Human Microbiota Intro (9) Flashcards
What are micro-organisms that cause disease called?
Virulent/pathogenic
Akaryote
Without a nucleus
Prokaryote
Genetic material in a single DNA chain, not enclosed in a nucleus (bacteria)
Eukaryote
Distinct nucleus (protocists, fungi, plants, animals)
Koch’s postulates
Robert Koch’s criteria used to decide if microorganism caused a disease
Koch’s postulate for genes
Genes encode virulence factors
- The gene encoding the trait of interest should be present and transcribed/translated in a virulent strain and be silent in a strain that does not cause disease; disruption of the gene in a virulent strain should result in the formation of a strain that is incapable of casing disease;
Problems with Koch’s postulates
- Difficulty of isolation the causative agent
- Impossible to grow some pathogens in artificial culture
- Ethical objections
- Animal models not sufficient/don’t behave same as humans
What are Viruses?
Obligate intracellular parasites
What are viruses comprised of?
Nucleic acid (DNA/RNA) core wrapped in a protein coat (capsomeres), some have a lipid envelope
Why are retroviruses unusual?
The virion carries an RNA copy of the genome but upon infection a host cell cDNA copy of virus genome is made using reverse transcriptase
Bacteriophage
Attacks bacteria
Bacterial shapes
Round, rod-shaped, icosahedral, brick-shaped, bullet-shaped
Viroids
Naked, infectious RNA molecules - plants suffer
Prions
Causes spongiform encephalopathies e.g. BSE/CZJ
Microfungi
Eukaryotic
What are most microfungi’s cell wall made of?
Chitin (polymer of N-acetyl glucosamine)
Where else is chitin found?
Exoskeleton of arthropods e.g. insects
Moulds
Fungi that grow in mats of tiny filaments (hyphae), form mats (mycelia), can be subdivided into separate compartments by cross walls (septa), multicellular organisms related to mushrooms
What genus is most common fungi?
Cladosporium
Yeast
Unicellular fungi e.g. Saccharomyces cerevisiae
What diseases do moulds form?
Superficial infections e.g. ringworm and athlete’s foot
What diseases do yeast form?
Thrush by Candida albicans
Protista
Unicellular eukaryotes, many free-living, some cause serious infections, can infect any human tissue
How are protista spread?
- Produce cysts to survive outside the body
- Insects
- Sex
