bacterial species that are beneficial to the human body.