Nutrition

process by which chemical substances (nutrients) are acquired from the environment and used for cellular activities

must be provided to an organism

macronutrients

micronutrients or trace elements

• required in large quantities; play principal roles in cell structure and metabolism 
• •proteins, carbohydrates

–required in small amounts; involved in enzyme function and maintenance of protein structure

•manganese, zinc, nickel

•Increase in cell number

•Populations increase at very rapid rates

• •Colonies of bacteria contain billions
• of cells

•Method of growth:  Binary fission

•Typical growth rates: 20-30 minutes

• Each new fission cycle increases the population by a factor of 2 – exponential or logarithmic
• growth.

Time required for a complete fission cycle 

• Each new fission cycle increases the population by a factor of 2 – exponential or logarithmic
• growth.

• Time required for population to double

• Typical generation time: 20 min

N^ƒ = (N^i)2^n

N^ƒ  is total number of cells in the population.

N^i is starting number of cells.

Exponent n denotes generation time.

2^n number of cells in that generation

Cells are not dividing

They are getting use to the environment

They are preparing

Cells are metabolically active

Vulnerable to antibiotics and radiation

Cells are dividing

Number of cells and number of live cells are equal

Number of dead cells is greater than number of live cells

Counting Chamber: the slide has a grid

Cheap and fast to use

–Plate count method - counts colonies, 12 hours; gives an accurate estimate of the number of viable cells

–Filtration

–Most probable number (MPN)

Viable

• lowest temperature that permits a microbe’s growth and metabolism

• highest temperature that permits a microbe’s growth and metabolism

• promotes the fastest rate of growth and metabolism

1.optimum temperature below 15oC; capable of growth at 0oC

1.optimum temperature 20o-40oC; most human pathogens

1.optimum temperature greater than 45oC