Bacterial Growth

I. Determine in terms of population size. Nature there is a of organisms living together. Nature there is a of organisms living together. How can we get a certain type of bacteria? How can we get a certain type of bacteria? - separating the progeny of a single bacterium from all others. - separating the progeny of a single bacterium from all others.

- interested in disease causing bacteria (major contributor to pure culture techniques). - interested in disease causing bacteria (major contributor to pure culture techniques). Initially grew bacteria on potato surface but had problem: Not enough for bacterial growth. Added gelatin as a solidifying agent. (Warm - pour, cool - solid) - simplest & most common method to isolate a single bacterium. - simplest & most common method to isolate a single bacterium. Hesse (Koch’s assistant) (polysaccharide extract from marine algae) - easier to work with then gelatin (solid over a wider range then gelatin). Julius Petri -

Streak-Plate Method

II. Bacterial growth formula to determine population size: formula to determine population size: b = B2 n = Number of cells at time zero (beginning). = Number of cells at time zero (beginning). = number a cells at any later time. = number of cell generations. = number of cell generations.

Review Why is agar used instead of gelatin or potato? Why is agar used instead of gelatin or potato? Why is the petri dish unique to prevent contamination? Why is the petri dish unique to prevent contamination? What is the advantage of bacterial growing by binary fission? What is the disadvantage? What is the advantage of bacterial growing by binary fission? What is the disadvantage? How many bacteria will there be after 10 hours if the bacteria double every 30 m inutes? How many bacteria will there be after 10 hours if the bacteria double every 30 m inutes?

A. Growth can be measured as an increase in (weight) of the population. A. Growth can be measured as an increase in (weight) of the population. B. Growth can be measured as an increase in. B. Growth can be measured as an increase in count the number of colonies on the medium counting the number of bacterium in an known volume of liquid.

III. Factors that influence microbial growth. A. Temperature 1. Most bacteria grow within or near. 2. groups of bacteria based upon their optimum growth temperatures. a. 5C - 20C b. 20C - 50C c. 50C - 80C d. +80C

Review Describe the difference between direct count and plate count method. Describe the difference between direct count and plate count method. What are the three temperate ranges that bacteria tend live in? What are the three temperate ranges that bacteria tend live in?

3. Food Preservation Refrigerators food spoilage because most of the microorganism that cause spoilage are. 4. Temperature & Human diseases. Human body 37C ( ). 20C - 25C ( ). Ex - leprosy (Mycobacterium leprae)- involves the regions of the body.

Review Why do we store our food in refrigerators? Why do we store our food in refrigerators? Why do you not want to keep heating and cooling the same leftover throughout the week? Why do you not want to keep heating and cooling the same leftover throughout the week? Which temperature range to most tend to live in and why? Which temperature range to most tend to live in and why?

B. Oxygen Requirements 1. - require free oxygen to grow will not grow in the presence of free oxygen, may even be killed. 3. -prefers the presence of low oxygen (2% - 10% Oxygen) lives in the presence of both: Growth occurs more rapidly in the presence of oxygen will grow in the presence of oxygen but do not posse an oxidative metabolism: Derive no benefit from the presence of oxygen.

Why can some bacteria thrive in the presence of oxygen but others are killed by it? Oxygen can be converted into a toxic form like (H2O2) & (O2-). Cells that do not die in the presence of oxygen produce enzymes () into a form (H20 & O2).

C. pH Most bacteria grow best in an medium with a pH of (neutral). Can live in a wider range Ex. Helicobacter pylori - live in very environments ( ) & may cause ulcers. Bacteria produce metabolic products that may acidic or basic. Need a ( ) to grow bacteria.

4. - pressure that is required to prevent the net flow of water across the cell membrane. effect water movement. Use salt as an factor in food preservation.

IV Cell multiplication requires a source of energy & raw material for synthesis of cell components. A. Bacterial Nutrients Raw Materials Carbon, Nitrogen, Oxygen, Hydrogen. all other compounds including ions. Two Purposes of nutrition 1. (Synthesize) protoplasm. 2. Supply energy to.

B. C. D. Small organic molecules other than carbon that bacteria must provide in order to grow (amino acids & vitamins).

V. Dynamics of population growth.