Study Guide

Prokaryotes In the Real World

  • Health


    Evolution of antibiotic resistance is a deeply troubling phenomenon. As antibiotics are increasingly overused, antibiotic resistance is growing. For a chart showing how quickly antibiotic resistant strains have emerged following development of any given treatment, please follow this link.

    Antibiotic resistance is alarming, but there are a number of things that we can do to deal with this.

    Antibiotics Should Be Finished to Completion

    Finishing antibiotic regimes is an important, but simple, thing to do. When you are prescribed antibiotics, be sure to finish the prescription. Exposing the bacteria in your body to low levels of antibiotics (as occurs if the regime is not finished), kills off the weaker bacteria and allow for hardier bacteria to proliferate. Ultimately this leads to proliferation of antibiotic-resistant bacteria.

    Don’t Use Antibiotics for Viral Infections

    Second of all, it’s important to know that antibiotics are not effective against most colds. Colds and flus are typically viral diseases, and antibiotics don’t have any effect on viruses. Excessive use of antibiotics, again, can lead to development of antibiotic resistance and spread of antibiotic bacteria.

    Reduce the Use of Antibiotics in Livestock

    A lot of antibiotic resistant bacteria follow from the practice of giving antibiotics to the animals that are grown for food, whether or not those animals are sick. You don’t need to be a pig farmer to implement this recommendation; you can choose food grown without using antibiotics.

    Find New Antibiotics

    Develop new antibiotics. People are looking for altogether new antibiotics and derivatives of existing ones. One promising way to think of new ways to modify existing antibiotics is to study how bacteria become resistant to existing antibiotics. In the "Themes in Biology: Evolution" section above we talked about how resistance to the antibiotic streptomycin comes from mutation of one amino acid residue in a ribosomal protein. Now that we know this information, we can study precisely how that antibiotic interacts with that protein and maybe design an antibiotic that would still work on the mutant protein as well as the normal ("wild type") one.

  • Economics

    Industrial Microbiology

    Microbes have been used in industry for a long time, principally for a process called fermentation. Fermentation is what happens when microbes use food for energy in environments without using oxygen.


    Vinegar is made from the fermentation of alcohol in wine, cider, or even beer by acetic acid bacteria. Yogurt is made from bacterial fermentation of a sugar (lactose) in milk to produce lactic acid. A number of other products are made by bacterial fermentation including pepperoni from meat, sauerkraut from cabbage, and pickles from cucumbers.

    In the laboratory we typically grow bacteria in petri dishes and test tubes, but in industry, bacteria are grown in much larger containers called fermenters, where they are used for a number of things.

    Image from here.

    Xanthan Gum: You’re Eating More Bacterial Products Than You Thought

    Xanthan gum is a thickening agent found in food (e.g. salad dressing) and cosmetic products (e.g. shampoo). Xanthan gum is the EPS of the bacterial species Xanthomonas campestris. Xanthan gum is produced by growing huge Xanthomonas campestris cultures and then purifying the EPS.

    Although Xanthomonas campestris naturally makes EPS, the strain used for industrial xanthan gum preparation is genetically manipulated to make it grow on whey, a cheap and readily available food source. Food industry scientists were scratching their heads over what to do with an excess of whey (a lactose-rich liquid by-product of cheese making). They decided to introduce genes into Xanthomonas campestris that would allow the bacterium to grow with lactose as a food source.


    Most antibiotics were identified from microbes and, to this day, are produced in large cultures of either bacteria or fungi (a kingdom of eukaryotes). These bacteria or fungi are genetically manipulated to make sure they are producing a lot of the antibiotic quickly. Bacteria are used to produce a number of other drugs beyond antibiotics as well as the components of vaccines.


    Another new application for microbes is the growing energy source of biofuels. Fossil fuels are made from the carbon remains of photosynthetic organisms that lived a long time ago, taking up energy from the sun and CO2 from the air. Of course, lots of plants are doing just that today, and represent a huge potential energy source, if we can learn how to tap it.

    Scientists are investigating methods of biofuel production from a number of different angles.
    Bacteria are obviously good at degrading things and growing in strange place. Many scientists are focused on finding ways to get bacteria (or some eukaryotic microbes) to break down leftover plant parts from crop harvests, such as corn stalks, into forms that are useful, safe, energy-rich fuels. Yet others are focusing on photosynthetic eukaryotic microbes themselves as the energy source.

  • History

    Behavior Changes and Diseases

    Bacteria cause a number of diseases. Pathogenic bacteria are often present in the environment but their ability to spread is affected by technological developments and the way we live. Our understanding of how disease works has helped in this process. If we understand how diseases are spread, we can often fix the problem.

    Cholera: Breakdowns in Clean Water Systems

    Cholera used to be important across the world, including in North America. It is still a big killer in developing countries, but has, for the most part, been eliminated from the developed world by universal access to clean drinking water. As soon as water systems are interrupted, however, cholera can quickly make incursions. This was seen after the 2010 earthquake in Haiti as well as in various ongoing warzones.

    Progress, however, continues to be made in both high-tech and lower-tech ways. Check out this cool success story about cholera in Bangladesh.

    Lyme Disease: Symptom of Suburbanization

    The bacteria that cause Lyme disease lived in deer for a long time. The disease only became a serious issue as the suburban population of humans increased, and natural predators of deer (like wolves) decreased. Humans now live in much closer contact with a larger deer population than they did before. This has resulted in the spread of the bacteria to humans and the high levels of Lyme disease we see today.

    Certified Lyme disease killers (below):

    Legionnaires’ Disease: A Disease of Climate Control

    Legionnaires’ disease is a deadly disease that begins with cold-like symptoms. It is named after its first appearance at an American Legion conference in Philadelphia in 1976. Legionnaires’ disease is caused by a bacterial infection of macrophages, cells involved in our immune systems.

    Legionella bacteria enter the body through inhalation of small droplets in liquid (called aerosols) into the lungs. Our exposure to Legionella-infected aerosols has risen with the invention and use of aerosol-generating equipment such as air conditioners and humidifiers.


    Each of these diseases follows from shifts in human behavior. Our approach to treating infectious diseases therefore needs to encompass both chemical agents like antibiotics as well as broader societal issues like wolf populations, clean water, and clean air conditioners.