Glucose is a simple sugar and the product of broken-down carbohydrates, such as starches. Most organisms, including humans, animals and bacteria, can use this six-carbon molecule to generate energy in the form of adenosine triphosphate, or ATP. Microaerophilic bacteria have the ability to use different pathways for breaking down glucose, depending on the amount of oxygen present in the environment.
Background
Obligate aerobic bacteria require oxygen to live and obligate anaerobes must live in environments without oxygen. Microaerophilic bacteria are able to survive in conditions with only a small amount of oxygen, according to the U.S. Food and Drug Administration. Examples of microaerophiles include Campylobacter jejuni, which is a common cause of foodborne illness from chicken, and Streptoccocus spp, which are common pathogens on dairy products, seafood and prepared foods. Microaerophilic bacteria can break down glucose to generate ATP in the presence or absence of oxygen.
Glycolysis
Glucose breakdown by microaerophilic bacteria may start with glycolysis, which does not require oxygen, according to Access Excellence. The steps of this pathway break down glucose into smaller carbon-containing molecules. The process of glycolysis requires two molecules of ATP and generates four molecules of ATP, for a net gain of two molecules of this high-energy compound. During glycolysis, microaerophilic bacteria produce pyruvate, which can go into aerobic respiration or into fermentation pathways, depending on available oxygen.
Aerobic Respiration
If oxygen is present, microaerophilic bacteria can use oxidative respiration to break down the pyruvate produced in glycolysis. In the Krebs cycle, each molecule of pyruvate becomes a molecule of acetyl CoA, according to The Biology Web at Clinton Community College. The acetyl CoA enters oxidative -- or aerobic -- respiration, consisting of an electron transport system in the mitochondria of the bacterial cell. Each molecule of glucose generates 36 to 38 molecules of ATP from the aerobic pathway.
Fermentation
Lactic acid bacteria are examples of microaerophilic bacteria that carry out fermentation to break down carbohydrates, according to FAO. Lactic acid bacteria, such as species of Lactobacillus and Streptococcus, are common in dairy products. The natural carbohydrate in milk is a sugar called lactose, which is made up of glucose and galactose, another six-carbon sugar. In lactic acid fermentation, microaerophilic bacteria do not require oxygen to break down glucose, and the product, lactic acid, may delay food spoilage.
References
- U.S. Food and Drug Administration: Bad Bug Book: Campylobacter Jejuni
- U.S. Food and Drug Administration: Bad Bug Book: Streptococcus Spp
- Access Excellence: Glycolysis: Part 1
- Interactive Concepts in Biochemistry: Oxidative Phosphorylation
- Food and Agriculture Organization of the United Nations: Bacterial Fermentations
- Access Excellence: Glycolysis: Part 2
- Clinton Community College: The Biology Web: Cellular Respiration
