Flashcards in Midterm Exam Deck (197)
How many americans die from sepsis?
How many americans are affected with sepsis every year?
What is requred for RNA polymerase to begin transcribing DNA?
where does sigma subunit bind?
Sigma subunit leaves RNA polymerase at what point?
When polymerase begins transcribing
Amino acids attach to the ____ end of a tRNA
what is the modified amino acid corresponding to the start codon in bacteria?
f-MET (formyl methionine)
the first tRNA in translation binds in the ___ site of the ribosome
what form of energy is used for translation?
Colonization of the body by an organism
capable of causing disease
infection that causes symptoms
: A bacterium occupies and multiplies in the human body
infected but asymptomatic
Capacity of a bacterium to cause disease
Often used interchangeably with
pathogenicity. Can also refer to the degree of
disease a bacterium has the capacity to cause
(e.g., highly virulent)
Virulence (pathogenicity) factor
A component of a
bacterium that is required for disease
Who studied anthrax?
What is Koch's first postulate?
The microbe must be associated with symptoms of the disease and must be present at the site of infection
What is Koch's second postulate?
The microbe must be isolated from the lesions of disease and grown as pure culture
What is Koch's third postulate?
a pure culture of the microbe, when inoculated into a susceptible host, must reproduce the disease in the experimental host
What is Koch's fourth postulate?
the microbe must be reisolated in pure culture from the experimentally infected host
What is the proposed fifth postulate for Koch?
Elimination of the disease-causing microbe from the infected host or prevention of exposure of the host to the microbe should eliminate or prevent disease.
Molecular Koch's first postulate
The gene (or its product) should be found
only in strains of a bacterium that cause
disease and not in strains that are avirulent
Molecular Koch's second postulate
The gene should be isolating by cloning
Molecular Koch's third postulate (a and b)
3a. Disrupting the gene in a virulent strain should reduce (attenuate) its virulence.
3b. Introducting the cloned gene into an
avirulent strain should render the strain
What approaches are used to identify new virulence factors?
What does the Biochemical approach to identifying new virulence factors entail?
purify the factor (e.g., a toxin) and demonstrate that it can reproduce disease symptoms.
What four ways can you identify new virulence factors using the molecular genetics approach?
a. Clone genes from pathogen into avirulent host (e.g., Escherichia coli) and show that the resulting strain is now virulent.
b. Mutagenize pathogen with a transposon and screen the resulting random insertion mutants for loss of virulence.
c. Measure virulence gene regulation using gene fusions. ( Fuse the promoter region of a given gene (or operon) to a reporter gene, which can be used to more easily measure gene expression)
d. Identify genes that are required for survival in the host.
Transposons experimentally introduced into cells often have _______ genes in order to isolate colonies with the transposon.
antibiotic resistance genes (selectable marker)