Spontaneous generation Vs Biogenesis

1. SESSION-1
Dr. Pulipati Sowjanya
Associate Professor
Vignan Pharmacy College, Guntur

2. HISTORICAL DISCOVERIES
•Invention of the microscope
•Disproving spontaneous generation

3. Antony van Leeuwenhoek (1632 –1723)
 Leeuwenhoek (1632 –1723) was a Dutch tradesman
and scientist.
 He is the first microbiologist.
 He is best known for his work on the improvement
of the microscope and for his contributions
towards the establishment of microbiology.
 Using his handcrafted microscopes, he was the
first to observe and describe single-celled
organisms.
Leeuwenhoek

4. Antony van Leeuwenhoek (1632 –1723)
 He described microorganisms in teeth scrapings, rain
water, and peppercorn infusions.
 He first accurately described the different shapes of
bacteria as cocci (spheres), bacilli (rods) and
spirochetes (spiral filaments) and communicated them
to Royal Society of London in 1683.
 His enthusiastic letters were read with interest by the
British scientists, but the importance of his discoveries
evidently went unappreciated.

5. DISCOVERY ERA:
Aristotle (384-322) and others believed that living
organisms could develop from non-living materials.
In 13th century, Rogen Bacon described that the disease
caused by a minute “seed” or “germ”.
Debate on Spontaneous
generation Vs Biogenesis

6. TRANSITION ERA:
Francesco Redi (1626 - 1697)
He showed that maggots would not arise from decaying meat,
when it is covered.
1. Unsealed – maggots on meat
2. Sealed – no maggots on meat
3. Gauze – few maggots on gauze, none on meat

7. Supporter of the spontaneous generation theory.
He proposed that tiny organism(animalcules) arose
spontaneously on the mutton gravy.
He covered the flasks with cork as done by Redi, Still the
microbes appeared on mutton broth.
John Needham (1713 – 1781)
John Needham
Microorganisms

8. Lazzaro spallanzai (1729 – 1799)
He demonstrated that air carried germs to the culture medium.
He showed that boiled broth would not give rise to microscopic forms of
life.

9. Needham 1745 Spallanzani 1765

10. Franz Schulze & Theodar Schwann
Schulze passed air through strong acid solutions into boiled infusions
Schwann passed air into the flask through red hot tubes.
In both the cases microbes did not appear
Believers of spontaneous generation were not convinced.
Acid & Heat altered the air so that it would not support the growth.

11. H. Schroder & T. Von Dusch
Schroder & Dusch performed more convincing
experiment by passing air through cotton into
flasks contained heated broth.
The microbes were filtered out of the air by the
cotton fibres, so that growth did not occur.

12. Louis Pasteur (1822-1895)
Louis Pasteur
Hypothesis: Microbes come from cells of
organisms on dust particles in the air; not the
air itself.
Pasteur put broth into several special S-
shaped flasks
Each flask was boiled and placed at various
locations
The special shaped was intended to trap any
dust particles containing bacteria
Did not turn cloudy
Microbes not found
Notice the dust that collected in the neck of
the flask

13. Pasteur's Experimental Results

14. Pasteur’s S-shaped flask kept microbes out but let air in.
Proved microbes only come from other microbes (life from
life) – biogenesis
Life come from life
The Theory of Biogenesis - 1864

15. John Tyndall conducted experiments in a
specially designed box to prove that dust
carried the germs.
He demonstrated that if no dust was
present, sterile broth remain free of
microbial growth for indefinite period of
time
John Tyndall

16. Heat stable form and a heat-sensitive form—He exposed infusions
to heat for varying time and concluded that bacteria existed in two
forms: a heat stable form and a heat-sensitive form.
Heat-stable forms were destroyed either by prolonged or
intermittent heating.
Heating at 80˚C for 20-45 minutes for 3 successive days
Intermittent heating, now called tyndallization, killed both forms
since the heat-stable forms changed to heat sensitive forms
between periods of heat treatment.
John Tyndall