BIOL 3340

Chapter 1 The History and Scope of Microbiology

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The Importance of Microorganisms

medical and most populous group of organisms and are found everywhere on the planet play a major role in recycling essential elements source of nutrients and some carry out photosynthesis benefit society by their production of food, beverages, antibiotics and vitamins causative agents of some important diseases

What is Microbiology?

 generally defined as the study of organisms too small to be clearly seen by the unaided eye (i.e., microorganisms )  these organisms are relatively simple in their construction and lack highly differentiated cells and distinct tissues

Members of the Microbial World

 procaryotic cells lack a true membrane delimited nucleus  eucaryotic cells have a membrane enclosed nucleus, are more complex morphologically and are usually larger than procaryotic cells

Procaryotes

 most are single-celled  most have peptidoglycan in cell wall  can survive broad range of environments  most are non-pathogenic and play major role in nutrient recycling

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Eucaryotes

 animals, plants and eucaryotic microorganisms  microorganisms include protists (unicellular algae, protozoa, slime molds and water molds) and fungi  most are larger than procaryotic cells

…….. Viruses

 acellular  smallest of all microbes (smallest is 10,000 times smaller than a typical bacterium

Importance of Microorganisms

 first living organisms on planet  live almost everywhere life is possible  more numerous than any other kind of organisms  global ecosystem depends on their activities  influence human society in many ways

Discovery of Microbes

Antony van Leeuwenhoek (1632-1723)  first person to observe and describe microorganisms accurately 

Developed early microscope

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First to observemicrobes:“animalcules”

…….. The Conflict over Spontaneous Generation

Spontaneous generation: living organisms can develop from nonliving or decomposing matter 1. Francesco Redi (1626-1697): • disproved spontaneous generation for large animals • showed that maggots on decaying meat came from fly eggs

2. John Needham (1713-1781): • his experiment : mutton broth in flasks  boiled  sealed with cork : • broth became cloudy & contained microorganisms 3. Lazzaro Spallanzani (1729-1799): • his experiment: boiled seeds in flasks & water  sealed  boiled: • no growth of microorganisms in sealed & open flasks had animicules

…….. Louis Pasteur (1822-1895)

4. Pasteur • • Mid to late-1800s French chemist and a “founder” of the modern science of microbiology • Settled the Spallanzani-Needham debate with the “swan-necked flask” experiment & put to rest the Spontaneous generation theory

……..Pasteur • boiled the solutions & left flasks exposed to air • results: no growth of microorganisms • placed nutrient solution in flasks with long, curved necks

…….. Pasteur

…….. Pasteur • Pasteur laid the foundation of aseptic techniques, techniques that prevent contamination by unwanted microbes. These techniques are based on Pasteur’s idea that microbes can be killed by heat and that procedures can be designed to inhibit the access of airborne microbes to nutrient environment.

• He dispprove the idea that microorganisms spontaneously generated from non-living matter through mystical forces is one of the greatest contributions of Pasteur in science

Final Blow to Theory of Spontaneous Generation

5. John Tyndall (1820-1893): • demonstrated that dust carries microorganisms • showed that if dust was absent, nutrient broths remained sterile, even if directly exposed to air • Demonstrated directly that the growth of microbes in contaminated flasks was due to microbial cells from airborne dust particles, not from spontaneous generation

Theory of biogenesis Vs Spontaneous generation : • The theory of biogenesis states that living things can only arise from living things and cannot be spontaneously generated. • The Spontaneous generation hypothesis proposed by scientists to explain the origin of the “animalcules” observed by Antoni van Leeuwenhoek in his magnifying lenses had received wide acceptance all over Europe from Antoni’s time until the time of Louis Pasteur .

The Golden Age of Microbiology (1857-1914)

• Many disease producing organisms were discovered • Microbial metabolism studies undertaken • Microbiological techniques refined • A better understanding of the role of immunity and ways to control and prevent infection by microbes

The Role of Microorganisms in Disease

• • was not immediately obvious establishing connection depended on development of techniques for studying microbes • once established, led to study of host defenses - immunology

Recognition of the Relationship between Microorganisms and Disease

Agostini Bassi (1773-1856): showed that a disease of silkworms was caused by a fungus M. J. Berkeley (ca. 1845): demonstrated that the great Potato Blight of Ireland was caused by a water mold Heinrich de Bary (1853): showed that smut and rust fungi caused cereal crop diseases Louis Pasteur : showed that the pébrine disease of silkworms was caused by a protozoan

Other evidences

Joseph Lister: • provided indirect evidence that microorganisms were the causal agents of disease • developed a system of surgery designed to prevent microorganisms from entering wounds as well as methods for treating instruments and surgical dressings • his patients had fewer postoperative infections

Robert Koch (1843-1910)

Robert Koch: • Established the relationship between Bacillus anthracis and anthrax • Develop the Koch’s postulates: used today to establish the link between a particular microorganism and a particular disease

..Koch Postulates

1.Similar pathogen must be present in every case of the disease.

2. The pathogen should be isolated from the diseased animal host and grown in pure culture.

3. A healthy laboratory animal inoculated with the pathogen taken from the pure culture must acquire the disease.

4. The pathogen must be isolated from the inoculated animal and should be the same from the microbe in the original animal.

The Development of Techniques for Studying Microbial Pathogens

 Koch’s work led to discovery or development of:     agar petri dish nutrient broth and nutrient agar methods for isolating microorganisms

Immunological Studies

Edward Jenner (ca. 1798) • used a vaccination procedure to protect individuals from smallpox Pasteur and Roux : • discovered that incubation of cultures for long intervals between transfers caused pathogens to lose their ability to cause disease • Pasteur and his coworkers developed vaccines for chicken cholera, anthrax, and rabies

  Emil von Behring (1854-1917) and Shibasaburo Kitasato (1852-1931)   developed antitoxins for diphtheria and tetanus evidence for humoral immunity Elie Metchnikoff (1845-1916)  discovered bacteria-engulfing, phagocytic cells in the blood  evidence for cellular immunity

The Development of Industrial Microbiology and Microbial Ecology

Louis Pasteur  demonstrated that alcohol fermentations and other fermentations were the result of microbial activity  developed the process of pasteurization to preserve wine during storage

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Additional Developments

 Sergei Winogradsky (1856-1953) and Martinus Beijerinck (1851-1931)  studied soil microorganisms and discovered numerous interesting metabolic processes (e.g., nitrogen fixation)  pioneered the use of enrichment cultures and selective media

Aseptic techniques

…….. Pure Culture Technique

Bibliography

 http://en.wikipedia.org/wiki/Scientific_ method  http://www.brighthub.com/science/me dical/articles/21169.aspx

 https://files.kennesaw.edu/faculty/jhend rix/bio3340/home.html

 Lecture PowerPoints Prescott’s Principles of Microbiology-Mc Graw Hill Co.