Lab 11

Question 1

growth

Answer 1

the increase in mass of protoplasm or an organism or population

Question 2

reproduction

Answer 2

increase in the number of individuals

Question 3

turbidity

Answer 3

a beam of light passes through a suspension of bacterial cells, light is scattered bc of the difference in refractive index (the instrument used to measure is a nephelometer.)

Question 4

Determination of dry weight

Answer 4

an aliquot of the culture is centrifuged and washed free of the soluble constituents of the medium by further centrifuge from water.

Question 5

Determination of dry weight

Answer 5

an aliquot of the culture is centrifuged and washed free of the soluble constituents of the medium by further centrifuge from water. If all the constituents remain in constant proportions, the measure of any constituent should suffice as a measure of growth.

Question 6

viable count

Answer 6

estimate the number of individual units capable of developing into a colony if placed in a suitable medium.

Question 7

direct microscope unit

Answer 7

direct counts can be made by placing a suitable dilution of the culture in the hemocytometer of the Petroff-Hauser chamber.

Question 8

Direct microscope count

Answer 8

Use: Rapid laboratory enumeration of cell suspension
Limitations: requires large number (>10^6 cells/ml) of cells for acuracy

Question 9

viable count

Answer 9

use: enumeration of viable cells in water, milk, and other products
Limitation: Time consuming requires proper medium for growth

Question 10

membrane filtration

Answer 10

enumeration of bacteria from water, milk, and other products especially when numbers are low
limitations: time-consuming requires proper medium for growth

Question 11

most probable number

Answer 11

enumeration of bacteria from water, milk, and other products
Time-consuming, requires a proper medium for growth, and provides an indirect estimate of numbers.

Question 12

Turbidimetric measurement

Answer 12

rapid estimation ofo cell density in a suspension

does not differentiate between viable and nonviable cells provides only estimate of cell density require > 10^6 cells/ml

Question 13

dry weight determination

Answer 13

determination of cell mass for industrial or a laboratory applications

time-consuming does not differentiate between viable and nonviable cells

Question 14

cell activity measurement

Answer 14

research applications to follow cell metabolism

involves extensive preparatory time