Partial Update: 2 May 2013
This page lists all of the current validly-published binomial names for the rhizobia, which currently consists of 98 species in 13 genera.
Rhizobia are nitrogen-fixing bacteria that form root nodules on legume plants. Most of these bacterial species are in the Rhizobiacae family in the alpha-proteobacteria and are in either the Rhizobium, Mesorhizobium, Ensifer, or Bradyrhizobium genera. However recent research has shown that there are many other rhizobial species in addition to these. In some cases these new species have arisen through lateral gene transfer of symbiotic genes. The list below is not 'official' by any means, and it is merely my compilation and interpretation of the literature. An alternative list is maintained by the "ICSP Subcommittee on the taxonomy of Rhizobium and Agrobacterium".
It is important to note that there are other non-rhizobial species present in these genera. For example in the Rhizobium genus, there is Rhizobium radiobacter — formerly known as Agrobacterium tumefaciens. However these species are not listed here, as the 'Agrobacteria' do not form nitrogen fixing symbiotic root nodules (unless they contain a symbiotic plasmid — see Velazquez et al., 2005). I have another page about these bacteria that could be confused with 'true' rhizobia. To see all of the currently valid members of a genus, including non-rhizobial species, click on the name of the genus in the text ineach section. This will take you to the LPSN taxonomy website.
This page was compiled from my own research; a paper by J.G. Howieson and J. Brockwell presented at the 14th Australian Nitrogen Fixation Conference, and the NCBI and LPSN websites. This page is updated regularly. If you know of any additions or corrections please email me. I do try to keep up, but finding new rhizobial genera in particular is diffucult. To compare the differences between updates check the change log. This page can be cited as:
Weir, B.S. (2012) The current taxonomy of rhizobia. NZ Rhizobia website. http://www.rhizobia.co.nz/taxonomy/rhizobia Last updated: 10 April, 2012
The genus Rhizobium (Frank 1889) was the first named (from Latin meaning 'root living'), and for many years this was a 'catch all' genus for all rhizobia. Some species were later moved in to new genera based on phylogenetic analyses. It currently consists of 30 rhizobial species (and 11 non rhizobial species). Rhizobium in New Zealand.
| Rhizobium alamii | Berge et al. (2009) |
| Rhizobium alkalisoli | Lu et al. (2009b) |
| Rhizobium cellulosilyticum | García-Fraile et al. (2007) |
| Rhizobium daejeonense | |
| Rhizobium endophyticum | López-López et al. (2011) |
| Rhizobium etli | |
| Rhizobium galegae | |
| Rhizobium gallicum | |
| Rhizobium giardinii | |
| Rhizobium hainanense | |
| Rhizobium herbae | Ren et al. (2011b) |
| Rhizobium huautlense | |
| Rhizobium indigoferae | |
| Rhizobium leguminosarum | Type species. See note A |
| Rhizobium loessense | formerly Rhizobium huanglingense |
| Rhizobium lusitanum | |
| Rhizobium mesosinicum | Lin et al. (2009) |
| Rhizobium miluonense | Gu et al. (2008) |
| Rhizobium mongolense | |
| Rhizobium multihospitium | Han et al. (2008) |
| Rhizobium oryzae | Peng et al. (2008) |
| Rhizobium phaseoli | Confirmed as a species. Ramirez-Bahena et al. (2008) |
| Rhizobium pisi | Ramirez-Bahena et al. (2008) |
| Rhizobium tibeticum | Hou et al. (2009) |
| Rhizobium sullae | formerly Rhizobium hedysari |
| Rhizobium tropici | |
| Rhizobium tubonense | Zhang et al. (2011) |
| Rhizobium undicola | formerly Allorhizobium undicola |
| Rhizobium vignae | Ren et al. (2011) |
| Rhizobium yanglingense |
A — Rhizobium trifolii is a later synonym of R. leguminosarum. R. phaseoli is a valid separate species, and some isolates formerly known as R. leguminosarum are now R. pisi (Ramirez-Bahena et al. 2008).
NB: for non rhizobia Rhizobium such as R. soli and R. radiobacter see the not rhizobia page.
The genus Mesorhizobium was described by Jarvis et al. in 1997. Several Rhizobium species were transferred to this genus. It currently consists of 21 rhizobia species (and 1 non-rhizobial species). Mesorhizobium in New Zealand.
| Mesorhizobium albiziae | Wang et al. (2007) |
| Mesorhizobium alhagi | Chen et al. (2010) |
| Mesorhizobium amorphae | |
| Mesorhizobium australicum | Nandasena et al. (2009) |
| Mesorhizobium camelthorni | Chen et al. (2011) |
| Mesorhizobium caraganae | Wang et al. (2007) |
| Mesorhizobium chacoense | |
| Mesorhizobium ciceri | formerly Rhizobium ciceri |
| Mesorhizobium gobiense | Han et al. (2008b) |
| Mesorhizobium huakuii | formerly Rhizobium huakuii |
| Mesorhizobium loti | formerly Rhizobium loti, Type species |
| Mesorhizobium mediterraneum | formerly Rhizobium mediterraneum |
| Mesorhizobium metallidurans | Vidal et al. (2009) |
| Mesorhizobium opportunistum | Nandasena et al. (2009) |
| Mesorhizobium plurifarium | |
| Mesorhizobium robiniae | Zhou et al. (2010) |
| Mesorhizobium shangrilense | Lu et al. (2009) |
| Mesorhizobium septentrionale | |
| Mesorhizobium tarimense | Han et al. (2008b) |
| Mesorhizobium temperatum | |
| Mesorhizobium tianshanense | formerly Rhizobium tianshanense |
The Sinorhizobium genus was described by Chen et al. in 1988. However some recent studies show that Sinorhizobium and the genus Ensifer (Casida, 1982) belong to a single taxon. Ensifer is the earlier heterotypic synonym (it was named first) and thus takes priority (Young, 2003). This means that all Sinorhizobium spp. must be renamed as Ensifer spp. according to the Bacteriological code. There has been some discussion in the literature if Ensifer or Sinorhizobium is correct Young (2010), this website follows the opinion of the Judicial Commission, and will use Ensifer. The genus currently consists of 17 species. Ensifer in New Zealand.
| Ensifer abri | D |
| Sinorhizobium americanum | F |
| Ensifer arboris | |
| Ensifer fredii | formerly Rhizobium fredii, former Type of Sinorhizobium G |
| Ensifer garamanticus | Merabet et al. (2010) |
| Ensifer indiaense | D |
| Ensifer kostiensis | |
| Ensifer kummerowiae | |
| Ensifer medicae | |
| Ensifer meliloti | formerly Rhizobium meliloti |
| Ensifer mexicanus | Lloret et al. (2007) |
| 'Sinorhizobium morelense' | E |
| Ensifer adhaerens | A |
| Ensifer numidicus | Merabet et al. (2010) |
| Ensifer saheli | B |
| Ensifer sojae | Li et al. (in press) |
| Ensifer terangae | C |
A — This name is a earlier heterotypic synonym of Sinorhizobium morelense (see Young, 2003)
B — This species is also known as Sinorhizobium sahelense (why?)
C — This species is incorrectly known as Sinorhizobium teranga
D — Although these species have been published (Ogasawara, et al. 2003), they have not yet been included in the "Validation List" of the International Journal of Systematic and Evolutionary Microbiology, and no type strains exist in international culture collections.
E — This name may be a later heterotypic synonym of Ensifer adhaerens Young (2003), or a distict species Martens et al. (2007).
F — Not yet formally renamed as Ensifer.
G — Ensifer xinjiangense is later heterotypic synonym of Ensifer fredii.
The Bradyrhizobium genus was described by Jordan in 1982. It currently consists of 9 rhizobia species (and 1 non rhizobial species). Bradyrhizobium in New Zealand .
| Bradyrhizobium canariense | |
| Bradyrhizobium denitrificans | formerly Blastobacter denitrificans; |
| Bradyrhizobium elkanii | |
| Bradyrhizobium iriomotense | Islam et al. (2008) |
| Bradyrhizobium japonicum | formerly Rhizobium japonicum, Type species |
| Bradyrhizobium jicamae | Ramírez-Bahena et al. (2009) |
| Bradyrhizobium liaoningense | |
| Bradyrhizobium pachyrhizi | Ramírez-Bahena et al. (2009) |
| Bradyrhizobium yuanmingense |
The Burkholderia genus currently contains seven named rhizobial members and others as Burkholderia sp. Burkholderia in New Zealand.
| Burkholderia caribensis | |
| Burkholderia cepacia | see note X below |
| Burkholderia mimosarum | |
| Burkholderia nodosa | Chen et al (2007) |
| Burkholderia phymatum | |
| Burkholderia sabiae | Chen et al (2008) |
| Burkholderia tuberum |
X — Note that although Burkholderia cepacia is considered to nodulate by Rasolomampianina et al. (2005) and Vandamme et al. (2002), Vandamme et al. (2007) (chapter 1, page 7) notes that recent experiments revealed that nodA and nif genes are not longer detected on these strains and he suggests that the strains lost the characteristic, or the original observation was based on experimental error.
The Phyllobacterium genus currently contains three rhizobial species. Phyllobacterium in New Zealand.
| Phyllobacterium trifolii | |
| Phyllobacterium ifriqiyense | Mantelin et al. (2006) F |
| Phyllobacterium leguminum | Mantelin et al. (2006) F |
F Note: isolated from nodules, but not proven to nodulate.
The Microvirga genus currently contains three rhizobial species. Microvirga in New Zealand.
| Microvirga lupini | New: Ardley et al. (in press) |
| Microvirga lotononidis | New: Ardley et al. (in press) |
| Microvirga zambiensis | New: Ardley et al. (in press) |
The Azorhizobium genus was described by Dreyfus et al. in 1988. It currently consists of 2 species.
| Azorhizobium caulinodans | Type species |
| Azorhizobium doebereinerae | formerly Azorhizobium johannae |
The Ochrobactrum genus currently contains two rhizobial species. Ochrobactrum in New Zealand.
| Ochrobactrum cytisi | Zurdo-Piñeiro et al. 2007 |
| Ochrobactrum lupini |
The Methylobacterium genus contains only a single rhizobial species. Methylobacterium in New Zealand.
| Methylobacterium nodulans |
Cupriavidus formerly Wautersia, formerly Ralstonia (some species), has recently undergone several taxonomic revisions. This genus currently contains a single rhizobial species.
| Cupriavidus taiwanensis |
The Devosia genus currently contains only a single rhizobial species (and 1 potentially non rhizobial species).
| Devosia neptuniae |
The Shinella genus currently contains a single rhizobial species.
| Shinella kummerowiae | Lin et al. (2008) |
A general excellent resource is:
List of Prokaryotic names with Standing in Nomenclature (LPSN). Available http://www.bacterio.cict.fr.
For the full list of references for each strain, please check my PhD thesis, Table 1.1, page 3. New References added since the publication of my thesis are listed below:
Chun Tao Gu, En Tao Wang, Chang Fu Tian, Tian Xu Han, Wen Feng Chen, Xin Hua Sui and Wen Xin Chen (2008). Rhizobium miluonense sp. nov., a symbiotic bacterium isolated from Lespedeza root nodules. Int J Syst Evol Microbiol 58: 1364-1368. Abstract
Valverde, Angel, Igual, Jose M., Peix, Alvaro, Cervantes, Emilio, Velazquez, Encarna. Rhizobium lusitanum sp. nov. a bacterium that nodulates Phaseolus vulgaris. Int J Syst Evol Microbiol 2006 56: 2631-2637. Abstract
Sophie Mantelin, Marion Fischer-Le Saux, Frederic Zakhia, Gilles Bena, Sophie Bonneau, Habib Jeder, Philippe de Lajudie and Jean-Claude Cleyet-Marel (2006) Emended description of the genus Phyllobacterium and description of four novel species associated with plant roots: Phyllobacterium bourgognense sp. nov., Phyllobacterium ifriqiyense sp. nov., Phyllobacterium leguminum sp. nov. and Phyllobacterium brassicacearum sp. nov. Int J Syst Evol Microbiol 56 (4): 827
Chen, Wen-Ming, James, Euan K., Coenye, Tom, Chou, Jui-Hsing, Barrios, Edmundo, de Faria, Sergio M., Elliott, Geoffrey N., Sheu, Shih-Yi, Sprent, Janet I., Vandamme, Peter. (2006) Burkholderia mimosarum sp. nov., isolated from root nodules of Mimosa spp. from Taiwan and South America. Int J Syst Evol Microbiol 56: 1847-1851. Abstract
Lloret L, Ormeno-Orrillo E, Rincon R, Martinez-Romero J, Rogel-Hernandez MA, Martinez-Romero E. (2007) Ensifer mexicanus sp. nov. a new species nodulating Acacia angustissima (Mill.) Kuntze in Mexico. Syst Appl Microbiol. Abstract
Martens, Miet, Delaere, Manuel, Coopman, Renata, De Vos, Paul, Gillis, Monique, Willems, Anne. (2007) Multilocus sequence analysis of Ensifer and related taxa Int J Syst Evol Microbiol 57: 489-503. Abstract
Garcia-Fraile, Paula, Rivas, Raul, Willems, Anne, Peix, Alvaro, Martens, Miet, Martinez-Molina, Eustoquio, Mateos, Pedro F., Velazquez, Encarna. (2007) Rhizobium cellulosilyticum sp. nov., isolated from sawdust of Populus alba Int J Syst Evol Microbiol 57: 844-848. Abstract
Zurdo-Pineiro, Jose Luis, Rivas, Raul, Trujillo, Martha E., Vizcaino, Nieves, Carrasco, Jose Antonio, Chamber, Manuel, Palomares, Antonio, Mateos, Pedro F., Martinez-Molina, Eustoquio, Velazquez, Encarna. (2007) Ochrobactrum cytisi sp. nov., isolated from nodules of Cytisus scoparius in Spain Int J Syst Evol Microbiol 57: 784-788. Abstract
Wang, Feng Qin, Wang, En Tao, Liu, Jie, Chen, Qiang, Sui, Xin Hua, Chen, Wen Feng, Chen, Wen Xin. (2007) Mesorhizobium albiziae sp. nov., a novel bacterium that nodulates Albizia kalkora in a subtropical region of China. Int J Syst Evol Microbiol 57: 1192-1199 Abstract
Wang, Feng Qin, WChen, Wen-Ming, de Faria, Sergio M., James, Euan K., Elliott, Geoffrey N., Lin, Kuan-Yin, Chou, Jui-Hsing, Sheu, Shih-Yi, Cnockaert, M., Sprent, Janet I., Vandamme, Peter (2007) Burkholderia nodosa sp. nov., isolated from root nodules of the woody Brazilian legumes Mimosa bimucronata and Mimosa scabrella Int J Syst Evol Microbiol, May 2007; 57: 1055 - 1059. Abstract
Han, Tian Xu, Wang, En Tao, Wu, Li Juan, Chen, Wen Feng, Gu, Jin Gang, Gu, Chun Tao, Tian, Chang Fu, Chen, Wen Xin. (2007) Rhizobium multihospitium sp. nov., isolated from multiple legume species native of Xinjiang, China Int J Syst Evol Microbiol 58: 1693-1699 Abstract
Chen WM, de Faria SM, Chou JH, James EK, Elliott GN, Sprent JI, Bontemps C, Young JP, Vandamme P. (2008) Burkholderia sabiae sp. nov., isolated from root nodules of Mimosa caesalpiniifolia. Int J Syst Evol Microbiol. 58(9):2174-9. Abstract
Tian Xu Han, Li Li Han, Li Juan Wu, Wen Feng Chen, Xin Hua Sui, Jin Gang Gu, En Tao Wang and Wen Xin Chen (2008) Mesorhizobium gobiense sp. nov. and Mesorhizobium tarimense sp. nov., isolated from wild legumes growing in desert soils of Xinjiang, China. Int J Syst Evol Microbiol. 58(11):2610-2618. Abstract
Guan, Su Hua, Chen, Wen Feng, Wang, En Tao, Lu, Yang Li, Yan, Xue Rui, Zhang, Xiao Xia, Chen, Wen Xin. (2008) Mesorhizobium caraganae sp. nov., a novel rhizobial species nodulated with Caragana spp. in China Int J Syst Evol Microbiol 2008 58: 2646-2653. Abstract
Ramirez-Bahena, Martha Helena, Garcia-Fraile, Paula, Peix, Alvaro, Valverde, Angel, Rivas, Raul, Igual, Jose M., Mateos, Pedro F., Martinez-Molina, Eustoquio, Velazquez, Encarna (2008) Revision of the taxonomic status of the species Rhizobium leguminosarum (Frank 1879) Frank 1889AL, Rhizobium phaseoli Dangeard 1926AL and Rhizobium trifolii Dangeard 1926AL. R. trifolii is a later synonym of R. leguminosarum. Reclassification of the strain R. leguminosarum DSM 30132 (=NCIMB 11478) as Rhizobium pisi sp. nov. Int J Syst Evol Microbiol 2008 58: 2484-2490. Abstract
Lin, Dong Xu, Wang, En Tao, Tang, Hui, Han, Tian Xu, He, Yu Rong, Guan, Su Hua, Chen, Wen Xin (2008) Shinella kummerowiae sp. nov., a symbiotic bacterium isolated from root nodules of the herbal legume Kummerowia stipulacea. Int J Syst Evol Microbiol 2008 58: 1409-1413 Abstract
Peng, Guixiang, Yuan, Qinghua, Li, Huaxing, Zhang, Wu, Tan, Zhiyuan (2008) Rhizobium oryzae sp. nov., isolated from the wild rice Oryza alta. Int J Syst Evol Microbiol 2008 58: 2158-2163 Abstract
Vidal, Celine, Chantreuil, Clemence, Berge, Odile, Maure, Lucette, Escarre, Jose, Bena, Gilles, Brunel, Brigitte, Cleyet-Marel, Jean-Claude. (2009) Mesorhizobium metallidurans sp. nov., a metal-resistant symbiont of Anthyllis vulneraria growing on metallicolous soil in Languedoc, France. Int J Syst Evol Microbiol 2009 59: 850-855 Abstract
Nandasena, Kemanthi G., O'Hara, Graham W., Tiwari, Ravi P., Willems, Anne, Howieson, John G. (2009). Mesorhizobium australicum sp. nov. and Mesorhizobium opportunistum sp. nov., isolated from Biserrula pelecinus L. in Australia Int J Syst Evol Microbiol 2009 59: 2140-2147 Abstract
Chen, Weimin, Zhu, Wenfei, Bontemps, Cyril, Young, J. Peter W., Wei, Gehong. Mesorhizobium alhagi sp. nov., isolated from root nodules of the wild legume Alhagi sparsifolia Int J Syst Evol Microbiol 2009 60: 958-962 Abstract
Lu, Yang Li, Chen, Wen Feng, Han, Li Li, Wang, En Tao, Zhang, Xiao Xia, Chen, Wen Xin, Han, Su Zhen. Mesorhizobium shangrilense sp. nov., isolated from root nodules of Caragana spp. Int J Syst Evol Microbiol 2009 59: 3012-3018 Abstract
Lu YL, Chen WF, Han LL, Wang ET, and Chen WX (2009). Rhizobium alkalisoli sp. nov., isolated from Caragana intermedia growing in saline-alkaline soils in the north of China. Int J Syst Evol Microbiol 59: 3006-3011. Abstract.
Ramirez-Bahena, Martha Helena, Peix, Alvaro, Rivas, Raul, Camacho, Maria, Rodriguez-Navarro, Dulce N., Mateos, Pedro F., Martinez-Molina, Eustoquio, Willems, Anne, Velazquez, Encarna Bradyrhizobium pachyrhizi sp. nov. and Bradyrhizobium jicamae sp. nov., isolated from effective nodules of Pachyrhizus erosus. Int J Syst Evol Microbiol 2009 59: 1929-1934 Abstract
Islam, M.S., Kawasaki, H., Muramatsu, Y., Nakagawa, Y., and Seki, T. "Bradyrhizobium iriomotense sp. nov., isolated from a tumor-like root of the legume Entada koshunensis from Iriomote Island in Japan." Biosci. Biotechnol. Biochem. (2008)72:1416-1429. Abstract doi:10.1271/bbb.70739
Berge, Odile, Lodhi, Asma, Brandelet, Geraldine, Santaella, Catherine, Roncato, Marie-Anne, Christen, Richard, Heulin, Thierry, Achouak, Wafa Rhizobium alamii sp. nov., an exopolysaccharide-producing species isolated from legume and non-legume rhizospheres. Int J Syst Evol Microbiol 2009 59: 367-372. Abstract
Lin, Dong Xu, Chen, Wen Feng, Wang, Feng Qin, Hu, Dong, Wang, En Tao, Sui, Xin Hua, Chen, Wen Xin Rhizobium mesosinicum sp. nov., isolated from root nodules of three different legumes. Int J Syst Evol Microbiol 2009 59: 1919-1923. Abstract
Hou, Bao Chao, Wang, En Tao, Li, Ying, Jr, Jia, Rui Zong, Chen, Wen Feng, Gao, Yu, Dong, Ren Jie, Chen, Wen Xin Rhizobium tibeticum sp. nov., a symbiotic bacterium isolated from Trigonella archiducis-nicolai (Sirj.) Vassilcz. Int J Syst Evol Microbiol 2009 59: 3051-3057. Abstract
Zhang, Rong Juan, Hou, Bao Chao, Wang, En Tao, Li, Ying, Jr, Zhang, Xiao Xia, Chen, Wen Xin Rhizobium tubonense sp. nov., isolated from root nodules of Oxytropis glabra. Int J Syst Evol Microbiol 2011 61: 512-517. Abstract
Zhou, Ping Fa, Chen, Wei Min, Wei, Ge Hong Mesorhizobium robiniae sp. nov., isolated from root nodules of Robinia pseudoacacia. Int J Syst Evol Microbiol 2010 60: 2552-2556. Abstract
Chen, Wei-Min, Zhu, Wen-Fei, Bontemps, Cyril, Young, J. Peter W., Wei, Ge-Hong Mesorhizobium camelthorni sp. nov., isolated from Alhagi sparsifolia. Int J Syst Evol Microbiol 2011 61: 574-579. Abstract
Li, Qin Qin, Wang, En Tao, Chang, Yue Li, Zhang, Yun Zeng, Zhang, Yan Ming, Sui, Xin Hua, Chen, Wen Feng, Chen, Wen Xin Ensifer (Sinorhizobium) sojae sp. nov., isolated from root nodules of Glycine max grown in saline-alkaline soils in Hebei province of China. Int J Syst Evol Microbiol 2010 0: ijs.0.025049-0. Abstract
Merabet, C., Martens, M., Mahdhi, M., Zakhia, F., Sy, A., Le Roux, C., Domergue, O., Coopman, R., Bekki, A., Mars, M., Willems, A., de Lajudie, P. Multilocus sequence analysis of root nodule isolates from Lotus arabicus (Senegal), Lotus creticus, Argyrolobium uniflorum and Medicago sativa (Tunisia) and description of Ensifer numidicus sp. nov. and Ensifer garamanticus sp. nov. Int J Syst Evol Microbiol 2010 60: 664-674 . Abstract
Ren, Da Wei, Chen, Wen Feng, Sui, Xin Hua, Wang, En Tao, Chen, Wen Xin Rhizobium herbae sp. nov. and Rhizobium giardinii-related bacteria, minor microsymbionts of various wild legumes in China. Int J Syst Evol Microbiol 2011 61:1912-1920 . Abstract
Da Wei Ren, En Tao Wang, Wen Feng Chen, Xin Hua Sui, Xiao Xia Zhang, Hong Can Liu, and Wen Xin Chen Rhizobium vignae sp. nov., a symbiotic bacterium isolated from multiple legume species nov. Int J Syst Evol Microbiol 2011 61: 580-586 . Abstract Aline Lopez-Lopez, Marco A. Rogel, Ernesto Ormeno-Orrillo, Julio Martinez-Romero, Esperanza Martinez-Romero Phaseolus vulgaris seed-borne endophytic community with novel bacterial species such as Rhizobium endophyticum sp. nov., Systematic and Applied Microbiology, Volume 33, Issue 6, October 2010, Pages 322-327, ISSN 0723-2020, DOI: 10.1016/j.syapm.2010.07.005. (http://www.sciencedirect.com/science/article/pii/S0723202010001013)
Julie K Ardley, Matthew A Parker, Sofie E. De Meyer, Robert D Trengove, Graham W O'Hara, Wayne G Reeve, Ron J Yates, Michael J Dilworth, Anne Willems and John G Howieson (in press) Microvirga lupini sp. nov., Microvirga lotononidis sp. nov., and Microvirga zambiensis sp. nov. are Alphaproteobacterial root nodule bacteria that specifically nodulate and fix nitrogen with geographically and taxonomically separate legume hosts. Int J Syst Evol Microbiol ijs.0.035097-0; published ahead of print December 23, 2011, doi:10.1099/ijs.0.035097-0 Abstract