Intro to Microbiology - LU3

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Conditions affecting Bacteria Growth

1. Sufficient nutrients
2. Oxygen requirements
3. Moisture
4. Temperature
5. pH
6. Effects of light
7. Osmotic pressure

Autotrophic Bacteria

1. Are those organisms that are self-nourishing; that is they make their own food.
2. They obtain their food by building organic compounds in their protoplasm from simpler inorganic
substances.

Heterotrophic Bacteria

1. Are organisms that obtain their food by
breaking down organic matter into simpler chemical substances.
2. Are responsible for numerous diseases in humans. ALL PATHOGENIC and MANY NON-PATHOGENIC bacteria are ________________.
3. Four Categories

Heterotroph Categories

1. Strict (obligate) saprophytes
2. Strict (obligate) parasites
3. Facultative saprophyte
4. Facultative parasite

Strict or Obligate

Means "they can only get their nourishment from one source". There can be no deviation.

Facultative

Means "able to do a number of things or can
do more than it appears".

Strict or Obligate Saprophyte

An organism that can ONLY survive on dead or decaying organic matter.

Strict of Obligate Parasite

1. An organism that is completely DEPENDENT ON ITS LIVING HOST for survival
2. It can ONLY gain nourishment from living matter and nothing else.

Facultative Saprophyte

Is an organism that USUALLY obtains nourishment from LIVING matter, BUT MAY OBTAIN it from DEAD organic matter

Facultative Parasite

Is an organism that USALLY obtains its nourishment from DEAD organic matter, BUT MAY OBTAIN it from LIVING matter.

Oxygen Requirement Categories

1. Strict (obligate) aerobe
2. Strict (obligate) anaerobe
3. Microaerophilic
4. Facultative aerobes
5. Facultative anaerobes

Aerobes

Are organisms that grow best in the presence of free atmospheric oxygen (man).

Anaerobes

Are those that cannot grow in free oxygen, but must obtain its oxygen from oxygen containing compounds.
2. Only a few Pathogens are ____________. Example: Clostridium is a Strict or Obligate _________________.

75% - 90%

Percentage of Water in a Bacterial Cell

Water will also dissolve food material in the environment of the bacterial cell so that the food can be absorbed.

Minimum Temperature

The lowest temperature at which organism will grow;
It is the temperature below which bacterial growth will not take place.

Maximum Temperature

The highest temperature at which growth is possible; The temperature above which bacterial growth will not take place

Optimum Temperature

The temperature at which an organism grows best

Psychrophiles or Cyrophiles

Organisms that thrive at temperatures between 0° C (32° F) and 25°C (77° F)

Cold retards or stops bacterial growth. Prolonged freezing destroys them.

Mesophiles

Bacteria that prefer moderate temperatures and develop best at temperatures between 25° C (77°
F) and 40° C (104° F)

Thermophiles

Bacteria that thrive best at temperatures between 40° C (104° F) and 70° C (158° F).

Proteins coagulate at 104° F.

High temperatures are much more injurious to bacteria than low ones.

6 to 8

pH range that is best for bacterial growth

7 to 9

pH range that is best for PATHOGENIC Bacterial growth

7

pH of the interior of a cell

Violet, Ultraviolet, Blue

1. Lights that are highly destructive to bacteria
2. Direct sunlight, because of its content of __________ light kills many bacteria within a few hours.
3. Daylight has an effect similar to sunlight but is less potent.

Osmosis

Is the movement of water (solvent) through a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Osmotic Pressure

Pressure that develops when two solutions of different concentrations are separated by a semi permeable membrane, such as the cell membrane found in bacteria.

Turgid

Swollen or Bloated

Under normal conditions there is a higher concentration of dissolved substances within the cell than outside it.
The greater osmotic pressure inside the cell keeps the protoplasm of the cell firmly against the cell wall, and the cell is said to be __________.

Hypotonic Solution

This solution has a lower concentration of solutes and higher concentration of solvent (water) than the solution with which the cell is compared.
Therefore, water molecules enter the bacterial cell faster than they can leave causing the bacterial cell to swell and burst.

Plasmoptysis

The bursting of a bacterial cell when placed in a hypotonic solution

Hypertonic Solution

This has a higher concentration of solutes and a lower concentration of water (solvent) than the solution with which the cell is compared.
Therefore, water molecules move out of the bacterial cell faster than they can enter which causes the
cell to shrink.

Plasmolysis

The shrinkage of a bacterial cell when placed in a hypertonic solution

Isotonic Solution

Is a solution in which the total concentration of water molecules and solute molecules are the same on both sides of the semi-permeable membrane.
If a bacterial cell happens to find itself in this type of solution - nothing will happen. It will not shrink nor swell.

Effect of Osmotic Pressure

Most bacteria can resist small changes in osmotic pressure, but are killed or inhibited by high
concentrations of either salt (as used in brine) or of sugar. This process is used in the preservation
of foods, such as syrups and jellies with sugar and in the preservatives of meats in brine (salt).

Symbiosis

Is a situation in which two dissimilar organisms live together.
Types:
1. Mutualism
2. Commensalism
3. Parasitism

Mutualism

Type of Symbiosis in which both organisms benefit

Commensalism

Type of Symbiosis in which one
organism benefits and the other is not affected

Parasitism

Type of Symbiosis in which one organism benefits at the other organism's expense.

Synergism

1. A special type of Symbiotic relationship
2. Occurs when the harmonious action of two microorganisms producing an effect that
neither could produce alone.

Antagonistic Relationship

A relationship in which the inhibition of one
microorganism inhibits the growth of another microorganism.

Binary Fission

1. Also called TRANSVERSE DIVISION
2. The way in which Bacteria Reproduce
3. This method of reproduction is an asexual process in which the cell splits into two parts, each of which
develops into a complete individual.
4. The complete process only takes 15-30 minutes from newborn to adult.

Bacterial Colony

1. Begins with one bacterial cell and through
binary fission one cell becomes multiple cells.
2. This is a visible group of bacteria growing on a solid
medium and presumably arising from a single microorganism.

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