(6) Microbial Growth

Question 1

mention some parameters of growth in microbial growth

Answer 1

increase in number of microbial cells, increase in microbial mass, refers to population

Question 2

what microorganism use binary fission to reproduce

Answer 2

amoeba, bacteria

Question 3

what microorganism use budding to reproduce

Answer 3

bacteria, yeast, corals,flatworms

Question 4

define binary fission

Answer 4

binary fission is an asexual reproduction where a parent cell splits into two daughter cells

Question 5

define budding

Answer 5

budding is an asexual reproduction where a new organism develops from a bud of its parent organism

Question 6

define multicellular

Answer 6

composed of more than once cell, with groups of cell differentiating and taking specialized functions

Question 7

define unicellular

Answer 7

made up of only one cell that carries out all function needed by the organism

Question 8

are algae and mold unicellular or multicellular

Answer 8

multicellular

Question 9

what is mycellium

Answer 9

a root-like structure of a fungus consisting of a mass brancing, thread-like hyphae

Question 10

what is hyphae

Answer 10

the long filamentous branching in fungus and actinobacteria

Question 11

where does the hyphae growth takes place

Answer 11

the apical zone (at the very tip. the cell wall extends and produce long hyphal tube)

Question 12

how to write microbial growth population

Answer 12

in one decimal (1 000 000= 1x10^6)

Question 13

what’s the limit of bacteria in fresh milk?

Answer 13

10^5 cell/mL

Question 14

what are the 4 stages in microbial growth curve

Answer 14

lag phase, exponential phase, stationary phase and death phase

Question 15

explain lag phase

Answer 15

when microbial population is inoculated into fresh medium. there are cellular activity but no growth. cells grow in size but no cell division.

Question 16

explain exponential phase

Answer 16

when the cells starts dividing in an logarithmic way. reproduction is high during this period. cells are active metabolically.

Question 17

explain stationary phase

Answer 17

exponential growth ceases. available nutrients are all used up and waste product starts to accumulate. no growth occurs. number of cell death equals to number of cell divisions.

Question 18

explain death phase

Answer 18

number of living cells decreases exponentially. population growth declines. number of cell death exceeds cell division.

Question 19

in what phase do bacteria starts to synthesize nutrients and prepare for cell division?

Answer 19

lag phase

Question 20

define growth rate in microbial kinetics

Answer 20

change in cell number/mass per unit time

Question 21

define generation in microbial genetics

Answer 21

interval for formation of two cells from one

Question 22

define generation time (doubling time)=G

Answer 22

the time required for formation of two cells

Question 23

what is the formula of G (generation time)?

Answer 23

G= t/n
t= time interval in hours or minutes
n= number of generation

Question 24

whats the formula to calculate the size of a population (n) over time
for binary fission

Answer 24

n= log X - log Xt/log 2

Question 25

Exercise: At initial time the number of bacteria is 10^3. After 5 h the number of bacteria is 10^7.
Calculate number of doubling (n) and the
generation time (G).

Answer 25

n = log Xt- log X/log2
n = log 10^7 - log 10^3/log2
n = 7- 3/0.301
n = 13.3

G=t/n
G=5/13.3=0.375 h
G=22.56 min

Question 26

how to directly measure cell number?

Answer 26

viable count, membrane filtration, direct microscopic counts

Question 27

how to indirectly measure cell mass?

Answer 27

turbidimetry

Question 28

how to measure cell mass?

Answer 28

dry weight

Question 29

explain what and how viable count method

Answer 29

viable count is determining the number of cells forming colonies.

method: spread plate, pour plate

Question 30

what is filtration method

Answer 30

measuring from the colony that is present on the plate or filter. it only countrs live cells.

Question 31

what and how to do direct microscopic count

Answer 31

a method to estimate microbial cell number. requires microscope, special slides, high power objective lens.

how: counting total microbe numbers one by one.

Question 32

what is turbidity measurement

Answer 32

method used to follow the rate of growth of the culture. uses spectrophotometer to send a visible light through the culture and measure how much light is scattered.

Question 33

in statonary phase, bacteria produces…

Answer 33

toxins, antibiotics and secondary metabollites

Question 34

in death phase, the total count of cell

Answer 34

decreases