Microbial Nutrition

Microbial Nutrition

I. Introduction

great diversity among microorganisms
fastidious

A. Macroelements (macronutrients)

1. Major elements: carbon, oxygen, hydrogen, nitrogen

2. Minor elements: sulfur, phosphorus, potassium, calcium

B. Trace Elements

manganese, zinc, copper, cobalt

II. Nutritional Types of Microorganisms

A. Nutritional Types Based on Carbon Utilization

1. Autotrophs

use CO₂ as primary source of carbon

fixing CO₂ is energy expensive

2. Heterotrophs

use complex molecules as carbon source

use organic nutrients as a carbon and an energy source

3. Prototroph

requires same nutrients as most members of the same species

4. Auxotroph

unable to synthesize an essential nutrient that other members of this species can make

B. Nutritional Types Based on Energy Source

1. Phototrophs

use light as energy source

2. Chemotrophs

energy form oxidation of chemicals

C. Nutritional Types Based on Source of Hydrogen Atoms (Electrons)

1. Lithotrophs

use reduced inorganic substances

2. Organotrophs

D. Nutritional Classes

1. Photoliphotrophic autotrophs (photoautotrophs)

use light as energy, and CO₂ as carbon source

2. Chemoorganotrophic heterotrophs (chemoheterotrophs)

use organic compounds as source of energy, carbon, and electrons

3. Photoorganotrophic heterotrophs

use light as energy, and organic matter as C source and electron donor

4. Chemolithotrophic autotrophs

use inorganic chemicals as energy and electron source, and CO₂ is used as carbon source

III. Growth Factors

essential organic molecules

A. Amino Acids

B. Purines and Pyrimidines

C. Vitamins

D. Heme

Haemophilus influenzae

IV. Uptake of Nutrients

A. Passive Diffusion

movement of molecules from a region of high concentration to low concentration

B. Facilitated Diffusion

carrier proteins (permeases) speed up passive diffusion

C. Active Transport

permeases and energy used to transport molecules against a concentration gradient

D. Group Translocation

molecule transported into a cell and modified at the same time
phosphoenolpyruvate: sugar phosphotransferase system (PTS)

E. Iron Uptake

iron needed by almost all living cells
little free iron available
siderophores: ferrichrome, enterobactin
siderophore receptor protein
Bind iron containing proteins

V. Culture Media

must provide all essential nutrients
not all microorganisms can be grown in the laboratory

A. Synthetic (Defined) Media

all components known

B. Complex Media

contain some nutrients of unknown chemical composition

nutritionally ‘rich'

contain peptones, beef extract, or yeast extract

LB (Lauria-Bertani)

C. Types of Media

1. Broth vs. agar

2. Selective

inhibits the growth of some species and allows the growth of others

e.g. mannitol salt agar, eosin methylene blue

3. Differential

distinguishes between different groups of bacteria based on colony appearance

e.g. sheep blood agar, mannitol salt agar, eosin methylene blue

Last updated June 11, 2007.