Download Microbiology - North Mac Schools


The ultimate outcome of metabolic
activity is reproduction

Growth refers to an increase in
population which is a discrete colony
Nutrients are chemicals

And are used for energy

How do bacteria get energy?

Autotrophs-make their own food

Heterotrophs-get food from other organisms

Chemotrophs-food from chemicals

Phototrophs-food from light

The most common chemical element in cells
(never a limiting nutrient) is Hydrogen
Bacterial Environments

Organotrophs-get e- from organic molecules

Lithotrophs-get e- from inorganic molecules

Obligate Aerobes-have to have oxygen

Obligate Anaerobes-oxygen is deadly

Facultative anaerobes-aerobes that can use
anaerobic pathways ex: fermentation
Most microbes can be placed in
1 of 5 categories
Photolithoautotrophy
 Photoorganoheterotrophy
 Chemolithoautotrophy
 Chemolithoheterotrophy
 Chemoorganoheterotrophy

Bacterial Environments

Aerotolerant anaerobes- don’t normally use oxygen but can
Ex: lactobacilli (cucumbers>pickles) (milk>cheese)

Microaerophiles-use small amounts of Oxygen
Ex: heliobacter pylori- stomach ulcers

Capnophile – needing high concentrations of CO2

Four toxic forms of oxygen
1.singlet O2- have lost e- during metabolism
2. superoxide radical (O2-)
3.peroxide anion (O2 2-)
4.Hydroxyl radical (OH.)
Nitrogen

What element is often a growth-limiting
nutrient- Nitrogen , needed to make
proteins

Few organisms can utilize nitrogen gas.

These four make up more than 95% of
the dry weight of cells C,H,O,N
Definitions

Trace elements- required in small amounts

Growth factors- vitamins

Minimum growth temperature- lowest temp needed
to survive

Maximum growth temperature-highest temp capable
of surviving at

Optimum growth temperature-desired temp
Loving Environments

Psychrophiles- super cold
Ex: ice, freezer, refrigerators, cold water, cause food spoilage

Mesophiles-best at 20-40 C (human body 37C)
Ex: human pathogens

Thermophiles- hot
Ex: hot springs, don’t cause disease

Hyperthermophiles-Archae, extremely hot
Ex: hydrothermal vents, volcanic necks

Neutrophiles- pH 6.5-7.5, human body

Acidophiles- acidic habitats
3 features of hyperthermophiles
that enable them to remain intact
Cytoplasmic membranes don’t contain
fatty acids so they don’t melt
2. DNA is unique heat-stable supercoils
3. Enzymes are heat stable
1.
2 regions of body that acidity
reduces microbes and what happens
if malfunctions
1. Stomach
Heliobacter pylori- neutralizes
stomach acid and causes ulcers
2. Vagina
-disruption causes yeast infection
ex:antibiotics
How can microbes survive in dry
conditions
1.
Cell wall retain water for months
2.
Spores & cysts can cease metabolic
activity for years

Hypertonic- greater amount of solutes

Hypotonic- lower amount of solutes

Plasmolysis- shriveling of cytoplasm

Obligate halophiles-high osmotic
pressure- Great Salt Lake, Dead Sea

Barophiles- extreme pressure
Relationships

Antagonistic relationships- one organism
harms or kills another

Synergistic relationships- each receive
benefits

Symbiotic relationships- interdependent
on each other rarely live outside the
relationship

Biofilms- complex community of bacteria
 Reading page 174

Quorum sensing-bacteria cell to cell
communication

http://www.youtube.com/watch?v=TVfm
Ufr8VPA
Culturing Microorganisms
medical labs must grow pathogens
 sample called inoculum is introduced
into a collection of nutrients called
medium
 Culture- cultivating microorganisms

Inocula
1. Environmental- ponds, streams, soil, air
 2. previous specimens kept in storage
 3. Clinical- from patients (feces, saliva, blood)
-very important that they are handled
correctly, prevent contamination of sample
and themselves
-universal precautions (CDC)

Pure Cultures (axenic)
- cultures composed of cells arising from a single
progenitor (may be single cell or group of related cells)
-termed colony-forming unit (CFU)
-want it to be sterile- free of any microbial contamination
How?
1. Streak Plates- inoculating loop spreads on Petri
dishes
-incubation- time for growth
2. Pour Plates- isolated colonies
Culture Media-pg 178
Nutrient Broth or Agar (solid)
1.most microbes can't digest agar
 2. powdered agar dissolves in water at
100C
 3. Agar solidifies at temps below 40C
 4. Doesn't melt below 100C- can culture
thermophiles


-make Petri plates or slant tubes

1. Defined- exact chemical composition is known

2. Complex- nutrients released by the partial
digestion of yeast, beef,
-soy, or proteins, exact makeup unknown,
blood often added
-supports many organisms
ex: soy agar, nutrient broth

3. Selective- substances that either favor growth
of microbes wanted or inhibit growth of
unwanted, differentiates between 2 species
ex: large NaCl for halophiles

4. Differential- either the presence of visible
changes in media or differences in colony
appearance
ex: may make color if digest certain
chemical

5. Anaerobic- protected from free oxygen
-stab cultures- into media
-reducing media- chemically combine with
free oxygen and remove it from the medium

6. Transport- carry clinical specimens
Special Culture Techniques
1. Animals & Cells
Mycobacterium leprae in armadillos,
parasites in bird eggs
 2. Low-Oxygen
carbon dioxide incubators, candle jars,
chemicals
ex: capnophiles- grow best at high CO2
 3. Enrichment- uses selective media, keep
isolating wanted bacteria
ex: oil
-cold enrichment- some survive, some don't,
ex: stool specimens

Preserving
1. Refrigeration
 2. Deep-freezing
 3. Lyophilization- removing water from
frozen culture w/ vacuum, preserves for
years

Reproduction

1.
2.
3.
4.
Binary Fission
Cell replicates DNA
Cell grows, DNA moves
apart
Forms a cross wall
2 new daughter cells

Spores
 Reproductive cells that can make a clone of
original organism

Budding
 Outgrowth of original cell receives genetic
material and enlarges
Endospore formation
Replicates DNA
2. Cytoplasm splits
3. Membrane grows to make spore coat
4. Endospore is released
1.
Exponential Growth
Occurs under ideal conditions... Unlimited resources or no predation
Bacteria reproduce on average every 20 minutes.
Starting with 1...
20 minutes – 2 bacteria
40 minutes – 4 bacteria
1 hour – 8 bacteria
2 hours – 64 bacteria
4 hours – 512 bacteria
1 day – 4,720,000,000,000,000,000,000 bacteria!
If this population growth went unchecked,
bacteria would cover the planet!
Carrying capacitylargest number of individuals
that a given environment can support
Phases of Growth

1. Lag Phase- adjusting to new
environment, synthesize enzymes to use
nutrients

2. Log Phase- rapid chromosome
replication, growth, reproduction
-population increases logarithmically

3. Stationary Phase- nutrients depleted,
wastes increase,rate decreases
# dying = #produced

4. Death Phase- nutrients not added,
wastes not removed
# dying › # produced
Measuring

1. Viable Plate Counts
 count the colonies on plates, multiply the number of bacteria
 Determines the number of living cells in a culture
 per ml of the original culture

2. Membrane Filtration
 large sample poured through a filter small enough to trap cells

3. Microscopic Counts
 sample on cell counter (gridded slide), # per square

4. Electronic Counters
 count cells as they interrupt an electrical current
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5. Most probable number
 stats based on more bacteria in sample, more dilutions required
to reduce # to 0
Indirect
1. Metabolic Activity
 2. Dry Weight
 3. Turbidity- Spectrophotometer
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