Unit 2: Microbial Identification, Genetics, and Growth Study Guide

Question 1

What are the three methods of microbial identification?

Answer 1

1. Metabolic/biochemical characteristics: aerobe vs anaerobe; uses cultures to identify metabolic properties of bacteria ex: adding H2O2 to see if it bubbles or DLA media to see if the bacteria ferment lactose
2. Serological/ Immunological: uses antibodies (antibodies present if organism has been exposed to pathogen)
3. Genetic and molecular analysis: uses cultures, extract their DNA, and identify it using PCR

Question 2

Binary fission

Answer 2

asexual reproduction used by bacteria (exponential or log growth) 1cell –> 2cells –> 4cells –> 8cells etc

Question 3

What are the three types of immunological identification?

Answer 3

1. Agglutination/precipitation: (clumping reactions)
2. Enzyme-linked immunoabsorbent assay (ELISA): using test tubes or well plates –> titer or determine a concentration to answer “what is antibody level” or “do I have a sufficient amount of antibodies”
3. Rapid testing: also uses antibodies but is rapid; + or - but this does not titer

Question 4

generation time

Answer 4

time it takes for a bacterial cell to divide or replicate

Ex: E. coli doubles in as little as 20 min

Question 5

Colony

Answer 5

is a group of clones/cells that result from a single cell undergoing binary fission

Question 6

Genome

Answer 6

total genetic material found in cell ( or virus) (nucleoid + plasmids + transposons)

Question 7

Plasmid

Answer 7

often circular, small pieces of DNA that are found OUTSIDE the nucleoid (cytoplasm). Confer benefits to the organism (antibiotic resistance)

Question 8

Mutation

Answer 8

• CHANGES to DNA
• causes: replication errors, radiation, chemical mutagens
• mutations can be neutral beneficial, or harmful (this is more common)

Question 9

Genetic recombination

Answer 9

reassortment of DNA that occurs between organisms

Ex: meiosis with gametes

Question 10

Antigenic shift

Answer 10

• MAJOR change to virus typically due to reassortment
• Two viruses infecting one cell at the same time. These two viruses swap genetic material and create a new version of that virus (influenza).
• Pandemic potential (no one would have immunity against a bran new virus

Question 11

Antigenic drift

Answer 11

• SLOW changes due to mutations while the virus replicates
• RNA viruses (influenza & SARS-CoV-2) have poor proofreading ability in their polymerases
• contribute to yearly vaccine development

Question 12

How many stages of Binary Fission are there?

Answer 12

Stage 1-4

Question 13

What happens in stage 1 of Binary Fission?

Answer 13

DNA replicates (replicates their genome and synthesize proteins)

Question 14

What happens in stage 2 of Binary Fission?

Answer 14

Septum begins to form (cell wall)

Question 15

What happens in stage 3 of Binary Fission?

Answer 15

Septum fully forms (antibiotics from cell wall inhibitors, like penicillin, prevent this step from occurring)

Question 16

What happens in stage 4 of Binary Fission?

Answer 16

Septum is fully forms and identical clones separate

Question 17

Describe the bacterial chromosome

Answer 17

1 chromosome that gets coiled is called a nuceloid

nucleoid is circular

Question 18

protein synthesis steps

Answer 18

CENTRAL DOGMA

DNA –> mRNA –> protein

transcription then translation

Question 19

What are three causes of mutations?

Answer 19

1. replication errors
2. radiation
3. chemical mutagens

Question 20

What two benefits does genetic recombination provide to organisms?

Answer 20

Genetic combination can lead to new strains or variants
- increased virulence
- resistance to drugs (or immune system)

Question 21

What are the three methods of gene transfer?

Answer 21

Conjugation
Transduction
Transformation

involve donor and recipient cell
horizontal gene transfer (sharing DNA), NOT progeny or reproduction

Question 22

Conjugation

Answer 22

• DIRECT CONTACT between donor cell and recipient through sex pilus
• at the end of conjugation both donor and recipient have the plasmid DNA
• intentional sharing of DNA

Question 23

Transduction

Answer 23

• bacteriophage/phage/virus picks up a piece of DNA from the donor cell and delivers it to the recipient
• happens by accident and most rare type of horizontal gene transfer

Question 23

Transformation

Answer 23

Recipient cell takes up NAKED DNA from a dead donor cell

• as nearby cells die off in the environment (human gut, soil, etc), the DNA from that donor becomes available for the taking
• NAKED = outside of organism

Question 24

What are 3 consequences of when new strains of microorganisms are created from genetic recombination?

Answer 24

1. gain or change to new host: now infect a new host or jump like HIV did 2. gain resistance: survive hotter temperatures, become drug resistant, resist immune system 3. Gain pathogenicity or virulence: invade host tissue, ability to attach to host tissue

Question 24

How do two influenza viruses undergo genetic recombination during antigenic shift?

Answer 24

- virus A and virus B exchange their nucleic acid in the host cell (ex: pig) and then virus C comes from it - Flu has greatest likelihood of shifting due to combinations of H and N proteins