Microbial Metabolism & Growth

Basic Organic Chem Review

• Four Basic Types of Macromolecules• A) Proteins (Made up of Amino Acids)• B) Nucleic Acids (Made up of Nucleotides)• C) Carbohydrates (Mainly Carbon, Hydrogen,

and Oxygen in a 1:2:1 ratio)• D) Lipids (Mainly Carbon & Hydrogen)

A. Proteins

• consist of long, complex chains of amino acids (20 kinds)

• the most abundant organic components of microbes

• function as structural materials as well as __________

• destruction of the proteins in an organism usually results in death

Protein structure: amino acids

• AMINO ACIDS are the building blocks of proteins

a specific amino acid

Protein structure: amino acids

NOTE: All amino acids look alike except for the highlightedportions. This is important in building many different proteins.

Peptide bonding of amino acids

• Proteins are built by linking amino acids end to end. Each link is a ____________.

Protein structure: Primary

Protein structure: Secondary

Protein structure: 3 dimensional • The 3 dimensional shape of a protein

dictates its function.• If the 3 dimensional shape is altered, the

protein is destroyed.

Protein structure: Quaternary (Hemoglobin)

Protein _________

Altered 3-D shape = destroyed protein

B. Nucleic Acids• Two types function in all living

things: • _____ ( deoxyribonucleic acid )

acts as the genetic material of the chromosome

• _____ ( ribonucleic acid ) functions

in the construction of proteins• Both DNA and RNA are composed

of repeating units called nucleotides

• As with proteins, the nucleic acids cannot be altered without disrupting the organism or killing it.

C. Carbohydrates

• 1. general formula = (CH2O)n

• 2. sugars, starches, cellulose, etc• 3. have a vital function as energy sources

in cells• 4. also found in several cellular structures

such as cell walls and bacterial capsules • 5. monosaccharides are the simplest

carbohydrates, the building blockse.g. ________, fructose C6H12O6

Carbohydrates• 6. disaccharides are double sugars (2

monosaccharides bonded together)– e.g. _______ (table sugar) is one glucose and

one fructose– C12H22O11: one H2O lost when bond forms

glucose fructose

NOTE: 2 monosaccharides linked together.

Dehydration Synthesis (Putting together) Hydrolysis (breaking apart)

OCH2OH CH2OH CH2OH CH2OH

H HH H

HH

H

H

H

H

H

H

HH

HH

H

HHO O O

OH

OHOH

OH OH OH

OH OH OHHO HO HO OHO H2O

OH

Dehydration SynthesisHydrolysis

Macromolecules (How to Make Them)

C. Carbohydrates

• 7. complex sugars are called polysaccharides or complex carbohydrates (e.g. starch, cellulose )

• long chains of sugars:

sugar—sugar—sugar—sugar—sugar—sugar—sugar—

D. Lipids• Broad group of organic compounds that

dissolve in oily solvents (e.g. acetone, or benzene) and alcohol but generally do not dissolve in water

• Mostly composed of carbon and hydrogen

D. Lipids• 1. Best known lipids are fats

– serve living organisms as important energy sources

– consist of glycerol and up to three long-chain fatty acids

• 2. Modified fats called phospholipids are the major components of membranes

• 3. Other types of lipids include waxes and steroids

glycerine fatty acid

Fatty Acids + Glycerol

Fats

Other important lipids you should know!

Steroids such as cholesterolPhospholipids

I. MICROBIAL PHYSIOLOGY

• _____________: the sum of all biochemical processes taking place in a living cell. Two phases:

• _____________: constructive metabolism; the synthesis reactions; small molecules bonded into larger molecules; energy is “used up”

• _____________: destructive metabolism; decomposition reactions; large molecules split into smaller molecules; energy is released

A._________

• the enzymes present in an organism determine the nature of its physiology

• enzymes are biological catalysts (catalysts are agents that speed up chemical reactions)

• Enzymes “are reusable protein molecules that brings about a chemical change while remaining unchanged itself”

________________= the amount of energy required to do the reaction

Without enzyme

lactose

With enzyme

lactose glucose + galactose

activation energy without enzyme

net energy released

glucose + galactose

activation energy with enzyme

net energy releasedfrom splitting of lactose

Activation Energy = the amount of energy required to do the reaction

Enzymes __________ = what the enzymes works on

________ = what is made

Enzymes

Competitive Inhibitor Noncompetitive inhibitor

Active Site Allosteric Site

Action of enzyme inhibitors

Examples of inhibitors:

1. Competitive=sulfa drug (sulfanilamide)

2. Noncompetitive=Certain poisons, such as cyanide and fluoride (enzyme poison in bacteria)

Factors influencing enzyme action:

• a. Terms:• optimum: the environmental state where the

enzyme works the fastest.• maximum: The maximum environmental limit

where the enzyme works at all.• minimum: The minimum environmental limit

where the enzyme works at all.• e.g. temperature: every enzyme has its optimum

temperature (where it works fastest). Curve is unusual:

enzyme activity vs temperature

pH• Measurement of acid/base balance

• Logarithmic scale• 0-6.9 = acid• 7.1-14 = basic

(alkaline)• 7 = neutral

(like pure water)

enzyme activity vs pH• every enzyme has its optimum pH (where

it works fastest). Bell curve

Naming of enzymes

• names end with -ase• name of substrate + ase

e.g. sucrose is digested by sucrase• kind of reaction + ase

e.g. an enzyme that causes oxidation is called oxidase

Types of Enzymes based on location

• endoenzymes: remain inside of the cell (work internally)– enzymes of cellular metabolism– vulnerable enzymes

• exoenzymes: released to the exterior of the cell (work externally)– digestive enzymes and enzymes of virulence

Constitutive vs Induced Enzymes

• ___________ enzymes: – always present– necessary for life of cell

• __________ enzymes:– produced only when substrates are present– e.g. digestive enzymes – provide efficiency and adaptability

B. Energy and ATP• Energy released from catabolism of foods is stored in a

compound called ATP (adenosine triphosphate)• a molecule of ATP acts like a portable battery—it’s instant

energy for a cell to use• ATP molecules are used everywhere in a cell to meet

energy needs. (When the supply is exhausted, the cell dies)

ADP + Phosphate + Energy = ATP

captures heat releases heat

ATP• Although ATP molecules are used everywhere in the

cell to meet energy needs, they are not suitable for storing energy. The molecules are large and bulky, and surplus takes up too much space in a cell.

• Therefore, cells synthesize or obtain small molecules such as glucose or lipids for energy storage. When needed, these energy storage molecules can be converted to ATP!

• glucose is a principle source of energy for ATP production.

C. Pathways of Energy Production• Most of a cell’s energy is produced from

carbohydrate catabolism • Glucose is the most commonly used

carbohydrate:

• C6H12O6 + 6 O2 + 38 ADP + 38 P 6 CO2 + 6 H2O + 38 ATP

• To produce energy (ATP) from glucose, microbes use 2 general processes:– 1. respiration

• in which glucose is completely broken down– 2. fermentation

• in which glucose is partially broken down

• Both processes usually start with the same first step (glycolysis), but follow different subsequent pathways

Glycolysis• the first stage in the breakdown of glucose

glucose

2 pyruvic acid

(energysource )

series of controlled reactions releasing a

little ATP

Overview of Respiration & Fermentation

glycolysis

respiration fermentationpathwayspathways

Aerobic=CO2 + H2O + 38 ATP an organic end-product

(like alcohol or lactic acid) with low ATP yield

Classification of organisms by oxygen use (study table 6.1)

• 1. obligate aerobes: (= strictly aerobic): must have oxygen to grow (go dormant without oxygen)

• 2. microaerophiles: grow best at low oxygen levels (less than atmospheric)

• 3. facultative anaerobes: use oxygen if it’s present, but can also grow anaerobically (capable of growing at any oxygen level, but greater growth with oxygen present)

• 4. aerotolerant anaerobes: never use oxygen, but not inhibited by it

• 5. obligate anaerobes: grow only in absence of oxygen (inhibited by oxygen)

Growth at different oxygen levels

E. Growth at different temperatures

• Each species has different temperature requirements• minimum growth temperature: lowest temperature at which

growth will occur (very slow growth at this temp)– below the minimum, most microorganisms go dormant,

but do not die• optimum growth temperature: temp at which most rapid

growth occurs• maximum growth temperature: highest temp at which

growth occurs– above this temp, enzymes are denatured and death

might occur• NOTE: Growth parallels rate of enzyme activity.

Growth speed vs temperature

Gro

wth

Sp

eed

F. Classification by temperature requirements

• _____________ (= cryophiles): cold-loving organisms; have optimum growth temp below 25° C

• _____________ (meso = middle): have optimum of 25-40°C

• ____________: heat-loving organisms; have optimum > 40°C

• ______________: growth range = 70-105oC; optimum > 90oC

mesophiles

hyperthermophiles

Growth versus temperature

Does size of pan (with same volume) matter?

G. pH and microbial growth

• every organism has its minimum, optimum, and maximum growth pH

• microorganisms often change the pH of their environment– usually create acidity– sometimes create alkalinity

Gro

wth

spe

ed

Thus, the requirements for bacterial growth include:

• Physical aspects– Temperature– pH– Osmotic pressure

• Chemical aspects– Carbon, nitrogen, sulfur, phosphorus, trace

elements, oxygen, and organic growth factors

H. Bacterial fission (cell division)

• less complex than mitosis (division of eucaryotic cells)– only one chromosome

• Binary fission (see figure 6.12)

Remember...• When we talk about microbial growth, we

are really referring to the number of cells, not the size of the cells.

• Microbes that are “growing” are increasing in number, accumulating into clumps of hundreds, colonies ( can be seen with naked eye ) of hundreds of thousands, or populations of billions.

How do we measure microbial growth?

• Plate counts and serial dilutions– We’ll do as part of the microbiology of water and milk lab– See figure 6.16

• Filtration– We’ll do as part of the microbiology of water lab– See figure 6.18

• Direct Microscopic Count– See figure 6.20

• Turbidity– Using the spectrophotometer– See figure 6.21

• Dry weight

I. Population dynamics

• potential populations:– huge– doubling time of 20-30 minutes for many

microorganisms– from 1 cell to over a million in 10 hours (with 30

minute generation)– See figure 6.13 & 6.14

• populations are self-limiting– depletion of food supply– accumulation of toxic metabolic wastes

• population growth curve

lag phase:slow growth

logarithmic (log)phase: rapid growth

maximumstationaryphase (aging population)

death phase:rapid decline

survivor phase

time