Chapter 6

NUTRITION AND GROWTH

Nutritional Requirements• EVERY LIVING ORGANISM MUST ACQUIRE TWO

THINGS FROM ITS ENVIRONMENT TO GROW AND REPRODUCE:

• STRUCTURAL UNITS• ENERGY SOURCE

• GROUPING ORGANISMS BASED ON NUTRITIONAL REQUIREMENTS (examples):

• PHOTOHETEROTROPHS• PHOTOAUTOTROPHS• CHEMOHETEROTROPHS• CHEMOAUTOTROPHS

How Do Organisms Acquire Their Nutritional Needs?

• MEDIA - LAB OR ENVIRONMENT

• ALL MEDIA MUST HAVE THE FOLLOWING CHEMICAL ELEMENTS FOR GROWTH

- CARBOBN (C)

- NITROGEN (N)

- WATER (H2O)

- MINERALS (S,P,CA,MG,NA, ETC.)

Carbon Sources

o CARBON DIOXIDE o CARBOHYDRATES

• CARBOHYDRATES ARE SELECTED BECAUSE:

• WATER SOLUBLE

• READILY ACCESSIBLE IN LAB AND NATURE

• USUALLY NON TOXIC IN DILUTE CONCENTRATION

• EASILY OXIDIZED AND REDUCED, LITTLE MODIFICATION NEEDED

Carbon Sources (Continued)

• SOME ORGANISMS CAN NOT USE CARBOHYDRATES AS A CARBON SOURCE.

• THEY WILL USE ALCOHOLS, AMINO ACIDS, FATS, ETC.

• NITROGEN SOURCES: 1) INORGANIC; 2) ORGANIC• INORGANIC SOURCE : NITROGEN GAS(N2) OR

NH4CL/(NH4)2SO4

- NITROGEN FIXATION

- SYMBIOTIC RELATIONSHIPS.

Nutritional Sources

• INORGANIC

– NITROGEN GAS(N2) OR NH4CL/(NH4)2SO4

- NITROGEN FIXATION

- SYMBIOTIC RELATIONSHIPS

• ORGANIC

Nutritional Sources•ORGANIC N SOURCE

– PROTEIN - BUILDING BLOCKS ARE AMINO ACIDS. PRIMARY, SECONDARY AND TERTIARY STRUCTURES OF PROTIEINS

– MINERALS:

» MICRONUTRIENTS: ZN, CU, CO, MN, MO

» MACRONUTRIENTS: P, MG, CA, S, Na

– WATER: BIOLOGICAL SOLVENT THAT COMPOSES 80-85% OF THE WEIGHT OF CELLS.

Other Substances in Media

• SUBSTANCES WHICH MAY BE ADDED TO MEDIA BUT ARE NOT ALWAYS REQUIRED.

• GROWTH FACTORS

• BUFFERS

• SOLIDIFYING AGENTSSTERILIZATION OF MEDIA

• AUTOCALVING

• FILTRATION: a) NEGATIVE b) POSITIVE

CLASSIFICATION OF MEDIA

• SYNTHETIC OR CHEMICALLY DEFINED MEDIA

• A CHEMICAL FORMULA CAN BE WRITTEN FOR EVERY INGREDIENT

• COMPLEX MEDIA• A CHEMICAL FORMULA CANNOT BE

WRITTEN FOR EVERY INGREDIENT

OXYGEN GAS REQUIREMENTS OF MICROORGANISMS

• OBLIGATE AEROBES• FACULTATIVES• AEROTOLERANTS• MICROAEROPHILICS• OBLIGATE ANAEROBES

GROWTH

• DEFINITION: INCREASE IN MICROBIAL MASS OR INCREASE IN THE NUMBER OF CELLS

• GENERATION TIME: THE TIME IT TAKES AN ORGANISM TO REPRODUCE

– BINARY FISSION

– SHORTER FOR PROKARYOTES THAN EUKARYOTE

– ENVIRONMENT EFFECTS GENERATION TIME

Binary Fission

WE CAN DEMONSTRATE TYPICAL BACTERIAL GROWTH BY PREPARING A

POPULATION GROWTH CURVE.

• THE BACTERIAL GROWTH CURVE– LAG PHASE– LOG OR EXPONENTIAL PHASE– STATIONARY PHASE– DEATH OR DECLINE PHASE

Growth Curve