Model Organisms & Systems — Cross-Cutting Comparison
This note compares the model organisms a biologist actually chooses between when designing an experiment — prokaryote vs unicellular eukaryote vs invertebrate vs vertebrate vs plant — across every Biology library note that touches a system. Each section tabulates the organisms used at that taxonomic level against the dimensions that drive selection (generation time, genome accessibility, ethical burden, translational distance). The final decision tree maps research question types onto the appropriate model so a starting graduate student can narrow from “I study X” to a workable organism in one read.
See also
- cell-molecular-biology
- genetics-and-genomics
- neuroscience-foundations
- immunology-foundations
- microbiology-foundations
- developmental-biology
- ecology-and-evolution
- plant-biology
- marine-biology
- structural-biology
- virology-and-vaccine-platforms
- synthetic-biology-and-bioengineering
- immunoengineering-and-cell-therapy
- single-cell-genomics-deep
- gene-and-rna-therapeutics-deep
- model-organisms-and-sequencing-tech
- cell-lines-and-antibody-catalog
1. The five dimensions every model choice answers
Before picking an organism, every PI implicitly scores against five axes. The textbook says “pick the simplest model that answers the question” — the practical reality is that funding, regulation, animal-facility access, and the local antibody supply chain shift the simplest answer by a tier.
| Dimension | Cheap end | Expensive end | Why it matters |
|---|---|---|---|
| Generation time | E. coli (20 min) | macaque (5 yr to sexual maturity) | how many generations you get per PhD |
| Genome size | M. genitalium (580 kb, 470 genes) | salamander (120 Gb, 40x human) | assembly cost; CRISPR-screen scope |
| Transgenic accessibility | yeast (LiAc-PEG, hours) | non-human primate ($100k+, IACUC, 18mo) | route from hypothesis to mutant |
| Ethical / regulatory burden | bacteria, yeast (none) | NHP (IACUC + USDA + IRB-adjacent) | shapes whether the work happens at all |
| Evolutionary distance from human | none | bacteria | translational relevance to medicine |
A useful rule: drop one tier in evolutionary distance per order of magnitude in throughput. Yeast screens 10⁵ deletions; mouse screens 10² genes well; macaque screens 1 condition. The deeper question is whether the biology you care about exists at that tier — synapses don’t exist in yeast, multicellularity doesn’t exist in E. coli, adaptive immunity doesn’t exist in invertebrates.
2. Prokaryotic models
The genetics workhorse layer. Most molecular biology textbooks were written from E. coli K-12 data; the rest are specialists chosen for a single biological phenomenon.
| Organism | Strain / sequence | Generation | Genome | Strength | When to use | Caveats | Linked note |
|---|---|---|---|---|---|---|---|
| E. coli K-12 | MG1655, DH5α, BL21(DE3) | 20 min | 4.6 Mb, ~4,300 genes | tooling depth — every plasmid, antibiotic, screen, biosensor | molecular biology, protein expression, synthetic biology, biosensors | not a real environmental organism; lab-adapted | microbiology-foundations / synthetic-biology-and-bioengineering |
| E. coli (pathogenic) | EHEC O157:H7, ETEC, UPEC | 20 min | 5.5 Mb | host-pathogen for enteric disease, T3SS biology | gut pathogen mechanisms, AMR | BSL-2 (O157:H7), distinct strain handling | microbiology-foundations |
| B. subtilis 168 | trpC2 marker | 25 min | 4.2 Mb | Gram-positive cell wall biology, sporulation, natural competence | sporulation, biofilm, cell-cycle in G+ context | distinct cell-envelope chemistry from E. coli | microbiology-foundations |
| M. tuberculosis H37Rv | also CDC1551, Erdman | 24 hr (extremely slow) | 4.4 Mb, ~4,000 genes | granuloma + macrophage pathogenesis, latency, drug discovery for TB | TB drug + vaccine pipelines | BSL-3 — only a few hundred labs worldwide; long experiments | microbiology-foundations / immunology-foundations |
| M. smegmatis | mc²155 | 3 hr | 7 Mb | fast-growing mycobacterium proxy | preliminary TB tooling, BSL-2 surrogate | physiology differs from M. tb | microbiology-foundations |
| V. cholerae | El Tor N16961, classical O395 | 30 min | 4 Mb (2 chromosomes) | quorum sensing (CqsA/LuxO), Type VI secretion, biofilm-to-virulence switch | quorum sensing, marine pathogen biology | requires BSL-2, two-chromosome layout is unusual | microbiology-foundations |
| C. crescentus CB15N | NA1000 | 90 min | 4 Mb | asymmetric cell division — stalked vs swarmer | cell-cycle asymmetry, polar protein localization | niche tooling, not universally adapted | cell-molecular-biology |
| R. sphaeroides 2.4.1 | 4 hr (photoheterotrophic) | 4.6 Mb (2 chromosomes + 5 plasmids) | photosynthesis machinery, anaerobic respiration | photosynthetic reaction center, redox biology | finicky photobioreactor handling | microbiology-foundations | |
| D. radiodurans R1 | ATCC 13939 | 100 min | 3.3 Mb (2 chrom + 2 plasmids) | survives 5,000 Gy ionizing radiation (1,000× lethal human dose) | DNA-damage repair, extremophile biology | requires γ-source for canonical experiments | microbiology-foundations |
| M. genitalium G37 | 16 hr | 0.58 Mb, 470 genes | minimal-genome paradigm — JCVI-syn3.0 (473 genes) derivative | minimal genome research, synthetic biology bottom-up | extremely slow; few traditional tools | synthetic-biology-and-bioengineering | |
| Synechocystis sp. PCC 6803 | 12 hr | 3.6 Mb | cyanobacterial photosynthesis, naturally competent | photosynthesis, carbon fixation, biofuels chassis | photoautotrophic culture requires light + CO₂ | microbiology-foundations | |
| S. coelicolor A3(2) | 4 hr | 8.7 Mb (linear) | secondary metabolite biosynthesis, sporulating mycelium | antibiotic discovery, BGC research | linear chromosome; complex life cycle | microbiology-foundations |
Decision logic at this tier:
- Need fast doubling + every plasmid/promoter ever made → E. coli K-12.
- Need Gram-positive context (cell wall, secretion, sporulation) → B. subtilis.
- Studying TB drugs/vaccines → M. tuberculosis H37Rv (BSL-3) or M. smegmatis (BSL-2 surrogate).
- Quorum sensing or T6SS → V. cholerae (or V. fischeri for the canonical LuxI/R).
- Photosynthesis → R. sphaeroides (anoxygenic) or Synechocystis (oxygenic).
- Radiation resistance / extreme DNA repair → D. radiodurans.
- Minimal-genome / chassis questions → M. genitalium (or now JCVI-syn3A descendants).
3. Unicellular eukaryotes
The genetics-with-eukaryotic-machinery tier. You get sexual reproduction, organelles, chromatin, true cell cycle, secretory pathway — without animal welfare burden.
| Organism | Strain | Generation | Genome | Strength | When to use | Caveats | Linked note |
|---|---|---|---|---|---|---|---|
| S. cerevisiae (budding yeast) | S288C, W303, BY4741 | 90 min | 12 Mb, ~6,000 genes | full genome deletion library, two-hybrid origin, cell-cycle (Hartwell), autophagy (Ohsumi) — multiple Nobels | basic eukaryotic cell biology, cell cycle, genetic screens | budding division is asymmetric; no metazoan signaling like Wnt/Hedgehog | cell-molecular-biology / genetics-and-genomics |
| S. pombe (fission yeast) | 972h⁻, 975h⁺ | 2.5 hr | 14 Mb, ~5,000 genes | symmetric fission, mammal-like cell cycle, cdc2/CDK1 paradigm (Nurse, Nobel 2001) | cell-cycle regulation, chromosome biology, RNAi (intact unlike S. cerevisiae) | tooling thinner than budding yeast | cell-molecular-biology |
| C. albicans | SC5314 | 90 min | 14 Mb, diploid | fungal pathogenesis, dimorphic yeast-hyphal switch | fungal pathogen biology, biofilms, host-pathogen | diploid + parasexual cycle complicates genetics | microbiology-foundations |
| A. fumigatus | Af293, CEA10 | 6 hr | 29 Mb | mold pathogen, melanin biology, invasive aspergillosis | invasive fungal infections, antifungal discovery | BSL-2, aerosolizable conidia | microbiology-foundations |
| N. crassa | OR74A, Mauriceville | 4 hr | 41 Mb | circadian rhythms (frq/FRQ), epigenetics (DIM-5 H3K9 methylation), RIP mutation | circadian biology, fungal genetics, methylation | dictionary of canonical mutants, fewer modern users | genetics-and-genomics |
| C. reinhardtii | CC-125, CC-503 | 8 hr | 121 Mb, 17 chromosomes | photosynthesis + flagellar assembly (IFT discovered here, Rosenbaum) | photosynthesis, cilium/flagellum, algal biofuels | mating-type maintenance burden | plant-biology / cell-molecular-biology |
| T. brucei | Lister 427, TREU927 | 6 hr (BSF) | 26 Mb | RNA editing, antigenic variation (VSG switching), kinetoplast biology | trypanosome biology, neglected tropical disease | BSL-2; bloodstream-form vs procyclic culture mode-shift | microbiology-foundations |
| Dictyostelium discoideum | AX2, AX3, AX4 | 8 hr | 34 Mb | facultative multicellularity (aggregation + slug + fruiting body), chemotaxis | chemotaxis, cell-cell signaling, social evolution, transition to multicellularity | unique cAMP signaling biology | cell-molecular-biology / developmental-biology |
| P. falciparum | 3D7, Dd2, HB3 | 48 hr blood cycle | 23 Mb, 14 chromosomes | malaria biology, antigenic variation (var genes), drug-resistance evolution | malaria drug + vaccine discovery | BSL-2, requires human RBC culture, slow | microbiology-foundations |
| T. gondii | RH, ME49, Pru | 7 hr | 65 Mb | apicomplexan biology, host-cell invasion, conditional cyst-forming life cycle | apicomplexan biology, host-pathogen, conditional cysts | BSL-2, requires HFF or mouse fibroblast feeders | microbiology-foundations |
| Naegleria gruberi | NEG | 5 hr | 41 Mb | rapid amoeba ↔ flagellate transition (90 min); de novo flagellar assembly | flagellar assembly, cytoskeletal regulation, amoeboflagellate transitions | niche; thinner toolset | cell-molecular-biology |
| T. thermophila | SB210 | 3 hr | 103 Mb (MAC) | telomerase discovery (Blackburn-Greider-Szostak, Nobel 2009), nuclear dimorphism | telomerase, ciliate biology, nuclear-dimorphism research | macronucleus vs micronucleus genetics is unique | genetics-and-genomics |
| P. tetraurelia | 51-S, d4-2 | 5 hr | 72 Mb | nuclear dimorphism, autogamy, IES excision | genome programmed-rearrangement, ciliate epigenetics | similar idiosyncrasies to Tetrahymena | genetics-and-genomics |
Decision logic at this tier:
- Eukaryotic genetics + every screen tool ever → S. cerevisiae.
- Mammal-like cell cycle / RNAi / symmetric division → S. pombe.
- Photosynthesis with mature genetics → C. reinhardtii.
- Multicellularity emergence / chemotaxis → Dictyostelium.
- Telomere/telomerase → T. thermophila.
- Trypanosome / kinetoplastid biology → T. brucei.
- Apicomplexan / malaria → P. falciparum (or T. gondii as faster lab proxy).
- Fungal pathogen → C. albicans (yeast) or A. fumigatus (mold).
4. Invertebrate models
Where you get nervous systems, multicellular development, behavior, and immune-like responses without vertebrate regulatory load.
| Organism | Strain | Generation | Genome | Strength | When to use | Caveats | Linked note |
|---|---|---|---|---|---|---|---|
| D. melanogaster (fruit fly) | Oregon-R, w¹¹¹⁸, Canton-S, Vienna Drosophila Resource Center (VDRC), BDRC stocks | 10 d at 25 °C | 144 Mb, ~14,000 genes | unmatched genetics toolkit — GAL4/UAS, FLP/FRT, balancer chromosomes, MARCM, Trojan exons, BDSC stocks; Hox cluster discovered here (Lewis, Nüsslein-Volhard, Wieschaus, Nobel 1995) | developmental genetics, neurobiology, behavior, aging, cancer (eye-disc models) | open circulatory system; no acquired immunity | developmental-biology / genetics-and-genomics / neuroscience-foundations |
| C. elegans | N2 Bristol, Hawaiian CB4856 | 3.5 d at 20 °C | 100 Mb, ~20,000 genes | complete cell lineage (Sulston), complete neural connectome (302 neurons, White 1986), apoptosis genetics (Horvitz, Nobel 2002), RNAi by feeding (Fire, Mello, Nobel 2006) | apoptosis, lineage, aging, neural circuits, RNAi screens | small size makes electrophysiology hard; hermaphroditism | developmental-biology / neuroscience-foundations |
| Aplysia californica | wild-collected | 1 yr | 927 Mb | gill-withdrawal reflex (Kandel, Nobel 2000); large identifiable neurons (~1 mm) | learning + memory, neurobiology, synaptic facilitation | wild-collected, expensive aquarium husbandry | neuroscience-foundations |
| Hydra vulgaris / magnipapillata | AEP, 105 | 3 d | 1.3 Gb | whole-body regeneration, simple nerve net (~5,600 neurons), interstitial stem cells | regeneration, stem cells, neural net minimum | clonal lines vary; molecular tools thinner than worm/fly | developmental-biology |
| D. pseudoobscura | various | 14 d | 161 Mb | speciation genetics (Dobzhansky 1930s+), reproductive isolation | speciation, reproductive isolation, population genetics | thinner toolkit than D. melanogaster | ecology-and-evolution |
| Schmidtea mediterranea | CIW4 sexual, asexual | 3 wk | 800 Mb | planarian whole-body regeneration, pluripotent neoblasts (~20% of cells) | regeneration, adult pluripotent stem cells, body-axis re-patterning | dynamic genome assemblies still improving | developmental-biology |
| Tribolium castaneum | Georgia-1, San Bernardino | 30 d | 204 Mb | short-germ embryogenesis (more ancestral than Drosophila long-germ), Hox + segmentation | segmentation evolution, evo-devo, RNAi by injection (systemic) | slower than fly; smaller community | developmental-biology / ecology-and-evolution |
| Daphnia pulex / magna | various | 7 d | 200 Mb | cyclical parthenogenesis, epigenetic inheritance of stress, environmental toxicology standard (OECD 211) | ecotoxicology, epigenetics, predator-induced plasticity | clonal lines required for genetics | ecology-and-evolution |
| Lymnaea stagnalis (pond snail) | wild-derived lab lines | 90 d | 2.8 Gb | memory consolidation in single identifiable neuron (RPeD1), aerial-respiration learning | memory consolidation, single-neuron learning | molecular tools sparse | neuroscience-foundations |
| Caenorhabditis briggsae | AF16 | 3.5 d | 108 Mb | sister species to C. elegans for comparative + ev-evo genomics | genome evolution, comparative behavior, hybrid breakdown | smaller community | ecology-and-evolution |
| Octopus bimaculoides | wild-collected | 1.5 yr | 2.7 Gb | RNA editing in cephalopod brain, complex behavior + camouflage | invertebrate cognition, RNA editing in nervous system | wild-collected, expensive husbandry, short-lived | neuroscience-foundations |
| Nematostella vectensis (starlet anemone) | CH2 | 90 d | 357 Mb | cnidarian biology, basal-metazoan body plan | basal-metazoan biology, evo-devo of bilaterians vs cnidarians | smaller community, slow generation | developmental-biology |
Decision logic at this tier:
- Genetics + behavior + development + neuro with the deepest toolkit → D. melanogaster.
- Lineage / connectome / RNAi / aging → C. elegans.
- Learning + memory at single-neuron resolution → Aplysia (or Lymnaea for pond-snail variant).
- Whole-body regeneration → Schmidtea (planarian) or Hydra.
- Evo-devo / segmentation outside the Drosophila long-germ paradigm → Tribolium.
- Aquatic ecotoxicology → Daphnia.
- RNA editing / cephalopod cognition → Octopus bimaculoides.
5. Vertebrate models
Where vertebrate body plan, adaptive immunity, true endoskeleton, and translational relevance live. Regulatory + cost ramp up sharply.
| Organism | Strain / line | Generation | Genome | Strength | When to use | Caveats | Linked note |
|---|---|---|---|---|---|---|---|
| D. rerio (zebrafish) | AB, TL, Tübingen, casper (no melanocytes) | 3 mo | 1.5 Gb, ~26,000 genes | external transparent embryos, large clutches (200 eggs), heart regeneration, GAL4-UAS, Tol2 transgenesis | developmental biology, neural circuits, cardiac regeneration, drug-toxicity screens | gene duplication from teleost WGD (~340 Mya) — paralog navigation | developmental-biology |
| X. laevis (African clawed frog) | wild, J-strain | 1 yr | 3.1 Gb (allotetraploid) | huge oocytes (1 mm) → electrophysiology + biochemistry, mitotic spindle assembly | cell-cycle biochemistry, oocyte maturation, transport channel expression | tetraploid genome complicates genetics | cell-molecular-biology / developmental-biology |
| X. tropicalis | Nigerian, Ivory Coast | 5 mo | 1.7 Gb (diploid) | diploid frog with smaller faster genetics than X. laevis | developmental genetics in a frog with TALEN/CRISPR ease | smaller eggs; smaller community than X. laevis | developmental-biology |
| G. gallus (chick embryo) | White Leghorn | 21 d incubation | 1.2 Gb | accessible embryo (window-in-egg surgery), classic neural crest discovery, electroporation | neural crest, limb development, cardiac development, classical embryology | adult genetics weak; husbandry IACUC-burdened post-hatch | developmental-biology |
| M. musculus (mouse) | C57BL/6J, BALB/c, 129, FVB, NSG/NRG (immunodeficient), Cre lines, TCGA-equivalents | 10 wk | 2.7 Gb, ~22,000 genes | Cre-lox, every cassette knockout/knockin, KOMP/IMPC, immune cell panel, every disease model | almost every disease question; immunology, cancer, neuro, metabolism | distinct immune system from humans; IACUC; cost | genetics-and-genomics / immunology-foundations / cell-lines-and-antibody-catalog |
| R. norvegicus (rat) | Sprague-Dawley, Wistar, Lewis, BN, F344 | 11 wk | 2.6 Gb | larger than mouse (better surgery + cannulation), classical behavior + cardiovascular | cardiovascular, neurobehavior, toxicology, surgical models | genetic tools lag mouse; CRISPR closed most of the gap by 2018 | neuroscience-foundations |
| Macaca mulatta (rhesus macaque) | Indian, Chinese origin | 4 yr | 3.1 Gb | closest practical NHP — vaccine + neural circuit + cognition | HIV vaccine, primate cognition, deep-brain interfaces (Neuralink-class) | extreme cost ($10k+ per animal), 18-mo IACUC pipeline, ethical scrutiny | neuroscience-foundations / immunology-foundations |
| Macaca fascicularis (cynomolgus) | Mauritian, Cambodian | 4 yr | 3 Gb | preferred for pharma toxicology + tox-PK | regulatory toxicology, ADA assays, biologic safety | post-COVID supply shock 2022+ — prices doubled | immunology-foundations |
| Pan troglodytes (chimpanzee) | research lines | 13 yr | 3.1 Gb | closest evolutionary relative (~98.8% protein identity) | comparative cognition, comparative genomics | research banned/retired in most jurisdictions (NIH 2015 retirement); use sparingly with extreme justification | ecology-and-evolution |
| Sus scrofa (pig, miniature) | Yucatan, Göttingen | 9 mo | 2.5 Gb | size + cardiovascular + skin similar to human, xenotransplant donor (eGenesis 10x KO pigs) | xenotransplant, cardiac surgery, wound healing | husbandry expensive | immunoengineering-and-cell-therapy |
| Marmoset (Callithrix jacchus) | colony-bred | 18 mo | 2.7 Gb | small NHP, twin births, fluorescent transgenics (Sasaki 2009) | NHP genetics, neural circuits at NHP scale with mouse-like tractability | husbandry expensive; smaller community | neuroscience-foundations |
| Dog (Canis lupus familiaris) | beagle | 18 mo | 2.4 Gb | spontaneous cancer model (osteosarcoma, lymphoma) | comparative oncology (NCI COTC), cardiology | regulatory + public-perception load | gene-and-rna-therapeutics-deep |
Decision logic at this tier:
- Cheap developmental genetics with transparent embryos → zebrafish.
- Oocyte biochemistry / cell-free extracts → Xenopus laevis (or tropicalis for CRISPR).
- Embryology + neural crest → chick.
- Mammalian disease + immunology + every Cre line ever → mouse.
- Larger surgery + behavior than mouse → rat.
- Translational primate (vaccine, neural circuit) → macaque (rhesus or cynomolgus).
- Cardiac / xeno → pig.
- Spontaneous oncology that mirrors human → dog.
6. Plant models
Plant biology has its own ecosystem because reverse genetics in plants behaves differently — long generation, polyploidy, distinct transgenic toolkits.
| Organism | Line | Generation | Genome | Strength | When to use | Caveats | Linked note |
|---|---|---|---|---|---|---|---|
| A. thaliana | Col-0, Ler-0, Ws | 6 wk | 135 Mb, 27,000 genes | small genome, T-DNA insertion lines (SALK, SAIL, GABI-Kat), every promoter ever | plant genetics, flowering, immunity, root development | not a crop — biology can diverge from monocots | plant-biology |
| Z. mays (maize) | B73, Mo17, W22 | 4 mo | 2.3 Gb | C4 photosynthesis, transposon biology (McClintock, Nobel 1983), heterosis, kernel layers as developmental fields | crop genetics, C4 biology, transposon biology | large stature; field requirements | plant-biology / genetics-and-genomics |
| O. sativa (rice) | Nipponbare (japonica), 93-11 (indica) | 5 mo | 389 Mb | monocot crop with smallest sequenced cereal genome | monocot biology, rice breeding, C3 monocot photosynthesis | tropical greenhouse requirements | plant-biology |
| Brachypodium distachyon | Bd21 | 12 wk | 272 Mb | grass model with Arabidopsis-like tractability | temperate grass biology, cell-wall research | smaller community | plant-biology |
| P. patens (moss) | Gransden, Villersexel | 4 mo | 480 Mb | high-frequency homologous recombination (gene targeting in plants), haploid-dominant life cycle | gene targeting in plants, evo-devo of land plants, polarity in apical growth | growth on agar plates (Knop medium) | plant-biology |
| M. polymorpha (liverwort) | Tak-1, Tak-2 | 8 wk | 226 Mb | basal land plant, dioecious | early land-plant evolution, hormone biology | smaller community | plant-biology |
| S. lycopersicum (tomato) | M82, Heinz 1706, Micro-Tom | 4 mo | 950 Mb | fleshy fruit ripening, RNAi (Flavr Savr 1994 — first GMO crop), efficient Agrobacterium transformation | fruit biology, breeding, hormone biology in dicots | large genome; long generation | plant-biology |
| Nicotiana benthamiana | LAB | 4 mo | 3 Gb (allopolyploid) | Agro-infiltration powerhouse for transient expression (a CRISPR-screening + vaccine antigen workhorse) | transient expression, plant-pathogen, VIGS | not for genetics — polyploid; LAB-strain RDR1 mutation | plant-biology |
| Glycine max (soybean) | Williams 82 | 4 mo | 1.1 Gb (paleopolyploid) | legume + nodulation model | nodulation, legume biology, oil-seed | paleotetraploid genome | plant-biology |
| M. truncatula (barrelclover) | A17 | 12 wk | 415 Mb | legume model with smaller faster genetics than soy | nodulation + mycorrhiza | smaller community | plant-biology |
| C. reinhardtii (Chlamydomonas) | CC-125 | 8 hr | 121 Mb | unicellular alga proxy for plant biology | photosynthesis, flagella, chloroplast biology | already listed under unicellular eukaryotes | plant-biology |
Decision logic at this tier:
- Plant genetics + every T-DNA insertion → A. thaliana.
- Monocot / cereal crop biology → maize (warm) or rice (tropical) or Brachypodium (lab grass model).
- Gene targeting via homologous recombination → P. patens.
- Transient protein expression / VIGS / Agro-infiltration → N. benthamiana.
- Fruit biology → tomato.
- Nodulation / legume → M. truncatula (or soy if you need crop relevance).
- Early-land-plant evolution → P. patens or M. polymorpha.
7. Five-axis cross-organism summary
Pulling the per-organism columns together. TT = transgenic tractability (1=trivial, 5=heroic); EB = ethical burden (1=none, 5=NHP IACUC).
| Organism | Gen time | Genome (Mb) | TT | EB | Translational distance |
|---|---|---|---|---|---|
| E. coli K-12 | 20 min | 4.6 | 1 | 1 | far (bacteria) |
| B. subtilis | 25 min | 4.2 | 1 | 1 | far |
| M. tuberculosis | 24 hr | 4.4 | 3 | 2 (BSL-3) | medium for TB |
| V. cholerae | 30 min | 4 | 2 | 2 (BSL-2) | medium for cholera |
| S. cerevisiae | 90 min | 12 | 1 | 1 | far for animals, near for cell bio |
| S. pombe | 2.5 hr | 14 | 2 | 1 | similar |
| C. albicans | 90 min | 14 | 2 | 2 (BSL-2) | direct for candidiasis |
| P. falciparum | 48 hr | 23 | 4 | 2 | direct for malaria |
| Dictyostelium | 8 hr | 34 | 2 | 1 | far |
| D. melanogaster | 10 d | 144 | 1 | 1 | medium |
| C. elegans | 3.5 d | 100 | 1 | 1 | medium |
| Hydra | 3 d | 1,300 | 3 | 1 | far |
| Schmidtea | 3 wk | 800 | 4 | 1 | far |
| D. rerio (zebrafish) | 3 mo | 1,500 | 2 | 2 | near for development |
| X. laevis | 1 yr | 3,100 (allotet) | 4 | 2 | medium |
| Chick | 21 d incub | 1,200 | 3 | 2 | near for development |
| Mouse | 10 wk | 2,700 | 1 (for KO/KI lines) | 3 (IACUC) | very near |
| Rat | 11 wk | 2,600 | 2 | 3 (IACUC) | near |
| Rhesus macaque | 4 yr | 3,100 | 5 | 5 (NHP) | very near |
| Pig (minipig) | 9 mo | 2,500 | 4 | 4 | near (cardio, skin, xeno) |
| Marmoset | 18 mo | 2,700 | 4 | 5 (NHP) | very near for neuro |
| A. thaliana | 6 wk | 135 | 1 (floral dip) | 1 | direct for plants |
| Maize | 4 mo | 2,300 | 3 | 1 | direct for crop |
| Rice | 5 mo | 389 | 3 | 1 | direct for crop |
| P. patens | 4 mo | 480 | 2 (HR-based) | 1 | direct for early land plants |
| N. benthamiana | 4 mo | 3,000 (allopolyploid) | 1 (Agro-infiltration) | 1 | direct for plant transient |
8. The Big Three for translational medicine
Most disease-relevant biology in 2026 happens in three organisms with overlapping but distinct strengths.
| Mouse (M. musculus) | Zebrafish (D. rerio) | Macaque (M. mulatta / fascicularis) | |
|---|---|---|---|
| Generation | 10 wk | 3 mo | 4 yr |
| Per-animal cost | $30–300 | $0.50–5 | $10–25k |
| Transgenic ease | trivial (KO/KI on demand at JAX) | moderate (Tol2 + CRISPR) | extreme (years; cost-prohibitive at scale) |
| Adaptive immunity | yes (distinct from human) | yes (similar lymphoid + V(D)J) | yes (~98% identical to human) |
| Per-PI capacity | 10,000+ animals (typical large lab) | 100,000+ (huge facility) | 10–50 |
| Strength | every genetic perturbation, every Cre line | high-throughput drug screens in vivo, transparent embryos | translational vaccine + neural-interface |
| Weakness | many drugs/biologics work in mouse but fail in humans | distance from mammal physiology | cost + ethics + slow |
| Linked note | immunology-foundations / immunoengineering-and-cell-therapy | developmental-biology | virology-and-vaccine-platforms |
This is why the standard preclinical pipeline goes (in vitro cell line) → mouse → cyno macaque → human: mouse covers genetics, macaque covers physiology, cell lines cover throughput.
9. The “organism-free” turn
In 2020–2026 a major shift: many questions that previously required model organisms now use iPSC-derived organoids (cerebral, intestinal, kidney, retina, lung, liver, cardiac), 3D-printed tissue constructs, microphysiological systems (MPS) / organ-on-chip, or human in-silico simulation (CompuCell3D, PhysiCell, Cellular Potts in 2026 with ML-trained parameter inference). Examples:
- Cerebral organoids (Lancaster + Knoblich, 2013+; now Pasca lab assembloids 2022+) reduce neurodevelopmental disease work from rodent to human cell context.
- Intestinal organoids (Clevers, 2009+) replace much enteric pathogen-host work formerly done in mouse.
- Kidney organoids (Takasato, Little, 2015+; Bonventre, Morizane, 2019+) advance nephrotoxicity screens.
- Retinal organoids (Sasai 2011+; Eldred 2018+) inform IRD gene therapy.
- Cardiac organoids / engineered heart tissue (EHT) (Eschenhagen lab 2002+; Lewis-Israeli 2021+) replace some rodent cardiac work.
- Assembloid + fused organoids (Pasca lab, Stanford 2020+) combine cortical + striatal + thalamic + spinal-cord neural tissue.
- MPS / OOC: Emulate Bio “lung-chip” + “liver-chip” + “intestine-chip”; Mimetas OrganoPlate; Hesperos human-on-chip; CN Bio PhysioMimix. FDA Modernization Act 2.0 (2022) explicitly allows OOC + organoid data in IND submissions.
These do not eliminate animal models — they shift earliest mechanism + safety work upstream of the rodent stage, which both improves translation and reduces animal use under the 3Rs framework (Russell-Burch 1959 — Replace, Reduce, Refine).
Adjacent
- Cells / antibodies / sequencing — cell-lines-and-antibody-catalog and model-organisms-and-sequencing-tech for the supply-chain catalog (JAX, ATCC, ECACC, Charles River, Taconic, BDSC, CGC, ZIRC, ZFIN).
- Genomics tooling — single-cell-genomics-deep for the sequencing platforms run on every organism above.
- Therapeutics — gene-and-rna-therapeutics-deep and immunoengineering-and-cell-therapy for what mouse + macaque preclinicals lead into.
- Structural biology — cryo-em-and-structural-determination for the proteins extracted from the organisms above.
- Ecology / wild biology — ecology-and-evolution for organisms used in the field rather than the lab.
- Plant systems specifically — plant-biology.
- Marine systems — marine-biology for additional aquatic models (sea urchin embryos, ascidians, sponges).
- Chemistry side — biochemistry-foundations for the molecules studied across these organisms.
When to pick what
Narrow by research-question type first; budget + regulatory + facility access second.
What's the question?
├─ Molecular biology of any conserved process
│ └─ E. coli (prokaryote) or S. cerevisiae (eukaryote) — cheapest fastest answer
├─ Cell-cycle regulation
│ ├─ Symmetric + mammal-like → S. pombe
│ └─ Asymmetric polar + landmark proteins → C. crescentus or budding yeast
├─ Photosynthesis
│ ├─ Anoxygenic + reaction center → R. sphaeroides
│ └─ Oxygenic + plant-like → Synechocystis or C. reinhardtii
├─ Multicellularity emergence
│ └─ Dictyostelium (chemotaxis aggregation) or N. vectensis (basal metazoan)
├─ Developmental biology
│ ├─ Genetics with infinite tools → D. melanogaster (long-germ) or C. elegans (lineage)
│ ├─ Short-germ ancestral pattern → Tribolium
│ ├─ Transparent vertebrate embryo → zebrafish
│ ├─ Oocyte biochemistry / cell-free extract → Xenopus
│ └─ Neural crest + window-in-egg → chick
├─ Regeneration
│ ├─ Whole-body, neoblast stem cells → Schmidtea (planarian)
│ ├─ Tissue regen + simple nerve net → Hydra
│ └─ Vertebrate heart regen → zebrafish (or axolotl outside this catalog)
├─ Neuroscience
│ ├─ Connectome / circuit at low N → C. elegans (302 neurons mapped)
│ ├─ Genetics + behavior + circuit at medium scale → Drosophila
│ ├─ Single large neurons + learning → Aplysia or Lymnaea
│ ├─ Mammalian circuits at scale → mouse (then rat for surgery)
│ └─ Primate cognition + BMI → macaque or marmoset
├─ Immunology + adaptive immunity
│ ├─ Genetics-heavy mechanism → mouse
│ ├─ Closer to human → cynomolgus macaque
│ └─ Innate-only invertebrate → Drosophila (Toll) or C. elegans
├─ Drug discovery
│ ├─ Target ID + screen → cell lines (see [[Sciences/Biology/Tier3/cell-lines-and-antibody-catalog]])
│ ├─ Whole-animal screen → zebrafish embryos at 96-well scale
│ ├─ Disease model → mouse (KO/KI as needed)
│ └─ Preclinical safety + PK/PD → rat + cynomolgus macaque
├─ Pathogen biology
│ ├─ Enteric → V. cholerae, EHEC E. coli
│ ├─ Mycobacterial → M. tuberculosis (BSL-3) or M. smegmatis (BSL-2)
│ ├─ Apicomplexan → P. falciparum or T. gondii
│ ├─ Fungal → C. albicans or A. fumigatus
│ └─ Viral → see [[Sciences/Biology/virology-and-vaccine-platforms]]
├─ Plant biology
│ ├─ Genetics workhorse → A. thaliana
│ ├─ Cereal crop → maize / rice / Brachypodium
│ ├─ Gene-targeting by HR → P. patens
│ ├─ Transient expression / VIGS → N. benthamiana
│ └─ Legume + nodulation → M. truncatula
├─ Aging / longevity
│ └─ C. elegans (fast, well-characterized) → fly → mouse
├─ Cancer
│ ├─ Genetics + KO → mouse
│ ├─ Spontaneous → dog (comparative oncology)
│ └─ Tumor + drug screen → patient-derived organoids + xenografts in NSG mouse
├─ Translational therapy (gene / cell)
│ └─ Mouse → NHP (cyno) → human (see [[Sciences/Biology/gene-and-rna-therapeutics-deep]])
└─ Question doesn't require an organism
→ iPSC-derived organoids + MPS + in silico (FDA Modernization Act 2.0 path)
The single biggest practical lesson 2010–2026: start the cheapest organism that contains your biology, scale up only once you know what to test. A 90 % loss in throughput per tier-up means the wrong starting organism multiplies cost by 100× before you ever get to the answer. The cheapest organism is rarely the one your PI used in their thesis.