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Diversity Takes Shape: Understanding the Mechanistic and Adaptive Basis of Bacterial Morphology

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Myriad morphologies have evolved throughout the bacterial domain.

Bacterial phylogeny derived from genome sequence data for selected species, with an emphasis on morphologically and phylogenetically diverse taxa. Sequence data gathered from the Joint Genome Institute [3] and the National Center for Biotechnology Information [4] were searched for reference genes and aligned using Phylosift [5]. FastTree [6] generated an approximate maximum likelihood tree from the resulting concatenated alignment. The final tree was formatted using iTol [7]. Black dots denote ancestral nodes of selected major taxa: DT, Deinococcus-Thermus; Ac, Actinobacteria; Cf, Chloroflexi; Cn, Cyanobacteria; Fi, Firmicutes (inclusive of Mollicutes); Sp, Spirochetes; PVC, Planctomycetes, Verrucomicrobia, Chlamydiae; Cb, Chlorobi; Bd, Bacteroidetes; α, β, γ, δ, ε, Proteobacteria subdivisions. 1. Bifidobacterium longum. 2. Streptomyces coelicolor (mycelial [multicellular] filament with hyphae and spores). 3. Corynebacterium diphtheriae (two cells, dumbbell and club shapes). 4. Herpetosiphon aurantiacus (filament of multiple cylindrical cells). 5. Calothrix (filament of multiple disk-shaped cells). 6. Mycoplasma genitalium. 7. Spiroplasma culicicola. 8. Lactococcus lactis (predivisional cell). 9. Borrelia burgdorferi. 10. Gimesia maris (previously Planctomyces maris, predivisional cell with proteinaceous stalk). 11. Prosthecochloris aestuarii. 12. Pelodictyon phaeoclathratiforme (filament of multiple trapezoidal cells). 13. Spirosoma linguale. 14. Muricauda ruestringensis (appendage includes nonreproductive bulb). 15. Desulfovibrio vulgaris (two cells, helical and curved shapes). 16. Helicobacter pylori. 17. Caulobacter crescentus (predivisional cell). 18. Hyphomonas neptunium (predivisional cell). 19. Rhodomicrobium vannielii (filament of multiple ovoid cells, one is predivisional). 20. Prosthecomicrobium hirschii. 21. Simonsiella muelleri (filament of multiple curved cells). 22. Nevskia ramosa (two cells with bifurcating slime stalk). 23. Beggiatoa leptomitiformis (filament of multiple, giant cylindrical cells). 24. Thiomargarita nelsonii (single, giant cell). 25. Escherichia coli. 26. Mariprofundus ferrooxydans (single cell with metal-encrusted stalk). Bacterial schematics are not to scale. Species names are colored according to morphology as indicated in the key. Colored dots are appended to indicate species with multiple morphologies. Names of species depicted in schematics are emphasized in large, bold font.

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