Micro Review 1 Flashcards
What is the lac operon
is an operon required for the transport and metabolism of lactose in Escherichia coli and many other enteric bacteria. Although glucose is the preferred carbon source for most bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available.
what is the metabolite of lactose?
Allolactose.
what is the function of allolactose?
it is an inducer.
What happens in the presence of glucose?
the operon is switched off until the glucose has been used. this suppression is catabolites repression.
What is required for the turn on of the lac operon?
cAMP
What happens with catabolites expression?
in the presence of glucose the lac operon is off. when the level of glucose decreases, cAMP increases. cAMP then binds to catabolites activator protein (CAP). the cAMP-CAP complex binds to a site near the promoter of the operon and facilities the binding of RNA polymerase to the promoter.
In the the presence of lactose, the lac repressor is inactivated and high level of cAMP facilitates binding of RNA polymerase to the promoter and transcription of lac operon happens
What are the genes of the lac operon
A, Y, Z
What is the gene Z
Gene Z -β-galactosidase is an exoglycosidase which hydrolyzes the β-glycosidic bond formed between a galactose and its organic moiety. It may also cleave fucosides and arabinosides but with much lower efficiency. It is an essential enzyme in the human body. Deficiencies in the protein can result in galactosialidosis or Morquio B syndrome. In E. coli, the gene of β-galactosidase, the lacZ gene, is present as part of the inducible system lac operon which is activated in the presence of lactose when glucose level is low.
What are the 4 types of bacterial transfer
conjugation, transformation, transduction and transposition
What is bacterial conjugation
is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells.[1] Discovered in 1946 by Joshua Lederberg and Edward Tatum,[2] conjugation is a mechanism of horizontal gene transfer as are transformation and transduction although these two other mechanisms do not involve cell-to-cell contact.[3]Bacterial conjugation is often regarded as the bacterial equivalent of sexual reproduction or mating since it involves the exchange of genetic material. During conjugation the donor cell provides a conjugative or mobilizable genetic element that is most often a plasmid or transposon.[4] Most conjugative plasmids have systems ensuring that the recipient cell does not already contain a similar element.transferable drug resistance
What are the key parts of the conjugation
F plasmid, F+cells, F- Cells and sex pili
What is Hfr conjugation
it is when the Plasmid can be incorporated into the bacterial chromosome through a cross over of F+ plasmid and the chromosome and the results in the Hfr.
What makes Hfr conjugation different from conjugation
its drags a whole copy of the chromosome into the existing chromosome into the F-cell instead of the a piece of the chromosome.
What is transduction
Transduction is the process by which DNA is transferred from one bacterium to another by a virus.[1] It also refers to the process whereby foreign DNA is introduced into another cell via a viral vector. Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in conjugation), and it is DNase resistant (transformation is susceptible to DNase). Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell’s genome.
What are the processes of transduction
generalized and specialized
What is transformation
Transformation is one of three processes by which exogenous genetic material may be introduced into a bacterial cell, the other two being conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of foreign DNA by a bacteriophage virus into the host bacterium). This process is more favorable to Streptococcus pneumonia, H. Influenza and some Bacillus. this tends to happen in cells that are in the late log phase during sporulation.
What happens to the DNA once its inside the cell for transformation
it is incorporated into the existing chromosomes of the cells by recombination in order to survive.
What are the components of the cell wall for GNB (3 distinct units)
Lipid A
Core polysaccarhide
Outer polysaccarhide
What is the function of the lipid A
it is a endotoxin that when in the bloodstream causes endotoxin shock
What is the function of the outer polysaccharide
up to 25 repeating units of 3 to 5 sugars. This is the important somatic antigenic determinant (O-antigen) used to ID certain bacteria in the laboratory.
