Infection Flashcards
What two substances are always found in Gram-positive bacterial cell walls?
Peptidoglycan and techoic acids
What type of antibiotic targets peptidoglycan?
Beta-lactam
What is the role of autolysin?
It is a bacterial enzyme that cleaves peptidoglycan in order to expand the cell wall.
What makes a bacterium acid-fast?
If it contains mycolic acid
True or false: Gram-positive cells have a thin layer of peptidoglycan, whereas Gram-negative cells have a thick layer.
False: Gram-positive = thick layer; Gram-negative = thin layer
Gram-negative bacteria have a layer outside the cell wall (an outer membrane). What important molecule is found in the outer membrane, and what effect does it have?
Lipopolysaccharide (LPS)–If disrupted, the lipid portion (Lipid A) may act as an endotoxin and cause uncontrolled activation of inflammatory reaction.
What species of bacteria lack cell walls entirely?
Mycoplasma
What is the difference between pili and fimbriae?
Pili are usually longer and sparser than fimbriae.
What function do pili have?
Attachment to other bacteria and conjugation
What function do fimbriae have?
Attachment to surfaces; they are key to formation of biofilms
How do prokayotes replicate?
Binary fission
What genera of bacteria form endospores?
Bacillus and clostridium (both Gram-positive)
What layers make up an endospore?
Two membrane layers with peptidoglycan between, and an outer spore coat
What are the three classes of virulence factors?
Exoenzymes, exotoxins, and endotoxins
What are the three classes of exotoxins?
A-B toxins, membrane-disrupting toxins, and superantigens
How do A-B toxins work?
The B portion binds to the host receptor for endocytosis, then the A portion alters cell function.
What endotoxin is released as a result of dead bacteria?
Lipid A–it causes fever, vasodilation, inflammation, shock, and blood clotting.
True or false: the prokaryotic genome is made up of circular, single-stranded DNA
False: it is circular, double-stranded DNA
What are the three types of prokaryotic horizontal gene transfer?
Transformation, transduction, and conjugation
Where does the recipient cell get DNA from during transformation?
From the environment, usually from a dead cell
What is the name for a cell which is able to take up DNA from the environment?
Competent cell
How does transduction take place?
A virus infects the bacteria and as new virus particles are self-assembling, bacterial DNA may be accidentally encapsulated. This virus “infects” a new cell, transferring the DNA.
How does conjugation take place?
An F pilus connects the donor to the recipient, allowing transfer of a copy of the F plasmid (which may contain many different genes.
Compared to transformation and transduction, what is unique about conjugation?
The donor cell lives through the process
