L 18 and 19 antibiotic resistance

Question 1

3 was genetic information can be shared within a species

Answer 1

transformation
conjugation
transduction

Question 2

exogenote

Answer 2

the DNA that was introduced from a donor cell

Question 3

endogenote

Answer 3

the cell’s own original chromosome

Question 4

transformation

Answer 4

the release of naked DNA into the environment by the lysis of the donor cells. The recipient cells uptake the DNA. Detergents and nucleases can interfere with transformation. Uptake is regulated/active process

Question 5

competence

Answer 5

the ability to take up DNA from the environment. Encoded on the chromosomal genes of many species of bacteria. The genes become active under certain environmental conditions and transformation occurs readily

Question 6

process of transformation in the gram+ bacterium Streptococcus pneumoiae

Answer 6

1. donor cells release naked DNA (by death, lysis, or trauma) Donor enzymes chop the released DNA into smaller pieces. Naked DNA is highly susceptible to environmental factors
2. pneumococcal cells secrete a protein competence factor that induces cells to synthesize special proteins needed for competence
3. protein on the cell surface binds to double stranded DNA indiscriminately. One strand is degraded as it passes into the membrane
4. the remain strain undergoes either: Degradation, circularization, or recomination

Question 7

circularization

Answer 7

if the exogenote can replicate it will be inherited as a plasmid

Question 8

Conjugation

Answer 8

aka mating bc it requires cell to cell contact. The donor cells contains a plasmid with the genes required for conjugation. The donor plasmid is called the conjugal plasmid.

Question 9

R plasmids

Answer 9

conjugal plasmids containing genes for antibiotic resistance. Many carry more than one antibiotic resistance gene. can replicate itself. evolve quickly.

Question 10

Process of conjugation by gram- E. coli

Answer 10

1. genes on the R plasmid encode for a sex pilus, which captures the recipient cell and then is retracted to form a mating pair.
2. conjugation bridge forms between the 2 cells and DNA is passed via transfer replication
3. cells detach

Question 11

transfer replication

Answer 11

replication initiates at the origin of transfer (oriT) and proceeds by the rolling circle mechanism. First one strand breaks and is pulled away from its complement through the conjugation bridge. The strands (one in each cell) then replicate to reform double stranded R plasmids

Question 12

transduction

Answer 12

mediated by bacteriophages. The phage contains a protein capsid with genomic nucleic acid inside (RNA or DNA). some bacteria are avirulent unless infected by a phage with genetic material coding for a toxin such as Vibrio cholerae or Corynebacteria diphtheria

Question 13

phage infections

Answer 13

a phage infects a cell by first aDsorbing or binding to a specific receptor on the cells surface and then injecting its genome into the interior of the cell

Question 14

2 types of phages

Answer 14

1. lytic

2. temperate

Question 15

lytic phages

Answer 15

virulent. Cause lysis of the host cell. the phage genome replicates, proteins are synthesized and assembled into capsids, the replicated genomes are packaged within those capsids, the host cell lyses and the progeny escape into the environment to continue the process

Question 16

Temperate phage

Answer 16

amy initiate a lytic growth process or enter a quiescent form called a prophage. The host continues to live with a latent prophage that it passes on to its dependents. AKA lysogen

the chromosome may either circularize as an autonomously replicating plasmid or by physically integrating into the host chromosome.

Question 17

transduction occurs in

Answer 17

gram - and gram + bacteria (both kinds of transduction) but is usually limited to their own species.

Question 18

clinical conditions associated with lysogenized bacteriophage

Answer 18

C. diphtheria B-phage and V. cholerae CTX

Question 19

what characteristics of R plasmid concern the medical community

Answer 19

1. most carry multiple genes for antibiotic resistance
2. are capable of spreading between species- rapid dissemination of resistant conjugal plasmids
3. mediate their own transfer through conjugation
4. nonpathogenic bacteria carry R plasmids creating a reservoir for neighboring pathogenic bacteria- if a pathogen picks up a R-plasmid with multiple resistances then it becomes very difficult to treat

Question 20

viron

Answer 20

a protein capsid enclosing a genomic nucleic acid

Question 21

plasmid geneome

Answer 21

always double stranded DNA
autonomous, self-replicating 
extra-chromosomal
circular or linear
varies in size
bacteria can have more than one

usually code for virulence factors i.e. pili or toxins and proteins that confer antibiotic resistance

Question 22

conjugative plasmids

Answer 22

usually F or R plasmids
can autonomously transfer themselves from one host to another, between individuals of the same species or in other species

Question 23

non-conjugative plasmids

Answer 23

cannot transfer themselves, however they can be transferred by a conjugative plasmid. used for genetic engineering

Question 24

bacteriophage genome

Answer 24

RNA or DNA
single or double stranded
linear or circular

can encode genes for virulence factors such as toxins (cholera or diptheria B- toxin)

Question 25

transposable elements

Answer 25

genetic units that mediate their own transfer from one location in a genome to anther location within the same genome or from one genome to another.

Do not transfer DNA from one cell to another by themselves

frequently carry antibiotic resistance

Question 26

Insertion sequence (IS) element

Answer 26

a segment of DNA about 1000 bp that only carries genes for its own transposition. These genes include: site-specific recombinase and two distinct nucleotide recognition sequences located at each terminus in inverted order.

can mediate their own transfer from one genome to another

if an IS element transposes into a gene its insertion will interrupt that gene and eliminate its function

Question 27

transposition

Answer 27

occurs infrequently
involves recognition by the recombinase of the terminal inverted repeats and a target area into which a new copy of the IS element will be inserted. So types of IS elements leave the original copy behind while others remove the original copy

Question 28

transposons

Answer 28

central core of genes bounded by two IS elements. Bc they contain two IS elements they carry the genes necessary for transposition. The core genes can encode for a variety of functions including resistance to antimicrobrial agents

Question 29

transposable prophage

Answer 29

2 IS elements flank a bacteriophage. Therefore the phage genes permit lysogenic infection of a host, after infection the phage can integrate virtually anywhere in a chromosome and can then transpose itself to new locations

Question 30

conjugan transposon

Answer 30

2 IS elements flank genes that encode antibiotic resistance and conjugal machinery

transposon can jump from location to location but can also mediate their own transfer to other cells (same or different species) Cannot replicate itself- relies on the host for replication

Question 31

clinical relevance of transformation

Answer 31

Streptococcus pneumoniae, Haemophilus influenzae
& Neisseria gonorrhea use transformation to alter appearance of clinically important surface antigens
permits evasion of host immune system*

Question 32

4 types of transposable elments

Answer 32

i) insertion sequence (IS) elements ; ii) transposons; transposable prophages; and iv) conjugal transposon.