Difference Between Yeast and Bacteria

The main difference between yeast and bacteria is that yeast is a eukaryote whereas bacteria are prokaryotes. Further, yeast belongs to the kingdom Fungi while bacteria belong to the kingdom Monera. And yeast has membrane-bound organelles, but bacteria has no membrane-bound organelles. Moreover, some of the other differences between yeast and bacteria cells are that chitin is the main component of the yeast cell wall but, murein is the main component of the bacterial cell wall. Further, yeast has a single nucleus per cell, but bacteria do not have a nucleus.

Yeast and bacteria are unicellular organisms. A cell wall surrounds both cells, and both yeast and bacteria may undergo anaerobic respiration.

Key Areas Covered

1. What is Yeast
     – Definition, Characteristics, Importance
2. What are Bacteria
     – Definition, Characteristics, Importance
3. What are the Similarities Between Yeast and Bacteria
     – Outline of Common Features
4. What is the Difference Between Yeast and Bacteria
     – Comparison of Key Differences

Key Terms: Bacteria, Cell Wall, Cell Structure, Metabolism, Yeast

What is Yeast

Yeast refers to a microscopic fungus, consisting of single oval cell that reproduces by budding, and converts sugar into alcohol and carbon dioxide in a process called ethanol fermentation. Generally, yeast is colorless. Though it is a unicellular organism, yeast is a eukaryote. Therefore, it contains a nucleus and membrane-bound organelles. Yeast grows on plants and warm-blooded animals in a symbiotic relationship. A few of them may be parasitic such as Candida albicans, which causes vaginal yeast infection. One of the most characteristic features of yeast is its asexual reproduction method known as budding. 

Figure 1: Baker’s Yeast

Yeast undergoes external digestion by secreting digestive enzymes onto an organic material in the environment and absorbing nutrients through the cell wall. Some uses of yeast are in baking and beer production due to its ability to undergo ethanol fermentation.

What is Bacteria

Bacteria refer to a member of a large group of unicellular microorganisms, containing a cell wall but, lacking organelles and an organized nucleus. The cell wall of bacteria is made up of peptidoglycans called murein. Bacteria contain 70S ribosomes, and bacterial DNA is arranged in the nucleoid. Some bacteria may contain flagella for their movement. The basic shapes of bacteria are coccus, bacillus, and spirillum. 

Figure 2: Bacteria Structure

The main reproduction method of bacteria is the asexual reproduction, which occurs by binary fission. They contain structures called pili that assist conjugation, the sexual reproduction method of bacteria. Bacteria may cause diseases such as TB, pneumonia, tetanus, cholera, food poisoning, and sore throats.

Similarities Between Yeast and Bacteria

• Yeast and bacteria are unicellular organisms.
• They have a cell wall made up of polysaccharides.
• Both undergo anaerobic respiration.
• Both undergo extracellular digestion.
• They are heterotrophs.
• They undergo asexual and sexual reproduction.
• Both can be either saprophytes or parasites. Hence, both may cause diseases in plants and animals.
• Antibiotics are used to treat both yeast and bacterial infections.

Difference Between Yeast and Bacteria

Definition

Yeast: A microscopic fungus, consisting of single oval cell that reproduces by budding, and capable of converting sugar into alcohol and carbon dioxide in a process called ethanol fermentation

Bacteria: A member of a large group of unicellular microorganisms, containing a cell wall but, lacking organelles and an organized nucleus

Organization

Yeast: Eukaryotes

Bacteria: Prokaryotes

Kingdom

Yeast: Fungi

Bacteria: Monera

Cell Wall

Yeast: Made up of chitin

Bacteria: Made up of murein

Nucleus

Yeast: Has a single nucleus per cell

Bacteria: No nucleus

Membrane-Bound Organelles

Yeast: Has mitochondria, ER, Golgi apparatus, lysosomes, etc.

Bacteria: No membrane-bound organelles

DNA

Yeast: Linear chromosomes

Bacteria: Single circular chromosome

Ribosomes

Yeast: 80S Ribosomes

Bacteria: 70S Ribosomes

Under the Microscope

Yeast: Large cells; oval-shaped; has a budding cell

Bacteria: Small cells; spherical or rod-shaped; arranged in clusters or chains

Respiration

Yeast: Ethanol fermentation

Bacteria: Either aerobic or anaerobic respiration

Motility

Yeast: Immobile

Bacteria: Mobile with flagella

Pili

Yeast: No pili

Bacteria: May have pili

Reproduction

Yeast: Mainly reproduce by budding

Bacteria: Mainly by binary fission

Optimal pH

Yeast: 4-4.6

Bacteria: 6.5-7

Diseases

Yeast: Candidiasis, mycosis, urinary, and vaginal infections

Bacteria: Pneumonia, tetanus, TB, cholera, food poisoning, and sore throats

Importance

Yeast: Used in the production of beer, bread, and antibiotics

Bacteria: Used in the production of antibiotics and other useful chemicals

Examples

Yeast: Saccharomyces cerevisiae (baking yeast) and Cryptococcus neoformans

Bacteria: S. aureus, Lactobacillus sp., Bacillus anthracis, E. coli, etc.

Conclusion

Yeast is a eukaryotic organism while bacteria are prokaryotes. Both yeast and bacteria are unicellular organisms with a cell wall. Yeast contains a nucleus and membrane-bound organelles but, bacteria lack a nucleus or membrane-bound organelles. The main difference between yeast and bacteria is the cellular organization of both types of microorganisms.

Reference:

1. “Yeast.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 27 Jan. 2017, Available Here
2. Vidyasagar, Aparna. “What Are Bacteria?” LiveScience, Purch, 23 July 2015, Available Here

Image Courtesy:

1. “S cerevisiae under DIC microscopy” By Masur – Own work (Public Domain) via Commons Wikimedia 
2. “Prokaryote cell” By Ali Zifan – Own work; used information from Biology 10e Textbook (chapter 4, Pg: 63) by: Peter Raven, Kenneth Mason, Jonathan Losos, Susan Singer · McGraw-Hill Education. (CC BY-SA 4.0) via Commons Wikimedia