Microbiology

Question 1

Differences between archeal and bacterial phospholipids

Answer 1

Archea

• Have phytanyl side chains
• Contain ether linkages (C-O)
• Contain L-glycerol

Bacteria

• Unbranched side chains
• Contain ester linkages (O=C-O)
• Contain D-glycerol

Question 2

Describe the external structures unique to prokaryotes

Answer 2

Glycocalix
- Slime layer made up of glycoprotein that allows the bacteria to adhere to their environment

Capsules
- Thick polysaccharide layer that prevents phagocytosis (Gram -ve only)

Pili and Fimbriae
- Allow for adherence to the host in pathogenic/parasitic relationships

Flagella
- Hollow tubules made of flagellin used for locomotion

Question 3

Define Binary Fission

Answer 3

Binary fission is when a bacterium splits into two equally sized daughter cells, each containing a copy of the mother cells genetic material

Question 4

Describe the stages of the bacterial cell cycle

Answer 4

B/G1 = Cell growth phase (time taken varies)
C = Chromosome replication (40mins)
D = Septum formation + cell division (20mins)

Question 5

Why does cell division time in bacteria vary?

Answer 5

Some bacteria can have a division time of <60 mins due to them starting another round of chromosome replication immediately before cell division. This means that the daughter cells acquire a chromosome that is already halfway through replication, speeding up the time taken to replicate rest of the chromosome.

Question 6

Name 2 methods of measuring bacterial growth

Answer 6

Spectrophotometry (measuring the optical density)

Dilution + plate count

Question 7

What makes a pathogen?

Answer 7

A microorganism that is able to cause disease in an animal, plant or insect. A pathogen shows both Invasiveness and Toxicity.

Question 8

Name 4 routes of transmission of bacteria

Answer 8

1. ) Inhalation of contaminated air –> Respiratory diseases
2. ) Ingestion of contaminated food/water –> intestinal diseases
3. ) Contact with another infected host –> STDs
4. ) Bites from an infected organism –> vector-borne diseases

Question 9

Name the methods underpinning invasiveness

Answer 9

• Colonisation
• Production of extracellular substances which facilitate invasion (invasins)
• Evasion of host defenses

Question 10

Name the methods underpinning toxicity

Answer 10

• Causing damage to the host by producing Exotoxins
• Destruction of cellular structures
• Can also produce Cytotoxins, Endotoxins and Neurotoxins

Question 11

How do antibiotics work?

Answer 11

They interfere with a bacteria-specific biological process, such as;

• cell wall synthesis
• cell membrane structure
• protein synthesis
• nucleic acid synthesis

Question 12

How do you define fungi?

Answer 12

Fungi are microorganisms that do not contain chlorophyll and have a rigid cell wall made of chitin or cellulose

Question 13

Name 2 microscopic and 2 macroscopic features of fungi

Answer 13

Micro

• Chitin cell walls
• Spore production

Macro

• Fruiting bodies
• Hyphae

Question 14

Describe how fungi obtain nutrition

Answer 14

Fungi assimilate a wide range of organic compounds and produce a wide range of secondary metabolites.
Fungi are responsible for decay and recycling of organic material as they are saprophytes.
They can also break down recalcitrant macromolecules like cellulose, keratin and lignin.

Question 15

Discuss fungal infection in humans

Answer 15

Most fungi are harmless to humans and tend to be opportunistic pathogens, so they typically infect those who are immunocompromised.
Only about 50 species are known to cause human
disease, serious infection tends to be rare, but superficial
infection is common
Fungal infection in more common in plants

Question 16

Discuss fungal infection in plants

Answer 16

Fungi affect plants by

• Producing degenerative enzymes
• Destruction of plant growth regulators
• Production of toxins that interfere with cell membranes + mitochondria
• Altering metabolic activities of the plant
• Blocking water transport and transpiration

Question 17

Discuss methods of controlling fungal infections

Answer 17

Antibiotics exploit differences between eukaryotic and prokaryotic cells, however, control is difficult as fungi develop resistance to anti-fungal agents and the host is likely to suffer from side effects

Question 18

Define Archea

Answer 18

Archea are prokayotic, unicellular organisms that inhabit ecological niches

Question 19

List the problems associated with thermophiles surviving at high temperature

Answer 19

• Denaturation of biomolecules – Particularly protein and nucleic acids
• Membrane fluidity – membranes become more fluid
• Solubility of gasses in liquids – decease in gas concentration proportional to temperature and pressure

Question 20

List the adaptions of thermophiles that allow them to survive at high temperatures

Answer 20

• Phospholipid monolayer
• Membranes can contain C rings
• More thermostable proteins
• Increased K+ levels protect DNA

Question 21

List the adaptions of psycrophiles that allow them to survive at low temperatures

Answer 21

• Cell membranes contain unsaturated lipids

- Use of anti-freeze proteins

Question 22

Define gene transfer

Answer 22

Gene transfer is the movement of genetic material. This can be horizontal (between organisms) or vertical (between generations.) eg./ photosynthesis was transferred between algae and euglena

Question 23

Define endosymbiosis in relation to gene transfer

Answer 23

Endosymbiosis is the process by which one cell engulfs another, this can also lead to horizontal gene transfer
This can be seen in Mitochondria and Chloroplasts:
• Contain DNA
• Contain own ribosomes
• Sensitive to antibiotics
• Sequencing data demonstrates gene transfer
• Eukaryotic nucleus contains bacterial genes

Question 24

What are the basic features and functions of viruses?

Answer 24

Features

• Nucleic acids surrounded by protein coat
• Replication is dependent on host cell
• Intracellular and extracellular phases

Functions

• Introduced into population
• Spread + infect other members
• Escape the bodies defenses
• Cause disease

Question 25

Name the 4 categories of virus

Answer 25

1. ) Retrovirus 2. ) Single-stranded RNA (+ and - sense) 3. ) Double stranded RNA virus 4. ) Double stranded DNA virus

Question 26

Describe how a Retrovirus infects a cell

Answer 26

1. ) Entry 2. ) Viral reverse transcriptase converts one RNA strand into ssDNA and the dsDNA 3. ) dsDNA reaches the nucleus 4. ) Viral integrase incorporates dsDNA into host DNA 5. ) Transcription and translation of viral DNA 6. ) Proteins produced to produce new virion casings 7. ) Virions encapsulated and released

Question 27

Describe how a -ve sense ssRNA virus infects a cell

Answer 27

1. ) Entry 2. ) -RNA strand converted to +RNA strand via viral RNA polymerase in nucleus 3. ) RNA replication 4. ) mRNA translated to produce viral proteins 5. ) Virions produced

Question 28

Describe how a +ve sense ssRNA strand infects a cell

Answer 28

1. ) Entry 2. ) RNA is translated in cytoplasm 3. ) Genome is replicated 4. ) Viral proteins used to produce new virions 5. ) Virions bud from cell

Question 29

Describe how a dsDNA virus infects a cell

Answer 29

1. ) Entry 2. ) Viral DNA transported to nuclues 3. ) Host RNA polymerase converts Viral DNA to mRNA 4. ) Viral mRNA translated, protein transported back to nucleus 5. ) Viral DNA replicated 6. ) Viral DNA and proteins re-assemble and released

Question 30

Describe how a dsRNA virus infects a cell

Answer 30

1.) Entry 2.) Proteins in virus develop into inner core 3.) 10 mRNA gene segments inserted into core 4.) -RNA strand is copied on viral mRNA to replicate genome 5.) Inner core used for: • mRNA transcription • Virion progeny production

Question 31

Describe the life cycle of a lytic bacteriophage

Answer 31

1. Attachment 2. Penetration 3. Transcription 4. Replication of phage DNA, Synthesis of proteins 5. Assembly 6. Release

Question 32

Describe the Life cycle – temperate bateriophage

Answer 32

1. Attachment 2. Linear phage DNA circularizes 3. Replication (lytic) or 3. Integration (lysogenic) • Excision/Replication 4. New virions formed 5. Cell lyses releasing phage virions

Question 33

Explain the biology of smallpox and why it is now extinct

Answer 33

Smallpox was a wide spread disease spread by person-to-person contact. It had a 20-30% mortality rate. The virus was eliminated via a successful vaccination program, smallpox was a good target for this as; - It was exclusive to humans - It had easy to spot symptoms allowing for easy quarantining of carriers - Only one serotype - Vaccine was 100% successful

Question 34

Pros and cons of an attenuated Polio vaccine

Answer 34

``` Pros • Effective • Lifelong immunity • Induces immune (antibody) response similar to natural infection • Indirect community immunization through spread of the attenuated virus • Administration (oral) • Booster vaccines not required ``` Cons • Vaccine-induced (iatrogenic) poliomyelitis • Spread to contacts without consent • Unsafe for immunodeficient individuals

Question 35

Pros and Cons of an inactivated Polio vaccine

Answer 35

Pros • Can be incorporated into routine immunizations with DPT • Good stability in transport and storage • No risk for poliomyelitis in recipients and contacts • Safe for immunodeficient individuals ``` Cons • Does not induce local (gut) immunity • Booster vaccines required • Administered as injection • Higher community vaccination levels required ```

Question 36

Name the two important proteins of the coat of an influenza virus and their functions

Answer 36

Hemagglutinin (HA) - Attaches to host receptors | Neurminidase (NA) - Breaks down sialic acid to allow budding

Question 37

What is the difference between antigenic shift and antigenic drift

Answer 37

Antigenic drift - Minor mutations occurring regularly (eg./ seasonal flu) Antigenic drift - Recombinance between flu strains that infect different species leading to re-assortment of the genome (eg./ Spanish flu)

Question 38

Ways that microbes obtain C and energy?

Answer 38

C - Photosynthesis/organic material | Energy - Respiration/fermentation

Question 39

Name some of the Biogeochemical cycles that microbes play a key role in

Answer 39

Carbon cycle Nitrogen cycle Sulphur cycle Iron cycle

Question 40

Name some positive interactions between microbes and other organisms

Answer 40

``` Mycorhizzae - between plant roots and fungi Lychens - Fungi and algae Rumminants Leaf cutter ants Gut microbiota ```

Question 41

Name methods of removing products from a fermentor

Answer 41

``` Common methods include: • Distillation, • Precipitation & Flocculation • Centrifugation • Filtration, • Solvent Extraction • Chromatography ```

Question 42

Define Algae

Answer 42

Eukaryotic microorganisms that contain cholorplasts and can perform photosynthesis, they can be both macro and microscopic