Aerobic vs. Anaerobic Bacteria: Comparison & Differences

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  • 0:00 Anaerobic World
  • 0:56 Bacteria
  • 1:41 Cellular Respiration Types
  • 2:13 Anaerobic Respiration
  • 3:22 Aerobic Respiration
  • 4:18 Helpful Anaerobes and Aerobes
  • 4:50 Harmful Anaerobes and Aerobes
  • 5:38 Lesson Summary
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Lesson Transcript
Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

Expert Contributor
Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson on aerobic and anaerobic bacteria, we'll learn the characteristics of each and how they are similar and different. We'll also give some examples of each type of bacteria.

Anaerobic World

Picture a world without oxygen. You might be imagining a barren wasteland like the moon, but in this scenario, the image is just the opposite. The environment is filled with hot volcanoes spewing life-giving chemicals into the aqueous world. Somehow creatures co-exist with thousands of other species, all thriving in this unique ecosystem. What are these creatures? They are anaerobic bacteria. They are single-celled organisms that don't need oxygen to survive, and in fact oxygen will kill them. They live in the hydrothermal vents of the deepest part of the oceans and use chemicals instead of sunlight to make food.

Today, we'll learn about anaerobic bacteria that do not need oxygen to survive, as well as their well-known counterparts, aerobes, which do need oxygen. But first, what are bacteria?


Bacteria are small, single-celled organisms that don't have a nucleus (a compartment to hold their DNA). They are called prokaryotes. Other more complex cells, like the ones in our bodies, are called eukaryotic.

Bacteria can be anaerobic or aerobic. Aerobic means involving oxygen, so anaerobic bacteria can survive without oxygen. Normally, organisms use oxygen to make energy, but these organisms have found ways to get around this. All organisms make energy through cellular respiration, but they do this differently depending on if they are anaerobic or aerobic. In this lesson we'll look at the different types of cellular respiration and then show some examples of each type of bacteria.

Cellular Respiration Types

Before we get started, let's go over some basics about cellular respiration. During cellular respiration, cells use a series of chemical reactions called oxidation-reduction reactions to move electrons around. Cells take electrons from sugar, or glucose, and use the energy stored in them to make ATP, or the energy currency of the cell. Think of cellular respiration as a factory where raw materials like glucose come in, are made into products, and then sold to make money or ATP.

Anaerobic Respiration

All anaerobic bacteria make energy without oxygen. They do this in one of two ways, either through lactic acid or alcoholic fermentation. During lactic acid fermentation, cells use a molecule called NADH to take electrons from glucose. The NADH use the energy stored in the electrons to make ATP, and convert glucose to pyruvate. This process is called glycolysis and is the first step in all forms of cellular respiration. In lactic acid fermentation, the next step is to pyruvate to lactic acid. Lactic acid, although a waste product for bacteria, can be used to make human foods, like yogurt.

The other way anaerobes make energy is through alcoholic or ethanol fermentation. Like in lactic acid fermentation, NADH takes electrons from glucose and turns it into pyruvate during glycolysis. From here, the pyruvate is converted to ethanol instead of lactic acid. This is the same ethanol that we find in beverages like wine and beer. Alcoholic fermentation also makes carbon dioxide, which gives beer the carbonation.

Aerobic Respiration

Aerobic bacteria are much more efficient at making energy. Anaerobes only make two ATP molecules per glucose, but aerobes can make up to 38 ATP per glucose. Aerobic respiration can be broken down into three steps: glycolysis, the citric acid cycle, and oxidative phosphorylation.

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Additional Activities

Everyday Bacteria

In this activity, students will be looking at different species of bacteria that are harmful or helpful in our life. Although some examples were discussed in the lesson, students will take this information further, researching individual species and additional examples. Students might start with a general search, such as "helpful aerobic bacteria" and then narrow their search down to find one particularly helpful species, such as Bacillus subtilis, which aids in soil decomposition and would affect students because it is important for healthy soil, which is necessary for growing the crops that we eat.


In this activity, you are going to be expanding your knowledge of aerobic and anaerobic bacteria. Through internet research from academic sources, you will investigate three aerobic and three anaerobic species. They can be harmful or helpful to humans. For each species, you will list the scientific name, its role in the ecosystem and how it affects your personal life. Afterward, answer the reflection questions.

Oxygen UseSpecies NameImportance in the EcosystemRelevance to Your Life

Reflection Questions

  1. Which organisms were easier to find, aerobic or anaerobic? Why do you think that?
  2. Was one type of organism more helpful to humans? Why do you think that is?
  3. Why do you think it is important to study different types of bacteria?

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