Glossary of General Microbiology Chapters 8 and 9

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What is an activator protein?
a reulatory protein that binds to specific sites on DNA and stimulates transcription; involved in positive control.
Allosteric enzyme
An enzyme that contains two binding sies, the active site (where the substrate binds) and the allosteric site (where an effector molecule binds)
A control system when the control occurs after initiaion of transcription but before its completion.
Feedback inhibition
a decrease in the activity of the first enzyme of a pathway caused by the final product of the pathway.
Gene expression
transcription and/or translation of genes.
Heat shock proteins
a series of proteins induced by a sudden upshift in temperature or certain other stress factors that function to refold partially denatured proteins.
production of an nzyme only when its substrate is present
an enzyme that adds a phosphoryl group to a compound
Negative Control
a mechanism for regulation gene expression in which a repressor protein functions to prevent transcription of a gene or genes
One or more genes transcribed into a single RNA and under the control of a single regulatory site
Positive Control
A mechanism for regulaing gene expression in which an activator protein functions to promote transcription of a gene or genes
Quorom sensing
A regulatory system in an organism that requires a certain density of cells of the same species be present before the regulatory events occur
Prevention of an enzyme's synthesis when the product of its reaction is present in excess
Repressor protein
a regulatory prtein that binds to specific sites on DNA and blocks transcription; involved in negative control
Response regulator protein
one of the members of a two-component system;a regulatory protein that is phosphorylated by a sensor kinase protein
a messenger RNA that can bind a specific small molecule near its 5' end that alters its secondary structure and makes it unavailable for translation
Sensor Kinase protein
one of the members of a two-component system; a membrane integrated protein that phosphorylates itself in response to an external signal and then transfers the phosphoryl group to a response regulator protein
Stringent Response
a global regulatory control that is activated by amino acid starvation
Two-component Regulatory System
A regulatory system contain two proteins: a sensor kinase and a response regulator
a virus that infect prokaryotic cells
Early protein
A protein synthesized soon after virus infection
Late protein
a protein synthesized toward the end of virus infection
a bacterium containing a prophage
Lysogenic pathway
a series of steps that, after virus infection, lead to a state (lysogeny) where the viral genome is replicated as a prophage along with that of the host.
Lytic pathway
a series of steps after virus infection that leads to virus replication and the destruction (lysis) of the host cell
Minus (negative)-strand virus
a virus with an RNA genome in which the RNA strand has the oppostie sense of (s complementary to) the mRNA of the virus
the complex of nucleic acid and proteins of a virus
a gene whose expression cases formation of a tumor
a zone of lyis or cell inhibition caused by virus infection of a lawn of sensitive cells
Plus (positive)-strand virus
a virus with an RNA or DNA genome in which the genome has the same complementarity as the mRNA of the virus
an infectious protein whose extracellular form contains no nucleic acid
the genome of temperate virus when it is prelicatin with, and usually integrated into the host chromosome
a virus whose RNA genome has a DNA intermediate as part of its replication cycle
Reverse transcription
the process of copying informationi found in RNA into DNA by the enzyme reverse transcriptase
Temperate virus
a virus whose genome is able to replicate along with that of its host and not cause cell death in a state called lysogeny
in eukaryotes, a pocess by which a normal cell becomes a cancer cell
the complete virus particle; the nucleic acid surroundd b a protein coat in some cases other material
Virulent virus
a virus that lyses or kills the host cell after infection; a nontemperate virus
a genetic element containing either RNA or DNA that replicates in cells but is characterized by having an extracellular state.
small, circular, single-stranded rna that causes various plant diseases.
Various phases of virus replication
1. attachement
2. penetration
3. Synthesis
4. Assembly
5. Release
The virion attaches to a susceptible host cell
occurs for the nucleic acid and protein by cell metabolism as redirected by the virus early in the infection. late in the infection, structural proteins that are subunits of the virus capsid are synthesized, 3rd step
The capsomers assemble (and membrane components in enveloped viruses) and nucleic acids are packaged into new virions, 4th step
Mature virions are released from the cell, 5th step
an enzyme that removes the phosphoryl group from the response regulator protein at a constant rate
Examples of 2-component Regulatory Systems
Assimilation in E. coli
Nitrogen fixation in Klebsiella and Rhizobium
Sporulation in Bacillus
Nar Regulatory System
controls a set of anaerobically induced genes and contains two different sensor kinases and two different resonse regulators
Steps in Regulation of Chemotaxis and Flagellar Rotation
1.Response to Signal
2. Controlling Flagellar Rotation
3. Adaption
Response to Signal
Step One of Flagellar Rot.
Methyl-accepting chemotaxis proteins bind attractants or repellents directly
Controlling Flagellar Rotation
CheY-P causes the flagella to rotate clockwise
CheZ dephosphorylates CheY-P
Repellents increase the level of CheY-P and lead to tumbling, whereas attractants lead to a lower level of cheY-P and smooth swimming
Step 3 in Flagellar Rotatioin
the feedback loop necessary to reset the system.
Virus Size
0.02 micometers- 0.3 micrometers
Protein Shell composed of a number of individual protein molecules called structural sbunits, which are arranged in precise and highly repetitive pattern around the nucleic acid
The smallest morphological unit that can be seen with the electron microscope
a symmetric structure containing 20 faces and is roughly spherical in shape.
The most efficient arrangement of subunits in a closed shell
End point dilution
The dilution at which, 1/2 the organisms are affected
Virus infectious Unit
the smallest unit that causes a detectable effect when added to a susceptible host
Latent period
the eclips and maturation periods of Virus replication; newly synthesized virions do not appear outside the cell
Burst Size
the number of virions released during release; from a few to a few thousand
contain a single stranded RNA genome, half of which are in the plus orientation and half in the minus configuration
circularly permuted molecules
appear to have been linearized by opening a circle but at different locations

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