Lesson 9: Principles of Bacterial Growth

Question 1

refers to increase in number of cells and not the size of cells.

Answer 1

bacterial/microbial growth

Question 2

which the bacteria undergo asexual cell division to produce two daughter cells genetically identical to the parent cell

Answer 2

binary fusion

Question 3

begins with DNA replication and segregation of nucleoids (distribution between the future daughter cells)

Answer 3

Cell division

Question 4

composed mainly of __________ assembled in the middle of the cell

Answer 4

Z-ring
FtsZ polymers

Question 5

recruits additional proteins that serve for septum formation and subsequent separation of the daughter cells

Answer 5

Z-ring

Question 6

is the time required for a bacterium to give rise to two daughter cells under optimum conditions.

Answer 6

Generation Time

Question 7

replicates and multiplies rapidly producing millions of cells within 24 hours.

Answer 7

bacterium

Question 8

Microbial concentration can be measured in terms of?

Answer 8

(i) cell concentration
(ii) biomass concentration

Question 9

the number of viable cells per unit volume of culture

Answer 9

cell concentration

Question 10

dry weight of cells per unit volume of culture

Answer 10

biomass concentration

Question 11

the number of bacteria at a given time can be estimated by performing a?

Answer 11

total count or viable count

Question 12

denotes the total number of bacteria in the sample, irrespective of wether they are living or dead.

Answer 12

total count

Question 13

this is done by counting the bacteria under the microscope using counting chamber or by comparing the growth with standard opacity tubes

Answer 13

total count

Question 14

indicates the number of living or viable bacteria

Answer 14

viable count

Question 15

series of sequential dilutions used to reduce a dense culture of cells to a more usable concentration

Answer 15

dilution method

Question 16

number of colonies that grow after a suitable incubation time

Answer 16

plating method

Question 17

represents the number of live cells in a bacterial population over a period of time

Answer 17

bacterial growth curve

Question 18

the time between inoculation and and beginning of multiplication. in this phase, the inoculated bacteria become acclimatized to the environment, switch on various enzymes, and adjust to the environmental temperature and atmospheric conditions. There is increase in size bacteria but no appreciable increase in number of bacterial cells

Answer 18

lag phase

Question 19

this phase is characterised by rapid exponential cell growth of bacteria at their maximum rate.

Answer 19

log phase

Question 20

are small and uniformly stained

Answer 20

bacterial cells

Question 21

are sensitive to adverse conditions, such antibiotics and other antimicrobial agents

Answer 21

log phase

Question 22

in this phase, the bacterial growth almost stops completely due to depletion of essential nutrients, water oxygen, change in pH of the medium, etc. and accumulation of their own toxic metabolic wastes (exotoxins)

Answer 22

stationary phase

Question 23

endospore start forming during this stage

Answer 23

stationary phase

Question 24

in this phase, the bacterial population declines due to death of cells due (a) accumulation of toxic products and autolytic enzymes and (b) exhaustion of nutrients

Answer 24

decline phase

Question 25

involution forms are common in this stage

Answer 25

decline phase

Question 26

is a method utilize for industrial and research purpose that is achieved by using a special device for replenishing nutrients and removing bacterial population.

Answer 26

continuous culture

Question 27

physical requirements for bacterial growth

Answer 27

temperature, pH, osmotic pressure

Question 28

the minimum and maximum temperatures for bacterial growth

Answer 28

30°C

Question 29

the lowest temperature at which a species will grow

Answer 29

minimum temperature

Question 30

when a species grow best

Answer 30

optimum temperature

Question 31

highest temperature at which a species can grow

Answer 31

maximum temperature

Question 32

refers to the alkalinity or acidity of a solution

Answer 32

pH

Question 33

Most bacteria grow best near ___________. Few grow _________ and help preserve some food by bacterial fermentation.

Answer 33

neutral pH (6.5 - 7.5) acidic pH (below 4)

Question 34

the pressure required to stop water/solution from diffusing through a barrier by osmosis.

Answer 34

osmotic pressure

Question 35

require water for growth and are made up of 80-90% water

Answer 35

microorganisms

Question 36

when solution outside the cell has higher concentration of solutes than inside the cell, water is diffused outside of cell and the cell shrinks

Answer 36

hypertonic environment

Question 37

when solution outside the cell has lower concentration of solutes than inside the cell, water is diffused inside of cell and the cells swells.

Answer 37

hypotonic

Question 38

when concentrations in two solutions are same, so cell will neither swells nor shrinks.

Answer 38

isotonic

Question 39

chemical requirements for bacterial growth

Answer 39

carbon, nitrogen, sulphur, phosphorus, trace elements, oxygen, organic growth factors

Question 40

important for all organic compounds that make up a living cells, consist half the dryweight of a typical bacterial cell

Answer 40

carbon

Question 41

helps from the amino group in amino acids

Answer 41

nitrogen

Question 42

used to synthesize sulfur-containing amino acids and vitamins

Answer 42

Sulphur

Question 43

important in synthesis of ATP, nucleic acids, phospholipids of cell membranes

Answer 43

phosphorus

Question 44

minerals that are minimally required by microbes, and are also essential in enzymatic reactions

Answer 44

trace elements

Question 45

required by aerobic microorganisms.

Answer 45

oxygen

Question 46

oxygen is toxic to anaerobic bacteria like?

Answer 46

clostridium tetanus

Question 47

what are the toxic form of oxygen

Answer 47

i. singlet oxygen ii. superoxide free radicals iii. peroxide anion iv. hydroxyl radical

Question 48

extremely reactive

Answer 48

singlet oxygen

Question 49

highly unstable, steals electron from neighboring molecules thereby increasing free radicals

Answer 49

superoxide free radicals

Question 50

most reactive form of oxygen

Answer 50

hydroxyl radical

Question 51

are essential organic compounds that cannot be synthesized by an organism thus must be obtained from the environment

Answer 51

organic growth factors

Question 52

example of organic growth factors

Answer 52

vitamins