Bacterial Morphology And Growth Flashcards
How many bacterial phyla are there?
Thousands
How many species of bacteria are there?
100 million ish
How many species of bacteria are there in the human gut?
500-1000
How many species of bacteria cause human disease?
<100
What are the 6 methods for classifying bacteria?
Size Gross structure Cell wall Differential strains Morphology Growth requirements
Where is DNA in bacteria?
Free in the cytoplasm
What is the bacterial membrane made up of ?
Peptidoglycan
Do bacteria have mitochondria
No
Do bacteria have membrane bound organelles?
No
What does a gram negative cell wall look like?
Extra outer membrane with integral lipopolysaccharides and periplasmic space
What does a gram positive cell wall look like?
Thick peptidoglycan layer which is integral with lipo and lipoteichoic acid
What does an acid fast cell wall look like?
Thick outer layer of mycolic acids linked by arabino-galactans integral with lipoarabinomannan
What is a gram stain?
A differential cell wall stain dividing bacteria into gram positive and gram negative
What colour does a gram positive bacteria go when it stains?
Purple/black
What colour does a gram negative bacteria go when it stains?
Red/pink
Give the steps in doing a gram stain
- Fix the bacteria
- Add crystal violet
- add iodine
- wash with alcohol
- add carbol fuschin or safranin
What is the purpose of adding the iodine in a gram stain?
Traps the crystal violet
What is the purpose of adding the alcohol in a gram stain?
Dissolves the crystal violet, so if its not strongly attached to the cell wall the colour disappears
What are the two types of acid fast stain?
Carbol fuschin and auramine
What colour is carbol fuschin?
Red
What colour is auramine?
Fluorescent
Why may some bacteria not stain?
Some bacteria don’t have a cell wall so can’t stain
What is an obligate aerobe?
A bacteria that requires some oxygen to make ATP
What are the three types of obligate aerobes? (don’t need names, just general description)
Most tolerate O2
Some only tolerate 5% O2
Some require a higher O2 conc than in air
What is a facultative anaerobe?
Use oxygen fermentation or anaerobic respiration
What is an aerotolerant anaerobe?
Cannot use oxygen but can tolerate it
What is an obligate anaerobe?
Oxygen is toxic to them
What can bacteria with the lac gene do?
Ferment lactose
What are the 8 factors that affect growth rate of bacteria?
- division rate
- lag phase time
- oxygen availability
- carbon availability
- temperature
- pH
- inhibitors
- growth factors
