Flashcards in Micro - Basic Bacteriology (Growth & Genetics) Deck (19):
Draw the bacterial growth curve, labelling its axes and 4 key phases.
See p. 125 (image bottom right); Axes: x = Time, y = Number of viable bacteria; Phases: (1) Lag phase (2) Exponential growth phase (3) Stationary phase (4) Death phase
What is the defining characteristic the lag phase of bacterial growth?
Metabolic activity without division
What is the defining characteristic of the exponential/log phase of bacterial growth?
Rapid cell division
In what phase of bacterial growth do penicillins and cephalosporins act, and why?
Exponential/log phase; Act here as peptidoglycan is being made
What is the defining characteristic of the stationary phase of the bacterial growth curve?
Nutrient depletion slows growth
In what phase of bacterial growth are spores formed, and why?
Stationary phase; Spore formation in some bacteria, due to nutrient depletion (which slows growth in this phase)
What is the defining characteristic of the death phase of bacterial growth?
Prolonged nutrient depletion and buildup of waste products lead to death
What is transformation? What is another term for this?
Ability to take up naked DNA (i.e., from cell lysis) from environment (also known as "competence")
What are examples of bacteria capable of transformation?
(1) S. pneumoniae (2) H. influenzae type B (3) Neisseria; Think: "SHiN in SHiNE SKiS" (from encapsulated bacteria mnemonic)
What kind of DNA can be used in transformation?
Any DNA can be used
What is a lab test/procedure relevant to transformation?
Adding deoxyribonuclease to environment will degrade naked DNA in medium --> no transformation seen
What are the possible kinds of conjugation?
(1) F+ x F- (2) Hfr x F-
What is the significance of the F+ plasmid? How is it transferred? What is the term for bacteria without this plasmid?
Contains genes required for sex pilus and conjugation; F+ plasmid (dsDNA) is replicated and transferred through pilus from F+ cell. No transfer of chromosomal genes; F-
What is an Hfr cell? What may result from replication in this case?
F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high-frequency recombination (Hfr) cell; Replication of incorporated plasmid DNA may include some flanking chromosomal DNA. Transfer of plasmid and chromosomal genes.
What is transposition? What may result from it?
Segment of DNA that can "jump" (excision and reintegration) from one location to another, can transfer genes from plasmid to chromosome and vice versa; When excision occurs, may include some flanking chromosomal DNA, which can be incorporated into a plasmid and then transferred to another bacterium
What are the types of transduction? What kind of event is each type?
(1) Generalized - a "packaging" event (2) Specialized - an "excision" event
What type of event is generalized transduction? What are the steps/results of generalized transduction?
A "packaging" event; Lytic phage infects bacterium, leading to cleavage of bacterial DNA. Parts of bacterial chromosome DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes
What type of event is specialized transduction? What are the steps/results of specialized transduction?
An "excision" event; Lysogenic phage infects bacterium; Viral DNA incorporates into bacterial chromosome. When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is packaged into phage viral capsid and can infect another bacterium.