HISTORICAL ASPECTS OF MICROBIOLOGY CONTENTS

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Discovery of Microorganisms


The advent of the microscope permitted the studying of microorganisms. The first microscopes were simple ground glass lenses that magnified images  of  previously  unseen  microorganisms.  Among  the  first  to observe  this  previously  unseen  and  invisible  microbial  world  were Robert Hooke and Anthony Van Leeuwenhoek.


1.        Robert   Hooke   (1635-1703),   an   English   mathematician   and natural historian.

.    He coined the term “cells” to describe the “little boxes” he

observed  in  examining  cork  slices  with  a  compound

microscope.

.    He   was   the   first   to   make   a   known   description   of microorganisms.

.    He   made   microscopic   observation   and   the   earliest description of many fungi.

.    Various  species  of fungi  were  clearly  identified  in  his

drawing and recorded in his book Micrographia.




Figure 2.1: Robert Hooke’s detailed diagram of fungi made in 1667

Source: Microorganisms in our World by Atlas R. M. (1995)


2.        Anthony Van Leeuwenhoek (1632-1723) lived in Delft, Holland.  .    He  is known  as the  father  of bacteriology  and the  first

person to publish extensive and accurate observations of microorganisms.

.    He was a draper and an amateur microscope builder.


.    He learned lens grinding as a hobby and made over  100

simple microscopes each capable of magnifying an image about 300 times.

.    By  using  simple  microscopes,  he  observed  microscopic

organisms which he called ‘animalcules’ .

.    He  discovered  bacteria  in  1676  while  studying  pepper

water infusion and reported his observations in a series of letters to Royal Society of London which published them

in 1684 in English translation.

.    He made sketches of the     different   shapes   of  bacteria.


(A)                                  (B)                        (C)



Figure 2.2: (A) Anthony van Leeuwenhoek (1632-1723)  (B&C) Leeuwenhoek’s microscopes.

Source: Microorganisms in our World by Atlas R. M. (1995)


After  Van  Leeuwenhoek’s  death,  the  study  of microbiology  did  not develop   rapidly   because   microscopes   were   rare   and   interest   in microorganisms was not high. Scientists then were debating the theory of spontaneous generation.


    The Spontaneous Generation Conflict


The concept spontaneous generation states that living organisms could develop  from  non-living  matter.  The  proponents  of  the  concept  of spontaneous generation claim that living organisms could develop from non living or decomposing matter.


1.         Francesco Redi (1626-1697) challenged this concept by showing that maggots on decaying meat came from fly eggs deposited on the meat, and not from the meat itself.

.    He carried out a series of experiments on decaying meat

and its ability to produce maggot spontaneously.


 He placed meat in three different containers, one was not

covered, and the second was covered with fine gauze to exclude flies.

.    Flies  laid  eggs  on  the  uncovered  meat  and  maggots

developed.

.    The two other meats did not produce maggots.

.    Spontaneously, flies were attracted to the gauze-covered

container  and  laid  their  eggs  on  the  gauze,  these  later produced maggots.

.    Hence, it become evident that the generation of maggots

resulted from the presence of fly eggs and that meat      (a    non-living matter)    did     not     spontaneously     generate maggots as previously believed.


2.        Louis Jablot (1670) conducted an experiment in which he divided a hay infusion that had been boiled into two containers: a heated container that was closed to the air and a heated container that was  freely  open  to  the  air.  Only  the  open  vessel  developed microorganisms. This further helped to disprove abiogenesis.


3.        John Needham (1713-1781) showed that mutton broth boiled in flasks and then sealed could still develop microorganisms, which supported the theory of spontaneous generation.


4.         Lazzaro Spallanzani (1729-1799) showed that flasks sealed and then boiled had no growth of microorganisms, and he proposed that air carried germs to the culture medium. He also commented that  external  air  might  be  needed  to  support  the  growth  of animals already in the medium. The latter concept was appealing to supporters of spontaneous generation.


5.         Louis  Pasteur  (1822-1895) was  a  Professor  of Chemistry.  He devised a series of swan necked flasks known as Pasteur-flasks, filled the flasks with broth and heated the broth to sterilisation. After cooling, the flasks were opened to the air, but bends on the neck of the flasks prevented microorganisms from falling on the broth and contaminating it rather the microorganisms fell on the neck  of  the  bottle.  Pasteur  proved  that  no  growth  occurred because dust and germs were trapped on the wall of the curved necks.  If the  neck  were  broken,  growth  will  occur.  By  these experiments he disproved and defeated the theory of spontaneous generation.


Figure 2.3: Pasteur’s experiment with the Swan-Necked bottles that defeated the spontaneous generation theory.

Source: Amoebamike, wordpress.com


Apart  from  the  defeat  of  the  concept  of  spontaneous  generation Pasteur’s contribution in microbiology included:


.    Pasteurization: an effective  sterilization method which involve

holding juices and milk at 62.8°C (145°F) for 30 minutes.

.    The discovery of the fact that, alcoholic fermentation was indeed

a process catalyzed by yeast cells.

.    The  development  of vaccines  for  the  control  of anthrax,  fowl

cholera and rabies diseases between 1880 and 1890.

.    The  establishment  of  Pasteur  Institute  in   1888  in  Paris,  in

recognition of his research on rabies by the French government. It was originally established as a clinical centre for treating rabies, but is now a major biomedical research centre for antiserum and vaccine production.

.    He  postulated  the  Germ  Theory  of Disease  which  states  that

microorganisms are the cause of infectious diseases.

.    His work ushered in the Golden Age of Microbiology.


   The  Recognition  of  the  Role  of  Microorganisms  In Disease


1.        Joseph   Lister   (1872-1912)   developed   a   system   of  surgery designed to prevent microorganisms from entering wounds. He implemented  the  use  of  sterile  surgical  instrument,  and  used carbolic acid (phenol) during surgery and on wound dressings.


2.        Robert Koch (1843-1910) was a German physician. He was the first  to  directly  prove  the  role  of microorganisms  in  causing diseases.   He   established   the   relationship   between   Bacillus anthracis  and  the  disease  it  causes,  anthrax.  Using  mice  as experimental animals, he demonstrated that when a small amount of blood  from  a  diseased  mouse  was  injected  into  a  healthy mouse, the healthy mouse quickly developed anthrax. From this work he developed Koch’s postulates which states that:


i.         The suspected disease-causing organism should be present

in all   cases   of  the   disease   and   absent   from  healthy animals.

ii.        The  suspected  organism  must  be  cultivated  in  a  pure

culture away from the animal body.

iii.       The   isolated   organism  must   cause  the   disease  when inoculated     into  a  healthy  susceptible  animal.  iv.  The organism must be re- isolated from these experimental

animals and culture again in the    laboratory                after

which it should still be the same as the original  organism.


Figure 2.4: Diagrammatic illustration of Koch’s Postulates

Using these principles, Koch discovered causative organisms of anthrax (1876), tuberculosis (1882) and cholera (1883).


.    He was the first to grow bacteria on solid culture media to get

pure culture; hence he developed the pure culture concept and

developed different solid media.

.    Koch’s discovery of solid culture media and pure culture concept

supplied   the   most   needed   tools   for   the   development   of microbiology as a field of science.

  For his contribution on tuberculosis, he was awarded the  1905

Nobel  Prize  for  Physiology  or  Medicine.  Today,  “Molecular Koch’s postulates” have been established in light of advances in the molecular biology of pathogenic microbes.


3.        Edward Jenner (ca. 1798) used a vaccination procedure to protect individuals from smallpox. 4. Emil Von Behring (1854-1917) and Shibasaburo  Kitasato  (1852-1931)  induced  the  formation  of diphtheria  tetanus  antitoxins  in  rabbits  which  were  effectively used to treat humans, thus demonstrating humoral immunity.


 The Development of Microbiology in this Century


Microbiology  established  a  closer  relationship  with  other  disciplines during   the   1940s   because   of   its   association   with   genetics   and biochemistry.


1.        George W. Beadle and Edward L. Tatum (ca. 1941) studied the relationship between genes and enzymes using the bread mould, Neurospora.

2.        Salvadore  Lurai  and  Max  Delbruck  (ca.   1943)  showed  that mutations were pontaneous and not directed by the environment.

3.        Oswald T. Avery, Colin M. Mcleod, and Maclyn McCarty (1944) provided  evidence  that  deoxyribonucleic  acid  (DNA)  was  the genetic    material    and    carried    genetic    information    during transformation.


  Era of Molecular Microbiology


This Began in the 1970s with the following:


.    Advancement   in   the   knowledge   of   bacterial   physiology, biochemistry and genetics.

.    Genetic manipulation which involves the transfer of DNA from

one  organism  into  another  or  a  bacterium  and  the  proteins encoded by the DNA harvested led to the  development of the

field of Biotechnology.

.    DNA   sequencing   revealed   the   phylogenetic   (evolutionary) relationships  among  bacteria  which  led  to  revolutionary  new concepts in microbial systematic.

.    In 1990s, DNA sequencing gave birth to the field of genomics.


SELF-ASSESSMENT EXERCISE


Observe a decay meat under the microscope and discuss your findings in the discussion forum.

                                       

 CONCLUSION


To conclude, the history of microbiology from 19th  century to date has been rich with contributions of many scientists who developed the field to what it is today. It is imperative to you as nursing students to know these    personalities    and    acknowledge    their    various    individual contributions towards the development of microbiology


    SUMMARY


In this unit you have been exposed to the circumstances that lead to the discovery  of  microorganisms,  the   spontaneous  generation  conflict, recognize   the   role   of  microorganisms   in   disease   causation,   the development of microbiology in this century and the era of molecular microbiology.


    TUTOR-MARKED ASSIGNMENT


1.        Write    short   note    on   Robert   Hooke    and   Anthony   Van Leeuwenhoek  contribution to the  discovery  of microorganisms (LO1)

2.        State the concept of spontaneous generation (LO2)

3.        Discuss  the  experiments  that  were  performed  to  disprove  the concept of spontaneous generation (LO2).

4.        Explain the steps involved in using Koch’s postulate to establish the link between a suspected microorganism and a disease (LO3).

5.        Explain development of microbiology in this century (LO4).

6.        Explain the era of molecular biology (LO5).


     REFERENCES /FURTHER READING


Atlas, R.M. (1995). Microorganisms in Our World. Mosby Year Book. Inc.


Kayser,  F.H.,  Bienz,  K.A.,  Eckert,  J.  &  Zinkernagel,  R.N.  (2005). Kayser, Medical Microbiology. Thieme, Stuttgart, Germany


Markey, B., Leonard, F., Archambault, M., Cullinane, A. & Maguire, D. (2013). Clinical Veterinary Microbiology. 2nd  Edition. MOSBY ELSEVIER


Medigan, M.T. et al. (2009). Brock Biology of Microorganisms.  12th Edition. Pearson Education Inc. Pelczar, M.J., Chan, E.C.S. & Krieg, R.N. (2001). Microbiology. 5th Edition. McGraw-Hill.


Mitchell, R. & Gu, J.-D. (editors) (2010). Environmental Microbiology. 2nd   Edition.  Hoboken,  New  Jersey,  John  Wiley  &  Sons,  Inc, Wiley-Blackwell


Struthers,  K.  (2017).  Clinical  Microbiology.  2nd   Edition.  CRC  Press, Taylor & Francis Group.


Talaro,  K.P.  &  Talaro,  A.  (2002).  Foundations  in  Microbiology.  4th Edition. The McGraw-Hill Companies.


Willey, J.M., Sherwood, L.M & Woolverton, C.J. (2008). Microbiology. 7th   Edition.   Boston   Bur   Bridge,   IL:   McGraw-Hill   Higher Education.

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