Central Mindanao University June 2019
Bio 50- General Microbiology
Class notes/Study notes & short assessment
Intro to microbiology 1.2 : Microscopy
By definition: Microorganisms are tiny organism that some microscope are
required to see them. Microorganism are said to be microscopic.
A. Using Metric System to express size of Microorganisms
-metric units (micrometers & nanometers) are used to express the sizes of
microorganisms
- meter (m) the basic unit of length in the metric system
Is equivalent to approximately 39.4 inches & is therefore, about 3.4 inches
longer than a yard
May be divided into 10 (101) equally spaced units called decimeters; 100 (102)
equally spaced units called centimeters; or 1000 (103) equally spaced units
called millimeters; or 1 million (106) equally spaced units called
micrometers; or 1 billion (109) equally spaced units called nanometers
Note: old terms “micron” and “millimicron” have been replaced by the terms
micrometer and nanometer respectively
The sizes of bacteria and protozoa are usually expressed in terms of micrometers
In microbiology laboratories, the sizes of microorganisms are measured using an ocular
micrometer (a tiny ruler within the eyepiece of the compound light microscope)
B. Microscopes
- an optical instrument that is used to observe tiny objects, often objects that
cannot be seen at all with the unaided human eye.
Simple Microscopes
-Defined as microscope containing only one magnifying lens (magnifying
glass can be considered as simple microscope). Images when using a
magnifying glass usually appear about 3 to 20 times larger than the actual
size.
- during the late 1600s, Anton van Leeuwenhoek used simple microscopes to
observe many objects including protozoa and bacteria. Because of his
unique ability to grind glass lenses, scientists believe that Leeuwenhoek’s
simple microscopes had a maximum magnifying power of about
300x (300 times)
, Compound Microscope
- Is a microscope that contains more than one magnifying lens. Although
the first person to construct and used a compound microscope is not
known with certainty, Hans Jansen and his son Zacharias are often
given credit for being the first.
- Compound light microscopes usually magnifying objects about 1000
times.
*photomicrographs- photographs taken through the lens system of
compound microscopes
- because visible light (from a built –in light bulb) is used as the source of
illumination, the compound microscope is also referred to as a compound
light microscope. When using compound light microscope, objects
cannot be seen if they are smaller than half of the wavelength of the visible
light.
- compound light microscope used in today’s laboratories contain two
magnifying lens systems . within the eyepiece/ ocular is a lens called
ocular lens; usually has a magnifying power of x10. The second
magnifying lens system is in the objective, positioned immediately above
the object to be viewed. The four objectives used in most laboratory compound
light microscopes are x4, x10, x40 and x100 objectives.
Table 2.2
Characteristics of Various Types of Microscopes
Type RESOLVING POWER USEFUL CHARACTERISTICS
MAGNIFICATI
ON
Brightfield 0.2000 μm 1,000x Used to observe morphology of
microorganisms such as bacteria,
protozoa, fungi, and algae in
living (unstained) and nonliving
(stained) state
Cant observe organisms less than
0.2 μm in diameter or thickness,
such as spirochetes and viruses
Darkfield 0.2000 μm 1,000x Unstained organisms are
observed against a dark
background
Useful for examining thin
spirochetes
Slightly more difficult to operate
than brightfield
Phase-contrast 0.2000 μm 1,000x Can be used to observed
unstained living organisms
Fluorescence 0.2000 μm 1,000x Fluorescent dye attached to
organism
Primarily an immunodiagnostic
technique (immunofluorescence)
Used to detect microorganisms in
cells, tissues, and clinical
Bio 50- General Microbiology
Class notes/Study notes & short assessment
Intro to microbiology 1.2 : Microscopy
By definition: Microorganisms are tiny organism that some microscope are
required to see them. Microorganism are said to be microscopic.
A. Using Metric System to express size of Microorganisms
-metric units (micrometers & nanometers) are used to express the sizes of
microorganisms
- meter (m) the basic unit of length in the metric system
Is equivalent to approximately 39.4 inches & is therefore, about 3.4 inches
longer than a yard
May be divided into 10 (101) equally spaced units called decimeters; 100 (102)
equally spaced units called centimeters; or 1000 (103) equally spaced units
called millimeters; or 1 million (106) equally spaced units called
micrometers; or 1 billion (109) equally spaced units called nanometers
Note: old terms “micron” and “millimicron” have been replaced by the terms
micrometer and nanometer respectively
The sizes of bacteria and protozoa are usually expressed in terms of micrometers
In microbiology laboratories, the sizes of microorganisms are measured using an ocular
micrometer (a tiny ruler within the eyepiece of the compound light microscope)
B. Microscopes
- an optical instrument that is used to observe tiny objects, often objects that
cannot be seen at all with the unaided human eye.
Simple Microscopes
-Defined as microscope containing only one magnifying lens (magnifying
glass can be considered as simple microscope). Images when using a
magnifying glass usually appear about 3 to 20 times larger than the actual
size.
- during the late 1600s, Anton van Leeuwenhoek used simple microscopes to
observe many objects including protozoa and bacteria. Because of his
unique ability to grind glass lenses, scientists believe that Leeuwenhoek’s
simple microscopes had a maximum magnifying power of about
300x (300 times)
, Compound Microscope
- Is a microscope that contains more than one magnifying lens. Although
the first person to construct and used a compound microscope is not
known with certainty, Hans Jansen and his son Zacharias are often
given credit for being the first.
- Compound light microscopes usually magnifying objects about 1000
times.
*photomicrographs- photographs taken through the lens system of
compound microscopes
- because visible light (from a built –in light bulb) is used as the source of
illumination, the compound microscope is also referred to as a compound
light microscope. When using compound light microscope, objects
cannot be seen if they are smaller than half of the wavelength of the visible
light.
- compound light microscope used in today’s laboratories contain two
magnifying lens systems . within the eyepiece/ ocular is a lens called
ocular lens; usually has a magnifying power of x10. The second
magnifying lens system is in the objective, positioned immediately above
the object to be viewed. The four objectives used in most laboratory compound
light microscopes are x4, x10, x40 and x100 objectives.
Table 2.2
Characteristics of Various Types of Microscopes
Type RESOLVING POWER USEFUL CHARACTERISTICS
MAGNIFICATI
ON
Brightfield 0.2000 μm 1,000x Used to observe morphology of
microorganisms such as bacteria,
protozoa, fungi, and algae in
living (unstained) and nonliving
(stained) state
Cant observe organisms less than
0.2 μm in diameter or thickness,
such as spirochetes and viruses
Darkfield 0.2000 μm 1,000x Unstained organisms are
observed against a dark
background
Useful for examining thin
spirochetes
Slightly more difficult to operate
than brightfield
Phase-contrast 0.2000 μm 1,000x Can be used to observed
unstained living organisms
Fluorescence 0.2000 μm 1,000x Fluorescent dye attached to
organism
Primarily an immunodiagnostic
technique (immunofluorescence)
Used to detect microorganisms in
cells, tissues, and clinical
