Chloroflexota
The Chloroflexota are a phylum of bacteria containing isolates with a diversity of phenotypes, including members that are aerobic thermophiles, which use oxygen and grow well in high temperatures; anoxygenic phototrophs, which use light for photosynthesis (green non-sulfur bacteria); and anaerobic halorespirers, which uses halogenated organics (such as the toxic chlorinated ethenes and polychlorinated biphenyls) as electron acceptors.
| Chloroflexota | |
|---|---|
| Scientific classification | |
| Domain: | Bacteria |
| Clade: | Terrabacteria |
| Phylum: | Chloroflexota Garrity and Holt 2021[1] |
| Classes | |
| |
| Synonyms | |
| |
The members of the phylum Chloroflexota are monoderms (that is, have one cell membrane with no outer membrane), but they stain mostly gram-negative.[2] Many well-studied phyla of bacteria are diderms and stain gram-negative, whereas well-known monoderms that stain Gram-positive include Firmicutes (or Bacillota) (low G+C gram-positives), Actinomycetota (high-G+C gram-positives) and Deinococcota (gram-positive diderms with thick peptidoglycan).
History
The taxon name was created in the 2001 edition of Volume 1 of Bergey's Manual of Systematic Bacteriology and is the Latin plural of the name Chloroflexus, the name of the type genus of the phylum, a common practice.[3]
In 1987, Carl Woese, regarded as one of the forerunner of the molecular phylogeny revolution, divided Eubacteria into 11 divisions based on 16S ribosomal RNA (SSU) sequences and grouped the genera Chloroflexus, Herpetosiphon and Thermomicrobium into the "green non-sulfur bacteria and relatives",[4][5] which was temporarily renamed as "Chloroflexi" in Volume One of Bergey's Manual of Systematic Bacteriology.[6]
Chloroflexota being a deep branching phylum (see Bacterial phyla), it was considered in Volume One of Bergey's Manual of Systematic Bacteriology to include a single class with the same name.[6] Since 2001, however, new classes have been created thanks to newly discovered species, and the phylum Chloroflexi is now divided into several classes.
"Dehalococcoidetes" is a placeholder name given by Hugenholtz & Stackebrandt, 2004,[7] after "Dehalococcoides ethenogenes" a species partially described in 1997.[8] The first species fully described was Dehalogenimonas lykanthroporepellens, by Moe et al. 2009,[9] but in the description of that species the class was not made official nor were families or orders laid out as the two species share only 90% 16S ribosomal RNA identity, meaning that they could fall in different families or even orders.[9]
Recent phylogenetic analysis of the Chloroflexota has found very weak support for the grouping together of the different classes currently part of the phylum.[10] The six classes that make up the phylum did not consistently form a well-supported clade in phylogenetic trees based on concatenated sequences for large datasets of proteins, and no conserved signature indels were identified that were uniquely shared by the entire phylum.[10] However, the classes Chloroflexi and Thermomicrobia were found to group together consistently by both the usual phylogenetic means and the identification of shared conserved signature indels in the 50S ribosomal protein L19 and the enzyme UDP-glucose 4-epimerase.[10] It has been suggested that the phylum Chloroflexi sensu stricto should comprise only the classes Chloroflexi and Thermomicrobia, and the other four classes ("Dehalococcoidetes," Anaerolineae, Caldilineae and Ktedonobacteria) may represent one or more independent phyla branching in the neighborhood of the Chloroflexi.[10]
Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[11] and National Center for Biotechnology Information (NCBI).[12]
| 16S rRNA based LTP_12_2021[13][14][15] | 120 marker proteins based GTDB 07-RS207[16][17][18] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
Taxonomy
Genus "Candidatus Chlorotrichoides" corrig. Oren et al. 2020 ["Candidatus Chlorothrix" Klappenbach & Pierson 2004 non Dyar 1921 non Berger-Perrot 1982[22]]
Genus "Candidatus Nitrocaldera" Spieck et al. 2020
Genus "Candidatus Nitrotheca" Spieck et al. 2020
Class "Limnocylindria" Mehrshad et al. 2018
- Order "Limnocylindrales" Mehrshad et al. 2018
- Family "Limnocylindraceae" Mehrshad et al. 2018 (SL56)
- Genus "Candidatus Aquidulcis" corrig. Rodriguez-R et al. 2020
- Genus "Candidatus Limnocylindrus" Mehrshad et al. 2018
- Family "Limnocylindraceae" Mehrshad et al. 2018 (SL56)
Class Ktedonobacteria Cavaletti et al. 2007 emend. Yabe et al. 2010
- Order Thermogemmatisporales Yabe et al. 2011
- Family Thermogemmatisporaceae Yabe et al. 2011
- Genus Thermogemmatispora Yabe et al. 2011[23]
- Family Thermogemmatisporaceae Yabe et al. 2011
- Order Ktedonobacterales Cavaletti et al. 2007
- Family Dictyobacteraceae Wang et al. 2019
- Genus Dictyobacter Yabe et al. 2017
- Genus Tengunoibacter Wang et al. 2019
- Family Ktedonobacteriaceae Cavaletti et al. 2007
- Genus Ktedonobacter corrig. Cavaletti et al. 2007
- Genus Ktedonospora Yabe et al. 2021
- Family Ktedonosporobacteraceae Yan et al. 2020
- Genus Ktedonosporobacter Yan et al. 2020
- Family Reticulibacteraceae Yabe et al. 2021
- Genus Reticulibacter Yabe et al. 2021
- Family Thermosporotrichaceae Yabe et al. 2010
- Genus Thermosporothrix Yabe et al. 2010[24]
- Family Dictyobacteraceae Wang et al. 2019
Class "Umbricyclopia" Mehrshad et al. 2018
- Order "Umbricyclopales" Mehrshad et al. 2018
- Family "Umbricyclopaceae" Mehrshad et al. 2018
- Genus "Candidatus Umbricyclops" Mehrshad et al. 2018 (TK10)
- Family "Umbricyclopaceae" Mehrshad et al. 2018
Class "Bathosphaeria" Mehrshad et al. 2018
- Order "Bathosphaerales" Mehrshad et al. 2018
- Family "Bathosphaeraceae" Mehrshad et al. 2018
- Genus "Candidatus Bathosphaera" Mehrshad et al. 2018 (JG30-KF-CM66)
- Family "Bathosphaeraceae" Mehrshad et al. 2018
Class Tepidiformia Kochetkova et al. 2020
- Order Tepidiformales Kochetkova et al. 2020
- Family Tepidiformaceae Kochetkova et al. 2020
- Genus "Tepidiforma Kochetkova et al. 2020
- Family Tepidiformaceae Kochetkova et al. 2020
Class Dehalococcoidia Löffler et al. 2013
- Order Dehalococcoidales Löffler et al. 2013
- Family Dehalococcoidaceae Löffler et al. 2013
- Genus Dehalococcoides Löffler et al. 2013
- Genus Dehalogenimonas Moe et al. 2009
- Family Dehalococcoidaceae Löffler et al. 2013
Class "Thermofontia" corrig. Ward et al. 2018
- Order "Phototrophicales" Zheng et al. 2022
- Family "Phototrophicaceae" Zheng et al. 2022
- Genus "Phototrophicus" Zheng et al. 2022
- Family "Phototrophicaceae" Zheng et al. 2022
Class Ardenticatenia Kawaichi et al. 2013
- Order Ardenticatenales Kawaichi et al. 2013
- Family Ardenticatenaceae Kawaichi et al. 2013
- Genus Ardenticatena Kawaichi et al. 2013
- Family Ardenticatenaceae Kawaichi et al. 2013
Class "Caldilineia" Oren, Parte & Garrity 2016 ex Cavalier-Smith 2020
- Order Caldilineales Yamada et al. 2006
- Family "Amarolineaceae" Andersen et al. 2019
- Genus "Candidatus Amarolinea" Andersen et al. 2019
- Family Caldilineaceae Yamada et al. 2006
- Genus Caldilinea Sekiguchi et al. 2003
- Genus Litorilinea Kale et al. 2013
- Family "Amarolineaceae" Andersen et al. 2019
Class Thermoflexia Dodsworth et al. 2014
- Order Thermoflexales Dodsworth et al. 2014
- Family Thermoflexaceae Dodsworth et al. 2014
- Genus "Candidatus Roseilinea" Thiel et al. 2016
- Genus Thermoflexus Dodsworth et al. 2014
- Family Thermoflexaceae Dodsworth et al. 2014
Class "Anaerolineia" Oren, Parte & Garrity 2016
- Family "Profundisolitariaceae" Mehrshad et al. 2018
- Genus "Candidatus Profundisolitarius" Mehrshad et al. 2018 (CL500-11)
- Order "Promineifilales"
- Family "Promineifilaceae"
- Genus "Candidatus Promineofilum" McIlroy et al. 2016
- Family "Promineifilaceae"
- Order Aggregatilineales Nakahara et al. 2019
- Family Aggregatilineaceae Nakahara et al. 2019
- Genus Aggregatilinea Nakahara et al. 2019
- Family Aggregatilineaceae Nakahara et al. 2019
- Order Anaerolineales Yamada et al. 2006
- Family Anaerolineaceae Yamada et al. 2006
- Genus Anaerolinea Sekiguchi et al. 2003 emend. Yamada et al. 2006
- Genus Bellilinea Yamada et al. 2007[21]
- Genus "Brevefilum" McIlroy et al. 2017
- Genus "Candidatus Denitrolinea" Okubo et al. 2021
- Genus "Desulfolinea" Van Vliet et al. 2020
- Genus Flexilinea Sun et al. 2015
- Genus Levilinea Yamada et al. 2006[19]
- Genus Leptolinea Yamada et al. 2006[19]
- Genus Longilinea Yamada et al. 2007[21]
- Genus Ornatilinea Podosokorskaya et al. 2013
- Genus Pelolinea Imachi et al. 2014
- Genus Thermomarinilinea Nunoura et al. 2013
- Genus "Thermanaerothrix" Gregoire et al. 2011[25]
- Genus "Candidatus" Villigracilis Nierychlo et al. 2019
- Family Anaerolineaceae Yamada et al. 2006
Class Thermomicrobiia Oren, Parte & Garrity 2016
- Order Sphaerobacterales Stackebrandt, Rainey & Ward-Rainey 1997
- Family Sphaerobacteraceae Stackebrandt, Rainey & Ward-Rainey 1997
- Genus Nitrolancea Sorokin et al. 2014 ["Nitrolancetus" Sorokin et al. 2012]
- Genus Sphaerobacter Demharter et al. 1989
- Family Sphaerobacteraceae Stackebrandt, Rainey & Ward-Rainey 1997
- Order Thermomicrobiales Garrity & Holt 2002
- Family Thermomicrobiaceae Garrity & Holt 2002
- Genus Thermomicrobium Jackson, Ramaley & Meinschein 1973
- Genus Thermorudis King & King 2014
- Family Thermomicrobiaceae Garrity & Holt 2002
Class Chloroflexia Gupta et al. 2013
- Genus "Dehalobium" Wu et al. 2002[26]
- Genus "Candidatus Lithoflexus" Saghai et al. 2020
- Genus "Candidatus Sarcinithrix" Nierychlo et al. 2019
- Order "Thermobaculales"
- Family "Thermobaculaceae"
- Genus "Thermobaculum" Botero et al. 2004
- Family "Thermobaculaceae"
- Order Kallotenuales Cole et al. 2013
- Family Kallotenuaceae Cole et al. 2013
- Genus Kallotenue Cole et al. 2013
- Family Kallotenuaceae Cole et al. 2013
- Order Herpetosiphonales Gupta et al. 2013
- Family Herpetosiphonaceae Gupta et al. 2013
- Genus "Candidatus Anthektikosiphon" Ward, Fischer & McGlynn 2020
- Genus Herpetosiphon Holt & Lewin 1968 [Flavilitoribacter García-López et al. 2020]
- Family Herpetosiphonaceae Gupta et al. 2013
- Order Chloroflexales Gupta et al. 2013
- Suborder Roseiflexineae Gupta et al. 2013
- Family Roseiflexaceae Gupta et al. 2013 ["Kouleotrichaceae" Mehrshad et al. 2018]
- Genus "Kouleothrix" Kohno et al. 2002
- Genus Heliothrix Pierson et al. 1986
- Genus Roseiflexus Hanada et al. 2002
- Family Roseiflexaceae Gupta et al. 2013 ["Kouleotrichaceae" Mehrshad et al. 2018]
- Suborder Chloroflexineae Gupta et al. 2013
- Family Chloroflexaceae Gupta et al. 2013
- Genus Candidatus Chloranaerofilum Thiel et al. 2016
- Genus Chloroflexus Pierson & Castenholz 1974 ["Chlorocrinis"]
- Family Oscillochloridaceae Gupta et al. 2013
- Genus Candidatus Chloroploca Gorlenko et al. 2014
- Genus Chloronema ♪ Dubinina & Gorlenko 1975
- Genus Oscillochloris Gorlenko & Pivovarova 1989
- Genus Candidatus Viridilinea Grouzdev et al. 2018
- Family Chloroflexaceae Gupta et al. 2013
- Suborder Roseiflexineae Gupta et al. 2013
Etymology
The name Chloroflexi is a Neolatin nominative case masculine plural of Chloroflexus, which is the name of the first genus described. The noun is a combination of the Greek adjective chloros, -a, on (χλωρός, -ά, -όν),[27] meaning "greenish-yellow," and the Latin masculine passive perfect participle flexus (of flecto),[28] meaning "bent."[6] The etymology is unrelated to chlorine, an element that was discovered in 1810 by Sir Humphry Davy and named after its pale green colour. Another phylum with the same root is Chlorobiota, whereas "Cyanobacteria" has the root cyanos (κύανος), meaning "blue-green."[29]
Unlike some other phyla, there is no theme root in the name of genera of Chloroflexota, and in fact many genera beginning with "Chloro-" or ending in "-chloris" are either cyanobacteria or chlorobi.
References
- ^ Oren A, Garrity GM (2021). "Valid publication of the names of forty-two phyla of prokaryotes". Int J Syst Evol Microbiol. 71 (10): 5056. doi:10.1099/ijsem.0.005056. PMID 34694987. S2CID 239887308.
- ^ Sutcliffe, I. C. (2010). "A phylum level perspective on bacterial cell envelope architecture". Trends in Microbiology. 18 (10): 464–470. doi:10.1016/j.tim.2010.06.005. PMID 20637628.
- ^ Don J. Brenner; Noel R. Krieg; James T. Staley (July 26, 2005) [1984(Williams & Wilkins)]. George M. Garrity (ed.). Introductory Essays. Bergey's Manual of Systematic Bacteriology. Vol. 2A (2nd ed.). New York: Springer. p. 304. ISBN 978-0-387-24143-2. British Library no. GBA561951.
- ^ Holland L. (22 May 1990). "Woese,Carl in the forefront of bacterial evolution revolution". Scientist. 4 (10).
- ^ Woese, C. R. (1987). "Bacterial evolution". Microbiological Reviews. 51 (2): 221–271. doi:10.1128/MMBR.51.2.221-271.1987. PMC 373105. PMID 2439888.
- ^ a b c Don J. Brenner; Noel R. Krieg; James T. Staley (July 26, 2005) [1984(Williams & Wilkins)]. George M. Garrity (ed.). Introductory Essays. Bergey's Manual of Systematic Bacteriology. Vol. 2A (2nd ed.). New York: Springer. p. 304. ISBN 978-0-387-24143-2. British Library no. GBA561951.
- ^ Hugenholtz, P.; Stackebrandt, E. (2004). "Reclassification of Sphaerobacter thermophilus from the subclass Sphaerobacteridae in the phylum Actinobacteria to the class Thermomicrobia (emended description) in the phylum Chloroflexi (emended description)". International Journal of Systematic and Evolutionary Microbiology. 54 (6): 2049–2051. doi:10.1099/ijs.0.03028-0. PMID 15545432.
- ^ Maymo-Gatell, X.; Chien, Y.; Gossett, J. M.; Zinder, S. H. (1997). "Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene". Science. 276 (5318): 1568–1571. doi:10.1126/science.276.5318.1568. PMID 9171062.
- ^ a b Moe, W. M.; Yan, J.; Nobre, M. F.; Da Costa, M. S.; Rainey, F. A. (2009). "Dehalogenimonas lykanthroporepellens gen. Nov., sp. Nov., a reductively dehalogenating bacterium isolated from chlorinated solvent-contaminated groundwater". International Journal of Systematic and Evolutionary Microbiology. 59 (11): 2692–2697. doi:10.1099/ijs.0.011502-0. PMID 19625421.
- ^ a b c d Gupta, R. S.; Chander, P.; George, S. (2012). "Phylogenetic framework and molecular signatures for the class Chloroflexi and its different clades; proposal for division of the class Chloroflexi class. nov. into the suborder Chloroflexineae subord. nov., consisting of the emended family Oscillochloridaceae and the family Chloroflexaceae fam. nov., and the suborder Roseiflexineae subord. nov., containing the family Roseiflexaceae fam. nov". Antonie van Leeuwenhoek. 103 (1): 99–119. doi:10.1007/s10482-012-9790-3. PMID 22903492. S2CID 17656551.
- ^ J.P. Euzéby. "Chloroflexi". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2018-07-20.
- ^ Sayers; et al. "Chloroflexi". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2014-03-20.
- ^ "The LTP". Retrieved 23 February 2021.
- ^ "LTP_all tree in newick format". Retrieved 23 February 2021.
- ^ "LTP_12_2021 Release Notes" (PDF). Retrieved 23 February 2021.
- ^ "GTDB release 07-RS207". Genome Taxonomy Database. Retrieved 20 June 2022.
- ^ "bac120_r207.sp_labels". Genome Taxonomy Database. Retrieved 20 June 2022.
- ^ "Taxon History". Genome Taxonomy Database. Retrieved 20 June 2022.
- ^ a b c d e Yamada, T.; Sekiguchi, Y.; Hanada, S.; Imachi, H.; Ohashi, A.; Harada, H.; Kamagata, Y. (2006). "Anaerolinea thermolimosa sp. nov., Levilinea saccharolytica gen. nov., sp. nov. And Leptolinea tardivitalis gen. nov., sp. nov., novel filamentous anaerobes, and description of the new classes Anaerolineae classis nov. and Caldilineae classis nov. in the bacterial phylum Chloroflexi". International Journal of Systematic and Evolutionary Microbiology. 56 (6): 1331–1340. doi:10.1099/ijs.0.64169-0. PMID 16738111.
- ^ Sekiguchi, Y.; Yamada, T.; Hanada, S.; Ohashi, A.; Harada, H.; Kamagata, Y. (2003). "Anaerolinea thermophila gen. nov., sp. nov. And Caldilinea aerophila gen. nov., sp. nov., novel filamentous thermophiles that represent a previously uncultured lineage of the domain Bacteria at the subphylum level". International Journal of Systematic and Evolutionary Microbiology. 53 (6): 1843–1851. doi:10.1099/ijs.0.02699-0. PMID 14657113.
- ^ a b c Yamada, T.; Imachi, H.; Ohashi, A.; Harada, H.; Hanada, S.; Kamagata, Y.; Sekiguchi, Y. (2007). "Bellilinea caldifistulae gen. nov., sp. nov. And Longilinea arvoryzae gen. nov., sp. nov., strictly anaerobic, filamentous bacteria of the phylum Chloroflexi isolated from methanogenic propionate-degrading consortia". International Journal of Systematic and Evolutionary Microbiology. 57 (10): 2299–2306. doi:10.1099/ijs.0.65098-0. PMID 17911301.
- ^ Klappenbach, J. A.; Pierson, B. K. (2004). "Phylogenetic and physiological characterization of a filamentous anoxygenic photoautotrophic bacterium 'Candidatus Chlorothrix halophila' Gen. Nov., sp. Nov., recovered from hypersaline microbial mats". Archives of Microbiology. 181 (1): 17–25. doi:10.1007/s00203-003-0615-7. PMID 14655000. S2CID 23854988.
- ^ Yabe, S.; Aiba, Y.; Sakai, Y.; Hazaka, M.; Yokota, A. (2010). "Thermogemmatispora onikobensis gen. nov., sp. nov. And Thermogemmatispora foliorum sp. nov., isolated from fallen leaves on geothermal soils, and description of Thermogemmatisporaceae fam. Nov. And Thermogemmatisporales ord. Nov. Within the class Ktedonobacteria". International Journal of Systematic and Evolutionary Microbiology. 61 (4): 903–910. doi:10.1099/ijs.0.024877-0. PMID 20495028.
- ^ Yabe, S.; Aiba, Y.; Sakai, Y.; Hazaka, M.; Yokota, A. (2009). "Thermosporothrix hazakensis gen. nov., sp. nov., isolated from compost, description of Thermosporotrichaceae fam. Nov. Within the class Ktedonobacteria Cavaletti et al. 2007 and emended description of the class Ktedonobacteria". International Journal of Systematic and Evolutionary Microbiology. 60 (8): 1794–1801. doi:10.1099/ijs.0.018069-0. PMID 19767365.
- ^ Grégoire, P.; Fardeau, M. L.; Joseph, M.; Guasco, S.; Hamaide, F.; Biasutti, S.; Michotey, V. R.; Bonin, P.; Ollivier, B. (2011). "Isolation and characterization of Thermanaerothrix daxensis gen. nov., sp. nov., a thermophilic anaerobic bacterium pertaining to the phylum "Chloroflexi", isolated from a deep hot aquifer in the Aquitaine Basin". Systematic and Applied Microbiology. 34 (7): 494–497. doi:10.1016/j.syapm.2011.02.004. PMID 21621938.
- ^ Wu, Q.; Watts, J. E. M.; Sowers, K. R.; May, H. D. (2002). "Identification of a Bacterium That Specifically Catalyzes the Reductive Dechlorination of Polychlorinated Biphenyls with Doubly Flanked Chlorines". Applied and Environmental Microbiology. 68 (2): 807–812. Bibcode:2002ApEnM..68..807W. doi:10.1128/AEM.68.2.807-812.2002. PMC 126686. PMID 11823222.
- ^ χλωρός. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
- ^ Lewis & Short...
- ^ κύανος. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project