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| Image of an Unknown Positive Rod Shaped Bacteria under Microscope (Source: Luo Zaini, Microbiology Batch 2015 UM) |
Thousand
years before, people believed an ancient idea of spontaneous generation in
which some living organisms were emerged from vital energy that present in
decomposing materials. The idea of spontaneous generation was further
strengthened by the observations like emerging of mice from loads of litter,
occurrence of fungi called mushroom on wood that are rotting and some other similar
events. Following 200 years after, scientists encountered an investigational
battle over two premises that could enlighten the origin of ubiquitous
creatures which are the microorganisms. Some adhered to the belief of abiogenesis
which embraced the spontaneous generation. On the other hand, some opposed the
idea of abiogenesis and clung to the idea of biogenesis that suggested the rise
of living forms from other living things of their same kind. Slowly, the idea
of abiogenesis was abandoned as the idea of biogenesis was convinced with some
proofs. The validations for the idea of biogenesis can be listed as series of
experimental events.
Redi’s
Experiment
Francesco
Redi from Italy carried out his first experiment to verify the theory of
spontaneous generation by placing a meat in a jar, covered it with fine wire
gauze and another meat in a different jar without covering it. Blockage of
flies that gathered at the jar that has been covered causes the flies to lay
their eggs on the outer part of gauze. Development of maggots without the
accessibility of meat indicated that maggots were the offspring of flies and
didn’t arise from vital force that present in the meat. This eventually
declined the theory of spontaneous generation.
Jablot’s
Experiment
Louis
Jablet from France conducted an experiment in which he distributed an infusion
that had been heated to kill any living organisms into two containers that
comprised of an uncovered heated container and a covered heated container. The
covered heated container remained clear without any microbial growth however
the uncovered heated container observed with heavy microbial growth. Dust in
the air was the factor that contributed to the development of microorganisms in
the uncovered container.
John
Needham
Needham
conducted a similar experiment as Jablot but using the mutton gravy. Experiment
conducted by him contradicted the conclusion made by Jablot as both the heated
and unheated test containers were observed with microorganisms. Regrettably,
Needham’s experiment was conducted before the understanding that microorganisms
that have resistance towards heat are not destroyed by simple boiling an in the
context of Jablot’s experiment, his infusions were sterile.
Shultze
and Schwann’s Test
Theoder
Schwann and Franz Shultze from Germany were so confident that air was the basis
of microorganisms and carried out a test by passing air via strong hot glass
tubes into infusions in the flasks that has been heated. The infusions remained
clear without any growth of microorganisms and the proponents of abiogenesis
demanded that the air treatment caused impairment for the development of
spontaneous generation.
In
the middle of 1880’s, Louis Pasteur, a microbiologist who was studying the
roles of microbes in wine and beer fermentation took up the chance to validate
the theory of biogenesis as he was so clear that occurrence of fermentation is
due to the microbial activities that were introduced from grains, air and
fruits into the beverage. He conducted an experiment in which he filled flasks
with openings and shaped their openings into tubes with swan and elongated
neck. Openings of the flasks were exposed to air but were bent that allows
gravitational force to deposit any airborne dust particles in the lower portion
of the necks. Flasks were then heated for broth sterilization and incubated.
Broth remained sterile when flask was intact but when the neck was broken, the
broth was infected directly by the microbes that present in the air. Finally,
Pasteur concluded “For I have kept from them, and am still keeping from them,
that one thing which is above the power of man to make; I have kept from them
the germs that float in the air, I have kept from them life.”
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