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 JOHN NEEDHAM (1713-1781): John Needham was an English priest, teacher and scientist who was a fellow of the Royal Society of London and who also propagated the theory of spontaneous generation, which was of the view that life emanated from non-life. He was also a strong believer of vitalism, which was an old-fashioned belief that the laws of physics and chemistry cannot be used to explain life. Needham performed experiments to support the theory of spontaneous generation or abiogenesis using mutton broth and hay infusions. John Needham showed that mutton broth boiled in flask and then sealed could still develop microorganisms, which supported the theory of spontaneous generation. He took hot boiling mutton gravy (also called meat infusion) in a flask and closed same with a cork. He later found the spoilage of the meat infusion and also observed animalcules in it.


Needham killed the living matter by boiling and thus concluded that animalcules arose spontaneously from the meat infusion, thus he put forth the notion that microorganisms arise by spontaneous generation. John Needham’s experimental works were later challenged and repeated by another scientist known as Lazzaro Spallanzani who modified Needham’s experiment by including a longer boiling time in his own experiment. However, John Needham’s attempt to offer scientific evidence and support in favour of abiogenesis (theory of spontaneous generation) was not long lasting because it was later refuted by Spallanzani – who carried out more detailed experimentation on the matter and showed that Needham’s broth (broth infusion) was not boiled long enough, and this resulted to the animalcules which he observed in them.


HANS CHRISTIAN JOACHIM GRAM (1853-1938): Hans Christian Joachim Gram was a Danish physician, botanist, pharmacologist and bacteriologist who discovered a concept of staining that is used for bacterial staining and identification even till date. Hans Gram developed a microbiological technique which is still used today in clinical microbiology practice and bacteriology in particular, for microbial identification, staining and classification. His technique is generally used in microbiology for differentiating and classifying bacteria into two major types based on their reaction to certain stains or dye. The technique he developed is called Gram staining technique; and it is used to distinguish bacteria into Gram positive bacteria or Gram negative bacteria depending on the cell wall of the bacteria and on their reaction to crystal violet dye (the primary stain retained by Gram positive bacteria) and safranin dye (the counter stain retained by Gram negative bacteria) respectively.

Hans Gram was a Danish bacteriologist and a physician; and his discovery of Gram staining technique was timely, and a procedure which is one of the most widely used protocol in medical microbiology. Though his discovery was defective as at the time, Hans Gram remarked that: “he is very aware that his technique is defective and imperfect, but that he hopes and believes that it would turn out to be useful for bacterial identification in the hands of other researchers”. It was later on, that the German-Jewish scientist, Carl Weigert (1845-1904) added the final stain (safranin) to the Gram staining technique, and this completed the technique and he came up with the concept of counterstaining used in Gram staining technique today. Hans Gram’s technique was lacking in counterstaining because he did not use the counterstain (safranin) which enabled the visualization of Gram negative bacteria.

Gram staining technique is one of the most applied physiological-biochemical staining technique which is very practical in the detection and differentiation of bacteria into Gram positive and Gram negative organisms based on the orientation of their cell wall and their individual reactions (response) to the primary (crystal violet) and secondary stains (safranin) used in the Gram staining technique. Though not all bacteria can be typed by the Gram staining technique (for example, Mycobacterium, Chlamydia, Mycoplasma, Rickettsia, Treponema and Borrelia), the Gram reaction or Gram staining technique is still very relevant in the practice of microbiology worldwide. 

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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