M4: Plating & Growth Process

Question 1

plating

Answer 1

process of spreading bacterial culture onto petri dish filled w/agar

Question 2

types of tools that can be used for plating (3)

Answer 2

• sterile loop
• sterile swab
• sterilized wire loop

Question 3

advantage of plating

Answer 3

• cells fixed in place –> environment supports formation & visualization of colonies (each from a single cell)

Question 4

primary method of isolating a microbe on an agar plate

Answer 4

quadrant streak (aka phase-dilution) approach

Question 5

how phase-dilution works

Answer 5

spread sample into 4 regions, each perpendicular to the last, to obtain a pure culture

Question 6

pure culture

Answer 6

• free of outside contaminants

- traceable to a single origin

Question 7

phase at which can see individual colonies

Answer 7

Phase 4 (occasionally 3 as well)

Question 8

common deviations of 4 phase dilution method (2)

Answer 8

• fewer phases (usually 3)

- passing sterile loop thru previous phase more than once

Question 9

growth process after streaking

Answer 9

1. plates inverted to prevent contaminants from settling onto agar
2. plates placed in 37C incubator for 12-24 hours

Question 10

creation of pure culture (after growth)

Answer 10

individual colonies ID’ed, isolated, picked, and reinoculated in nutrient broth or nutrient agar

Question 11

inoculation

Answer 11

introducing microorganisms into a culture where they can grow and reproduce

Question 12

optimal temperature for bacterial growth (general)

Answer 12

37C

Question 13

optimal temperature for yeast growth

Answer 13

30C

Question 14

optimal temperature for pathogenic bacterial growth

Answer 14

25C