DISCOVERY OF MICROORGANISMS (Robert Hooke, Antony Van Leeuwenhoek and Ferdinand Cohn)

 ·  The existence of microscopic organisms was discovered during the period 1665 – 1683 by two Fellows of The Royal Society, Robert Hooke and Antoni van Leeuwenhoek.

·       Robert Hooke and Anton van Leeuwenhoek, deserve the credit for discovering microorganisms in the 17^th century.  

·   In the book “Micrographia” (Small Drawings) (1665), Robert Hooke presented the first published depiction of a microorganism, the fungus Mucor sp.

·       Later in 1676, Anton van Leeuwenhoek observed and described microscopic protozoa and bacteria.

ROBERT HOOKE AND HIS BOOK MICROGRAPHIA

·       Robert Hooke coined the term “Cell” in a biological context, as he described the microscopic structure of cork like a tiny bare room or monk’s cell in his landmark discovery of plant cells with cell walls.

·    From Robert Hooke’s excellent drawing in Micrographia (1665), Mycologists identify Hooke’s specimen as the Mucor, the common bread mold. This was the first known description of microorganisms.

·       Robert Hooke called the Mucor as a “Microscopical Mushroom.” Although he attempted to observe the “seed” (now called Sporangiospores) from which it develops, the relatively low magnifying power of his microscope made that effort impossible. 

·   In Micrographia, Robert Hooke also illustrated microscopic views of diverse biological objects, including sponges, wood, seaweed, leaf surfaces, hair, peacock feathers, fly wings, eggs of silkworms, mites, a flea, and a louse as well as that of a mold.

Figure – 1: A drawing of the microscope used by Robert Hooke in 1665

ANTONY VAN LEEUWENHOEK

·       Antony Van Leeuwenhoek was a Dutch merchant.

·       The first person to see bacteria, the smallest microbial cells was Antony van Leeuwenhoek.

·   Antony van Leeuwenhoek constructed many Microscopes with a single lens which consisted of a spherical lens mounted between two small metal sheets of silver or brass. The specimen was placed on the point of a blunt pin and brought into focus by manipulating two perpendicular and a linear screws.

 

·    In 1676, Antony Van Leeuwenhoek observed some bacteria from his own teeth, pond water, sperm, pepper infusions, saliva and feces. He named them as “Animalcules”. He reported his observations in a series of letters to the prestigious Royal Society of London, which published them in English translation in 1684.

Figure – 2: Antony Van Leeuwenhoek’s drawing of Bacteria

·       He was way ahead of his time and many scientists too did not believe him.  But now, he was recognized as “Father of Microbiology”.

·       He was also considered as the “Father of Protozoology”.

FERDINAND COHN

·       Ferdinand Julius Cohn was a German Biologist. His classification of bacteria into four groups based on shape (Spherical, Short rods, Threads and Spirals) is still in use today.

·      Ferdinand Cohn’s interests in microscopy led him to the study of Unicellular Algae and later to Bacteria, including the large sulfur bacterium Beggiatoa.

Ferdinand Cohn was particularly interested in heat resistance in bacteria, which led to his discovery that some bacteria form Endospores. Cohn described the life cycle of the Endospore-forming bacterium Bacillus (Vegetative cell  to  Endospore to Vegetative cell) and showed that Vegetative cells but not endospores were killed by Boiling.