2 - metabolism and growth

Copyright © 2010 Pearson Education, Inc.

Metabolism and Growth


Requirements for Growth: chemical

NOT COPS

N Organic growth factors Trace elements

C O P S


What is the function of carbon, nitrogen, sulfur, phosphorus and trace elements?


Chemical Requirements

Carbon Structural organic molecules, energy source Chemoheterotrophs use organic carbon sources Autotrophs use CO2



Nitrogen In amino acids and proteins Most bacteria decompose proteins Some bacteria use NH4+ or NO3–

A few bacteria use N2 in nitrogen fixation



Sulfur In BAT: Biotin, amino acids, and protein

Phosphorus In DNA, RNA, ATP, and membranes



Trace elements Inorganic elements required in small amounts Usually as enzyme cofactors

Copyright © 2010 Pearson Education, Inc. Table 6.1

The Effect of Oxygen (O2) on Growth


Organic Growth Factors

Where are organic growth factors obtained? from the environment

What are organic growth factors involved with? Vitamins, amino acids, purines, and pyrimidines


Catabolic and Anabolic Reactions

Metabolism: The sum of the chemical reactions in an organism

catabolism, require water: cells break down sugars

anabolism, dehydration synthesis: formation of proteins from amino acids


Catabolic and Anabolic Reactions

A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell A - B, B - C, C - D A cannot make D

Metabolic pathways are determined by enzymes

Enzymes are encoded by genes


Enzymes

Proteins Biological catalysts Produced by living cells Catalyze chemical reactions by lowering activation

energy Speed up a chemical reaction without being

permanently altered


Enzyme Components

Biological catalysts Speed up a chemical reaction without being altered Are specific (active site) – act on specific substance

(substrate) Crucial function: speed up biochemical reactions at a temp

which is compatible with a living, normal functioning cell


Factors influencing Enzymatic Activity

Temperature pH Substrate concentration Inhibitors


Inhibitors

Function: control bacteria by control of enzymes

Competitive – compete with the normal substrate for the active site shape and chemical structure are similar to normal

substrate Ex. Sulfa drug

Noncompetitive – interact with another part of the enzyme, changes shape = nonfunctional


Carbohydrate Catabolism

The breakdown of carbohydrates to release energy Glucose most commonly used carbohydrate Glycolysis: breaking down glucose to pyruvic

acid


Carbohydrate Catabolism

Glycolysis: glucose broken down Leads into cellular respiration (aerobic/anaerobic)

or fermentation

Aerobic Anaerobic Fermentation

Krebs cycle: high energy

Part of Krebs cycle: low energy

No Krebs

Electron transport chain

Electron Transport chain

No ETC

Final Acceptor: O2

Final acceptor: does not use O2

Various organic end products

Inorganic product


Metabolic Diversity among Organisms

Photoautotrophs Photoheterotrophs Chemoautotrophs Chemoheterotrophs

Autotrophs – fix carbon Heterotrophs – cannot fix carbon Chemotrophs – energy from oxidation Phototrophs – energy from light


The Requirements for Growth: Physical

Physical requirements Temperature pH Osmotic pressure


Physical Requirements

Temperature Minimum growth temperature Optimum growth temperature Maximum growth temperature


Temperature

Three primary Groups

1.Psychrophiles – cold loving

2.Mesophiles – moderate

3.Thermophiles – heat loving

Copyright © 2010 Pearson Education, Inc. Figure 6.1

Typical Growth Rates and Temperature


Psychrotrophs

Grow between 0°C and 20–30°C Cause food spoilage


Food Preservation Temperatures


pH

Most bacteria grow between pH 6.5 and 7.5 Molds and yeasts grow between pH 5 and 6 Acidophiles grow in acidic environments


Biofilms

Microbial communities Form slime or

hydrogels Form on teeth, contact

lenses and catheters

Copyright © 2010 Pearson Education, Inc. Applications of Microbiology, p. 57

Biofilms

Share nutrients Sheltered from

harmful factors 70% bacterial

infections are from biofilms

100X more resistant to antibiotics than free swimming microbes


Agar

Complex polysaccharide Used as solidifying agent for culture media in Petri

plates, slants, and deeps Generally not metabolized by microbes Liquefies at 100°C Solidifies at ~40°C


Culture Media

Chemically defined media: Exact chemical composition is known

Complex media: Extracts and digests of yeasts, meat, or plants Nutrient broth Nutrient agar


Anaerobic Culture Methods

Reducing media Contain chemicals (thioglycolate or oxyrase) that combine

O2

Heated to drive off O2

Used to grow anaerobes


An Anaerobic Chamber


Selective Media

Suppress unwanted microbes and encourage desired microbes


Differential Media

Make it easy to distinguish colonies of different microbes.


The Streak Plate Method


Preserving Bacterial Cultures

Deep-freezing: –50° to –95°C Lyophilization (freeze-drying): Frozen (–54° to –

72°C) and dehydrated in a vacuum


Measuring Microbial Growth

Direct Methods Plate counts Filtration MPN Direct microscopic count

Indirect Methods Turbidity Metabolic activity Dry weight


Standard plate count Viable count

Microscopic count No incubation time

Growth phase gram + is suseptible to penic. LOG phase

2 - metabolism and growth

Science

pearson education

chemical requirements

chemical requirements

chemical structure

catalyzed chemical reactions

cops n organic growth

energy glucose

typical growth rates