Textbook Question
Mycobacterium avium-intracellulare was considered relatively harmless until the late 20th century, when it became common in certain infections. Explain how this bacterium’s pathogenicity changed.
1136
views
Ch. 19 - Pathogenic Gram-Positive Bacteria
Bauman6th EditionMicrobiology with Diseases by TaxonomyISBN: 9780134832302
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch. 1 - A Brief History of Microbiology31
- Ch. 2 - The Chemistry of Microbiology28
- Ch. 3 - Cell Structure and Function39
- Ch. 4 - Microscopy, Staining, and Classification25
- Ch. 5 - Microbial Metabolism51
- Ch. 6 - Microbial Nutrition and Growth37
- Ch. 7 - Microbial Genetics51
- Ch. 8 - Recombinant DNA Technology21
- Ch. 9 - Controlling Microbial Growth in the Environment36
- Ch. 10 - Controlling Microbial Growth in the Body: Antimicrobial Drugs21
- Ch. 11 - Characterizing and Classifying Prokaryotes29
- Ch. 12 - Characterizing and Classifying Eukaryotes34
- Ch. 13 - Characterizing and Classifying Viruses, Viroids, and Prions23
- Ch. 14 - Infection, Infectious Diseases, and Epidemiology35
- Ch. 15 - Innate Immunity34
- Ch. 16 - Adaptive Immunity21
- Ch. 17 - Immunization and Immune Testing29
- Ch. 18 - Immune Disorders22
- Ch. 19 - Pathogenic Gram-Positive Bacteria25
- Ch. 20 - Pathogenic Gram-Negative Cocci and Bacilli28
- Ch. 21 - Rickettsias, Chlamydias, Spirochetes, and Vibrios25
- Ch. 22 - Pathogenic Fungi47
- Ch. 23 - Parasitic Protozoa, Helminths, and Arthropod Vectors44
- Ch. 24 - Pathogenic DNA Viruses23
- Ch. 25 - Pathogenic RNA Viruses30
- Ch. 26 - Applied and Industrial Microbiology29
- Ch. 27 - Microbial Ecology and Microbiomes22
Bauman6th EditionMicrobiology with Diseases by TaxonomyISBN: 9780134832302Not the one you use?Change textbook
Chapter 19, Problem 1
Why are mycoplasmas able to survive a relatively wide range of osmotic conditions, even though these bacteria lack cell walls?
Verified step by step guidance1
Understand the typical role of the bacterial cell wall: It provides structural support and protection against osmotic pressure changes, preventing the cell from bursting in hypotonic environments.
Recognize that mycoplasmas lack a cell wall, which usually makes bacteria more vulnerable to osmotic stress because they don't have this rigid protective layer.
Identify the unique feature of mycoplasmas that compensates for the absence of a cell wall: their cell membrane contains sterols (such as cholesterol), which are uncommon in most bacteria.
Explain how sterols in the membrane increase membrane stability and rigidity, allowing mycoplasmas to maintain their shape and resist osmotic lysis despite lacking a cell wall.
Conclude that the presence of sterols in the plasma membrane is the key adaptation that enables mycoplasmas to survive a wide range of osmotic conditions.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mycoplasma Cell Structure
Mycoplasmas are unique bacteria that lack a rigid cell wall, unlike most bacteria. Instead, they have a flexible plasma membrane reinforced with sterols, which provides structural support and helps maintain cell integrity under varying environmental conditions.
Recommended video:
Guided course
05:59
Overview of Prokaryotic Cell Structure
Osmotic Pressure and Cell Wall Function
In typical bacteria, the cell wall protects against osmotic lysis by resisting internal turgor pressure. Without a cell wall, cells are usually vulnerable to bursting in hypotonic environments, but mycoplasmas compensate through membrane adaptations to survive osmotic stress.
Recommended video:
Guided course
05:42Cell Junctions
Role of Sterols in Membrane Stability
Sterols, such as cholesterol, are incorporated into the mycoplasma membrane, increasing its rigidity and reducing permeability. This adaptation stabilizes the membrane against osmotic fluctuations, allowing mycoplasmas to endure a wider range of osmotic conditions despite lacking a cell wall.
Recommended video:
Guided course
03:23Types of Membrane Proteins
Related Practice
Textbook Question
How does Staphylococcus aureus affect the matrix between cells in the human body?
a. S. aureus triggers blood clotting, which coats the matrix and inhibits cellular
communication.
b. S. aureus produces an enzyme that dissolves hyaluronic acid and thus enables it to pass between the cells.
c. S. aureus possesses a hyaluronic acid capsule that causes leukocytes to ignore the bacterium as if it were camouflaged.
d. S. aureus does not affect the matrix but instead produces a necrotizing agent that dissolves body cells.
42
views
Textbook Question
Which of the following bacteria causes a common type of food poisoning?
a. Streptococcus sanguis
b. Clostridium tetani
c. Staphylococcus aureus
d. Streptococcus pyogenes
34
views
Textbook Question
Label acetylcholine. Color the sites of action of botulism toxin on a nerve cell.
1105
views
Textbook Question
Match the genera of pathogens to their appearance in stained smears: Actinomyces, Bacillus, Clostridium, Mycobacterium, Staphylococcus, Streptococcus.
(a) Methenamine silver <IMAGE>
(b) Gram <IMAGE>
(c) Gram <IMAGE>
(d) Acid fast <IMAGE>
(e) Gram <IMAGE>
(f) Gram <IMAGE>
1027
views
Textbook Question
For each of the following diseases or conditions, indicate the genus (or genera) of bacterium that causes it.
___ Scalded skin syndrome
___ Osteomyelitis
___ Pharyngitis
___ Scarlet fever
___ Pyoderma
___ Rheumatic fever
___ Glomerulonephritis
___ Sinusitis
___ Otitis media
___ Anthrax
___ Myonecrosis
___ Diphtheria
___ Leprosy
___ Dental caries
___ Acne
A. Staphylococcus
B. Streptococcus
C. Mycobacterium
D. Listeria
E. Propionibacterium
F. Corynebacterium
G. Bacillus
H. Clostridium
I. Actinomyces
967
views