Exogenous bacteria

Microorganisms introduced to closed biological systems from the external world

Exogenous bacteria are microorganisms introduced to closed biological systems from the external world.[citation needed] They exist in aquatic and terrestrial environments, as well as the atmosphere. Microorganisms in the external environment have existed on Earth for 3.5 billion years.[1] Exogenous bacteria can be either benign or pathogenic. Pathogenic exogenous bacteria can enter a closed biological system and cause disease such as Cholera, which is induced by a waterborne microbe that infects the human intestine.[2] Exogenous bacteria can be introduced into a closed ecosystem as well, and have mutualistic benefits for both the microbe and the host.[1] A prominent example of this concept is bacterial flora, which consists of exogenous bacteria ingested and endogenously colonized during the early stages of life.[3] Bacteria that are part of normal internal ecosystems, also known as bacterial flora, are called Endogenous Bacteria. A significant amount of prominent diseases are induced by exogenous bacteria such as gonorrhea, meningitis, tetanus, and syphilis.[4] Pathogenic exogenous bacteria can enter a host via cutaneous transmission, inhalation, and consumption.[5]

## Difference with endogenous bacteria

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Only a minority of bacteria species cause disease in humans; and many species colonize in the human body to create an ecosystem known as microbiota. Bacterial flora is endogenous bacteria, which is defined as bacteria that naturally reside in a closed system.[6] Disease can occur when microbes included in normal bacteria flora enter a sterile area of the body such as the brain or muscle.[6] This is considered an endogenous infection. A prime example of this is when the residential bacterium E. coli of the GI tract enters the urinary tract.[6] This causes a urinary tract infection. Infections caused by exogenous bacteria occurs when microbes that are noncommensal enter a host.[6] These microbes can enter a host via inhalation of aerosolized bacteria, ingestion of contaminated or ill-prepared foods, sexual activity, or the direct contact of a wound with the bacteria.[6]

## Diseases

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### Waterborne and foodborne

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Microbial ecosystems in aquatic environments depend on a variety of factors including pH, temperature, and light exposure.[1] Exogenous bacteria supported in specific aquatic environments can enter a host via consumption. Additionally, exogenous bacteria can enter a secondary host through an intermediate host such as insects and parasites.[7] Exogenous bacteria can also enter an enclosed ecosystem via ingestion of contaminated food. Food-borne diseases such as Salmonella poisoning are transmitted by food not properly cooked or by individuals infected with the pathogen.

#### Salmonella enterocolitis

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One of the most common food-borne illnesses, Salmonella poisoning is caused by ingestion of unsanitary conditions during food preparation.[8] Salmonella can also be transmitted to humans via reptiles like turtles and iguanas, which are known carriers of pathogen.[8] Symptoms include chills, diarrhea[8] and fever.

#### Cholera

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Cholera is a waterborne infection caused by the bacterium Vibrio cholerae, and is transmitted via food or water that is contaminated with fecal matter.[9] Vibrio cholerae releases a toxin that induces an increased amount of water in the small intestines.[9] Symptoms primarily observed include, watery diarrhea and vomiting that can cause dehydration and death if not treated.[9] An estimated 3-5 million cases of Cholera occur yearly around the world.[10] The exogenous bacteria derived infection is primarilyfound in Africa, Asia, as well as Central and South America.[9]

#### Campylobacter

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Campylobacter infections are transmitted to a host via contaminated water and food, sexual activity, and interaction with infected animals.[5] Symptoms include diarrhea, cramping, and abdominal pain.[11] Campylobacter can cause disease in both humans and animals, and most human cases are induced by the species Campylobacter jejuni.[11]

### Terrestrial exogenous bacteria

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Of all the residential microbes found in soil, bacteria is the smallest and most abundant.[12] According to studies, there is an estimated 60,000 different types of bacteria that reside in the soil.[12] Terrestrial bacteria can characteristically be either aerobic or anaerobic, and some can be pathogenic if consumed by a host.[12]

#### Anthrax

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Anthrax is a disease caused via a bacterium that resides in soil, and predominately affects animals more than humans.[8] Anthrax is also considered a zoonotic disease and is transmitted to humans via contact with an infected animal host.[5] The disease is caused by gram-positive Bacillus anthracis (B. anthracis) and is found globally.[5] B. anthracis can enter a host via cutaneous transmission, inhalation, and/or consumption.[5]

#### Botulism

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Botulism is a rare disease caused by the bacterium Clostridium botulinum. This microbe is primarily found in the soil or untreated water.[13] Botulism spores can survive in unproperly canned or ill-prepared foods.[13] Even ingesting trace amounts of the spores can lead to severe poisoning that causes symptoms such as vomiting, nausea, and even paralysis.[13]

## See also

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* Bacterial flora
* Cholera
* Waterborne diseases

## References

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1. ^ a b c Willey, Sherwood & Woolverton 2011, pp. 673–737.
2. ^ Willey, Sherwood & Woolverton 2011, pp. 964–72.
3. ^ Arumugam, Manimozhiyan; Raes, Jeroen; Pelletier, Eric; Le Paslier, Denis; Yamada, Takuji; Mende, Daniel R.; et al. (2011). "Enterotypes of the human gut microbiome". Nature. 473 (7346): 174–80\. doi:10.1038/nature09944. PMC 3728647. PMID 21508958.
* Carl Zimmer (April 20, 2011). "Bacterial Ecosystems Divide People Into 3 Groups, Scientists Say". The New York Times.
4. ^ "Exogenous Bacteria." Bacteria Microbes. N.p., n.d. Web. 29 Apr 2012. <http://bacteria.health-tips-diseases.com/2009/02/exogenous-bacteria-and-disease.html>.
5. ^ a b c d e Willey, Sherwood & Woolverton 2011, pp. 964–5.
6. ^ a b c d e "Bacteria." ENotes. ENotes.com Inc., 2012. Web. 29 Apr 2012. <http://www.enotes.com/bacteria-reference/bacteria-171754>.
7. ^ "Mosquitoes and Disease." Prevention and Control. Illinois Department of Public Health, n.d. Web. 28 Apr 2012. <http://www.idph.state.il.us/envhealth/pcmosquitoes.htm>
8. ^ a b c d MedlinePlus Encyclopedia: Salmonella enterocolitis
9. ^ a b c d "Cholera." PubMed Health. US National Library of Medicine, n.d. Web. 28 Apr 2012. <https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001348/>.
10. ^ "Cholera." Media Centre. World Health Organization, n.d. Web. 28 Apr 2012. <http://www.who.int/mediacentre/factsheets/fs107/en/index.html>
11. ^ a b "Campylobacter." National Center for Emerging and Zoonotic Infectious Diseases. Center for disease Control and Prevention, n.d. Web. 28 Apr 2012. <https://www.cdc.gov/nczved/divisions/dfbmd/diseases/campylobacter/>.
12. ^ a b c "Soil Bacteria." Soil Biology Basics. n. page. Web. 28 Apr. 2012.<http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0017/41642/Soil_bacteria.pdf>.
13. ^ a b c "Botulism." PubMed Health. US National Library of Medicine, n.d. Web. 29 Apr 2012. <https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001624/>.

## Sources

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* Willey, Joanne; Sherwood, Linda; Woolverton, Christopher (2011). Prescott's Microbiology (8th ed.). New York: McGraw Hill. ISBN 978-0-07-337526-7.