Microbes and Microbiology

Question 1

What are the main characteristics of viruses?

Answer 1

Viruses require a host cell to replicate, have DNA or RNA genomes, and can be enveloped or non-enveloped. They infect all life forms and are more numerous than bacteria and fungi.

Question 2

What are the main characteristics of bacteria?

Answer 2

Bacteria are single-celled prokaryotes with peptidoglycan-based cell walls, varying shapes (cocci, rods, spirochetes), and can be Gram-positive or Gram-negative

Question 3

What are the main characteristics of fungi?

Answer 3

Fungi are eukaryotic and exist as unicellular yeasts or multicellular moulds. Their cell walls contain unique polysaccharides and mannoproteins, lacking peptidoglycan.

Question 4

How do viruses interact with their hosts?

Answer 4

Viruses bind to specific cell receptors (e.g., ACE2 for SARS-CoV-2), enter the cell, and use the host’s machinery to replicate. Viral evolution occurs through mutations or genetic reassortment.

Question 5

What is antigenic drift?

Answer 5

Antigenic drift is a process where viruses accumulate small mutations, leading to gradual changes and allowing adaptation to hosts.

Question 6

What is antigenic shift?

Answer 6

Antigenic shift occurs when two viruses infect the same cell and exchange genetic material, resulting in new viral strains.

Question 7

Describe the bacterial cell wall structure for Gram-positive bacteria.

Answer 7

Gram-positive bacteria have a thick layer of peptidoglycan, which provides structural integrity and is a target for antibiotics.

Question 8

Describe the bacterial cell wall structure for Gram-negative bacteria.

Answer 8

Gram-negative bacteria have a thin peptidoglycan layer and an additional outer membrane, which acts as a barrier to certain antibiotics.

Question 9

What is unique about fungal cell walls?

Answer 9

Fungal cell walls lack peptidoglycan and contain unique polysaccharides and mannoproteins, making them distinct targets for antifungal treatments.

Question 10

What are growth-dependent methods for identifying pathogens?

Answer 10

Pathogens are cultured on agar plates and tested biochemically, such as by using carbon source tests.

Question 11

What is MALDI-TOF mass spectrometry used for in microbiology?

Answer 11

What is MALDI-TOF mass spectrometry used for in microbiology?

Question 12

How do immunoassays work for pathogen identification?

Answer 12

Immunoassays detect specific antibodies or antigens related to pathogens, useful for cases like syphilis where culturing may be difficult.

Question 13

What is the role of PCR in pathogen identification?

Answer 13

: PCR amplifies DNA from pathogens, allowing quick identification of bacteria, fungi, and viruses.

Question 14

What is the purpose of rapid tests in clinical microbiology?

Answer 14

Rapid tests are low-cost and detect infection markers in fluids, such as indicators for urinary tract infections.

Question 15

What makes enveloped viruses distinc

Answer 15

Enveloped viruses have a lipid layer that helps protect against the immune system but makes them more vulnerable to detergents.

Question 16

How does the influenza virus evolve?

Answer 16

Through antigenic drift (mutations) and antigenic shift (recombination of genome fragments), leading to new viral strains.

Question 17

Through antigenic drift (mutations) and antigenic shift (recombination of genome fragments), leading to new viral strains.

Answer 17

Gram-positive bacteria have a thick peptidoglycan cell wall, while Gram-negative bacteria have a thin peptidoglycan layer and an additional outer membrane.

Question 18

What shapes can bacteria take?

Answer 18

Bacteria can be cocci (spherical), rods, comma-shaped (vibrio), or spiral-shaped (spirochetes).

Question 19

What is a dimorphic fungus?

Answer 19

A dimorphic fungus can switch between yeast and mould forms depending on environmental conditions.

Question 20

What are the primary components of the fungal cell wall?

Answer 20

Fungal cell walls contain polysaccharides and mannoproteins, making them distinct from bacterial cell walls.

Question 21

What are three main diagnostic methods in clinical microbiology?

Answer 21

Growth-dependent methods (e.g., agar culture), immunoassays, and molecular assays like PCR.

Question 22

How does MALDI-TOF mass spectrometry help identify pathogens?

Answer 22

It analyzes protein profiles from bacterial colonies to identify species based on a mass-to-charge ratio.

Question 23

How are rapid tests used in clinical microbiology?

Answer 23

Rapid tests detect markers like nitrites and leukocytes in urine to diagnose infections like UTIs.

Question 24

What are the two main forms of fungi?

Answer 24

Fungi exist as unicellular yeasts and multicellular moulds.

Question 25

What is a dimorphic fungus?

Answer 25

A dimorphic fungus can alternate between yeast and mould forms depending on environmental conditions.

Question 26

What is the structure of moulds?

Answer 26

Moulds grow as hyphae, which are cylindrical tubes that connect to form a mycelium.

Question 27

What are the key components of the fungal cell wall?

Answer 27

The fungal cell wall contains unique polysaccharides and mannoproteins, but no peptidoglycan

Question 28

Why is the fungal cell wall a target for antifungal treatments?

Answer 28

The fungal cell wall is unique to fungi, containing components not found in human cells, making it a suitable target for antifungal drugs.

Question 29

How does Candida albicans differ in its yeast and mould forms?

Answer 29

As a yeast, Candida albicans is mostly harmless, but in its mould form, its hyphae can penetrate tissue and become pathogenic.

Question 30

What roles do fungi play in relation to humans?

Answer 30

Fungi can be symbionts, commensals, or pathogens, affecting humans in various ways from mutual benefit to disease.

Question 31

What does the term “eukaryote” signify for fungi?

Answer 31

Fungi are eukaryotes, meaning they have a defined nucleus and organelles, distinguishing them from prokaryotic bacteria.

Question 32

Metagenomics definition

Answer 32

The genomic study of genetic material recovered directly from encironemntal samples

Question 33

Differences between Illumina sequences and long-read platforms:

Answer 33

Illumina:
- widely used
- for short reads (150-250 nucleotiddes)
- high output
- low error rate

Long-read platforms:
- >10,000 nucleotide reads
- higher error rate
- more expensive

Question 34

Metagenomic techniques

Explain 16S gene profiling and its features

Answer 34

• Sequence a conserved marker gene, encoding the RNA in the small subunit of ribosomes (bacterial species have a unique 16S rRNA sequence)
• Cheap and easy to analyse
• You know what bacteria (not viruses, fungi) are there but no info on gene content

Question 35

Metagenomic techniques

Describe metagenomic sequencing and its features

Answer 35

• Sequence all DNA isolated from a sample
• Completely covers all microbiota (not just bacteria but fungi and viruses)
• Info on presence of functionally important genes, involved in virulence, antibiotic resistance
• Expensive and difficult to analyse