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32 Cards in this Set
- Front
- Back
17.1
transformation |
- pick up of bacterial DNA found in the extracellular environment by a bacterium
- extracellular DNA can be the remnants of lysed, dead bacterial cells - absorbed DNA is then combined with the host genome -> DNA scavenging |
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17.2
transduction |
- injection of genetic info tino a bacterium by a bacterial virus (bacteriophage)
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17.3
conjugation |
- transfer of genetic info from one bacterium to another
- requires the presence of an extra-chromosomal DNA molecule called a plasmid - also requires cell-to-cell contact |
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17.4
streptococcal pneumonae |
- avirulent strain (rough strain)
- lacks a carbohydrate capsule |
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17.5
general recombination |
- occurs when any fragment that comes in contact with the cell is absorbed in an attempt to transform the cell
- requires a large region of homology between the fragment of DNA and the host genome - requires a number of gene products. (RecA = very important) - is a non-additive process. The new DNA replaces the corresponding host DNA |
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17.6
recA |
- it makes sure that the two strands for recombination lines up correctly and overall mediates the recombination process
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17.7
single stranded DNA binding protein |
- shield single-stranded DNA from digestion
- protects the single-stranded DNA until it is intertwined with the resident chromosome before recombination |
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17.8
phases of cell growth |
- initially: lag phase = growth is slow
- 2nd: log phase = burst of exponential growth - 3rd: late log phase = growth slows |
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17.9
when does the cell become competent |
- during the late log phase and early stationary phase of the bacteria growth curve
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17.10
competence factor |
- needed for cell to become competent
- small protein - made and secreted out into the environment - act on cell receptors on the same cell or on a different nearby cell to induce signal cascade -> expression of new genes - these genes produce proteins that are also secreted and then acts to modify the cell surface, allowing DNA to be taken up (exposing DNA receptors on the cell surface) - when competence factors are secreted in an environment, all the surrounding cells become competent, not just one |
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17.11
constitutively competent |
- can take up DNA all the time, because they have an internal mechanism that allows them to be competent without a competent factor
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17.12
Com proteins |
- help with the entrance into the cell
- form a pore in the hydrophobic membrane of the cell - DNA enters into the cell via the pore, and is digested by a nuclease, which fragments the double stranded DNA -> single strand - remaining strand is protected by a single-stranded DNA binding protein |
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17.13
endonucleases |
- if DNA fragments are too long and can't enter the cell, surface endonucleases will shorten these longer fragments.
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17.14
quorum sensing |
- occurs when the population of the cells is high enough to produce a critical concentration of the signaling molecules
- microorganisms communicate and coordinate their behavior by the accumulation of signaling molecules - a form of cell-to-cell communication |
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17.15
biofilms |
- bacteria flock to each other, forming communities
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17.16
receptor protein |
- DNA entrance into the cell
- associated with the inner cell wall pore, taking the DNA out from the periplasmic space |
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17.17
second receptor protein (DR) |
- found in gram-negative bacteria
- screens DNA as it comes into the cell - acts as a gate-keeper that only allows DNA with specific sequences that are common to the particular bacterial species |
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17.18
internally competent |
- a form of competence that does not involve a secreted external environmental factor
- ex: haemophilus influenzae |
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17.19
transformasomes |
- found on the surface of competent cells, serve as receptors for DNA
- fragments can recognize and bind to these receptors, but the receptors only recognize specific base pair sequences scattered about the DNA - only 'self' strains of DNA are taken into the cell - DNA enters the cell through transformasome |
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17.20
chemical induction |
- solution containing a high concentration of salt in introduced to the bacterial strain
- followed by alternating periods of heat and cold shock, which destabilizes membrane molecules, allowing extracellular DNA to enter the bacterium - artificially induce competence |
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17.21
electroporation |
- bacterial cells are electrocuted
- electrocuted produces transient pores or channels with electric voltages - extracellular DNA can be transfered into the cell via electric shock - artificially induce competence |
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17.22
filamentous |
- a type of virus
- simplest form of bacteria, loop of nucleic acid with a helix of protein around it, contains approx. 3-10 genes |
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17.23
icosohedral |
- still simple bacteria, but more complex than filamentous bacteriophage
- has spike to anchor the bactiophage at the ends and has an icosahedra shape to the head. - will contain 10-20 genes |
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17.24
complex |
- contain multiple parts: head, tail, appendages
- contain 30-300 genes |
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17.25
nucleic acid of bacteriophages |
- double stranded DNA
0 single stranded DNA, single stranded RNA and double stranded RNA are possible, but less frequently |
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17.26
capsid |
- protein coat of bacteriophages
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17.27
nucleocapsid |
- a capsid surround nucleic acid
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17.28
lytic infection |
- results in the killing of the infected bacterial cell
- involves infection by virulent phage - early genes -> instructions for the process of DNA replication - late genes -> mass production of the structures of the bacteriophage (head and tail) - lysis of the bacterium -> release more phages into the environment to propagate infection |
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17.29
lysin |
- protein that dissolves the cell wall, releaseing the phage into the environment
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17.30
temperate phase |
- the phage DNA is incorporated and integrated into the host genome and establishes a relationship with the host
- viral DNA will then be replicated along with the host genome producing colonies of infected bacteria - phage that enters this route is termed a Progphage - sometimes, a prophage will exit the bacterial chromosome and initiate the lytic cycle |
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17.31
characteristics of the temperate phase: |
- additive recombination of the bacterial and phage chromosomes
- site specific recombination, observed at certain positions - requires only a small region of homology - a viral protein, integrase, is involved in recorgnizing the integration site, called ATT site |
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17.32
repressor gene |
- there is a struggle between which path the phage will choose (lytic growth or lysogenic growth), dpending on the expression of this gene
- when this gene is expressed, the gene product will block the promoter for the genes that produce the structures of the page -> lysogenic phase - most of the time, ene is not expressed -> phage enters lytic phase |