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The gap from Leeuwenhoek to Pasteur is a very long one. When L is mentioned, Would it be better to talk about why L. did do than what he did not.?[[User:DavidGoodman|DavidGoodman]] 21:02, 24 November 2006 (CST)
The gap from Leeuwenhoek to Pasteur is a very long one. When L is mentioned, Would it be better to talk about why L. did do than what he did not.?[[User:DavidGoodman|DavidGoodman]] 21:02, 24 November 2006 (CST)
:The statments that visible /invisible have exceptions occurs at least 5 times, 1 in each section.
:The statments that visible /invisible have exceptions occurs at least 5 times, 1 in each section.
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[[Image:Anabaena_heterocyst.jpg|frame|Filaments of joined cells the cyanbacterium ''Anabaena'' magnified about 4,000 times. In this prokayotic organism there are two types of cell. The occcasional cells that have a distinct appearance are 'heterocysts', specialized to fix nitrogen gas. [http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371%2Fjournal.pbio.0040299  Cooperation among Microorganisms Ned S. Wingreen, Simon A. Levin PLoS Biol 4(9): e299. DOI:10.1371/journal.pbio.0040299 2006 ] ]]
[[Image:Anabaena_heterocyst.jpg|frame|Filaments of joined cells the cyanbacterium ''Anabaena'' magnified about 4,000 times. In this prokayotic organism there are two types of cell. The occcasional cells that have a distinct appearance are 'heterocysts', specialized to fix nitrogen gas. [http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371%2Fjournal.pbio.0040299  Cooperation among Microorganisms Ned S. Wingreen, Simon A. Levin PLoS Biol 4(9): e299. DOI:10.1371/journal.pbio.0040299 2006 ] ]]
'''Microorganism''' is the scientific word for germs. Germs are almost everywhere humans can venture, and in many places on the planet where we cannot ever go, but they are an invisible presence.
Many people automatically assume germs are bad, because they cause infectious disease, but most germs (or microbes, as they are also called) are no pathogenic, and both the working of the living world and biological cycling of matter on earth, and human survival on intimately dependent on the diverse chemical activities of microbes.
Another reason microbes are important is that all other life descended from them. Current scientific investigation of microbes are revealing clues about the earliest stages in evolution of life on earth which occurred some 4 billion years ago. Microbes are also important for teaching us about genetics, - the science of inheritance - because of the ease with which large numbers of them can be grown has enable biologists to work out the intricate details of inheritance in living cells, and led to discovery that DNA is the chemical through which traits are passed from generation to generation.
Investigation of microbes and their genetic behavior led to a great flowering of the biological sciences during last century, starting in the mid-1940.




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The study of micro-organisms is called [[microbiology]].
The study of micro-organisms is called [[microbiology]].
==Paragraph to introduce major types by illustative example==
Less detail the better


==Importance==
==Importance==
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===Use in food===
===Use in food===
<ref>{{cite web |url=http://www.foodsci.uoguelph.ca/dairyedu/micro.html |title= Dairy Microbiology |accessdate=2006-10-09 |publisher= University of Guelph}}</ref>
<ref>{{cite web |url=http://www.foodsci.uoguelph.ca/dairyedu/micro.html |title= Dairy Microbiology |accessdate=2006-10-09 |publisher= University of Guelph}}</ref>
lactobacilli = lactobacter? [[User:Robert Tito|Robert Tito]] | <span style="background:black">&nbsp;[[<font color="red"><b>Talk</b></font>]]&nbsp;</span>


=== Use in science ===
=== Use in science ===
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== Microorganisms and human health ==
== Microorganisms and human health ==


 
I'd like to add a whole section on normal flora- that's a concept that is really poorly conveyed in most health education. [[User:Nancy Sculerati MD|Nancy Sculerati MD]] 18:00, 17 March 2007 (CDT)
=== Diseases and immunology ===
=== Infectious disease ===
Microorganisms are the cause of many infectious diseases. The organisms involved include bacteria, causing diseases such as [[bubonic plague|plague]], [[tuberculosis]] and [[anthrax]]: protozoa, causing diseases such as [[malaria]], [[sleeping sickness]] and [[toxoplasmosis]]; and also fungi causing diseases such as [[ringworm]], [[candidiasis]] or [[histoplasmosis]]. However, other diseases such as [[influenza]], [[yellow fever]] or [[AIDS]] are caused by [[viruses]], which are not living organisms and are not therefore microorganisms.
 
[[Immunology]] is the study of human animal responses to infection and cancer. It is a major field af medical science allied to medical microbiology.


== Hygiene ==
== Hygiene ==
'''[[Hygiene]]''' is the avoidance of [[infection]] or [[food]] spoiling by eliminating microorganisms from the surroundings. As microorganisms, particularly [[bacteria]], are found practically everywhere, this means in most cases the reduction of harmful microorganisms to acceptable levels. However, in some cases it is required that an object or substance is completely sterile, i.e. devoid of all living entities and [[virus]]es. A good example of this is a [[hypodermic needle]]. In food preparation, microorganisms are reduced by preservation methods (such as the addition of [[vinegar]]), clean utensils used in preparation, short storage periods or by cool temperatures. If complete sterility is needed, the two most common methods are [[irradiation]] and the use of an [[autoclave]], which resembles a [[pressure cooker]].
There are several methods for investigating the level of hygiene in a sample of food, drinking water, equipment etc. Water samples can be filtrated through an extremely fine filter. This filter is then placed in a [[nutrient medium]]. Microorganisms on the filter then grow to form a visible colony. Harmful microorganisms can be detected in food by placing a sample in a [[nutrient broth]] designed to enrich the organisms in question. Various methods, such as [[Selective medium|selective media]] or [[PCR]], can then be used for detection. The hygiene of hard surfaces, such as cooking pots, can be tested by touching them with a solid piece of [[nutrient medium]] and then allowing the microorganisms to grow on it.
There are no conditions where all microorganisms would grow, and therefore often several different methods are needed. For example, a food sample might be analysed on three different [[nutrient medium]]s designed to indicate the presence of "total" [[bacteria]] (conditions where many, but not all, bacteria grow), [[mold]]s (conditions where the growth of [[bacteria]] is prevented by e.g. [[antibiotic]]s) and [[Coliform Index|coliform]] [[bacteria]] (these indicate a sewage contamination).


==History==
==History==
=== Evolution ===
=== Evolution ===
Single-celled microorganisms were the [[Origin of life|first forms of life]] to develop on earth, approximately [[1 E17 s|4 billion years ago]]. For about 3 billion years, all life was microscopic, and many of the same biological and chemical processes that these microorganisms developed are used today in higher order organisms as well as microbes <ref>{{cite book | author = Knoll, Andrew H.;| title = Life on a Young Planet: the First Three Billion Years of Evolution on Earth | edition = 1st ed. | publisher = Princeton University Press | year = 2003 | id = ISBN 0-691-00978-3 }}</ref>. Most microorganisms reproduce rapidly and in great number. This, coupled with a high [[mutation]] rate and many other means of [[Bacteria#Genetic variation|genetic variation]], allows microorganisms to swiftly [[biological evolution|evolve]] (via [[natural selection]]) to survive in new environments . This has led, notably, to the recent development of '[[antibiotic resistance|super-bugs]]' - [[pathogenic]] [[bacteria]] that are resistant to modern [[antibiotic]]s. Another notorious example of this is [[HIV]], which has evolved an immunity to all drugs used against it so far, although as a [[virus]], it is not, according to some definitions, a microorganism.


=== Discovery ===
=== Discovery ===
Before [[Anton van Leeuwenhoek]]'s [http://www.sciences.demon.co.uk/wav-mics.htm invention of the microscope] and discovery of microorganisms with it in 1676, it had been a mystery as to why [[grapes]] could be turned into [[wine]], [[milk]] into [[cheese]], or why food would spoil. Leeuwenhoek did not make the connection between these processes and microorganisms, but he did establish that there were forms of life that were not visible to the naked eye. Leeuwenhoek's discovery, along with subsequent observations by [[Lazzaro Spallanzani]] and [[Louis Pasteur]], ended the long-held belief that life could [[Abiogenesis|spontaneously appear]] from non-living substances.
Before [[Anton van Leeuwenhoek]]'s [http://www.sciences.demon.co.uk/wav-mics.htm invention of the microscope] and discovery of microorganisms with it in 1676, [[Lazzaro Spallanzani]] and [[Louis Pasteur]], ended the long-held belief that life could [[Abiogenesis|spontaneously appear]] from non-living substances.


Spallanzani found that microorganisms could only settle in a broth if the broth was exposed to the air; he also found that boiling the broth would sterilise it, killing the microorganisms. Pasteur expanded upon these findings by exposing boiled broths to the air in vessels that contained a filter to prevent all particles from entering, or in vessels with no filter but with air being admitted via a curved tube that would not allow dust particles to come into contact with the broth. By first boiling the broth, Pasteur ensured that there were no microorganisms alive in the broths at the start of his experiment. Nothing grew in the broths during his experiments, showing that the living organisms that grew in such broths came from outside, as [[spore]]s on dust, rather than spontaneously generated within the broth. Thus, Pasteur decisively refuted the theory of spontaneous generation and supported [[Germ theory of disease|germ theory]].
Spallanzani found that microorganisms Pasteur ensured that there were no microorganisms alive in the broths at the start of his experiment. Nothing grew in the broths during his experiments, showing that the living organisms that grew in such broths came from outside, as [[spore]]s on dust, rather than spontaneously generated within the broth. Thus, Pasteur decisively refuted the theory of spontaneous generation and supported [[Germ theory of disease|germ theory]].


In 1876, [[Robert Koch]] showed that microbes can cause disease, by showing that the blood of cattle that were infected with [[anthrax]] always contained large numbers of [[Bacillus anthracis]]. Koch also found that he could transmit anthrax from one animal to another by taking a small sample of blood from the infected animal and injecting it into a healthy one, causing the healthy animal to become sick. He also found that he could grow the bacteria in a nutrient broth, inject it into a healthy animal, and cause illness. Based upon these experiments, he devised criteria for establishing a causal link between a microbe and a disease in what are now known as [[Koch's postulates]]. Though these postulates are no longer strictly accurate, they remain historically important in the development of scientific thought.
In 1876, [[Robert Koch]] showed that microbes can cause disease, by showing that the blood of cattle that were infected with [[anthrax]] always contained large numbers of [[Bacillus anthracis]].[[Koch's postulates]]. Though these postulates are no longer strictly accurate, they remain historically important in the development of scientific thought.


[[Image:Tree_phylogeny_3_domain.gif|thumb|300px|left|A [[phylogenetic tree]] of life based on differences in [[rRNA]], showing the separation of [[bacteria]], [[archaea]], and [[eukaryote]]s.]]
[[Image:Tree_phylogeny_3_domain.gif|thumb|300px|left|A [[phylogenetic tree]] of life based on differences in [[rRNA]], showing the separation of [[bacteria]], [[archaea]], and [[eukaryote]]s.]]
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Microorganisms can be found in almost all branches of  the [[taxonomy|taxonomic]] organization of life on the planet. [[Bacteria]] and [[archaea]] are almost always microscopic, whilst a number of [[eukaryote]]s are also microscopic, including most [[Protista|protists]] and a number of [[fungus|fungi]]. Increasingly, the practical identification and classification of micro-organisms is being based on the genetic code, that is, the [[nucleotide sequence]] of the [[RNA]] in the small [[ribosome]] subunit <ref> [http://rdp.cme.msu.edu/ Ribosomal Database Project II]</ref> . [[Viruses]] are generally regarded as not living in the same sense as other organisms and are, strictly speaking, not microbes, although the field of [[microbiology]] also encompasses the study of viruses.
 
=== Bacteria ===
=== Bacteria ===
[[Image:Escherichia_coli.jpg|right|frame|''Escherichia coli'' magnified approx. 14,000 fold by transmission electron microscopy. The filamentous structures are ''flagella''. CDC/Elizabeth H. White, M.S  PLoS Biol. 2006 January; 4(1): e13. Published online 2005 December 20. doi: 10.1371/journal.pbio.0040013]]
[[Image:Escherichia_coli.jpg|right|frame|''Escherichia coli'' magnified approx. 14,000 fold by transmission electron microscopy. The filamentous structures are ''flagella''. CDC/Elizabeth H. White, M.S  PLoS Biol. 2006 January; 4(1): e13. Published online 2005 December 20. doi: 10.1371/journal.pbio.0040013]]
{{main|Bacteria}}
''[[Bacteria]]'', sometimes called [[eubacteria]] <i>(true bacteria)</i> to distinguish them from ''[[Archaea]]'' (formerly called archeobacteria) are structurally the simplest and biochemically the most diverse and widespread [[organism]]s on Earth. Generally they consist of simple rod-like or spherical (coccus, pl. cocci) cells about 1 micron in size without a defined nucleus (and are thus classified as [[prokaryote]]s but also classified as [[Monera]] in the alternative five-kingdom taxonomy) (''see [[Bacterial cell structure]]''}.


Bacteria are practically all invisible to the naked eye, with few extremely rare exceptions, such as ''[[Thiomargarita namibiensis]]''. They are [[unicellular]] organisms and lack organelles. Their genome is a single string of [[DNA]], although they can also harbour small pieces of [[DNA]] called [[plasmid]]s. [[Bacteria]] are surrounded by a [[cell wall]]. They reproduce by [[binary fission]]. Some species form [[spore]]s, but for [[bacteria]] this is a mechanism for survival, not reproduction. Their [[generation time]] can be as short as 15 minutes.


Bacteria inhabit practically all environments where some liquid water is available and the temperature is below +140 °C. They are found in [[sea water]], [[soil]], [[Gastrointestinal tract|human gut]], [[hot spring]]s and in [[food]]. Practically all surfaces which have not been specially sterilised are covered in bacteria. The number of bacteria in the world is estimated to be around five million trillion trillion, or 5 &times; 10<sup>30</sup>.<ref>[http://www.uga.edu/columns/090898/campnews.html University of Georgia Campus News]</ref>
=== Archaea ===


=== Archaea ===
{{Main|Archaea}}
[[Archaea]] are single-celled organisms lacking defined nuclei and are therefore prokaryotes. They were originally identified in extreme environments, but have since been found in diverse types of habitats. A single organism from this domain has been called an 'archaean'. Although archaea are superficially similar to bacteria when viewed through the light microscope, consisting of rods or cocci a micron or two in size, the details of their chemistry and molecular structure show they have distinct differences from bacteria, for instance in their membrane fats which employ a different stereo isomer of glycerol phosphate in the membrane fat, are ''ether'' rather than ''ester'' derivatives of glycerol (glycerol di-ethers and tetra-ethers), and based on the isoprenes to form the hydrophobic chain of the fats. These fundamental differences in biochemistry fit with the concept that Archaea and Bacteria diverged in evolution very early in the history of life <ref>[http://www.pnas.org/cgi/content/full/98/3/805 Pace Norman R. (2001) The universal nature of biochemistry PNAS vol. 98  no. 3 p 805-808]</ref>.


=== Eukaryotes ===
=== Protists ===
{{main|Eukaryote}} {{main|Protist}} {{main|Fungi}}
[[Image:Chaos diffluens.jpg|thumb|250px|right|An [[amoeba]], a typical eukaryotic microorganism]]
All living things, including [[human]]s, which are ''individually'' visible to the naked eye  are eukaryotes, with some exceptions, such as ''[[Thiomargarita namibiensis]]''. However, many [[eukaryote]]s are also microorganisms. Eukaryotes are characterised by the presence of [[organelle]]s in the [[cell (biology)|cell]]s; these structures are absent in [[bacteria]] and [[archaea]]. The [[nucleus]] is an [[organelle]] which houses the [[DNA]].<ref>"Eukaryota: More on Morphology." [http://www.ucmp.berkeley.edu/alllife/eukaryotamm.html] (Accessed 10 October 2006)</ref>
A [[mitochondrion]] is vital in production and conversion of energy inside a cell. The mitochondr]] have evolved from symbiotic [[bacteria]]. [[Plant cell]]s also have [[cell wall]]s and [[chloroplast]]s in addition to other organelles. [[Chloroplast]]s produce energy from [[light]] by [[photosynthesis]]. They were also originally symbiotic bacteria.


Unicellular eukaryotes consist of a single cell throughout their life cycle (note that most multicellular eukaryotes consist of a single cell at the beginning of their life cycles). Unicellular organisms usually contain only a single copy of their [[genome]] when not undergoing [[cell division]], although some organisms have multiple cell nuclei (see [[coenocyte]]). However, not all microorganisms are unicellular. Microbial eukaryotes can have multiple cells.
===Fungi===


Of the eukaryotic groups, the [[Protista|protists]] are always unicellular, and thus microorganisms. This is a diverse group of organisms which do not fit into other groups of eukaryotes. Several [[algae]] [[species]] are unicellular [[plants]]. The [[Fungus|fungi]] also have several unicellular species, such as baker's yeast (''[[Saccharomyces cerevisiae]]''). [[Animal]]s are always multicellular, although they may not be visible to the naked eye.


== Microorganisms in fiction ==
Microorganisms have frequently played an important part in [[science fiction]], both as agents of disease, and as entities in their own right. Some notable uses of microorganisms in fiction include:
* ''[[The War of the Worlds]]'', where microorganisms play important thematic and plot-related roles.
* ''[[Fantastic Voyage]]'', in which some scientists are miniaturised to microscopic size and observe microorganisms from a new perspective
* ''[[Blood Music]]'', in which a colony of microorganisms is given [[intelligence]]
* ''[[The Andromeda Strain]]'', in which extraterrestrial microorganisms kill several people


==References==
==References==

Latest revision as of 19:02, 10 November 2007

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The gap from Leeuwenhoek to Pasteur is a very long one. When L is mentioned, Would it be better to talk about why L. did do than what he did not.?DavidGoodman 21:02, 24 November 2006 (CST)

The statments that visible /invisible have exceptions occurs at least 5 times, 1 in each section.
The section on eukaryotic microorganisms neeeds to specifiy just what is included--a good trick--(my first research exerience was in protozoology, as it was then called). As you undoubtedly intend to include fungi, you'll have to explain that they are not plants. We should probably do a fngii article fairly early on. I'll start one from WP.DavidGoodman 20:51, 25 November 2006 (CST)


Complete rewrite

I think this article starts badly and is boring bland. I propose to start from scratch and De WP edia it. This will take time. I will do it so that access to the current one is preserved. An I am giving fair notice, in case there is disagreement. Im the only one to edit it here anyway. David Tribe 07:29, 17 March 2007 (CDT)

NEW DRAFT OF ARTICLE

Filaments of joined cells the cyanbacterium Anabaena magnified about 4,000 times. In this prokayotic organism there are two types of cell. The occcasional cells that have a distinct appearance are 'heterocysts', specialized to fix nitrogen gas. Cooperation among Microorganisms Ned S. Wingreen, Simon A. Levin PLoS Biol 4(9): e299. DOI:10.1371/journal.pbio.0040299 2006

Microorganism is the scientific word for germs. Germs are almost everywhere humans can venture, and in many places on the planet where we cannot ever go, but they are an invisible presence.

Many people automatically assume germs are bad, because they cause infectious disease, but most germs (or microbes, as they are also called) are no pathogenic, and both the working of the living world and biological cycling of matter on earth, and human survival on intimately dependent on the diverse chemical activities of microbes.

Another reason microbes are important is that all other life descended from them. Current scientific investigation of microbes are revealing clues about the earliest stages in evolution of life on earth which occurred some 4 billion years ago. Microbes are also important for teaching us about genetics, - the science of inheritance - because of the ease with which large numbers of them can be grown has enable biologists to work out the intricate details of inheritance in living cells, and led to discovery that DNA is the chemical through which traits are passed from generation to generation.

Investigation of microbes and their genetic behavior led to a great flowering of the biological sciences during last century, starting in the mid-1940.



Some unicellular protists and unusually large bacteria (Epulopiscium fishelsoni and Thiomargarita namibiensis) are visible to the naked eye [1]

The study of micro-organisms is called microbiology.

Paragraph to introduce major types by illustative example

Less detail the better

Importance

Habitats and ecology

Extremophiles

Use in food

[2]

lactobacilli = lactobacter? Robert Tito |  [[Talk]] 

Use in science

Microorganisms and human health

I'd like to add a whole section on normal flora- that's a concept that is really poorly conveyed in most health education. Nancy Sculerati MD 18:00, 17 March 2007 (CDT)

Infectious disease

Hygiene

History

Evolution

Discovery

Before Anton van Leeuwenhoek's invention of the microscope and discovery of microorganisms with it in 1676, Lazzaro Spallanzani and Louis Pasteur, ended the long-held belief that life could spontaneously appear from non-living substances.

Spallanzani found that microorganisms Pasteur ensured that there were no microorganisms alive in the broths at the start of his experiment. Nothing grew in the broths during his experiments, showing that the living organisms that grew in such broths came from outside, as spores on dust, rather than spontaneously generated within the broth. Thus, Pasteur decisively refuted the theory of spontaneous generation and supported germ theory.

In 1876, Robert Koch showed that microbes can cause disease, by showing that the blood of cattle that were infected with anthrax always contained large numbers of Bacillus anthracis.Koch's postulates. Though these postulates are no longer strictly accurate, they remain historically important in the development of scientific thought.

A phylogenetic tree of life based on differences in rRNA, showing the separation of bacteria, archaea, and eukaryotes.

Classification

Bacteria

Escherichia coli magnified approx. 14,000 fold by transmission electron microscopy. The filamentous structures are flagella. CDC/Elizabeth H. White, M.S PLoS Biol. 2006 January; 4(1): e13. Published online 2005 December 20. doi: 10.1371/journal.pbio.0040013


Archaea

Protists

Fungi

References

Citations

  1. ↑ Annu Rev Microbiol. 2001;55:105-37. Big bacteria. Schulz HN, Jorgensen BB.
  2. ↑ Dairy Microbiology. University of Guelph. Retrieved on 2006-10-09.

Further reading

  • Dixon, Bernard (1994). Power Unseen: How Microbes Rule the World, 1st ed.. W. H. Freeman, Oxford and New York. ISBN 0-7167-4504-6. 
  • Krasner, Robert I. (2002). The Microbial Challenge: Human-Microbe Interactions, 1st.. ASM Press, Washington, DC. ISBN 0-13-144329-4. 
  • Knoll, Andrew H. (2003). Life on a Young Planet: the First Three Billion Years of Evolution on Earth, 1st ed.. Princeton University Press. ISBN 0-691-00978-3. 
  • Postgate, John (1992). Microbes and Man, 3rd ed.. Cambridge University Press, UK. ISBN 0-521-42355-4. 

External links

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