Microbes and Microbiology Flashcards
What are the main characteristics of viruses?
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.
What are the main characteristics of bacteria?
Bacteria are single-celled prokaryotes with peptidoglycan-based cell walls, varying shapes (cocci, rods, spirochetes), and can be Gram-positive or Gram-negative
What are the main characteristics of fungi?
Fungi are eukaryotic and exist as unicellular yeasts or multicellular moulds. Their cell walls contain unique polysaccharides and mannoproteins, lacking peptidoglycan.
How do viruses interact with their hosts?
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.
What is antigenic drift?
Antigenic drift is a process where viruses accumulate small mutations, leading to gradual changes and allowing adaptation to hosts.
What is antigenic shift?
Antigenic shift occurs when two viruses infect the same cell and exchange genetic material, resulting in new viral strains.
Describe the bacterial cell wall structure for Gram-positive bacteria.
Gram-positive bacteria have a thick layer of peptidoglycan, which provides structural integrity and is a target for antibiotics.
Describe the bacterial cell wall structure for Gram-negative bacteria.
Gram-negative bacteria have a thin peptidoglycan layer and an additional outer membrane, which acts as a barrier to certain antibiotics.
What is unique about fungal cell walls?
Fungal cell walls lack peptidoglycan and contain unique polysaccharides and mannoproteins, making them distinct targets for antifungal treatments.
What are growth-dependent methods for identifying pathogens?
Pathogens are cultured on agar plates and tested biochemically, such as by using carbon source tests.
What is MALDI-TOF mass spectrometry used for in microbiology?
What is MALDI-TOF mass spectrometry used for in microbiology?
How do immunoassays work for pathogen identification?
Immunoassays detect specific antibodies or antigens related to pathogens, useful for cases like syphilis where culturing may be difficult.
What is the role of PCR in pathogen identification?
: PCR amplifies DNA from pathogens, allowing quick identification of bacteria, fungi, and viruses.
What is the purpose of rapid tests in clinical microbiology?
Rapid tests are low-cost and detect infection markers in fluids, such as indicators for urinary tract infections.
What makes enveloped viruses distinc
Enveloped viruses have a lipid layer that helps protect against the immune system but makes them more vulnerable to detergents.
How does the influenza virus evolve?
Through antigenic drift (mutations) and antigenic shift (recombination of genome fragments), leading to new viral strains.
Through antigenic drift (mutations) and antigenic shift (recombination of genome fragments), leading to new viral strains.
Gram-positive bacteria have a thick peptidoglycan cell wall, while Gram-negative bacteria have a thin peptidoglycan layer and an additional outer membrane.
What shapes can bacteria take?
Bacteria can be cocci (spherical), rods, comma-shaped (vibrio), or spiral-shaped (spirochetes).
What is a dimorphic fungus?
A dimorphic fungus can switch between yeast and mould forms depending on environmental conditions.
What are the primary components of the fungal cell wall?
Fungal cell walls contain polysaccharides and mannoproteins, making them distinct from bacterial cell walls.
What are three main diagnostic methods in clinical microbiology?
Growth-dependent methods (e.g., agar culture), immunoassays, and molecular assays like PCR.
How does MALDI-TOF mass spectrometry help identify pathogens?
It analyzes protein profiles from bacterial colonies to identify species based on a mass-to-charge ratio.
How are rapid tests used in clinical microbiology?
Rapid tests detect markers like nitrites and leukocytes in urine to diagnose infections like UTIs.
What are the two main forms of fungi?
Fungi exist as unicellular yeasts and multicellular moulds.
What is a dimorphic fungus?
A dimorphic fungus can alternate between yeast and mould forms depending on environmental conditions.
What is the structure of moulds?
Moulds grow as hyphae, which are cylindrical tubes that connect to form a mycelium.
What are the key components of the fungal cell wall?
The fungal cell wall contains unique polysaccharides and mannoproteins, but no peptidoglycan
Why is the fungal cell wall a target for antifungal treatments?
The fungal cell wall is unique to fungi, containing components not found in human cells, making it a suitable target for antifungal drugs.
How does Candida albicans differ in its yeast and mould forms?
As a yeast, Candida albicans is mostly harmless, but in its mould form, its hyphae can penetrate tissue and become pathogenic.
What roles do fungi play in relation to humans?
Fungi can be symbionts, commensals, or pathogens, affecting humans in various ways from mutual benefit to disease.
What does the term “eukaryote” signify for fungi?
Fungi are eukaryotes, meaning they have a defined nucleus and organelles, distinguishing them from prokaryotic bacteria.
Metagenomics definition
The genomic study of genetic material recovered directly from encironemntal samples
Differences between Illumina sequences and long-read platforms:
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
Metagenomic techniques
Explain 16S gene profiling and its features
- 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
Metagenomic techniques
Describe metagenomic sequencing and its features
- 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
