Introduction to Microbiology Flashcards
What is an akaryote?
A cell without a nucleus.
What is a prokaryote?
A single-celled organism that lacks a membrane-bound nucleus, mitochondria and other membrane-bound organelles.
What is a eukaryote?
An organism with DNA contained in chromosome in a distinct nucleus.
What proportion of the cells in the human body are not of human origin?
Over 90%.
What are the cells in the human body that are not of human origin called?
Commensal flora/microbiota.
- mainly bacteria
- some fungi/protista
Why are viruses not described as human commensal flora?
They don’t have a cellular structure, and can only infect host cells.
What is the main type of bacteria found on teeth?
Streptococcus mutans.
-commensal, but also causes disease
What is the main type of bacteria found on the tongue?
Streptococcus salivarius.
What is responsible for the initiation of ‘dental caries’, and what is the main risk factor?
Streptococcus mutans.
-high sugar diets
Are most microorganisms beneficial or harmful?
Most are beneficial.
What is responsible for providing most of the vitamin K we require?
Gut commensals.
Who set out the criteria to decide whether bacteria cause disease?
Robert Koch (1834-1910). -Koch's postulates
What does Koch’s postulates state? (4)
Causative organism must:
- be isolated from every individual
- be artificially cultivated
- lead to symptoms
- be recovered from individuals infected experimentally
What does Koch’s postulate state for viruses?
- The gene should be present in a virulent strain, but not in a virulent strain
- Antibodies against the gene should protect subjects
What are the main problems of Koch’s postulates?
- Difficult to isolate causative agents
- Impossible to culture some pathogens
- Ethics - animal models not sufficient
Give an example of a bacterium that is difficult to isolate.
Mycobacterium tuberculosis.
Give an example of a bacterium that cannot be cultured.
MYCOBACTERIUM LEPRAE
-except in armadillos due to low body temperature
TREPONEMA PALLIDUM
-causes syphilis
What different illnesses does Salmonella typhi cause in mice and humans?
MICE - gastroenteritis
HUMANS - typhoid fever
What different illnesses does Salmonella typhimurium cause in mice and humans?
MICE - fatal infection similar to typhoid fever
HUMANS - gastroenteritis
What type of parasites are viruses?
Intracellular parasites.
-rely upon other cells for replication
What is the general structure of a virus?
Nucleic acid core surrounded by a protein coat.
-some also have a lipid envelope
What can viruses infect?
Every class of organism. -including bacteria
What is the nucleic acid core in viruses made up of?
Either DNA or RNA.
-not both
What is unusual about retroviruses?
RNA genome»_space; cDNA copy upon infection of the host cell using reverse transcriptase.
What makes up the protein coat on viruses?
Capsomeres.
What area of the body does the syncytial virus infect?
Respiratory tract.
What is the special class of virus that attacks bacteria?
Bacteriophage.
What type of virus infects plants?
Viroids.
-naked infectious RNA molecules
What type of viral protein is thought to cause spongiform encephalopathies?
Prions.
What type of organisms are fungi?
Eukaryotes.
What is the cell wall of most fungi made up of?
Chitin.
-polymer of N-acetyl glucosamine
Where else is chitin found?
Exoskeleton of arthropods.