composition of the microbial world and turning points in microbiological research ,micro organism and evolution of earth,modern age of microbiology

1. COMPOSITION OF THE MICROBIAL WORLD
TURNING POINTS IN MICROBIAL RESEARCH
MICROORGANISMS AND THE EVOLUTION OF THE EARTH
MODERN AGE OF MICROBIOLOGY

2. MICROBIOLOGY
Microbiology is a branch of biology dealing with
study of microorganisms

3. DISCOVERY OF MICROBIAL LIFE
The exact beginning of the knowledge about the existence
of microorganisms can be traced back only to the latter
part of the seventeenth century

4. Antony van Leeuwenhoek first recorded observations of
microorganisms ( bacteria,yeasts and protozoa) seen in
water,faeces,teeth scrappings etc ….

5. Antony van Leeuwenhoek
* began making and using simple microscopes
* often made a new microscope for each specimen
* examined water and visualized fungi,algae and
protozoa : ‘animalcules’

6. COMPOSITION OF THE MICROBIAL WORLD
Viruses
Bacteria
Archaea
Protozoans
Fungi
Algae

7. BACTERIA
 Single celled
 Lacks well organized nucleus
 The nuclear material is not surrounded by nuclear
membrane (nucleoid)
 Some bacteria are autotrophic;they possess
bacteriochlorophyll
 May be saprophytic,mutualistic or parasitic

9.  Bacterial cell wall is a dense layer, surrounding the
plasma membrane
 The main constituent of the cell wall is peptidoglycan
 It gives shape & rigidity to the cell
 The organelles like mitochondria,endoplasmic
reticulum,golgi apparatus are absent

10.  Bacteria reproduce asexually
 Multiply most commonly by binary fission
 The motile bacteria possess one or more flagella

11. ARCHAEA
 They often occur in extreme aquatic & terrestrial
habitats, which may be anaerobic,hypersaline or
hyperthermophilic
 They also seen in very low temperature environments
 Rod - shaped,spherical,spiral,lobed,
plate shaped,irregularly shaped or pleomorphic

13.  Some are unicellular,others are filamentous or
aggregates
 Diameter – 0.1 to 15 micrometer
 Both gram positive & gram negative are present
 Reproduction - binary fission,fragmentation,budding

15. ALGAE
They are mostly photoautotrophs
Primarily they inhabit aquatic habitats
The vegetative body does not show any differentiation
into various tissue systems

17. They possess mostly unicellular sex organs without a
jacket of sterile cells around them
They show progressive complexity in reproduction
They do not develop embryo after fusion of gametes
during sexual reproduction
They show distinct alternation of generations

18. PROTOZOANS
o Protozoa are mostly free living
o They are mostly aquatic,inhabiting fresh and marine
waters and damp places
o Parasitic and commensal protozoa live over or inside
the bodies of animals and plants

19. o Protozoa are unicellular
o They contain one or more nuclei and organelles,with
little or no histological differentiation into tissues and
organs
o They occur singly or form loose colonies in which
individuals remain alike and independent
o Vegetative body of protozoa is naked or bounded by a
pellicle

20. o The shape of the cell usually constant but changes with
changing environment
o The single cell performs all the essential vital activities
hence there is little or no physiological division of
labour
o Locomotary organs are pseudopodia or flagella or
cilia;they may be absent

21. o Nutrition – may be holozoic (animal like), halophytic
(plant like),saprophytic or parasitic
o Reproduction – asexually by binary or multiple fission &
budding
o Sexually by conjugation of the adults or by the fusion of
gametes

22. FUNGI
 Vegetative body is usually represented by a filament
called hyphae
 Hyphae together are referred to as mycelium
 Hyphae are septate or non-septate
 Cell wall is mainly made up of chitin often called
‘fungus cellulose’

24.  Vegetative body is not divided into root,stem and
leaves
 Has no specialized tissues for the internal transport of
water & nutrients
 They are heterotrophs;may be parasites or saprophytes
 They lack chlorophyll

25.  Food is stored in the form of glycogen
 Both, sexual & asexual reproduction are present
 Asexual reproduction – Sporangiospores & Conidia
 Sexual reproduction – Antheridia & Oogonia

26. VIRUSES
All viruses are obligate parasites
They multiply only within their living host cells
Metabolically inert outside the host cell
They are ultramicroscopic; can only be viewed with
electron microscope

27. Viruses are actually nucleoproteins
The proteinaceous coat surrounds the nucleic
acid,which forms the central core of the virus particles
The viral genetic material ,may be either DNA or RNA
They are easily transmitted from infected host to the
healthy ones through various agencies

28. Viruses are host specific
They have no metabolic activities of their own
They utilize the metabolism of host cells

29. MICROBES AND ORIGIN OF LIFE
Abiogenesis
• Men of ancient times believed that all living organisms
could spring forth spontaneously from non – living
matter
• This belief has been referred to as Doctrine of
Spontaneous Generation or Abiogenesis

30. • They believed that frogs,snakes and mice could be
born of moist soil
• Flies could emerge from the manure,and that maggots
could arise from the decaying corpses
• This idea continued until the mid 19th century with great
oppositions against it

31. Redi’s Experiment (1626-1679)
• Francesco Redi,an italian physician, demonstrated that
abiogenesis does not exist
• He took rotting meat pieces and placed them in jars
• He sealed some of these jars tightly and left others
open
• In a few days, maggots appeared in open jars only

32. • Redi concluded that the maggots arise from the eggs
laid down by the parent flies
• That the maggots can not appear spontaneously

33. John Needham’s Experiment (1745)
• Needham heated chicken broth and nutrient fluids
before pouring them into covered flasks
• The cooled solutions showed existence of tiny
organisms in them
• He claimed that the organisms are originated
spontaneously from the nutrient fluids

34. Pasteur’s Experiment (1861)
 In his swan-necked flask experiment he took various
type of broths (yeast water,sugared yeast water,urine
etc)
 Then,softened the neck of the flasks under a flame &
drew it out in the shape of ‘S’ looking like the neck of
swan

35. • The broths of these flasks were boiled until they
steamed through the necks,and then cooled
• The broths so treated in the flasks did not decay
• There were no signs of microbes in them after
days,weeks and even months though they were open
to free air

36. • Pasteur’s unique swan-necks of the flasks trapped air –
borne microorganisms before they could reach the
broth and flourish in it
• Definitely discredited the doctrine of spontaneous
generation

37. LANDMARK EVENTS IN MICROBIAL RESEARCH
contributor year contribution
Jansen & Jansen 1590 microscope
Leeuwenhoek 1677 animalcules
Edward Jenner 1798 Smallpox vaccination
Pasteur 1860 fermentation
Robert Koch 1876-77 Causation of anthrax
Robert Koch 1882 Causation of TB
Metchnikoff 1882 phagocytosis
Christian Gram 1884 Gram staining
Pasteur 1885 Rabies vaccine
Richard petri 1887 Petri dish
Landsteiner 1902 Blood group

38. Svedberg 1923 ultracentrifuge
Fleming 1929 penicilin
Knoll & Ruska 1932 Electron microscope
Avery,Macleod & Mc
Carty
1944 DNA hereditary
material
Watson & Crick 1953 Double helix model
Salk & sabin 1957 Polio vaccine
Jacob & monod 1961 Operon concept
T.O.Diener 1971 Discovery of viroids
Boyer et al 1972-73 DNA cloning
technique
Lue Montagnier 1983 Discovery of HIV
Mullis 1983 - 84 PCR

39. MODERN AGE OF MICROBIOLOGY
• Biochemistry
• Microbial genetics
• Molecular biology
• Recombinant DNA technology
• Gene therapy
• Serology
• Immunology
• Chemotherapy

40. Biochemistry
Microbes used as model systems for biochemical
reactions
Practical applications:
 Design of herbicides & pesticides
 diagnosis of illness and monitoring responses to
treatment
 Treatment of metabolic diseases
 Drug design

41. Microbial genetics
Avery,MacLeod and McCarty : genes are contained in
molecules of DNA
Beadle and Tatum :
• a gene’s activity is related to protein function
• Translation of genetic information into protein explained
• Rates and mechanisms of genetic mutation
investigated
• Control of genetic expression by cells described

42. Molecular biology
• Explanation of cell function at the molecular level
• Pauling proposed that gene sequences could provide
understanding of evolutionary relationships

43. Serology
The study of blood serum
Immunology
The study of the body’s defence against specific pathogens
Chemotherapy
Treatment of a disease with chemicals
Chemotherapeutic agents are obtained from the
microbes,plants & animals

44. Recombinant DNA technology
It is a technology which allows DNA to be produced via
artificial means
Gene therapy
Inserting a missing gene or repairing a defective one in
humans by inserting desired gene into host cells