11.1 Structure and Classification of Bacteria Flashcards
Do prokaryotes or eukaryotes have a cell wall?
Prokaryotes
List the two kinds of acellular microbes
- Bacteriophage
- Virus
What do the subgroupings of bacteria naming suggest?
- Point mutations (could alter binding of antibiotics/targets of bacteria)
- Horizontal transfer (from other bacteria)
What are some positives of bacteria in society?
- Nutrient Cycling
- Biotechnology (ethanol, genetic manipulation, food supplements)
What are some negatives of bacteria to society?
- Spoiling food (pork roast)
- Pathogens (disease for plants and animals, bioterrorism)
Why can bacteria be harmful in the case of viral infection? Give an example of this
- Can come on as a secondary infection to a viral infection
- e.g. Bacterial pneumonia following influenza infection
What are morbidity and mortality? Are they typically over-reported or under-reported?
Morbidity: Disease
Mortality: Death
Typically under-reported, especially morbidity, since people may not tell health professionals about illness.
Give one example of direct damage from bacterial infection
Bacteremia (bacteria in blood)
Give two examples of indirect damage from bacterial infection
- Gastric cancer
- Crohn’s Disease
Are infectious diseases more of an issue in low income or high income countries?
Low income (less resources: antibiotics, hygiene etc.)
Where is the site of gene expression and metabolic activity in bacteria? Why?
- Located in cytoplasm
- Genome is located in cytoplasm; no discrete organelles
Describe the chromosome of a bacterial cell, including length
- Single, circular, double-stranded DNA molecule
- <1Mb to ~8Mb
Describe the plasmid(s) of a bacteria cell, including length
- Circular DNA molecules
- Vary in size (~2-200kb)
- Vary in number (1-30+)
Describe the relationship between a bacteria’s genome size and its requirements for growth
Bigger genome -> less fastidious requirements
Describe three methods of DNA exchange in bacteria
- Conjugation (given a copy of a plasmid)
- Transformation (uptake of “free” DNA)
- Transduction (transfer by bacteriophage)
What are endospores? How are they formed?
- Complex intracelluar structures, containing DNA protected by many layers of protein
- They are formed when certain strains of bacteria replicated under high temperature, low water content, excessive radiation etc.
Why are endospores important clinically?
- Can cause deep tissue infection
- Can express toxins that cause mild-serious disease
Where is ATP generated in bacteria?
The cell membrane
What is the function of peptidoglycan in cell walls?
- Gives bacteria their shape
- Protects against osmotic pressure
What are the cell walls of gram positive bacteria made of? How many layers is it made of, and what kind of gaps does it contain?
Entirely peptidoglycan. Contains up to 100 layers, and contains interbridge gaps in peptidoglycan through which proteins can travel.
Is the peptidoglycan layer of gram positive or gram negative bacteria larger?
Gram positive
What are the two layers of the cell wall of gram negative bacteria?
- Outer membrane
- Peptidoglycan layer
What allows transport of molecules across the outer membrane of gram-negative bacteria?
Porins
What is the function of lipopolysaccharides in the outer membrane of gram-negative bacteria?
Attachment of bacteria to surfaces
What is the area of the space between the plasma membrane and the peptidoglycan layer?
Periplasmic space
Which type of bacteria (gram positive/negative) require more complex systems for protein secretion? Why?
- Gram negative
- Two layers of cell wall makes it more complicated for proteins to travel into the external environment during secretion, and so a more complex system is needed
Which type of bacteria stains which colour under a gram stain?
Gram +ve (like high pH): Purple
Gram e-ve (like low pH): Pink
Describe (with adjectives) the cell wall of mycobaceria
Waxy and hydrophobic
Describe (with technical terms) the cell wall of mycobacteria
- Plasma membrane
- Peptidoglycan
- Arabinogalactan
- Mycolic acids
- Outer lipid layer
Why is a waxy cell wall advantageous for mycobacteria?
- Macrophage resistance
- Tolerates disinfectants
What is chemotaxis?
The movement of an organism or entity in response to a chemical stimulus.
List three kinds of arrangements of flagella
- Monotrichous
- Lophotrichous
- Peritrichous
What are the fine, hair-like protein chains on bacteria called?
- Fimbriae
- Pili
How can fimbriae/pili be involved in virulence?
Attachment:
- To other cells (plant or animal)
- To surfaces (prelude to biofilms)
What is the function of an F-pilus?
To connect a donor and recipient bacteria during conjugation
What is a capsule in the context of bacteria? Does it exist in all bacteria?
Polysaccharide layer that exists beyond the cell wall. It is not in all bacteria, but can be found in both gram positive and negative bacteria.
What do capsules protect bacteria from?
- Desiccation (removal of moisture)
- Phagocytosis
Give on example of where a capsule gives a bacteria its virulence. How is this useful?
- Without capsule, streptococcus pneumonia is avirulent
- Capsule can be used in vaccine
