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25 Cards in this Set
- Front
- Back
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What are the differences between gram negative and gram positive bacteria?
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Gram Positive:
-thick peptidoglycan layer -stains purple/blue ex. Staphylococcus, Streptococcus, Bacillus Gram Negative: -LPS: lipopolysaccharide -Pore (porin proteins) -thin peptidoglycan layer -red/pink staining ex. E coli, Salmonella, Pseudomonas |
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What are the forms of DNA?
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E coli chromosome - 1 mm
Bacterium - several micrometers in length DNA - 1000x longer than bacterium and must be condensed (supercoiling) DNA in prokaryotes is a shape of a closed circle DNA in eukaryotes are coiled in a double helix, have supercoils |
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What is the Bacterial Genome?
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collection of genes carried by a bacterium on its chromosome and on its extrachromosomal genetic elements (plasmids)
Geome: double stranded DNA circular DNA Haploid: 1 set of genome only (mycoplasma) chemical structure: A, C, G, T (exception = unmethylated CpG) |
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What is a gene?
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specific nucleotide sequence of DNA which determines the synthesis of polypeptide, or replication of suitable molecule of RNA
nucleoid - genes essential for bacterial growth carried on a single chromosome, also where that bacterial DNA resides all bacterail cells are haploid |
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What are plasmids?
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small genetic elements capable of independent replication in bacteria
replication is initiated by means of special sequences and regulatory proteins. including region ORI; controled by feedback loops most are circular double stranded DNA, but some are linear they may carry a gene that give the bacterium a selective advantage abundant in nature: -interons = directly repeated sequences that regulate plasmid bacterial cell count make their presence by conferring phenotypes of cells harboring them |
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What is Vector pUC19?
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plasmid cloning factor
has multiple cloning site has many restriction enzymes site of origin = site of replication ampR = resistance genes, ex. antibiotic resistance genes antibiotic resistance in bacteria |
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What is a bacterial plasmid and examples?
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small, circular molecules of DNA that carry genes for both their own replication and one or more cellular functions
Examples of 4 E. Coli plasmids: F (fertility) factor = enables conjugation, a bridge between 2 bacteria in contact Col (collicinogenic) factor = proteins that can kill other bacteria R factors = resistance to Ab or poisons; inactivate antimicrobials or reduce bacterial cell permeability Cryptic plasmids - no known function |
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What are Virulence Plasmids?
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Ent = enterotoxin production
Hly = hemolysin production CFA-1,CFA-II - adhesins production |
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What are the different procedures for bacterial disease diagnosis?
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Gram Stain and AFB stain are most important for lab diagnosis
Gram Stain used for: -identify bacterial cause of disease -staining done on samples like pus, sputum -preliminary AB treatment |
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What are characteristics of the Bacterial Growth Curve?
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four phases:
Lag: -metabolic activity but no cell division -initial phase -detoxifying medium -turning on enzymes to utilize medium Log: -rapid cell division -generation time = time it takes one cell to divide into two -metabolically active (bacteria most vulnerable to Ab) Stationary: -rate of division equals rate of death = steady state -nutrients used up -toxic products produced acid-alkalies Death: -rate of death exceeds rate of division |
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What are the distinguishable features of Viruses, Viroids, and Prions?
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Viruses:
-obligate intracellular agents -consist of either DNA or RNA, surrounded by a protein coat Viroids: -obligate intracellular agents -consist only of RNA, no protein coat Prions: -Obligate intracellular agents -consist only of protein; no DNA or RNA |
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What are some properties of Viruses?
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filterable agents (discovered this way)
obligate intracellular parasites - depend for biochemical machinery of host cell for energy, proteins reproduction is by self-assembly of individual components in host cell may be RNA or DNA but not both have a naked caspid or envelope morphology viruses are not living and must be infectious to endure in nature |
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What are some properties of Virions?
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DNA or RNA + structural proteins, +/- enzymes and nucleic acid = nucleocapsid (naked caspid virus)
enveloped virus = nucleocapsid, glycoprotein, and membrane 300 nm visible and 1/4th size of staphylococcus bacteria |
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What are Bacteriophages?
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Virulent bacteriophage:
-causes a lytic cycle, resulting in a death of a cell and production of new phage particles Lysogenic bacteriophage: -DNA integrates into bacterial chromosome, but does not cause lysis and production new phage particles prophage - integrative phage's DNA into host DNA A bacterial cell with prophage is called lysogenic cell Phages are very useful because: 1. simple genomes 2. rapidity of multiplication 3. enormous number of progeny produced in small volumes |
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What is the Phage Multiplication Cycle? (Lytic and Lysongenic)
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Lytic cycle:
1. adsorption of phage particle to host cell (phage replication) 2. injection of DNA 3. replication of phage DNA and synthesis of phage proteins 4. self-assembly of phage components 5. release of new phage particles, cell lysis example is formation of plaque Lysogenic cycle: 1. Phage attaches to host cell and injects DNA 2. Phage DNA integrates within the bacterial chromosome, becoming a prophage 3. Bacterium reproduces normally |
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What is induction and what can induce the induction process?
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definition:
-process where a temperate phage switch life cycle from lysogenic to lytic cycle ex. UV radiation, specific viral proteins, carcinogens |
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What is Gene Transfer?
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transfer of genetic material between prokaryotes is called horizontal or lateral gene transfer
3 ways: 1. Transformation: -involves naked DNA 2. Conjugation: -nvolves direct cell contact 3. Transduction: involves phages/virus |
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What is Transformation?
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-discovered by Griffiths in 1928 during experiment with Streptococcus pheumoniae
-later Avery, McCarty and MacLeod discovered DNA as transforming agent -DNAase degrades DNA, thereform transformation is affected by DNAase -the state of recipient cell is called competence competence is dependent on several conditions: -certain stages of bacterial culture's growth (exponential phase) -secretion of a small protein. called competence factor, stimulates production of 8-10 new proteins required for transformation (DNA-binding protein, endonucleases, and autolysins) |
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What is conjugation?
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-discovered in 1946 by Laderberg and Tatum
-in 1952 Hayes demonstrated gene transfer was polar -polarity is mediated by plasmid known as F-factor -donor (F+ fertile) and recipient (F- nonfertile) -F- bacteria results from a one-way genetic material transfer from male to female common in Gram Negative -transfer of genetic material by direct contact, esp. important in Gram negatives -mediated by pili (F pili) -allows transfer of plasmids -direct contract between 2 bacterial cells |
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Who was given the Nobel Prize in Physiology in 1958?
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George Beadle, Edward Tatum, and Joshua Lederberg
first half by beadle and tatum for discovering that genes act by regulating definite chemical events second half is to Lederberg for genetic recomination and organization of genetic material in bacteria |
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What is the pathway for Gene Transfer by conjugation?
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1. An F+ and an F- make contact and form a cytoplasmic bridge
2. One strand of the plasmid is nicked 3. Strand elongation at the 3' end displaces the 5' end into the bridge 4. The single strand end is cut after out after one complete circle is transferred. At the same time the complementary plasmid strand is synthesized in the F- cell 5. The ends are ligated restoring the double stranded circular configuration Conjugation is very useful in genetic mapping of bacteria (ex. E Coli) |
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How was transduction discovered and what is DNA transfer transduction?
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discovered by Zinder and Lederberg in 1951-1953, classified as transfer of bacterial DNA with bacteriophages
-two good examples of bacteriorphages are Phage T4 and Phage Lamda -T4 multiplies by lytic cycle which kills the host and lambda multiplies by lysogenic cycle which does not cause death of the cell -in lysogeny the phage DNA remains latent in the host until it breaks out in a lytic cycle |
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What is Generalized Transduction?
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Steps of cycle:
-phage attacks cell wall and injects DNA -bacterial chromosome breaks and biosynthesis of phage DNA and protein occurs -cell lyses releasing phages carrying bacterial DNA -phages infect other bacterial cells -crossing over can occur producing a recombinant cell -The bacteriophage incorporates a random piece of host-DNA during packaging which is an error in viral packaging during the lytic cycle -occurs in Gram Positive (Staph and Strep) |
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What is Specialized Transduction?
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STEPS:
-specialized attachment sites into bacterial genome -phage becomes lysogenic and replicates as part of bacterial genome during normal DNA replication for a long period of time (prophage) -some later time prophage detaches from bacterial chromosome carrying a number of bacterial genes -prophage then enters lytic cycle to produce numerous phage particles which are incorrectly excised from site of attachment -results in HIGHER frequency of recombinants ex. Corynbacterium diphtherieae |
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Who won the Nobel Prize for Physiology in 2005?
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Barry Marshall and Robin Warren for discovery of bacterium Helicobacter pylori and role in gastritis and peptic ulcer disease
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