CONFLICTS OVER SPONTANEOUS GENERATION -2

 Several investigators attempted to arguments.

Theodore Schwann

• Theodore Schwann (1810–1882) allowed air to enter in a flask containing a sterile nutrient solution after that air has been passed through a red-hot tub. flask remained sterile.
  

Georg Friedrich Schroder and Theodor von Dusc

• Georg Friedrich Schroder and Theodor von Dusch allowed air to enter a flask of heat-sterilized medium after that it has been passed through sterile cotton wool.
• No growth occurred in the medium even though the air had not been heated.

Felix Pouchet

French naturalist Felix Pouchet claimed in 1859 to have carried out experiments proving that microbial growth could occur without air contamination.

Louis Pasteur

• Louis Pasteur (1822–1895) to settle matter once and for all. Pasteur first filtered air through cotton and found that objects resembling plant spores had been trapped.
• If a piece of cotton was placed in sterile medium after air has been filtered, microbial growth occurred.
• He placed nutrient solutions in flasks,heated necks in a flame, and drew them out into a variety of
  curves, while keeping ends of the necks open to the atmosphere.
• Pasteur boiled the solutions for a few minutes and  allowed them to cool.
• No growth took place in the contents of the flasks were exposed to the air. 
• Pasteur pointed out that no growth occurred because of dust and germs trapped on the walls of the curved necks.
•  If the necks were broken, growth commenced immediately.

Pasteur has not only resolved by 1861 but also had shown how to keep solutions sterile. 

 John Tyndall 

 

• English physicist John Tyndall (1820–1893) dealt a final
  blow to spontaneous generation in 1877 by demonstrating that
  dust carries germs and if dust was absent, broth remained sterile even if directly exposed to air.
• During,course of his studies, Tyndall provided evidence for the existence of exceptionally heat-resistant forms of bacteria.

Ferdinand Cohn

• Independently,German botanist Ferdinand Cohn (1828–1898) discovered existence of heat-resistant bacterial endospores.

  

THE CONFLICT OVER SPONTANEOUS GENERATION-1

• Spontaneous generation—living organisms could develop from nonliving matter.
• Aristotle (384–322 B.C.) thought some simpler invertebrates arise by spontaneous generation.

Francesco Redi

• Italian physician Francesco Redi(1626–1697), who carried out a series of experiments on decaying meat and its ability to produce maggots spontaneously.
• Redi placed meat in three containers.
• One was uncovered,
• Second was covered with paper, and 
• Third was covered with a fine gauze would exclude flies.
• Flies laid their eggs on uncovered meat and maggots developed.
• Other two pieces of meat did not produce maggots spontaneously.
• Flies were attracted to gauze-covered container and laid their eggs on the gauze; eggs produced maggots.
• Thus,Generation of maggots by decaying meat resulted from presence of fly eggs, and meat did not spontaneously generate maggots as previously believed.
• Similar experiments,others helped discredited the theory for
  larger organisms. 
  
• Discovery of microorganisms renewed by scientist "Antony van Leeuwenhoek".
• Some proposed that larger organisms didnot arose by spontaneous generation even through microorganisms.
• Microorganisms after sitting for a while,would give rise to   boiled extracts of hay or meat.

John Needham 

• In 1748, English priest John Needham (1713–1781) reported the results of his experiments on spontaneous generation.
• Needham boiled mutton broth  and then tightly stoppered the flasks.
• Many of  flasks became cloudy and contained microorganisms.
• He thought organic matter contained a vital force that could confer properties of life on nonliving matter.

Lazzaro Spallanzani 

• A few years later,  Italian priest and naturalist Lazzaro Spallanzani (1729–1799) improved on Needham’s experimental designed first sealing glass flasks that
  contained water and seeds. 
  
• Sealed flasks were placed in boiling water for 3/4 of an hour, no growth took place as long as  flasks remained sealed.
• He proposed that in the medium, air carried germs to the culture medium,and external air might be required for growth of animals.
• Supporters of spontaneous generation maintained heating and the air must be sealed in flasks to destroy its ability to support life.

CONTINUEDD.........
  

THE DISCOVERY OF MICROORGANISMS

• Some investigators suspected their existence and responsibility for disease.
• Roman philosopher Lucretius (about 98–55 B.C.) and the
  physician Girolamo Fracastoro (1478–1553) suggested that disease  caused by invisible living creatures. 
• Earliest microscopic observations appears between 1625 and 1630 on bees and weevils by the Italian Francesco Stelluti,
  using a microscope probably supplied by Galileo. 
• In 1665, First drawing of microorganism was published in Robert Hooke'S Micrographia.
• First person to publish,accurate observations of microorganisms was the amateur microscopist Antony van Leeuwenhoek (1632–1723) of Delft, The Netherlands.
• Leeuwenhoek earned his living as a draper and haberdasher  spent much of his spare time constructing simple microscopes composed of double convex glass lenses held between two silver plates.
  
• His microscopes could magnify around 50 to 300 times, and he may have illuminated his liquid specimens by placing them between two pieces of glass and shining light on them at a 45° angle to the specimen plane.
• A form of dark-field illumination in which the organisms appeared as bright objects against a dark background and made bacteria clearly visible.
• Beginning year 1673, Leeuwenhoek describing his discoveries to the Royal Society of London. It is clear from his descriptions that he saw both bacteria and protozoa.
• Leeuwenhoek’s observations was the development of microbiology essentially languished for next 200
  years.
• Little progress made primarily because microscopic
  observations of microorganisms do not provide sufficient information to understand their biology.
• Techniques for isolating and culturing microbes in the laboratory were needed.
• Many of these techniques began to be developed as
  scientists grappled with conflict over the Theory of
  Spontaneous Generation. 
• This conflict and  subsequent studies on the role played by microorganisms in causing disease ultimately led to what is now called the Golden Age of Microbiology.  

 CONTINUED...............

IMPORTANT CHARACTERISTIC OF MICROORGANISMS

•  Last few decades, great progress made three areas profoundly affect microbial classification.
• First, learned about detailed structure of microbial cells
  from the use of electron microscopy.
•  Second, microbiologists has determined biochemical and physiological characteristics of many different microorganisms. 
• Third,Sequences of nucleic acids and proteins from a wide variety of organisms.

COMPARISON OF ribosomalRNA (rRNA):

• Carl Woese in the 1970s, instrumental in demonstrating two very different groups of prokaryotic organisms: Bacteria and Archaea.
• Bacteria and Archaea, which has been classified as Monera in the five-kingdom system.
• Studies based on rRNA comparisons suggested Protista was not cohesive taxonomic unit and that it should be divided into three or more kingdoms.
• Studies and others have led many taxonomists to conclude that the five-kingdom system is too simple.
• A number of alternatives  suggested,that microbiologists believe that organisms should be divided among three domains: Bacteria (the true bacteria or eubacteria), Archaea, and Eucarya (all eucaryotic organisms).

• A brief description of the three domains and of the microorganisms placed in them follows:
• Bacteria are prokaryotes that are usually single-celled organisms .
  
• Most have cell walls that contain the structural molecule peptidoglycan.
• They are abundant in soil, water, and air and are also major inhabitants of our skin, mouth, and intestines. 
• Some bacteria live in environments that have extreme temperatures, pH, or salinity.
• some bacteria cause disease, many play more beneficial roles such as cycling elements in the biosphere, breaking down dead plant and animal material, and producing vitamins. 
• Cyanobacteria produce significant amounts of oxygen through the process of photosynthesis.
• Archaea are prokaryotes that are distinguished from Bacteria by many features, most notably their unique ribosomal RNA sequences.
• Unusual metabolic characteristics, such as the methanogens, which generate methane gas.
• Many archaea are found in extreme environments. Pathogenic archaea have not yet been identified. 
• Domain Eukarya includes microorganisms classified as protists or Fungi. Animals and plants are also placed in this domain.
• Protists are generally larger than prokaryotes and include unicellular algae, protozoa, slime molds, and water molds. 
• Algae are photosynthetic protists that together with the cyanobacteria produce about 75% of the planet’s oxygen. They are also the foundation of aquatic food chains.
• Protozoa are unicellular, animal-like protists that are usually motile. 
• Many free-living protozoa function as the principal hunters and grazers of the microbial world. 
• Nutrients by ingesting organic matter and other microbes.
• Many different environments and normal inhabitants of the intestinal tracts
  of animals, where they aid in digestion of complex materials such as cellulose.
• Slime molds are protists like protozoa in one stage of their life cycle, but are like fungi in another.
•  protozoan phase, they hunt and engulf food particles, consuming decaying vegetation and other microbes. 
• Water molds, implies,that are found on the surface water of freshwater sources and moist soil. They feed on decaying vegetation such as logs and mulch. 
• Some water molds has produced devastating plant infections, including Great Potato Famine of 1846–1847.
• Fungi are   diverse group of microorganisms ranges from unicellular forms (yeasts) to molds and mushrooms.
• Molds and mushrooms are multicellular fungi that form thin, threadlike structures called hyphae.
• They absorb nutrients from their environment, including the organic molecules that they used as a source of carbon and energy. 
• Because of their metabolic capabilities, many fungi play beneficial roles, including making bread rise, producing antibiotics, and decomposing dead organisms. 
• Other fungi cause plant diseases and diseases in humans and other animals.
• Viruses are acellular entities that invade a host cell in
  order to replicate.
•  They are smallest to all microbes (the smallest is 10,000 times smaller than a typical bacterium).
• Small size belives their power—they cause many animal and plant diseases and have caused epidemics that have shaped human history. 
• The diseases that cause include smallpox, rabies, influenza, AIDS, the common cold, and some cancers.

 THIS IS THE  NOTES OF HISTORY AND SCOPE OF MICROBIOLOGY.IF YOU LIKEMY NOTES PLEASE FOLLOW MY BLOG EVERYDAY.THANK YOU

  

1.1 MEMBERS OF THE MICROBIAL WORLD

 MEMBERS OF THE MICROBIAL WORLD 

• Microbiology is defined as the study of organisms and agents are too small to be seen clearly by unaided eye i.e; the study of microorganisms. 
• Less than about one millimeter in diameter cannot be seen clearly and must be examined with a microscope.
• Some microorganisms, particularly eucaryotic microbes, are visible without microscopes.For example, bread molds and filamentous algae are studied by microbiologists, yet are visible to naked eye, as two bacterias  Thiomargarita and Epulopiscium.

IMPORTANT CHARACTERISTICS OF MICROORGANISMS.

• Large and multicellular relatively simple in their construction, lacking highly differentiated cells and distinct tissues.
• Microbiologists, first isolated a specific microorganism from a population
  and then culture it. 
  
• Microbiology employs techniques—such as sterilization and the use of culture media that are necessary for successful isolation and growth of microorganisms. 
• Microorganisms are diverse, and their classification has always been a challenge for microbial taxonomists. 
• Some microbes are motile like animals, but also have cell walls and are photosynthetic like plants.  Such microbes cannot be placed easily into one kingdom or another. 
  
• Important factor in classifying microorganisms is that some are composed of prokaryotic cells and others of eukaryotic cells. 
• Prokaryotic cells  have a much simpler morphology than eukaryotic cells and lack a true membrane-delimited nucleus. [organisms with a primordial nucleus].
• In contrast, eukaryotic cells  have a membrane-enclosed nucleus; they are more complex morphologically and are usually larger than prokaryotes.
• Development of a classification scheme that divided organisms into five kingdoms: the Monera, Protista, Fungi, Animalia, and Plantae.
• Microorganisms (except for viruses, which are acellular and have their own classification system) were placed in the first three kingdoms.

continued............

HISTORY AND SCOPE OF MICROBIOLOGY

PREVIEW

1. Microbiology is not only defined only size but also techniques used to study them.

2. Microorganisms include acellular entities (e.g; viruses),prokaryotic cells and Eukaryotic cells.

3.Cellular microorganisms are found in a three domains of life:Bacteria,Archaea,Eucarya

4.Development of microbiology as scientific discipline depends on availability of microscopic and ability to isolate and grow pure cultures of microorganisms.

5.Development of techniques in large part of studies disproves the Theory of Spontaneous Generation and establishment of microorganisms can cause diseases.

6.Microbiology is a large discipline.It has to continue with a great impact on other areas of biology and general human welfares.

IMPORTANCE OF MICROORGANISMS

• Number and mass  estimated that microbes contain 50% of the biological carbon and 90% of the biological nitrogen on Earth.
• Certain microorganisms carry out photosynthesis, rivaling plants in their role of capturing carbon-dioxide and releasing oxygen into the atmosphere.
• Microbes inhabit humans also play important roles, including helping the body digest food and producing vitamins B and K.
• Society in general benefits from microorganisms, as they are necessary for the production of bread, cheese, beer, antibiotics, vaccines, vitamins, enzymes, and many other important products. 
• Modern biotechnology rests upon a microbiological foundation.  
• Majority of microorganisms play beneficial roles, some harm humans and have disrupted society.
• Microbial diseases played a major role in historical events such as decline of the Roman Empire and the conquest of the New World. 
• In 1347, plague or black death, an arthropod-borne disease, struck Europe with brutal force, killing 1/3 of the population (about 25 million people)
  within four years.
• Over next 80 years, the disease struck again and again, eventually wiping out 75% of the European population.
• Today ,struggle by microbiologists and others against killers like AIDS and malaria continues.  
  
• First we will discuss about the microbial world to provide a general idea of the organisms and agents that microbiologists study.
• Then we will discuss about historical development of the science of microbiology and its relationship to medicine and other areas of biology.
• Finally, we will discuss about the scope, relevance, and future of modern microbiology.

THIS IS JUST AN INTRODUCTION OF HISTORY AND SCOPE OF MICROBIOLOGY.

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