(Section C: Bacteriology) Lecture 18: Flashcards
3 Domains of Life
- Bacteria
- Archaea
- Eukaryotes
What domains of life are prokaryotes?
Bacteria and Archaea
Characteristics of Prokayotes
- Small
- Simple
- Most abundant cells on Earth
- Lack a nucleus
- Lack complex organelles
What do bacteria grow by?
Binary Fission
What are the 4 stages of growth for bacteria?
- Lag phase
- Logarithmic growth phase
- Stationary phase
- Death phase
What is generation time?
Doubling time
* The time needed for one generation
What are the rates of growth for bacteria?
- Some are fast (double in ~10 minutes)
- Some are slow (double in ~24 hours)
Bacteria Shape
- Coccus
- Rod
- Spirillum
What are the 5 types of bacterial classification by O2 utilization?
- Obligate aerobe
- Obligate anaerobe
- Facultative anaerobe
- Aerotolerant anaerobe
- Microaerophile
Bacterial classification by O2 utilization:
Obligate aerobe
Requires oxygen for growth
Bacterial classification by O2 utilization:
Oligate anaerobe
Oxygen is toxic for growth
Bacterial classification by O2 utilization:
Facultative anaerobe
Can use oxygen if present, but can also grow without oxygen
Bacterial classification by O2 utilization:
Aerotolerant anaerobe
Doesn’t use oxygen but oxygen is not toxic
Bacterial classification by O2 utilization:
Microaerophile
Grows best with low levels of oxygen
In taxonomy, what are the three most important groups when talking about bacteria?
- Genus
- Species
- Strain
How is genetic diversity of bacteria compared to humans?
Human genome is 99.5% identical
Bacteria genomes are very different even in the same species (e.x. E. coli has only 60% identical genome between same species)
What is the main components of a bacterial cellular structure?
- Cytoplasm
- Nuceloid
- Cytoplasmic membrane
- Cell wall
What comprises of the cell envelope in a bacteria?
Cell wall + Cytoplasmic membrane
Who was the Gram Stain named after?
Hans Christian Gram (1853-1938)
What are the two types of bacteria in Gram Stain?
- Gram positive = Purple
- Gram negative = Pink
Compare:
Gram positive vs. Gram negative cell envelope
Gram positive:
* Cytoplasmic membrane
* Cell wall outside
Gram negative:
* Cell wall sandwiched between two membranes
* Lipoproteins on the outer membrane
What are bacterial cell walls made up of?
Peptidoglycan
Describe:
Structure of Peptidoglycan
Glycan backbone:
* N-acetlyglucosamine (G)
* N-acetylmuramic acid (M)
Peptide cross-linkage
What are defining features and functions of peptidoglycan?
Rigid structure
* Prevents osmotic lysis
What is lipopolysaccharide?
An endotoxin
O-specific polysaccharide
Also called O-antigen
* Antigenic
* Highly variable
Lipid A
Disaccharide with fatty acid groupos
* Recognized by innate immune system, causes septic shock
* Part of LPS
How is a nucleoid different from a nucleus?
- No surrounding membrane
- Single, circular chromosomes (not all bacteria)
- Haploid genomes
What does haploid mean?
One set of chromosomes
Plasmids
- Extra-chromosomal genetic elements
- Usually not required for bacterial growth
What do plasmids encode for?
Often encode for ‘fitness’ factors (e.g. antibiotic resistance)
True or False:
Plasmids stay with one bacteria
False, they can be transferred from bacteria to bacteria
What are the 3 forms of host-microbe relationships?
- Commensalism
- Mutualism
- Parasitism
Commensalism
One benefits without helping or hurting the other
Mutualism
Both benefit (the host and the microbe)
Parasitism
One benefits (usually the microbe) at the expense of the other (usually the host)
What factors will make a bacterial pathogen successful?
- Colonization
- Invasion/toxicity
- Immune evasion
- Transmission
Virulence factors
Produced by pathogens
* Molecules produced by the pathogen that contribute to disease
What are virulence factors categorized into?
- Surface
- Secreted
Examples:
Surface virulence factors
- LPS (endotoxin)
- Flagella
- Pili and adhesins
- Capsules
- Secretion systems
Examples:
Secreted virulence factors
Exotoxins
What do flagella allow bacteria to do?
Allows some bacteria to be motile (chemotaxis)
How will a bacteria move depending on the flagella?
- Counterclockwise flagella rotation: Causes run (move forward)
- Clockwise flagella rotation: Causes tumble (turning)
When will bacteria have directed movement?
When an attractant is present
What are pili used for?
Attachment to:
* Surfaces
* Host tissue
* Other bacteria
Describe:
Capsules
Usually made of (exo)polysaccharides
* Forms biofilms
* Can sometimes used in vaccines
What do capsules do?
- Attachment to host tissues
- Protection from host immune system
What are the 5 stages of biofilm formation and development?
- Attachment
- Microcolony development
- Biofilm development
- Maturation
- DIssolution/Disperal (allows for spread of bacteria from the biofilm)
What are endospores?
Highly differentiated cells formed within the parent cell
What are characteristics of endospores?
High resistant to:
* Heat
* Harsh chemicals
* Radiation
True or False:
Endospores are active
False, they are a “dormant” stage of the life cycle
Where are endospores most common in?
- Soil
- Bacillus and Clostridium genera
What are exotoxins secreted from bacteria?
- Hemolysins
- Toxins that function inside host cells
- Extracellular enzymes
- Superantigens
What can exotoxins be used for?
Inactivated exotoxins can be used as vaccines
How can some bacteria become intracellular pathogens?
- Taken up and survive within phagocytic cells
- ‘Force’ their own uptake into epithelial cells
- Allows bacteria to hide from different components of the immune system
