Lec 5 - Bacterial Growth

increase in number of cells not cell size

1 cell becomes a colony of million cells

Time required for cell to divide for population to double

Average generation time for bacteria

Generation time for E. coli

No. of generations & GT for 1 cell to become 1 million cells

making new enzymes in response to new medium

Length of lag phase depends on

logarithmic or exponential phase: bacterial cells start dividing and their number increase by geometric progression with time

Bacteria have a high rate of _________

Bacteria are more sensitive to ______

nutrients becoming limited or waste products becoming toxic

Death rate = ______

After sometime , rate of multiplication and death becomes almost equal which maybe due to

in this phase, death exceeds division thus population decreases due to death of cells

Death is due to ____

Enumerate ways to measure bacterial growth

2 methods of Inoculate Petri plates from serial dilutions

Formula for serial dilution (no. of bacteria per mL)

• pH - measure of H+

• temperature

• salt concentration

• moisture

• nutrition

• oxygen requirements

optimum pH range 1-4

optimum pH range 8.5-11

optimum pH range 4-7

optimum pH range 2.2-2.8

optimum pH range 4-6

Internal pH regulated by _____ and near neutral adjusted by _____

pH 7.2+/- 0.2

_____ or _______of environment can greatly affect microbial growth

Most organisms grow best between ph ___ and __

Internal pH of cell must be relatively close to ____ even though external pH is highly acidic or basic

Acidophiles grow best at

2 examples of acidophiles

Alkaliphiles grow best at _____

example of alkaliphiles

Temperature below which growth ceases or lowest temperature at which microbes will grow

Temperature at which growth rate is fastest; most favors development

Optimum temperature is between

Temperature above which growth ceases or highest temperature at which microbes will grow

0 to 15’C

midrange temperature

Most representatives inhabit permanently cold environment

Found in warm-blooded animals in terrestrial and aquatic environments in temperate and tropical latitudes

Room temperature

Body temperature

50 to 70’C

greater than 80’C

Organisms inhabit hot environments like boiling hot springs, and undersea hydrothermal vents that can have temperatures greater than 100’C

wide range of temperature

narrow range of temperature

grow best at reduced water potential and some extreme halophiles require high levels of salt for growth

example of halophiles

can tolerate some reduction in water activity of their environment but generally grow best in the absence of added solute

Sexample of halotolerant

able to grow in very dry environment

medium for streptococcus

medium for tubercle bacilli

long chains in fluid, short chains on agar

can survive in dry environment

CO2 as sole source of carbon

organic source of carbon

living host

viruses

non-living matter

cause disease; all heterotrophic

Require oxygen for metabolism; obligate

require oxygen in small amounts

grow without oxygen

grow with or without oxygen

Number of cells in 1 generation

Number of cells in 2 generation

Number of cells in 3 generation

Number of cells in 4 generation

Number of cells in 5 generation