Biology 261Microbiology and Immunology for

Health professionProf. Victor Santos

Medgar Evers College, CUNY

Microbiology - study of microorganisms. Microbiology is a broad term or field that

includes others branches.

• Branches of Microbiology1. Bacteriology – study of bacteria2. Mycology – study of fungi3. Phycology- study of

algae4. Protozoology – study of protozoa5. Virology - study of viruses6. Parasitology – study of parasites

Members of the microbial world

• All organisms can be placed in one of three large groups known as Domains. These domains are Bacteria, Archaea, and Eucarya.

• Members of the microbial world include organisms from all domains.

http://www.google.com/url?sa=i&rct=j&q=3+domains&source=images&cd=&cad=rja&docid=CzrPXsBRB3ACRM&tbnid=vnIui9OPXegfnM:&ved=0CAUQjRw&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FKingdom_(biology)&ei=K4weUp2GE5e14APrnYCABQ&bvm=bv.51495398,d.cWc&psig=AFQjCNGKfDbGzKx1fFrcFmkq8-MayKSjqQ&ust=1377820059299416

Bacteria

• Are prokaryotes

• Unicellular

• Three basic shapes; rod, sphere, and spiral.

• Divide by binary fission

• Diverse in terms of habitat

• Have a cell wall that consists of a macromolecule called peptidoglycan.

• Most bacteria are motile and can move by means of an appendage called a flagellum.

http://www.google.com/url?sa=i&rct=j&q=3+bacterial+shapes&source=images&cd=&cad=rja&docid=DaqxYCkMXX7JuM&tbnid=SAO6Lhp2aO-BtM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.sparknotes.com%2Fbiology%2Fmicroorganisms%2Fmonera%2Fsection1.rhtml&ei=aIweUoeQDYWw4APW3oGQBw&bvm=bv.51495398,d.cWc&psig=AFQjCNFvW3asyjsXJnaYPx2VmMlsxqLLJQ&ust=1377820127113363

Archaea

• Similar to bacteria in terms of size, shape, and replication.

• Three main differences are

1- Biochemistry of the cell wall. Peptidoglycan is not found in the cell wall of archaea.

2- the presence of ether lipids in the cell membrane.

http://upload.wikimedia.org/wikipedia/commons/4/46/Archaea_membrane.svg

3- Archaea are also known for their ability to live in extreme environments. Some can withstand high salt level (halophiles), extreme heat (thermophiles), and extreme cold (cryophiles).

• Halophiles- salt halococcus

• Thermophiles- heat thermus aquaticus

• Cryophiles- cold ocean water arthrobacter

Halobacteria

Eucarya

• Are eukaryotes

• Include unicellular organisms and multicellular organisms that cause disease.

• These include algae, protozoa, fungi and multi-cellular animals such as arthropods and helminths.

Algae

• Unicellular or multi-cellular

• Photosynthetic

• Live in either salt or fresh water

• Cell wall is composed of cellulose

• Algae do not directly cause disease in humans but do so indirectly by secreting toxins that are consumed by marine life eaten by humans.

Cyanophyta recovered from Lake Champlain

Protozoa

• Eukaryotes

• Unicellular

• are both terrestrial and aquatic in nature

• Have no cell wall

• are classified according to their mode of motility; pseudopods, cilia, or flagellum.

Euglena

Fungi

• Eukaryotes

• Unicellular or multi-cellular

• Gain their energy by breaking down organic materials.

• Mostly terrestrial in nature

Amanita muscaria

Large multi-cellular animals

2 groups of larger multi-cellular animals are also included in our study because they cause disease in humans and we can apply the same immunological and microscopic techniques to study them. These are the arthropods and helminths.

Arthropods

• Include insects such as mosquitoes, fleas, and lice. Also included are ticks and mites which are arachnids. Arachnids differ from insects in that they lack wings, antenna, and their thorax and abdomen are fused together.

• Arthropods are mainly vectors such as mechanical or biological. They are known as disease carriers!

Helminths

• Are parasitic in nature

• Include tapeworms, roundworms, and flukes.

• Unlike the arthropods that only act as vectors to spread disease, the helminths can cause serious diseases in humans.

• Helminths include the roundworms (nematodes), tapeworms (cestodes), and the flukes (trematodes).

roundworm

Infectious agents

Virus

• A piece of nucleic acid surrounded by a protein coat

• They are obligate intracellular parasites

• They infect all forms of life.

Viroid

• A single short piece of nucleic acid, specifically RNA.

• They can only reproduce inside a cell

• Are known to cause diseases in plants

• Prions

• Agents that consists of only proteins that have been known to cause neurodegenerative diseases in humans and other animals and are usually fatal.

Beneficial applications of microorganisms

A. Normal flora1. Beneficial metabolic functions2. Antagonistic effect - prevents invasion pathogens,

over growth of potential pathogens

B. Environmental importance1. Decomposers2. Produce oxygen3. Food chain

C- Food/beverage production

1- Microorganisms are used in the production of such foods as bread, cheese, yogurt, buttermilk and probiotics

2- The brewery industry depends on microorganisms for the production of beer and other fermented drinks

D- Bioremediation

1- microorganisms are used to break down dangerous pollutants such as PCB (polychlorinated biphenyls), DDT, and trichloroethylene.

2- microorganisms are also used to break down oil, and radioactive waste.

E- Products

1- Cellulose

2-Hydrobutyric acid used in the production of disposable diapers and plastics

3-Antibiotics used in treatment of disease

F- Molecular Biology studies

1- Microorganisms serve as model organism to study more complex life forms.

2- genetic engineering to manipulate organisms and produce useful products

History of Microbiology

Anton van Leeuwenhoek (1674)

1. Used simple instrument to examine stagnant H2O, etc.

2. Observed microscopic organisms and is credited with being the first to observe bacteria.

Theory of Spontaneous Generation

1. This theory existed to explain the origin of some forms of life

2. Living organisms arose “spontaneously” from nonliving, decaying organic matter.

3. This theory was formulated by Aristotle.

• Francesco Redi

1.Performed experiments that disproved theory of SG for more complex forms of life (began approx.1668).

Louis Pasteur (1861)

1. Performed experiments to disprove Theory of SG.

a. He accepted the challenged to re-create the experiment and leave the system exposed to air.

b. Placed boiled infusion broths in “swan-necked” flasks

c. Flasks remained sterile unless tilted or neck broken.

2. His experiments finally disprove the theory of SG.

John Tyndall (1875)

• English physicist who finally explained the differences in the previous experiments. He concluded that different organisms required different boiling temperatures to be sterilized.

• He stated that organisms can exist in a cell state easily killed by boiling and a heat resistant form.

• One year later Ferdinand Cohn discovered endospores.

Golden Age of Microbiology (approx. 1875 - 1918)

1.Period (about 50 years) of rapid development.

2.Causes of diseases identified, control methods developed, work began on viruses.

Robert Koch

While studying anthrax ( a disease of cattle) a. Identified a bacterium as cause of anthrax (first bacterium that caused a disease).

b. Introduced “solid medium” using agar, observed differences in colony morphology and Introduced the inoculating loop to transfer bacteria and prepare pure cultures.c. Introduced “Koch’s Postulates” and the concept that a disease is caused by a single organism.

Joseph Lister (1865)

a. Introduced the “aseptic technique” to the field of Microbiology.

b. Use of phenol (carbolic acid) as disinfectant.

Size in the microbial world

• Members of the microbial world cover a tremendous range in their sizes. They range in size from mm to nm.

• The basic unit of length is the meter