Flashcards in Microbiology Deck (94)
What is meant by an akaryote?
Without a nucleus
What percentage of cells within the body are human body cells?
What is the difference between human commensal flora and human microbiota?
Theyre the same thing
What is the human microbiota made up of?
Mostly bacteria, but some fungi and protists aswell
Are viruses considered part of human microbiota?
No, as dont have a cellular structure and all they can achieve outside of a host cell is infection of another host cell
In what 2 ways can viruses persist in the body?
1) As latent infections
2) Persistent sub-clinical infections
Microbiota varies depending on anatomical site - what microbiota tends to be found on the teeth and what on the tongue?
Teeth - Streptococcus mutans
Tongue and other soft tissues of the mouth - Streptococcus salivarius
Which microbiota is responsible for dental caries, in which people are they most common?
Streptococcus mutans - microbiota found on the teeth
Common in people with a diet high in sugar
What 2 terms are used to describe microorganisms which may cause disease?
Virulent or pathogenic
Which vitamin would we require a constant supply of in the absence of gut commensal flora?
What is Koch's Postulates?
Criteria used to decide if a microorganism caused disease
What are Koch's 4 postulates?
1) The causative organism must be isolated from every individual suffering from the disease in question
2) The causative organism must be cultivated artificially in pure culture
3) When the causative organism is inoculated from the pure culture, they typical symptoms of the infection must result
4) The causative organism must be recoverable from individuals who are infected experimentally
What extra postulate would possibly be added to Koch's postulates in modern day?
Ab to be raised against the causative organism in natural cases and in organisms infected artficially
What are Koch's postulates for genes? 6
1) The gene encoding the trait should be present and transcribed/translated in virulent strain
2) The gene encoding the trait of interest should not be present or should be silent in a strain that does not cause disease
3) Disruption of the gene in a virulent strain should result in formation of a strain which is incapable of causing disease
4) Introduction of the gene into a strain that previously did not cause disease should transform the strain into one that does cause disease (NB. some virulence traits may require the expression of more than one gene)
5) The gene must be expressed during infection
6) Ab raised against the gene product or the appropriate cell-mediated immunity should protect experimental subjects against disease
What are the 4 problems with Koch's postulates?
1) Difficulty of isolating the causative agent
2) Impossible to grow some pathogens in artificial culture
3) Ethical objections
4) Animal models not sufficient
Name one microorganism which can be difficult to isolate, what does it cause?
Mycobacterium tuberculosis, causes TB is very difficult to isolate
Name 2 pathogenic microorganisms which cannot be grown in artificial culture, what do they cause?
1) Mycobacterium leprae - causes leprosy, cannot be grown in artificial culture except in the foot of the 9 banded armadillo
2) Treponema pallidum causes syphillis
What do viruses consist of?
A nucleic acid core wrapped in a protein coat - some are enveloped and some are naked
Do viruses have DNA or RNA core?
Either but not both
Why are retroviruses unusual in terms of their action upon infection?
Contain an RNA copy of a genome but on infection of host cell a cDNA copy is made using reverse transcriptase which is then incorporated into the host cell DNA
What is the name of the units that make up the protein coat surrounding viruses?
What is the name of the class of viruses which attacks bacteria?
What is the name of viruses which infect plants?
What (in prevailing opinion) causes spongiform encephalopathies?
Infectious proteins known as prions
Are all fungi, prokaryotes, eukaryotes or akaryotes?
What is chitin?
Polymer of N-acetyl glucosamine that is found in the cell walls of the majority of fungi
Other than fungi what other organisms is chitin found in the cell walls of?
Exoskeleton or arthropods
What are moulds?
Fungi that grow in mats of tiny filaments known as hyphae that form mats called mycelia
What is the difference between aseptate hyphae and septate hyphae?
Hyphae may or may not be seperated into compartments by cross walls known as septa
Septate hyphae tend to be more advanced fungi than aseptate hyphae