Week 3 - Intro to Microbiology and Bacteria

Question 1

What are the types of Microbes

Answer 1

• Bacteria
• Viruses
• Parasites
• Fungi
• Prions

Question 2

What’s the difference between Prokaryotes and Eukaryotes

Answer 2

• Prokaryotes are always unicellular while eukaryotes are often multi-celled organisms.
• Eukaryotes are more complex and larger cells than prokaryotic cells
• DNA in eukaryotes is stored within a nucleus while DNA is just floating freely in the cytoplasm of prokaryote cells

Question 3

What is bacteria

Answer 3

Bacteria are small prokaryotic organisms that are found in every habitat on earth

Question 4

Example of bacteria

Answer 4

E. Coli
Strep mutans

Question 5

What are the main characteristics of bacteria

Answer 5

• capsules
• endospores

Question 6

What is this structure and its function

Answer 6

Flagellum
Acts like a tail and propels the bacteria through substances

Question 7

What is this structure and its function

Answer 7

Capsule
- Serves as a shield which protects the cell from physical evade the host immune system.
- The ‘stickiness’ of the capsule promotes cell adhesion to surfaces, a survival advantage.

Question 8

What is this structure and its function

Answer 8

Cell Wall
- Complex semi rigid structure used to separates the exocellular and intracellular environments
- It’s also important in maintaining osmotic pressure and prevent the cell from popping
- Gram positive cell walls
- Gram negative cell walls

Question 9

What is this structure and its function

Answer 9

Cell membrane
Flexible semipermeable phospholipid bi layer which regulates the transfer of particles into the cell

Question 10

What is this structure and its function

Answer 10

Fimbriae
Fimbriae are long filamentous polymeric protein structures located at the surface of bacteria cells. They enable the bacteria to bind to specific receptor structures and thereby to colonies specific surfaces.

Question 11

What is this structure and its function

Answer 11

Plasmids
Additional genetic information which can be used by the bacteria or transferred to another bacteria through congregation. This can provide a survival advantage.

Question 12

What are endospores

Answer 12

Endospores are formed by certain bacteria. They are released when environmental conditions are unfavourable which forces the bacteria into a dormant state that lasts until conditions become favourable again.
E.g. Clostridium tentani (Tetanus)

Question 13

What’s the structure of a gram positive cell wall

Answer 13

• A thick layer of peptidoglycan
• Plasma membrane
• Has teichoic acid
• Turns purple after gram stain due to the thick peptidoglycan which can hold the stain well

Question 14

What’s the structure of a gram negative bacterial cell wall

Answer 14

• Thin layer of peptidoglycan
• Outer cell membrane
• Porins
• Lipopolysaccharides (LPS)
• Turns pink after gram stain because the thin peptidoglycan layer doesn’t hold the purple stain well.

Question 15

What are the Macromolecules of the Cell Wall

Answer 15

• Peptidoglycan
• Teichoic Acid (only in gram positive)
• Lipopolysaccharides (LPS) (only in gram negative)

Question 16

What are the different shapes of bacteria

Answer 16

• Coccus (sphere)
• Bacillus (rod)
• Spirochete (spiral) - don’t really need to know

Question 17

What macromolecule is found in gram indeterminant bacteria cell wall

Answer 17

Mycolic Acid

Question 18

What are the phases of bacteria growth

Answer 18

1. Lag time
2. Exponential phase
3. Stationary phase
4. Death phase

Question 19

Explain lag phase in the phases of bacteria growth

Answer 19

The initial phase where the bacteria are adjusting to their environment and the bacteria are not dividing.

Question 20

Explain exponential phase in the phases of bacteria growth

Answer 20

Period of rapid cell division (binary fission), bacteria multiplies at a constant rate, leading to a logarithmic growth

Question 21

Explain stationary phase in the phases of bacteria growth

Answer 21

Stage where nutrients become limited, waste product accumulates or other environmental factors impact growth. Growth rate slows and the number of new cells being producing equals the number of cells dying causing population to stabilize

Question 22

Explain death phase in the phases of bacteria growth

Answer 22

Number of dying cells exceeds the number of new cells produced and conditions become increasingly unfavorable for bacteria growth leading to the decline in population. At this stage endospores may be released to make the bacteria dormant.

Question 23

What factors impact bacteria growth

Answer 23

Main
-pH
- Water and osmotic pressure
- Oxygen and atmosphere

Others
- nutrients
- temperature
*all bacteria require different requirements

Question 24

What are Obligate Anaerobe

Answer 24

Bacteria which don’t grow in oxygen
e.g. Prevotella

Question 25

What are Aerobe

Answer 25

Bacteria which requires oxygen to survive e.g. Myobacterium tuberculosis

Question 26

What are Faculative Anaerobes

Answer 26

Bacteria which can grow with or without oxygen e.g. staphylococcus spp

Question 27

What are aerotolerant bacteria

Answer 27

grows in the presence of oxygen but doesn't use it. e.g. Lactobacillus

Question 28

What is Microaerophilic bacteria

Answer 28

Requires low levels of oxygen e.g. Neisseria spp

Question 29

What is capnophilic bacteria

Answer 29

Requires CO2 e.g. Campylobacter jejuni

Question 30

How do bacteria reproduce

Answer 30

Binary Fission - process by which prokaryotic organisms divide and reproduce

Question 31

Explain the steps of bacteria reproduction (binary fission)

Answer 31

1.The genetic material (DNA) is replicated 2. Bacteria elongates and the genetic material and organelles move to other sides of the cell 3. A new cell wall forms down the middle of the bacteria cell 4. Two daughter cells pull apart

Question 32

Why does bacteria horizontal gene transfer occur

Answer 32

- Creates biodiversity in population which increases resilience in the population - Creates evolutions and mutations such as antibiotic resistance which favours the bacteria population - transfer of genetic material - creates diversity in population - Genes for antibiotic resistance, ability to use new metabolites

Question 33

What are the types of horizontal gene transfer in Bacteria

Answer 33

- Transformation - Transduction - Conjugation

Question 34

Explain process of transformation (bacteria horizontal gene transfer)

Answer 34

The uptake of free genetic material from the environment. This only occurs if the bacteria is competent (the ability to take up free DNA) 1. Free DNA is transported across the cell membrane and entered a new bacteria cell 2. Homages recombination occurs which is where the foreign DNA aligns with similar sequences in the bacterial genomes and incorporates itself into it resulting in new proteins or the development of new traits

Question 35

Explain the process of transduction (bacteria horizontal gene transfer)

Answer 35

The transfer of foreign genetic material by a virus 1. A bacteriophage (virus) attaches to a bacteria cell and injects its genetic material 2. The viral genetic material is integrated into the bacteria's DNA and is directed to replicate the phages DNA and produce new phage particles 3. Occasionally fragments of the bacterial DNA is mistakenly packaged into the new phase particle instead of viral DNA and is released to infect new bacterial cells 4. The phage particle infects another bacterial cell and injects bacterial DNA which is integrated into the gene of the new bacteria. This may lead to the production of new proteins and traits

Question 36

Explain the process of conjugation (bacterial horizontal gene transfer)

Answer 36

The transfer of genetic material between 2 bacteria using cell to cell contact - the transfer is unidirectional and the donor cell contains the fertility factor making it a F+ cell and it has the sex pilus structure 1. Donor cell creates physical contact with a precipitant cell using its pilus 2. The pilus creates a channel like structure where the F- plasmid is transferred to the recipient cell 3. The recipient cell now carrying the transmitted genetic material can now express the fertility factor and a F- cell

Question 37

What are the different types of host microorganism association

Answer 37

- Mutualism - Commensalism - Parasitism - Opportunism

Question 38

What is mutualism in a host microorganism association

Answer 38

Microorganism and host live together to their mutual benefit E.g. Bacteria in stomach of ruminants break down cellulose and in return they receive nutrients

Question 39

What is commensalism in a host microorganism association

Answer 39

Microorganism benefit while host is unharmed (non of this relationship occurs in humans) E.g. Mosses on trees

Question 40

What is parasitism in a host microorganism association

Answer 40

Microorganism benefits at the expense of the host E.g. Most infections caused by microorganisms (bacteria, viruses, parasites)

Question 41

What is opportunism in a host microorganism association

Answer 41

Microorganisms that would not normally cause an infection, but do so because of an alteration in host or change in environment E.g. - Oral bacteria enter bloodstream, causes infective endocarditis - occurs when you floss and cause bleeding opens blood vessels to oral bacteria - Antibiotic use allows Candida to flourish which causes thrush. Antibiotics will remove a lot of oral microbes which allows the growth of Candida

Question 42

What is the acid only found in Gram positive bacteria

Answer 42

Teichoic Acid

Question 43

What is the acid only found in gram negative bacteria

Answer 43

Lipopolysaccharide

Question 44

Where is it not normal to find any micoorganisms

Answer 44

Blood vessels

Question 45

What is a Mycoplasma

Answer 45

Type of bacteria with no cell wall but is protected from osmotic pressure as they live inside other cells.