Editing Plasmodium falciparum (section)

== Structure ==
[[File:Plasmodium falciparum 02.jpg|thumb|Blood smear from a ''P. falciparum'' [[Malaria culture|culture]] (K1 strain - asexual forms) - several red blood cells have ring stages inside them. Close to the center is a schizont and on the left a trophozoite.]]
[[File:Malaria falciparum ring forms.jpg|right|thumb|Ring forms in red blood cells (Giemsa stain)]]
''P. falciparum'' does not have a fixed structure but undergoes continuous change during its life cycle. A sporozoite is spindle-shaped and 10–15 μm long. In the liver, it grows into an ovoid schizont of 30–70 μm in diameter. Each schizont produces merozoites, each of which is roughly 1.5 μm in length and 1 μm in diameter. In the erythrocyte the merozoite forms a ring-like structure, becoming a trophozoite. A trophozoite feeds on the haemoglobin and forms a granular pigment called [[haemozoin]]. Unlike those of other ''Plasmodium'' species, the gametocytes of ''P. falciparum'' are elongated and crescent-shaped, by which they are sometimes identified. A mature gametocyte is 8–12 μm long and 3–6 μm wide. The ookinete is also elongated measuring about 18–24 μm. An oocyst is rounded and can grow up to 80 μm in diameter.<ref>{{cite book|last1=Lucius|first1=R.|last2=Roberts|first2=C.W.|editor1-last=Lucius|editor1-first=R.|editor2-last=Loos-Frank|editor2-first=B.|editor3-last=Lane|editor3-first=R.P.|editor4-last=Poulin|editor4-first=R.|editor5-last=Roberts|editor5-first=C.W.|editor6-last=Grencis|editor6-first=R.K.|title=The Biology of Parasites|date=2017|publisher=John Wiley & Sons|isbn=978-3-527-32848-2|pages=190–198|chapter-url=https://books.google.com/books?id=w8bXDQAAQBAJ|chapter=Biology of Parasitic Protozoa}}</ref> Microscopic examination of a blood film reveals only early (ring-form) trophozoites and gametocytes that are in the peripheral blood. Mature trophozoites or schizonts in peripheral blood smears, as these are usually sequestered in the tissues. On occasion, faint, comma-shaped, red dots are seen on the erythrocyte surface. These dots are [[Maurer's cleft]] and are secretory organelles that produce proteins and enzymes essential for nutrient uptake and immune evasion processes.<ref>{{cite journal|last1=Lanzer|first1=Michael|last2=Wickert|first2=Hannes|last3=Krohne|first3=Georg|last4=Vincensini|first4=Laetitia|last5=Braun Breton|first5=Catherine|title=Maurer's clefts: A novel multi-functional organelle in the cytoplasm of ''Plasmodium falciparum''-infected erythrocytes|journal=International Journal for Parasitology|date=2006|volume=36|issue=1|pages=23–36|doi=10.1016/j.ijpara.2005.10.001|pmid=16337634}}</ref>

The apical complex, which is a combination of organelles, is an important structure. It contains secretory organelles called rhoptries and micronemes, which are vital for mobility, adhesion, host cell invasion, and parasitophorous vacuole formation.<ref name=garcia06/> As an [[apicomplexan]], it harbours a plastid, an [[apicoplast]], similar to plant [[chloroplast]]s, which they probably acquired by engulfing (or being invaded by) a [[eukaryotic]] [[Algae|alga]] and retaining the algal plastid as a distinctive [[organelle]] [[Symbiogenesis|encased within four membranes]]. The apicoplast is involved in the synthesis of [[lipid]]s and several other compounds and provides an attractive drug target. During the asexual blood stage of infection, an essential function of the apicoplast is to produce the isoprenoid precursors [[isopentenyl pyrophosphate]] (IPP) and [[dimethylallyl pyrophosphate]] (DMAPP) via the [[MEP pathway|MEP (non-mevalonate) pathway]].<ref>{{Cite journal|last1=Yeh|first1=Ellen|last2=DeRisi|first2=Joseph L.|date=2011-08-30|title=Chemical Rescue of Malaria Parasites Lacking an Apicoplast Defines Organelle Function in Blood-Stage ''Plasmodium falciparum''|journal=PLOS Biol|volume=9|issue=8|pages=e1001138|doi=10.1371/journal.pbio.1001138|issn=1545-7885|pmc=3166167|pmid=21912516 |doi-access=free }}</ref>

=== Genome ===

In 1995 the Malaria Genome Project was set up to sequence the genome of ''P. falciparum''. The genome of its [[mitochondrion]] was reported in 1995, that of the nonphotosynthetic [[plastid]] known as the apicoplast in 1996,<ref>{{cite journal |last1=Wilson |first1=(Iain) R.J.M. |last2=Denny |first2=Paul W. |last3=Preiser |first3=Peter R. |last4=Rangachari |first4=Kaveri |last5=Roberts |first5=Kate |last6=Roy |first6=Anjana |last7=Whyte |first7=Andrea |last8=Strath |first8=Malcolm |last9=Moore |first9=Daphne J. |last10=Moore |first10=Peter W. |last11=Williamson |first11=Donald H. |title=Complete Gene Map of the Plastid-like DNA of the Malaria Parasite ''Plasmodium falciparum'' |journal=Journal of Molecular Biology |date=August 1996 |volume=261 |issue=2 |pages=155–172 |doi=10.1006/jmbi.1996.0449}}</ref> and the sequence of the first nuclear [[chromosome]] (chromosome 2) in 1998. The sequence of chromosome 3 was reported in 1999 and the entire genome was reported on 3 October 2002.<ref name="gardner">{{cite journal |last1=Gardner |first1=Malcolm J. |last2=Hall |first2=Neil |last3=Fung |first3=Eula |last4=White |first4=Owen |last5=Berriman |first5=Matthew |last6=Hyman |first6=Richard W. |last7=Carlton |first7=Jane M. |last8=Pain |first8=Arnab |last9=Nelson |first9=Karen E. |last10=Bowman |first10=Sharen |last11=Paulsen |first11=Ian T. |last12=James |first12=Keith |last13=Eisen |first13=Jonathan A. |last14=Rutherford |first14=Kim |last15=Salzberg |first15=Steven L. |last16=Craig |first16=Alister |last17=Kyes |first17=Sue |last18=Chan |first18=Man-Suen |last19=Nene |first19=Vishvanath |last20=Shallom |first20=Shamira J. |last21=Suh |first21=Bernard |last22=Peterson |first22=Jeremy |last23=Angiuoli |first23=Sam |last24=Pertea |first24=Mihaela |last25=Allen |first25=Jonathan |last26=Selengut |first26=Jeremy |last27=Haft |first27=Daniel |last28=Mather |first28=Michael W. |last29=Vaidya |first29=Akhil B. |last30=Martin |first30=David M. A. |last31=Fairlamb |first31=Alan H. |last32=Fraunholz |first32=Martin J. |last33=Roos |first33=David S. |last34=Ralph |first34=Stuart A. |last35=McFadden |first35=Geoffrey I. |last36=Cummings |first36=Leda M. |last37=Subramanian |first37=G. Mani |last38=Mungall |first38=Chris |last39=Venter |first39=J. Craig |last40=Carucci |first40=Daniel J. |last41=Hoffman |first41=Stephen L. |last42=Newbold |first42=Chris |last43=Davis |first43=Ronald W. |last44=Fraser |first44=Claire M. |last45=Barrell |first45=Bart |title=Genome sequence of the human malaria parasite ''Plasmodium falciparum'' |journal=Nature |date=October 2002 |volume=419 |issue=6906 |pages=498–511 |doi=10.1038/nature01097|pmid=12368864 |bibcode=2002Natur.419..498G |pmc=3836256 }}</ref> The roughly 24-megabase genome is extremely AT-rich (about 80%) and is organised into 14 chromosomes. Just over 5,300 genes were described. Many genes involved in [[antigenic variation]] are located in the [[subtelomeric]] regions of the chromosomes. These are divided into the ''var'', ''rif'', and ''stevor'' families. Within the genome, there exist 59 ''var'', 149 ''rif'', and 28 ''stevor'' genes, along with multiple [[pseudogenes]] and truncations. It is estimated that 551, or roughly 10%, of the predicted nuclear-encoded [[proteins]] are targeted to the [[apicoplast]], while 4.7% of the [[proteome]] is targeted to the mitochondria.<ref name="gardner"/>