JOHN TYNDALL (1820-1893) AND FERDINAND J. COHN (1828-1898)

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JOHN TYNDALL (1820-1893): John Tyndall was an Irish physicist and Professor of Physics whose works in physics was notable as at the time; and he discovered a process known as tyndallization through which bacterial spores can be destroyed. Tyndall’s work also affirmed the germ theory of disease which was discovered as at the time, and which helped scientists to establish the causative agents of infectious diseases. One of the traditional arguments against abiogenesis was the claim that the heat used to sterilize the air or specimens was destroying a vital force of life which did not allow microorganisms to spontaneously appear. People believed for many centuries the concept of spontaneous generation, i.e., the creation of life from organic or inorganic matter.

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The proponents of spontaneous generation believed that living organisms could generate from non-living things. John Tyndall conducted his experiments in a specially designed box called “Tyndall chamber” with which he proved that dust carried germs. He showed that dust did carry microbes, and if dust was absent the sterile broth will still remain sterile for indefinite period of time even if it was directly exposed to air. Tyndall’s work in 1877 led to the development of a process called “Tyndallization” – which is used for the complete sterilization of food by alternate heating and cooling. He observed that boiling the infusion for more than 5 hours was not sufficient enough to sterilize it, and he concluded that bacteria has both thermo-stable and thermo-labile phases, thus proving the existence of heat resistant forms of bacteria (i.e., endospores) as was also confirmed by Ferdinand Cohn.

FERDINAND J. COHN (1828-1898): Ferdinand Cohn was a German biologist who made significant contributions and discoveries in the fields of bacteriology and microbiology in general. Cohn was the first to classify algae (a type of microorganism) and differentiate them from green plants. He is also one of the founders of modern microbiology and bacteriology due to his notable contributions in the area of bacterial classification and algal discovery. Cohn also discovered heat resistant forms of bacilli and he is a pioneer of microbial taxonomy and physiology. He also discovered that the life cycle or reproductive stages of some bacteria contained a spore formation stage that allowed the organisms to form heat resistant structures.

Ferdinand Cohn successfully distinguished algae from plants, and he also classified bacteria into four (4) different groups in terms of their characteristic shapes (rods, spirals, spherical and threads). The bacterial classification made by Cohn is still in use in bacteriology till date, and it provided microbiologists with a better way of classifying microorganisms as against the old method used then. Cohn is one of the founding fathers of the field of bacteriology, and he also provided a basis for the classification of bacteria based on their shape and size. He was trained as a botanist and became an excellent microscopist, and this led him to study algae (unicellular plant-like microorganisms) and later, photosynthetic bacteria.

He discovered that bacteria multiply by dividing into two cells (a process known as binary fission), and that certain bacteria form an extremely resistant structure called endospore in the cell. His work and interest in heat resistant bacteria has led us to know about bacterial endospores. He described the entire life cycle of the endospore forming bacteria, Bacillus (vegetative cell – endospore – vegetative cell), and discovered that the vegetative form of this bacteria was killed by heating, but their endospores were not killed in the process of heating. His work in this area of heat resistant forms of bacteria helped his contemporaries as at the time to know why boiling is an unreliable means of preventing fluid infusions from supporting microbial growth. Cohn is credited with the use of cotton plugs for closing flasks and tubes to prevent the contamination of sterile culture media in the early 1860s. Ferdinand Cohn also studied the large sulphur bacterium, Beggiatoa mirabilis and was the first to identify the small granules present in the cells of this bacterium that are made of sulphur (which are produced from the oxidation of hydrogen sulphide, H2S).

Further reading

Brooks G.F., Butel J.S and Morse S.A (2004). Medical Microbiology, 23rd edition. McGraw Hill Publishers. USA. Pp. 248-260.

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of microorganisms. 12th edition. Pearson Benjamin Cummings Publishers. USA. Pp.795-796.

Nester E.W, Anderson D.G, Roberts C.E and Nester M.T (2009). Microbiology: A Human Perspective. Sixth edition. McGraw-Hill Companies, Inc, New York, USA.

Prescott L.M., Harley J.P and Klein D.A (2005). Microbiology. 6th ed. McGraw Hill Publishers, USA. Pp. 296-299.

Singleton P and Sainsbury D (1995). Dictionary of microbiology and molecular biology, 3d ed. New York: John Wiley and Sons.

Slonczewski J.L, Foster J.W and Gillen K.M (2011). Microbiology: An Evolving Science. Second edition. W.W. Norton and Company, Inc, New York, USA.

JOHN TYNDALL (1820-1893): John Tyndall was an Irish physicist and Professor of Physics whose works in physics was notable as at the time; and he discovered a process known as tyndallization through which bacterial spores can be destroyed. Tyndall’s work also affirmed the germ theory of disease which was discovered as at the time, and which helped scientists to establish the causative agents of infectious diseases. One of the traditional arguments against abiogenesis was the claim that the heat used to sterilize the air or specimens was destroying a vital force of life which did not allow microorganisms to spontaneously appear. People believed for many centuries the concept of spontaneous generation, i.e., the creation of life from organic or inorganic matter. The proponents of spontaneous generation believed that living organisms could generate from non-living things. John Tyndall conducted his experiments in a specially designed box called “Tyndall chamber” with which he proved that dust carried germs. He showed that dust did carry microbes, and if dust was absent the sterile broth will still remain sterile for indefinite period of time even if it was directly exposed to air. Tyndall’s work in 1877 led to the development of a process called “Tyndallization” – which is used for the complete sterilization of food by alternate heating and cooling. He observed that boiling the infusion for more than 5 hours was not sufficient enough to sterilize it, and he concluded that bacteria has both thermo-stable and thermo-labile phases, thus proving the existence of heat resistant forms of bacteria (i.e., endospores) as was also confirmed by Ferdinand Cohn.

FERDINAND J. COHN (1828-1898): Ferdinand Cohn was a German biologist who made significant contributions and discoveries in the fields of bacteriology and microbiology in general. Cohn was the first to classify algae (a type of microorganism) and differentiate them from green plants. He is also one of the founders of modern microbiology and bacteriology due to his notable contributions in the area of bacterial classification and algal discovery. Cohn also discovered heat resistant forms of bacilli and he is a pioneer of microbial taxonomy and physiology. He also discovered that the life cycle or reproductive stages of some bacteria contained a spore formation stage that allowed the organisms to form heat resistant structures. Ferdinand Cohn successfully distinguished algae from plants, and he also classified bacteria into four (4) different groups in terms of their characteristic shapes (rods, spirals, spherical and threads). The bacterial classification made by Cohn is still in use in bacteriology till date, and it provided microbiologists with a better way of classifying microorganisms as against the old method used then. Cohn is one of the founding fathers of the field of bacteriology, and he also provided a basis for the classification of bacteria based on their shape and size. He was trained as a botanist and became an excellent microscopist, and this led him to study algae (unicellular plant-like microorganisms) and later, photosynthetic bacteria.

He discovered that bacteria multiply by dividing into two cells (a process known as binary fission), and that certain bacteria form an extremely resistant structure called endospore in the cell. His work and interest in heat resistant bacteria has led us to know about bacterial endospores. He described the entire life cycle of the endospore forming bacteria, Bacillus (vegetative cell – endospore – vegetative cell), and discovered that the vegetative form of this bacteria was killed by heating, but their endospores were not killed in the process of heating. His work in this area of heat resistant forms of bacteria helped his contemporaries as at the time to know why boiling is an unreliable means of preventing fluid infusions from supporting microbial growth. Cohn is credited with the use of cotton plugs for closing flasks and tubes to prevent the contamination of sterile culture media in the early 1860s. Ferdinand Cohn also studied the large sulphur bacterium, Beggiatoa mirabilis and was the first to identify the small granules present in the cells of this bacterium that are made of sulphur (which are produced from the oxidation of hydrogen sulphide, H2S).

Further reading

Brooks G.F., Butel J.S and Morse S.A (2004). Medical Microbiology, 23rd edition. McGraw Hill Publishers. USA. Pp. 248-260.

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of microorganisms. 12th edition. Pearson Benjamin Cummings Publishers. USA. Pp.795-796.

Nester E.W, Anderson D.G, Roberts C.E and Nester M.T (2009). Microbiology: A Human Perspective. Sixth edition. McGraw-Hill Companies, Inc, New York, USA.

Prescott L.M., Harley J.P and Klein D.A (2005). Microbiology. 6th ed. McGraw Hill Publishers, USA. Pp. 296-299.

Singleton P and Sainsbury D (1995). Dictionary of microbiology and molecular biology, 3d ed. New York: John Wiley and Sons.

Slonczewski J.L, Foster J.W and Gillen K.M (2011). Microbiology: An Evolving Science. Second edition. W.W. Norton and Company, Inc, New York, USA.

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