Bio

• Bikonts

  Ancestors have a kinetid with 2 flagella, anterior & posterior
• Fusion of the genes of thymidylate synthase (TS) & dihydrofolate reductase (DHFR)


  One protein with 2 functions
• Unikonts

  Ancestors have simple kinetid with 1 basal body & 1 flagellum
• Unikonts

  • Opisthokonta
  • Amoebozoa
• Bikonts

  • Archaeplastida
  • Excavata
  • Rhizaria
  • Chromalveolata
• Alveolates

  • Ciliates
  • Apicomplexa
  • Dinoflagellates
• Alveolates

  • Presence of cortical alveoli underlying the plasma membrane
  • Speciose aquatic unicells, numerous flagella & dimorphic nucleus
  • Macronucleus → gene transcription ; micronucleus → inactive germ nucleus
• Ciliates

  • Cilia → movement or feeding ; most have cell mouth Cytostome
  • Macronucleus: vegetative, synthesis of DNA/RNA
  • Micronucleus: reproductive, transmission of hereditary characteristics
  • The body is covered with a pellicle
• Ciliates - Reproduction

  1. Sexual repro: conjugation, exchange of micronucleus

  2. Asexual repro: transverse binary fission
• Ciliate organelles

  • Trichocysts: anchorage during feeding; protection in Paramecium
  • Toxicysts: defense, capturing preys by paralysis & cytolysis in Didinium
  • Mucocysts: formation of cysts/protective covering in Colpidium
• Apicomplexa

  • Have apical complex → attachment & penetration to host cell; includes: micronemes, rhoptries, dense granules, polar rings of microtubules & conoid (some species)
  • Nearly all are obligate intracellular parasites
• Life cycle of Plasmodium falciparum

  1. Human infection with sporozoites

  2. Asexual reproduction

  3. Sexual reproduction
• Plasmodium falciparum - Human infection

  Infected female anopheles →bites a person→injects saliva with sporozoites into the bloodstream
• Plasmodium falciparum - Asexual reproduction

  1. Exoerythrocytic: Sporozoites→liver cells, in 6-7 days, sporozoites multiply→schizonts→merozoites→bloodstream

  2. Erythrocytic: Merozoites→red blood cells→ring stage: trophozoite→immature erythrocytic schizont→mature schizont→merozoites→bloodstream→parasitaemia
• Plasmodium falciparum - Sexual reproduction

  1. Female anopheles→bites an infected person→blood meal with gametocytes

  2. Gametocytes→gametogenesis: microgametes(male) & macrogametes(female)

  3. In mosquito gut, microgamete→3-time division→8 nuclei; each one fertilizes a macrogamete→zygote→ookinete→penetrates the midgut wall→oocyst(protect the ookinete)

  4. In oocyst, ookinte nucleus divides→thousands of sporozoites→sporogony
• Rhizaria

  • Speciose unicellular eukaryotes, described mainly from rDNA sequences
  • Vary in forms, no clear morphological distinctive characters
  • Most are biciliate amoeboflagellates, produce shells called tests, may be structurally complex and make up the majority of protozoan fossils
• Rhizaria pseudopodia

  • Reticulopodia: reticulated structure forming network, blend to form irregular mesh
  • Filopodia: slender, filamentous, has pointed end, branched or unbranched, consist mostly of cytoplasm and supported by microfilaments (actin)
  • Axopodia: long, thin, supported by microtubules & specialized with phagocytosis
  • Lopopodia: short, blunt & typical for amoeba
• Actinopods

  • Acantharia
  • Heliozoa
  • Radiolaria
• Acantharia

  • The cell consists of central endoplasm and peripheral ectoplasm(calymma), separated by a perforated central capsule
  • Endoplasm contains nucleus, other organelles, & is often brown, red or black. While the ectoplasm contains digestive vacuoles
  • The cell has axopodia that are stiffened by an axoneme
  • They have: 1) skeleton of strontium sulfate/celestite(SrSO4), 2) cell body covered with an outer pellicle & periplasmic cortex, 3) mayonemes, contractile filaments grouped around the spicules
• Heliozoa

  • Spherical, the body consists of outer cortex containing food & contractile vacuoles, and a medulla containing one/many nuclei & base of axopods
  • Covered with shell(test) made of silica or organic material secreted by the organism in form of scales or pieces in a gelatinous covering
• Radiolaria

  • Spherically symmetrical, have complex tests composed of silica, perforated in several patterns forming either lattice-like plate or loose needle-like spicules. Pseudopodia extend through it
  • Chitinous central capsule: encloses the nuclei, divides the cytoplasm, the outer cytoplasm contains many vacuoles and control the buoyancy
• Foraminiferans

  • Globigerina
  • Elphidium
• Foraminiferans

  • Marine, they are benthic or attached to objects
  • Have microscopic snail-like shell of CaCO3 full of tiny holes for reticulopodia projection which make the shells distinctive & preserve well
• Excavata

  • Most are amitochondriate organisms having modified forms of mitochondria (hydrogenosome or mitosome)
  • Those having mitochondria, the cristae are tubular, discoidal or laminar
  • Most have 2,4 or more flagella, many have a ventral feeding groove supported by microtubules with a characteristic ultrastructure
• Kinetoplastida

  • Flagellated protists having a kinetoplast (organelle with large massed DNA) located within the single mitochondrion associated with the flagellar base
  • Many are parasites, some are found in soil & aquatic environment
• Kinetoplastida groups

  • Biflagellate bodonids (order bodonina)
  • Uniflagellate trypanosomatids (order Trypanosomatida)
• Bodonids

  • Have a leading & trailing flagellum, the latter may/may not be attached to cell side. The flagella are used for locomotion & attachment. Their bases are located in the same location of cytostome
• Kinetoplastid diseases

  • African sleeping sickness by Trypanosoma brucei
  • Chagas disease by Trypanosoma cruzi
  • Leishmaniasis by Leishmania
• Life cycle of Trypanosoma brucei

  1. Infected tsetse fly bite→metacyclic trypomastigotes(arrested) in mammalian bloodstream→proliferating long slender forms→ bloodstream infection→penetrate endothelium & invade extravascular tissues including CNS

  2. In bloodstream, long slender forms→arrested short stumpy forms; Fly bites infected person→infected blood meal to midgut-short stumpy form→procyclic trypomastigotes→divide-midgut infection→migrate to proventriculus→asymmetric division→long epimastigote & short epimastigote→ salivary glands

  3. Short epimastigote→attached to epithelium→replication-asymmetric division→free metacyclic trypomastigote
• Metamonada

  • Primitive flagellate amitochondriates who lost mitochondria and retain nuclear genes and organelles(hydrogenosome & mitosome)
  • Have 4 flagella associated with the nucleus → karyomastigont
• Metamonada groups

  • Parabasalids
  • Diplomonads
• Parabasalia

  • Only associated with animals. Some are pathogens (Trichomonas vaginalis causes STD). Parabasalians are commensals/beneficial symbionts, some Trichomonas species live in human gut and mouth
  • Trichomonadids have an axostyle composed of microtubules, connected anteriorly with blepharoplasts & run through the body length. It functions as a supporting rod
  • They have 3-5 free flagella and a recurrent one forming an undulating membrane
• Diplomonadida

  • Small amitochondriate heterotrophic protists. Some are free living but most are commensals in animals' intestines. Some are parasites causing diseases such as Giardia which causes giardiasis (hiker's diarrhea)
  • They have 2 sets of organelles, nuclei, 4 flagella, adhesive disks & one ventral groove. There are two median bodies behind the disks with unknown functions
• Amoebozoa


  • Amoeboid protists possessing lobose pseudopods & tubular mitochondria cristae
  • Includes Entamoeba, Peloxyma & Amoeba. Live as parasites(cause illness)or symbionts
  • Thin elastic plasmalemma; retains & allows the passage of water, O2 & CO2
  • Rigid ectoplasm: plasmagel, fluid endoplasm: plasmasol
  • Have disk-like nucleus, contractile vacuole (osmotic pressure), and food vacuoles
• Amoebozoa - Locomotion


  Endoplasm flows forwards & is converted into ectoplasm, ectoplasm runs backwards, formation of pseudopodium, attachment on surface, cell mass moves towards the pseudopodium
• Amoebozoa - Feeding

  By phagocytosis, surrounds the food with pseudopods, seals it into vacuole to be digested. Some have uroid which accumulates waste and detaches from the cell. When food Is scarce → cysts → new environment
• Amoebozoa pseudopods

  • Lopopods: composed of ecto- & endoplasm
  • Filopods: only ectoplasm
  • Reticulopods: like filopods but mesh-like
  • Axopods: no axoneme, with spiraled microtubules & only to ingest food
• Lobosa

  • Tubilinidae (naked)
  • Arcellinidae (shelled)
• Tubilinidae

  • Naked with asymmetric body & lobopods. Reproduce asexually by binary fission/ budding. Some are parasites, most are endoparasites(in insects,annelids&vertebrates)
  • Most are free-living and some are commensals
• Arcellinidae (Thecamoeba)


  • Have tests with a single aperture or pseudopods emerging. The tests may be secreted from organic material (Arcella) or composed of cemented particles (Difflugia). Asexual reproduction (binary fission)