Editing Microorganism (section)

===Eukaryotes===
{{Main|Eukaryote}}

Most living things that are visible to the naked eye in their adult form are [[eukaryote]]s, including [[human]]s. However, many eukaryotes are also microorganisms. Unlike [[bacteria]] and [[archaea]], eukaryotes contain [[organelle]]s such as the [[cell nucleus]], the [[Golgi apparatus]] and [[mitochondrion|mitochondria]] in their [[cell (biology)|cells]]. The nucleus is an organelle that houses the [[DNA]] that makes up a cell's genome. DNA (Deoxyribonucleic acid) itself is arranged in complex [[chromosome]]s.<ref>[http://www.ucmp.berkeley.edu/alllife/eukaryotamm.html Eukaryota: More on Morphology.] (Retrieved 10 October 2006)</ref>
[[Mitochondrion|Mitochondria]] are organelles vital in [[metabolism]] as they are the site of the [[citric acid cycle]] and [[oxidative phosphorylation]]. They evolved from [[symbiotic]] bacteria and retain a remnant genome.<ref name=Dyall>{{Cite journal |author=Dyall, S. |author2=Brown, M. |author3=Johnson, P. | title=Ancient invasions: from endosymbionts to organelles | journal=Science | volume=304 | issue=5668 | pages=253–257 | year=2004|pmid=15073369 | doi=10.1126/science.1094884|bibcode=2004Sci...304..253D |s2cid=19424594 }}</ref> Like bacteria, [[plant cell]]s have [[cell wall]]s, and contain organelles such as [[chloroplast]]s in addition to the organelles in other eukaryotes. Chloroplasts produce energy from light by [[photosynthesis]], and were also originally symbiotic bacteria.<ref name=Dyall/>

Unicellular eukaryotes consist of a single [[Cell (biology)|cell]] throughout their life cycle. This qualification is significant since most [[multicellular organism|multicellular]] eukaryotes consist of a single cell called a [[zygote]] only at the beginning of their life cycles. Microbial eukaryotes can be either [[haploid]] or [[diploid]], and some organisms have multiple [[cell nucleus|cell nuclei]].

Unicellular eukaryotes usually reproduce asexually by [[mitosis]] under favorable conditions. However, under stressful conditions such as nutrient limitations and other conditions associated with DNA damage, they tend to reproduce sexually by [[meiosis]] and [[Fertilization|syngamy]].<ref name=Bernstein>{{cite book |last1=Bernstein |first1=H. |last2=Bernstein |first2=C. |last3=Michod |first3=R. E. |year=2012 |chapter-url=https://www.novapublishers.com/catalog/product_info.php?products_id=31918 |title=DNA repair as the primary adaptive function of sex in bacteria and eukaryotes.  |chapter=Chapter 1 |pages=1–49 |series= DNA Repair: New Research |editor-first1=Sakura |editor-last1=Kimura |editor-first2=Sora |editor-last2=Shimizu |publisher=Nova Sci. Publ. |isbn=978-1-62100-808-8 |url-status=dead |archive-url=https://web.archive.org/web/20180722155931/https://www.novapublishers.com/catalog/product_info.php?products_id=31918 |archive-date= Jul 22, 2018 }}</ref>

====Protists====
{{Main|Protista}}
[[File:Euglena mutabilis - 400x - 1 (10388739803) (cropped).jpg|thumb|upright=0.8|''[[Euglena|Euglena mutabilis]]'', a [[photosynthetic]] [[flagellate]]]]

Of [[Eukaryote|eukaryotic]] groups, the [[protists]] are most commonly [[unicellular]] and microscopic. This is a highly diverse group of organisms that are not easy to classify.<ref>{{Cite journal|author=Cavalier-Smith T |author-link=Thomas Cavalier-Smith |title=Kingdom protozoa and its 18 phyla |journal=Microbiol. Rev. |volume=57 |issue=4 |pages=953–994 |date=1 December 1993|pmid=8302218 |pmc=372943 |doi=10.1128/mmbr.57.4.953-994.1993 |doi-access=free }}</ref><ref>{{Cite journal|last=Corliss |first=J. O. |title=Should there be a separate code of nomenclature for the protists? |journal=BioSystems |volume=28 |issue=1–3 |pages=1–14 |year=1992 |pmid=1292654 | doi=10.1016/0303-2647(92)90003-H|bibcode=1992BiSys..28....1C }}</ref> Several [[algae]] [[species]] are [[multicellular]] protists, and [[slime mold]]s have unique life cycles that involve switching between unicellular, colonial, and multicellular forms.<ref>{{Cite journal|author=Devreotes, P. |title=Dictyostelium discoideum: a model system for cell-cell interactions in development |journal=Science |volume=245 |issue=4922 |pages=1054–1058 |year=1989 |pmid=2672337 | doi=10.1126/science.2672337|bibcode=1989Sci...245.1054D }}</ref> The number of species of protists is unknown since only a small proportion has been identified. Protist diversity is high in oceans, deep sea-vents, river sediment and an acidic river, suggesting that many eukaryotic microbial communities may yet be discovered.<ref>{{Cite journal|author=Slapeta, J. |author2=Moreira, D. |author3=López-García, P. |title=The extent of protist diversity: insights from molecular ecology of freshwater eukaryotes |journal=Proc. Biol. Sci. |volume=272 |issue=1576 |pages=2073–2081 |year=2005 |pmid=16191619 |doi=10.1098/rspb.2005.3195 |pmc=1559898}}</ref><ref>{{Cite journal |author=Moreira, D. |author2=López-García, P. |title=The molecular ecology of microbial eukaryotes unveils a hidden world |journal=Trends Microbiol. |volume=10 |issue=1 |pages=31–38 |year=2002 |pmid=11755083 | url=http://download.bioon.com.cn/view/upload/month_0803/20080326_daa08a6fdb5d38e3a0d8VBrocN3WtOdR.attach.pdf | doi=10.1016/S0966-842X(01)02257-0}}</ref>

====Fungi====
{{Main|Fungus}}

The [[fungus|fungi]] have several unicellular species, such as baker's yeast (''[[Saccharomyces cerevisiae]]'') and fission yeast (''[[Schizosaccharomyces pombe]]''). Some fungi, such as the pathogenic yeast ''[[Candida albicans]]'', can undergo [[phenotypic switching]] and grow as single cells in some environments, and [[Hypha|filamentous hyphae]] in others.<ref>{{Cite journal |author=Kumamoto, C.A. |author-link1=Carol Kumamoto|author2=Vinces, M. D. |title=Contributions of hyphae and hypha-co-regulated genes to Candida albicans virulence |journal=Cell. Microbiol. |volume=7 |issue=11 |pages=1546–1554 |year=2005 |pmid=16207242 | doi=10.1111/j.1462-5822.2005.00616.x|doi-access=free }}</ref>

====Plants====
{{Main|Plant}}

The [[green algae]] are a large group of photosynthetic eukaryotes that include many microscopic organisms. Although some green algae are classified as [[protist]]s, others such as [[charophyta]] are classified with [[embryophyte]] plants, which are the most familiar group of land plants. Algae can grow as single cells, or in long chains of cells. The green algae include unicellular and colonial [[flagellate]]s, usually but not always with two [[flagellum|flagella]] per cell, as well as various colonial, [[Chlorococcales|coccoid]], and filamentous forms. In the [[Charales]], which are the algae most closely related to higher plants, cells differentiate into several distinct tissues within the organism. There are about 6000 species of green algae.<ref>{{Cite book |author=Thomas, David C. |title=Seaweeds |publisher=Natural History Museum |location=London |year=2002 |isbn=978-0-565-09175-0 }}</ref>