Ch. 20 - Pathogenic Gram-Negative Cocci and Bacilli

Bauman - Microbiology with Diseases by Taxonomy 6th Edition

Bauman6th EditionMicrobiology with Diseases by TaxonomyISBN: 9780134832302Not the one you use?Change textbook

Bauman 6th Edition

Ch. 20 - Pathogenic Gram-Negative Cocci and Bacilli

Problem 1

Chapter 20, Problem 1

Label the following drawing using these words: adhesin, exotoxin, H antigens, hemolysin, iron-binding protein, K antigens, outer membrane (with common antigen, lipid A, and O antigen), fimbria, plasmid virulence genes, type III secretion system.

Verified step by step guidance

Begin by identifying the bacterial cell surface structures in the drawing. Label 'fimbria' as the hair-like appendages on the surface, which help in attachment to host cells.

Locate the 'adhesin' molecules, which are typically found at the tips of fimbriae or pili and are responsible for binding to host cell receptors.

Identify the 'outer membrane' of the Gram-negative bacterium. Within this membrane, label the 'common antigen', 'lipid A', and 'O antigen' as components of the lipopolysaccharide (LPS) layer.

Mark the 'H antigens' which are associated with flagella, and 'K antigens' which are capsular polysaccharides surrounding the cell, providing protection and aiding in immune evasion.

Label the 'hemolysin' as a secreted exotoxin that lyses red blood cells, and the 'exotoxin' as other secreted proteins that disrupt host cell functions. Also, indicate the 'iron-binding protein' which helps the bacterium acquire iron from the host, the 'type III secretion system' as a needle-like structure used to inject virulence factors, and 'plasmid virulence genes' as genetic elements often depicted inside the cell that encode for these virulence factors.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Bacterial Surface Structures and Antigens

Bacterial surface components like fimbriae, H antigens (flagellar proteins), K antigens (capsular polysaccharides), and outer membrane elements (including lipid A and O antigen) play key roles in bacterial identification, immune evasion, and pathogenicity. Understanding their structure and function helps in labeling and distinguishing bacterial parts.

Virulence Factors and Their Functions

Virulence factors such as adhesins, exotoxins, hemolysins, and iron-binding proteins enable bacteria to infect hosts, cause damage, and acquire nutrients. Recognizing these factors and their roles is essential for correctly identifying and labeling components related to bacterial pathogenicity.

Type III Secretion System and Plasmid Virulence Genes

The Type III secretion system is a specialized protein apparatus used by some bacteria to inject virulence proteins into host cells, facilitating infection. Plasmid virulence genes are mobile genetic elements that encode factors enhancing bacterial pathogenicity. Both concepts are crucial for understanding bacterial mechanisms of disease.

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Related Practice

Textbook Question

Match each bacterium with the disease or manifestations it causes.

1. _____ Escherichia coli

2. _____ Klebsiella pneumoniae

3. _____ Proteus mirabilis

4. _____ Salmonella enterica serotype Typhi

5. _____ Shigella flexneri

6. _____ Yersinia pestis

A. Bubonic plague

B. Typhoid fever

C. Gastroenteritis

D. Kidney stones

E. Pus-filled, bloody stools; cramps; fever; and diarrhea

F. Pneumonia

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Textbook Question

A physician prescribes fluid replacement to treat a patient with diarrhea. Although tests showed that a pathogenic enteric bacterium was the cause of the intestinal distress, an antimicrobial drug was not prescribed; why not?

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Textbook Question

The presence of lipid A in the outer membranes of Gram-negative bacteria.

a. Affects the formation of blood clots in the host

b. Causes these bacteria to be oxidase positive

c. Triggers the secretion of a protease enzyme to cleave IgA in mucus

d. Enables enteric bacteria to ferment glucose anaerobically

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