1. The Microbial world:

• Definition of (size)- generally 1 mm or smaller in size (unaided eye cannot see anything smaller than a 0.1 mm or 100 mm).
• Members- algae, fungi, protozoa, algae, some multicellular parasites (all have a eukaryotic cell structure), and the smallest of the microbes the Bacteria and Archaea (both have a prokaryotic cell structure). Viruses, viroids, and prions are not microorganisms (have an acellular structure), but are microscopic. What is so unique about Thiomargarita namibiensis? Do viruses have the hallmarks of living systems?

2. Why study Microbiology?

• They are part of our every day world!
• Examples of the bad and good sides of the microbial world.
• Goal of microbiology from a medical point of view.

3. Discovery of microorganisms: Anton van Leeuwenhoek discovered the microbial world. Discovery raised question "Where do they come from?"

4. The Theory of Spontaneous Generation:

• Stated that life could arise from nonliving material.
• Louis Pasteur and John Tyndall are given credit for disproving the theory. What experiment did Pasteur conduct to disprove theory?

5. The Germ Theory of Disease:

• Stated that specific microbes were responsible for certain diseases (previously believed that microbes present were a consequence of the disease process).
  
• Robert Koch- developed as set of premises or conditions, known as Koch Postulates, by which one can prove that a certain disease is causes by a microorganism. Koch demonstrated that disease known as anthrax was caused by a certain bacterium, Bacillus anthracis.
  
  • Kock's Postulates- postulates are just as valid today as they were when established.

Learning Objectives:

• define the microbial world with respect to size and members (major groups).
• Provide examples of the importance/significance of the microbial world.
• Compare the theory of spontaneous generation with that of biogenesis.
• What did people like van Leeuwenhoek, Pasteur, Tyndall, and Koch contribute to the history and development of microbiology.
• What is meant by the germ theory of disease?

Overheads displayed-

Hallmarks of living Systems:

• metabolism- ability to take up nutrients from environment.
• reproduction- use nutrients to reproduce (grow).
• differentiation- ability undergo cell change (morphological and physiological change).
• communication- abilty to communicate, using chemical signals, between like and dissimilar cells (organsisms).
• evolution- ability to acquire new biological properties.

Examples of the Involvement of Microbes in Human History:

• 1347-1349: Bubonic Plague- During the middle ages one-third of the European population (9-11 million people) died of bubonic plague, also known as the black death, caused by the bacterium Yersinia pestis.
  
• 1500's: Smallpox- During the conquest of Mexico by Spain some 12 million Aztecs died of smallpox, a viral disease brought by the Spaniards. Proportionately, this epidemic was worse than plague and worse than the 1918 pandemic of influenza.
  
• 1753: Smallpox in North American Native American population- First documented case of biological warfare occurred when blankets from smallpox victims were given to the highly susceptible Native American population. Is smallpox still major concern, and if not why?
  
• 1845: Irish potato attacked by a fungus, Irish diaspora, which lead to one million people starving to death, and was the stimulus for the immigration of the Irish to the US.
  
• 1918: Influenza Pandemic, caused by a virus, spread throughout the world killing some 21.64 million people in North America, Europe and Parts of Asia combined; 500,000 people died in US. Pandemic was preceded by World War 1 (1914-1918) considered one of the deadliest wars of all time.
  
• 1960's-present: Rise in sexually transmitted disease- Diseases such as gonorrhea (GC), chlamydia infections, and to a lesser extent syphilis, all caused by different bacterial species. It is possible to trace GC back to around 1546.
  
• 1981- First reported case of AIDS caused by the HIV. By 2010 it is estimated that a total of 40 million will have died from AIDS!
  
• use of microbes and viruses for bioterrorism.

From a medical point of view the goals of microbiology are:

• to understand why some microbes/viruses are pathogenic and others not.
• to understand how disease is transmitted, and can be contained.
• identify the various host defenses, and understand how they are brought into play to try an minimize the chance of infection and development of disease.
• Identify remedies, namely chemotherapeutic agents, that can be used to treat disease, and develop procedures to minimize infection/disease, immunization.
• methods to protect against and respond to bioterrorism.

Without microorganisms:

• global cycling of certain elements would not occur (carbon dioxide and dinitrogen gas).
• we would be more vulnerable to infection and disease (normal flora. How numerous is the normal human flora?).
• we would not be able to treat many bacterial infections (antibiotics).
• what types of foods/drinks would we be without?
• the field of genetic engineering would not have developed.

Koch's Postulates:

• The microorganism must be present in every case of the disease.
• The microorganism must be grown in pure culture from the diseased host.
• The same disease must be reproduced when a pure culture of the microorganism is inoculated into a healthy, susceptible host.
• The microorganism must then be recovered from the experimentally infected host.

6/13/2009