Bacteriology Flashcards
What are the three components of a gram positive bacteria’s cell wall?
- Teichoic acid
- Peptidoglycan
- Plasma membrane
What are the five components of a gram negative bacteria’s cell wall?
- Lipopolysaccharide
- Phospholipid
- Lipoprotein
- Peptidoglycan
- Plasma membrane
Peptidoglycans contain… held together by…
repeating units of sugars held together by peptide chains
All gram+ cell walls contain…
teichoic acid
Where can teichoic acid be found?
Gram+ cells
Which type of bacteria will stain pink?
Which will stain purple?
Gram- stains pink
Gram+ stains purple
Teichoic acid protrudes above the cell wall, what is the effect?
A negative charge is imparted to the cell
Stains have a ___ charge, allowing for stronger bonding with cells with a ___ charge.
Stains have a negative charge, allowing for stronger bonding with cells with a positive charge.
Which feature of a gram+ cell wall is required for infection by streptococcus spp only?
M protein
How does M protein function in a gram+ cell wall?
Protrudes from cell wall making cell too large to phagocytize
Is M protein likely to mutate?
Yes, highly susceptible to mutation
Mycolic acid in a gram+ cell wall is found only in…
Mycobacterium spp
What is the structure and function of mycolic acid in a gram+ cell wall?
Waxy lipid inside cell wall structure that acts as a barrier against antibiotics and host defenses
What is the unique outer layer of a gram- cell wall?
Lipopolysaccharide
Beneath the outer membrane of a gram- cell wall lies…
a thin layer of peptidoglycan
What is the role of lipid A in a gram- cell wall?
Endotoxin that is released when cell dies
O Polysaccharides are part of…
lipopolysaccharides of the outer layer of gram- cell wall
What is the function of the O polysaccharide portion of a lipopolysaccharide?
Used as a diagnostic marker by the gram- cell
What is the primary stain of Gram stain?
Crystal violet
What is the mordant of Gram stain?
Gram’s iodide
What is the decolorizer of Gram stain?
95% ethanol
What is the secondary stain of Gram stain?
Safranin
What is the function of Gram’s iodide as a mordant in Gram stain?
Fixes dye to the material (cells, tissue, etc)
Glycocalyx consists of…
a capsule and slime layer
Many organisms are not infectious without a…
capsule (glycocalyx)
What is the function of the glycocalyx’ capsule around bacteria?
Inhibits phagocytosis
Are genes transferrable through the glycocalyx’ capsule?
Yes
Are genes transferrable through the glycocalyx’ slime layer?
Yes
Which bacterial structure is associated with dental decay?
Glycocalyx: slime layer
Describe the adherence of the glycocalyx’ slime layer to its surface
Very loose adherence to surface
What is the structure and function of fimbriae?
Sticky projections used for adherence
Where can fimbriae be found?
Gram- organisms
Are genes transferrable in the fimbriae?
Yes
What are pili?
What is their function?
Bacterial conjugations
Motility through twitching
Pili are involved in the development of…
biofilms
What feature of e. coli allows for movement from colon to bladder?
Flagella
What is the function of flagella?
Motility from one area of the body to another
What are four possible flagellar arrangements?
- Monotrichous
- Amphitrichous
- Lophotrichous
- Peritrichous
What determines whether the bacteria runs or tumbles, moving the microbe?
Direction of flagellar rotation
Which flagellar arrangement has one straight flagella?
Monotrichous
Which flagellar arrangement has one curly flagella?
Amphitrichous
Which flagellar arrangement has multiple flagella from one origin?
Lophotrichous
Which flagellar arrangement has multiple flagella from multiple origins?
Peritrichous
Endoflagella is made up of…
axial filaments
Rotation of axial filaments follows what general pattern?
Corkscrew
Axial filaments provide the ability to…
bore through tissue
Describe the speed of axial filaments’ movements
Very slow moving
What is the clinical significance of flagella and axial filaments?
- Opportunistic infections
- Escape from host defenses
- Systemic infection
What are plasmids?
DNA “doughnuts”
Extra-chromosomal pieces of DNA in bacteria
Which component of bacteria carries genes for toxins and antibiotic resistance?
Plasmids
How are plasmids transferred between bacteria?
Via pili during conjugation
Endospores are a response to…
environmental stress
Endospores are only found in…
soil-dwelling gram+ rods
What are endospores extremely resistant to?
- Heat
- Desiccation
- Toxic chemicals
- UV radiation
- Antibiotics
What are three spore formers?
- Clostridium tetani
- Clostridium botulinum
- Bacillus anthracis
What are the physical requirements for bacterial growth?
- Temperature
- pH
- Osmotic pressure
Psychrophiles and psychrotrophs are bacteria that prefer ___ for optimal growth
low temperatures
Mesophiles are bacteria that prefer ___ for optimal growth
moderate temperature
Thermophiles and hyperthermophiles are bacteria that prefer ___ for optimal growth
high temperatures
How does increased temperature affect bacteria?
Breaks chemical bonds
Human pathogens fall into the ___ temperature range.
mesophile or moderate temperature range
Majority of bacteria grow best at ___ pH.
neutral (7.0)
Pathogens prefer ___ pH
blood (7.34)
How would an alkaline (basic) pH affect bacteria?
Breaks bonds, altering protein structure, a lethal event
How would an acidic pH affect bacteria?
Breaks bonds, altering protein structure, a lethal event
What is osmotic pressure when referring to bacteria?
Pressure exerted on bacteria by their environment, especially water
High salt concentrations create a ___ environment leading to ___
hypertonic environment leading to plasmolysis
What is halophilic bacteria?
Salt-loving bacteria
What are the requirements of obligate halophilic bacteria?
High salt concentration
What are the requirements of extreme halophilic bacteria?
Very high levels of salt
What are the requirements of facultative halophilic bacteria?
Can grow with or without salt in the environment
Bacteria share many of the same requirements as…
humans
What is the relationship of most bacteria to oxygen?
Many do not require oxygen for growth and some die in its presence
What are the two types of bacteria that can grow in presence of oxygen?
- Aerobes
- Facultative anaerobes
What are obligate aerobes?
Bacteria that require O2 to grow
What are facultative anaerobes?
Bacteria that can grow with or without O2
What are obligate anaerobes?
Bacteria that die in the presence of O2
What is a binary fission of bacteria?
The process whereby bacteria increase their numbers by splitting
What is a generation of bacteria?
Each division of bacteria is a generation
By what method do bacteria divide?
Binary fission
What is generation time of a bacteria?
Time between divisions
Name the four phases of the bacterial growth curve
- Lag phase
- Exponential log phase
- Stationary phase
- Death phase
At what phase of the bacterial growth curve are there the most live cells?
Log phase (exponential growth)
What occurs to the bacteria during the lag phase of their growth?
Bacteria are adjusting to their environment
What occurs to the bacteria during the log phase of their growth?
Bacteria double exponentially with a constant minimum doubling time
How long will the log phase of bacterial growth last?
Until resources are depleted
During what growth phase are bacteria most metabolically active?
Log phase
During what growth phase are bacteria most susceptible to antibiotics?
Log phase
What happens with bacterial growth during the stationary phase?
Number of cells dividing equals the number of cells dying
(resource availability is decreasing)
The death phase of bacterial growth is also known as…
logarithmic decline phase
What are two causes of the death phase of bacteria?
Exhaustion of resources or toxicity of environment
Describe the number of bacteria during the death phase of their growth
Continuous decline in the number of dividing cells, many die
