Lab 4271

Introduction:

Anthony van Leeuwenhoek

Robert Hooke

The microscope is perhaps the most basic tool used by biologists. Light microscopy was first applied to biological materials in the seventeenth century by such researchers as Robert Hooke and Anthony van Leeuwenhoek. The impact of this invention on the course of human endeavor is easily underestimated. Within a short span of time, that which was invisible to the human eye became visible. An entire world of living organisms previously unknown was now available for study. The microscope remains a pivotal tool in learning biology to this day, with most laboratories being equipped with one or more research instruments.

The part of the microscope;

Body Tube-The body tube holds the objective lenses and the ocular lens at the proper distance

Nose Piece-The Nose Piece holds the objective lenses and can be turned to increase the magnification

Objective Lenses-The Objective Lenses increase magnification (usually from 10x to 40x)

Stage Clips-These 2 clips hold the slide/specimen in place on the stage

Diaphragm-The Diaphragm controls the amount of light on the slide/specimen

Light Source-Projects light upwards through the diaphragm, the specimen and the lenses ; Some have lights, others have mirrors where you must move the mirror to reflect light

Ocular Lens/Eyepiece-Magnifies the specimen image

Arm-Used to support the microscope when carried. Holds the body tube, nose piece and objective lenses

Stage-Supports the slide/specimen

Coarse Adjustment Knob-Moves the stage up and down (quickly) for focusing your image

Fine Adjustment Knob-This knob moves the stage SLIGHTLY to sharpen the image

Base-Supports the microscope

Magnification-To determine your magnification…you just multiply the ocular lens by the objective lens ; Ocular 10x, Objective 40x:10 x 40 = 400x ; So the object is 400 times “larger” ; Ocular lenses usually magnifies by 10x

Using a Microscope-Start on the lowest magnification ; Don’t use the coarse adjustment knob on high magnification…you’ll break the slide!!! ; Place slide on stage and lock clips ; Adjust light source (if it’s a mirror…don’t stand in front of it!) ; Use fine adjustment to focus

The Bright-Field Microscope-produces a dark image against a brighter background ; has several objective lenses- parfocal microscopes remain in focus when objectives are changed ; total magnification- product of the magnifications of the ocular lens and the objective lens

Objectives:

Learn to use a simple bright-field microscope correctly
Learn the parts of a compound light microscope and their functions.
Learn how to calculate the magnification of a compound light microscope.
Learn how to make a wet mount slide.
Understand how the orientation and movement of the specimen’s image changes when viewed though a compound light microscope.
Learn the proper use of the low and high power objective lenses.
Learn the proper use of the coarse and fine adjustments for focusing.

Results:

Stained Cell

Species: Streptococcus sp. ;
Magnification : 40x

Species: Streptococcus sp. ;
Magnification : 100x

Species: Streptococcus sp. ;
Magnification : 400x

Wet mount

Species: Saccharomyces cerevisiae ;
Magnification : 1000x

Species: Lactobacillus fermentum ;
Magnification : 1000x

Discussion:

Morphology,

in biology, the study of the size, shape, and structure of animals, plants, and microorganisms and of the relationships of the parts comprising them. The term refers to the general aspects of biological form and arrangement of the parts of a plant or an animal. The term anatomy also refers to the study of biological structure but usually suggests study of the details of either gross or microscopic structure. In practice, however, the two terms are used almost synonymously.

Stained Cell

Streptococci are a diverse genus, infecting a barrage of different animals, including humans, with diseases ranging from strep throat to necrotizing fasciitis.

They have come to public attention recently as antibiotic-resistant strains have started appearing and causing epidemics. In an effort to battle the evolution of these clever pathogens, researchers have sequenced the genomes of 9 different strains in 4 different species of Streptococcus.

Streptococci are nonmotile, Gram-positive, nonsporeforming bacteria, that live in pairs or chains of varying length. They are characteristically round or ovoid in shape. Most Streptococci are facultative anaerobes, although some are obligate anaerobes.

They usually require a complex culture medium in order to grow. Many streptococci imitate aspects of their host in order to escape detection. The capsule of Streptococcus pyogenes is chemically similar to that of it's host's connective tissue, and therefore, is nonantigenic, and it's cytoplasmic membrane has antigens similar to human cardiac skeletal and smooth muscle.

Wet mount

Saccharomyces cerivisiae is a species of yeast. It has developed as a model organism because it scores favorably on a number of these criteria.

As a single celled organism S. cerevisiae is small with a short generation time (doubling time 1.25–2 hours at 30 °C or 86 °F) and can be easily cultured. These are all positive characteristics in that they allow for the swift production and maintenance of multiple specimen lines at low cost.
S. cerevisiae can be transformed allowing for either the addition of new genes or deletion through homologous recombination. Furthermore, the ability to grow S. cerevisiae as a haploid simplifies the creation of gene knockouts strains.
As a eukaryote, S. cerevisiae shares the complex internal cell structure of plants and animals without the high percentage of non-coding DNA that can confound research in higher eukaryotes.
S. cerevisiae research is a strong economic driver, at least initially, as a result of its established use in industry.

Lactobacillus fermentum is a Gram-positive species of bacterium in the genus Lactobacillus. It is associated with active dental caries lesions.

L. fermentum belongs to the genus Lactobacillus. Species in this genus are used for a wide variety of applications. These applications include food and feed fermentation. It has been found that some strains for L. fermentum have natural resistances to certain antibiotics and chemotherapeutics. They are considered potential vectors of antibiotic resistance genes from the environment to humans or animals to humans.
Lactobacillus fermentum can also be a normal inhabitant of the human intestinal tract and some strains have been associated with cholesterol metabolism.

Conclusion:

We learnt the correct way to view sample of microorganisms by using simple bright-field microscope ( used different magnification 40x, 100x, 400x, 1000x to observe the microorganisms). We able to identify that how the orientation and movement of the specimen’s image changes when viewed though a compound light microscope.From the image obtain through microscopy, we are able to illustrate the diversity of cells and microorganisms and the description of morphology of the cells can be done.We examined a stained cell Streptococcus sp. , Saccharomyces cerevisiae, and Lactobacillus fermentum is the first experience in using light microscope.We used a lot of material and method to conduct this experiment and wet mount such as microscope, slides, cover slips, lens paper, and oil.

References: