Unit 5: Bacteria and Human Disease
Ever since Louis Pasteur first theorized that microorganisms were the source of infectious diseases, scientists have labored to learn more about the causes of disease and, more generally, the field of microbiology as a whole. As a result, the majority of microbiology research has focused on human disease and immunology (the study of the immune system). The following unit will discuss microorganisms and the diseases that they cause.
We will begin with bacteria, learning that they are mainly classified as cocci, bacilli, or spiral shaped. They are also differentiated via gram staining procedures, which indicate the amount of peptidoglycan present in a cell wall. If a bacterium contains a lot of peptidoglycan in its cell wall, it will take up the primary gram stain (crystal violet) and will appear purple (gram positive). However, if the bacterium contains a small amount of peptidoglycan and an outer membrane, it will not take up the primary stain. It will instead take up the secondary stain (safranin) and will appear red (gram negative). Each of the classes listed below has been selected for its importance to modern microbiology; take the time to learn all of their names!
Completing this unit should take you approximately 22 hours.
Upon successful completion of this unit, you will be able to:
- describe how pathogenesis occurs;
- describe the common infection sites for common bacterial species; and
- discuss pathogenic bacteria and their epidemiology.
5.1: Pathogenesis
Read this chapter. Take advantage of the PowerPoint lecture slides as you study.
5.2: Gram Positive and Negative Cocci
5.2.1: Staphylococcus
Read the section titled "Staphylococci." Watch the "Catalase Test Movie" under Fig.7. Take advantage of the PowerPoint lecture slides as you study. Study Figures 3 to 5 and 8 for micrographs.
Complete this quiz. After clicking on the link above, scroll down to "Self-Quiz" at the bottom of the page. After completing the quiz return to the first page and click on "Answers" to see the correct answers. There is a detailed introduction to this assessment above the "Self-Quiz." Be sure to visit the "Results" section, also note that clicking on the links under the empty frames brings you to annotated micrographs.
5.2.2: Streptococcus
Read this chapter on Streptococci. Take advantage of the PowerPoint lecture slides as you study. Make sure to view the last image in the left panel to identify Streptococcus.
5.2.3: Enterococcus
Read this article to learn about this microorganism, which is commonly found in fecal matter. Click on every link that is embedded in the text to explore the content.
Complete this quiz. After clicking on the link above, scroll down to "Self-Quiz" at the bottom of the page. After completing the quiz return to the first page and click on "Answers" to see the correct answers. There is a detailed introduction to this assessment above the "Self-Quiz." Be sure to visit the "Results" section, also note that clicking on the links under the empty frames brings you to annotated micrographs.
5.2.4: Neisseria
Read the section titled "Neisseria," located near the bottom of the page. The Neisseria genus includes two major classes, N. gonorrhoeae and N. meningitidis. The former causes gonorrhea, while the latter is one major cause of bacterial meningitis. The term "diplococcic" means "two cocci" or "a pair of cocci." Take advantage of the PowerPoint lecture slides as you study.
5.3: Gram-Positive Bacilli
5.3.1: Bacillus
Read this six-page article on Bacillus. Make sure you understand the relationship between Bacillus and other spore forming bacteria. Note that Bacillus anthracis causes anthrax, a disease commonly associated with bioterrorism.
5.3.2: Clostridium
Read the section titled "Anaerobic Spore-Formers (Clostridia)." The clostridium genus produces the botulinum toxin that causes botulism. The toxin is a major cause of human food poisoning throughout the world. Take advantage of the PowerPoint lecture slides as you study.
5.3.3: Listeria
Read this three-page chapter on listeria.
5.3.4: Mycobacterium and Corynebacterium
Read this chapter about Mycobacterium and Corynebacteria. The Mycobacterium genus of bacteria causes many serious diseases, including tuberculosis and leprosy. By the end of this reading, you should be able to identify which species causes which disease. Take advantage of the PowerPoint lecture slides as you study.
5.3.5: Actinomyces and Nocardia
Read this article. Focus on learning the differences between Actinomyces, Nocardia, and Streptomyces. Take advantage of the PowerPoint lecture slides as you study.
5.4: Gram-Negative Bacilli
5.4.1: Pseudomonas
Read the section titled "Pseudomonas aeruginosa".
5.4.2: Brucella
Read this article from the CDC to learn about Brucella, which typically infects only animals but can also infect humans with as little as 10 to 100 Brucella cells.
5.4.3: Bordetella and Legionella
Read this chapter covering Bordetella, Haemophilus, and Legionella. Take advantage of the PowerPoint lecture slides as you study. There is a very helpful diagram on the binding of pertussis toxin to the cell membrane. To access the diagram, click on the link to the diagram about half way down the left side panel.
5.4.4: Escherichia, Salmonella, Shigella, and Yersinia
Read the sections "Escherichia coli," "Shigella," "Salmonella," and "Yersinia." Some of these names might be familiar to you. For example, you might have heard of Escherichia before; it is the "E" in E. coli, one of the most commonly studied organisms in microbiology. Meanwhile, Salmonella is most commonly found on uncooked meats and raw vegetables and is one of the most common agents of food poisoning. Salmonella has nothing to do with the fish, salmon; it was named after Daniel Salmon, the first individual to hold a doctorate in veterinary medicine in America. Lastly, Yersinia is the cause of the bubonic plague, one of the deadliest diseases in human history. Also known as the "Black Death," it wiped out entire cities and killed hundreds of millions of people. It was so devastating that the total population of Europe was not able to recoup its numbers until more than a century later, permanently altering the course of European history.
5.5: Other Bacteria
5.5.1: Treponema and Leptospira
Read the sections titled "Treponema pallidum" and "Leptospirosis." The Treponema genus causes syphilis, a common sexually transmitted disease. Take advantage of the PowerPoint lecture slides as you study.
5.5.2: Vibrio and Campylobacter
Read the sections titled "Vibrio Species" and "Campylobacter and Helicobacter." Vibrio cholerae causes cholera. Take advantage of the PowerPoint lecture slides as you study.
5.5.3: Chlamydia
Read this article on Chlamydia. Chlamydia, a common sexually transmitted disease, is caused by Chlamydia trachomatis. Take advantage of the PowerPoint lecture slides as you study.
5.5.4: Mycoplasma
Read this chapter, which covers Mycoplasma and Ureaplasma. All Mycoplasma species lack a cell wall. Because they lack a cell wall, they are unaffected by many antibiotics (such as penicillin) that destroy bacteria by targeting cell walls. Take advantage of the PowerPoint lecture slides as you study.
Complete this quiz. After clicking on the link above, scroll down to "Self-Quiz" at the bottom of the page. After completing the quiz return to the first page and click on "Answers" to see the correct answers. There is a detailed introduction to this assessment above the "Self-Quiz." Be sure to visit the "Results" section, also note that clicking on the links under the empty frames brings you to annotated micrographs.
5.6: Antibiotics
Read this chapter on the antibiotic medication used to kill microorganisms in humans and animals.
Complete this assessment. After clicking on the link above, select the "Self-Quiz" link to download the assessment PDF file, afterwards click on "Answers" and compare your responses. There is a detailed introduction to this assessment above the "Self-Quiz." Be sure to visit the "Results" section, and click on the links to study annotated figures.