Influence of Chemical and Physical Factors in Environment --- Microbial Growth Influence of Chemical and Physical Factors in Environment

I. Objectives How do bacteria grow? What is generation time and how do we plot this How do we measure this What are the requirements for growth? How do we provide these requirements?

II. How do they grow? A. Culturing microbes Batch method Continuous

B. Mechanics of Growth 1. Binary fission 2. Four phases

3. Plotting growth curves Generation time Plotting exponential growth

4. Mathematical Calculation Growth equation: n = log N - No / 0.301 So, can calculate generation time:

5. Phases of growth

C. Measurement of Growth 1. Direct a. plate count (viable)

b. Direct microscopic count

c. Other direct methods for special cases Dilute samples

Growth not possible on solid media

2. Indirect methods a. Turbidity b. Metabolic activity c. Dry weight

III. Environmental factors affecting growth

A. Temperature effects

1. Cardinal temperatures

2. Microbial adaptations to temperature Typical bacteria Others:

3. Physiological and structural adaptations

B. Effect of pH What is pH Types of bacteria

C. Osmotic requirements

D. Effects of oxygen on growth 1. Terminology

2. Why obligate anaerobes?

3. Culture techniques Aerobes Anaerobes

IV. Media requirements A. Major macronutrients

B. Minor macronutrients and trace elements

C. Types of media

V. Once we can grow them. . .