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

the bacteria undergo asexual cell division to produce two daughter cells genetically identical to the parent cell. These two daughter cells produce four, then eight and so on.

Answer 2

Binary fission

Question 3

the time required for a bacterium to give rise to two daughter cells under optimum conditions. A bacterium replicates and multiplies rapidly producing millions of cells within 24 hours.

Answer 3

Generation time

Question 3

Binary fission subsequent events

Answer 3

1. begins with DNA replication and segregation of nucleoids (distribution between the future daughter cells)
   2 a Z-ring composed mainly of FtsZ polymers is assembled in the middle of the cell.
2. the Z-ring recruits additional proteins that serve for septum formation and subsequent separation of the daughter cells.

Question 4

Generation time of E. coli

Answer 4

20 minutes
In 7 hors 20 generation
1 million cells
And in 24 hours 10^21 cells
until arrested

Question 5

Microbial concentrations can be measured in terms of

Answer 5

Cell concentration or biomass concentration

Question 6

the number of viable cells per unit volume of culture

Answer 6

Cell concentration

Question 7

dry weight of cells per unit volume of culture

Answer 7

biomass concentration

Question 8

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

Answer 8

total count or viable count

Question 9

denotes the total number of bacteria in the sample, irrespective of whether they are living or dead. This is done by counting the bacteria under the microscope using counting chamber or by comparing the growth with standard opacity tube

Answer 9

Total counts

Question 10

indicates the number of living or viable bacteria.

Answer 10

Viable count

Question 11

Viable count can be obtain by

Answer 11

Dilution method or plating method

Question 12

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

Answer 12

Dilution method

Question 13

Four phases of growth curve

Answer 13

1. Lag phase
2. Log phase
3. Stationary phase
4. decline phase

Question 13

number of colonies that grow after a suitable incubation time

Answer 13

Plating method

Question 13

The time between inoculation 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. During this phase, there is an increase in size of bacteria but no appreciable increase in number of bacterial cells. The cells are active metabolically.

Answer 13

Lag phase

Question 14

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

Answer 14

The bacterial growth curve

Question 15

This phase is characterized by rapid exponential cell growth of bacteria at their maximum rate. The bacterial cells are small and uniformly stained. The microbes are sensitive to adverse conditions, such as antibiotics and other antimicrobial agents.

Answer 15

Log phase

Question 16

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). Death rate of bacteria exceeds the rate of replication of bacteria. Endospores start forming during this stage

Answer 16

Stationary phase

Question 17

a method utilized for industrial and research purpose that is achieved by using a special device for replenishing nutrients and removing bacterial population continuously so that bacteria growth is not inhibited due to lack of nutrients or due to accumulation of toxic bacterial metabolites.

Answer 17

Continuous culture

Question 17

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

Answer 17

Decline phase

Question 18

The Bacterial Physical requirements are

Answer 18

Temperature
pH
Osmotic Pressure

Question 19

Requirements of bacterial growth

Answer 19

Physical requirements
chemical requirements

Question 20

The bacterial chemical requirements are

Answer 20

Carbon
Nitrogen
sulfur
Phosphorus
trace elements
oxygen
organic growth factors

Question 21

most bacteria grow within a limited, and the minimum and maximum are only 30°C apart. Minimum is the lowest at which a species will grow.

Answer 21

Temperature

Question 22

Bacteria grow poorly beyond the

Answer 22

minimum and maximum temperature

Question 22

when a species grow best

Answer 22

Optimum temperature

Question 23

refers to the alkalinity or acidity of a solution. Most bacteria grow best near neutral (6.5 – 7.5). Few grow in acidic (below 4) and help preserve some food (pickles, sauerkraut, cheese) by bacterial fermentation

Answer 23

pH

Question 23

the highest
temperature at which a species can grow.

Answer 23

Maximum Temperature

Question 24

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

Answer 24

Osmotic Pressure

Question 25

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

Answer 25

Isotonic

Question 25

Microorganisms require water for growth and are made up of ____________. They often obtain nutrients in solution from surrounding.

Answer 25

80-90% of water

Question 26

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 26

Hypertonic environment

Question 27

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

Answer 27

Hypotonic

Question 28

important for all organic compounds that make up a living cell;
consist half the dry weight of a typical bacterial cell.

Answer 28

Carbon

Question 29

helps form the amino group in amino acids

Answer 29

Nitrogen

Question 29

used to synthesize sulfur-containing amino acids and

Answer 29

Sulphur

Question 30

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

Answer 30

Phosphorus

Question 31

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

Answer 31

Trace elements

Question 32

Oxygen is toxic to anaerobic bacteria like

Answer 32

clostridium tetanus

Question 33

required by aerobic microorganism

Answer 33

Oxygen

Question 34

Toxic forms of oxygens

Answer 34

Singlet oxygen
superoxide free radicals
Peroxide anion
Hydroxyl Radical

Question 35

Most reactive form of oxygen

Answer 35

Hydroxyl Radical

Question 35

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

Answer 35

Superoxide free radicals

Question 35

extremely reactive

Answer 35

Singlet oxygen

Question 36

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

Answer 36

Organic growth factors