Dr. Eden S. P. Bromfield

Image Eden S. P. Bromfield
Research Scientist

Research focuses on agriculturally significant symbiotic nitrogen fixing bacteria (Bradyrhizobium and Ensifer species) associated with crop legumes such as soybeans and alfalfa; beneficial bacteria; biological nitrogen fixation; nitrogen biofertilizers (bioinoculants); bacterial phylogenetics, systematics (taxonomy) and genomics (complete genome sequencing); bacterial population ecology and evolution; novel bacterial species discovery, characterization and formal description; identification of novel symbiotic nitrogen fixing bacteria with potential as efficient /ecologically adapted inoculant strains for agricultural legumes; horizontal gene transfer between symbiotic bacteria in the field; comparative genomics of photosynthetic bacteria.

Current research and/or projects

Proposal ID 3200: Taxonomy and molecular systematics of symbiotic nitrogen fixing bacteria (Bradyrhizobium​)

  • Phylogenomic, molecular and phenotypic characterizatio​n and formal description of novel symbiotic bacteria (Bradyrhizobium species and symbiotic varieties) isolated from agricultural, native and invasive legumes in Canada. This includes novel bacteria that  have potential as ecologically adapted and efficient nitrogen fixing inoculant strains for Canadian soybeans.
  • Comparative genomics and phylogenetics to elucidate the evolution of agriculturally significant nitrogen fixing and photosynthesis genes in novel Bradyrhizobium species and further the understanding and implications for agriculture of horizontal genetic exchange between symbiotic bacteria in the field.

Proposal ID 3407: Managing AAFC's biological collections

  • Objectives include complete genome sequencing of key reference strains of agriculturally significant symbiotic nitrogen fixing bacteria in the genera Bradyrhizobium, Ensifer, Rhizobium and Phyllobacterium; novel bacterial species/varieties with high agricultural or research potential made available to the public and scientific community.

Research and/or project statements

Areas of expertise:

  • Agriculturally significant symbiotic nitrogen fixing bacteria (rhizobia) associated with crop legumes such as soybeans and alfalfa.
  • Biological nitrogen fixation
  • Beneficial bacteria
  • Nitrogen biofertilizers/ bioinoculants for agricultural legumes
  • Bacterial phylogenetics and systematics.
  • Novel  bacterial species discovery, molecular taxonomic characterization and formal description
  • Comparative genomics (complete genome sequencing) of beneficial bacteria
  • Bacterial population ecology and genetics.

International experience and/or work

1980-1982 Research scientist at Rothamsted Experimental Station, United Kingdom in collaboration with the International Centre for Research in the Semi-Arid Tropics (ICRISAT) Hyberabad, India, to characterize native symbiotic nitrogen fixing bacteria associated with agricultural pulses (Pigeonpea and Chickpea); to conduct research on applied aspects of the ecology of these symbiotic bacteria.

1977-1979 Research scientist at Rothamsted Experimental Station, United Kingdom in collaboration with the International Institute of Tropical Africa (IITA), Ibadan, Nigeria, to establish efficient nitrogen fixing bacterial-Soybean symbioses on acid soils in West Africa; to characterize indigenous symbiotic bacteria associated with locally adapted soybean cultivars.

Key publications

62. Bromfield ESP and Cloutier S. (2021) Bradyrhizobium septentrionale sp. nov. (sv. septentrionale) and Bradyrhizobium quebecense sp. nov. (sv. septentrionale) associated with legumes native to Canada possess rearranged symbiosis genes and numerous insertion sequences. International Journal of Systematic and Evolutionary Microbiology, 71:004831 https://doi.org/10.1099/ijsem.0.004831

61. Darbyshire S, Francis A, Bromfield ESP, Mechanda S (2021). The biology of Canadian weeds. XX. Galega officinalis L. Canadian Journal of Plant Science, https://doi.org/10.1139/CJPS-2020-0327

60. Wasai-Hara S, Minamisawa K, Cloutier S and Bromfield ESP (2020). Strains of Bradyrhizobium cosmicum sp. nov., isolated from contrasting habitats in Japan and Canada possess photosynthesis gene clusters with the hallmark of genomic islands. International Journal of Systematic and Evolutionary Microbiology, 70:5063-5074. https://doi.org/10.1099/ijsem.0.004380

59. Bromfield ESP, Cloutier S and Nguyen HDT. (2020) Description and complete genome sequences of Bradyrhizobium symbiodeficiens sp. nov., a non-symbiotic bacterium associated with legumes native to Canada.  International Journal of Systematic and Evolutionary Microbiology 70:442-449. https://doi.org/10.1099/ijsem.0.003772

58. Cloutier S and Bromfield ESP (2019). Analysis of the complete genome sequence of the widely studied strain Bradyrhizobium betae PL7HG1T reveals the presence of photosynthesis genes and a putative plasmid. Microbiology Resource Announcements, 8 (46), e01282-19. https://doi.org/10.1128/MRA.01282-19.

57. Bromfield, ESP, Cloutier S, Nguyen HDT (2019) Description and complete genome sequence of Bradyrhizobium amphicarpaeae sp. nov. harboring photosystem and nitrogen fixation genes. International Journal of Systematic and Evolutionary Microbiology. 69:2841-2848. https://doi.org/10.1099/ijsem.0.003569

56. Bromfield, ESP, Cloutier, S, Robidas, C, Tran Thi, TV, Darbyshire, SJ (2019). Invasive Galega officinalis (Goat's rue) plants in Canada form a symbiotic association with strains of Neorhizobium galegae sv. officinalis originating from the Old World. Ecology and Evolution 9:6999-7004. https://doi.org/10.1002/ece3.5266

55. Nguyen HDT, Cloutier S, Bromfield ESP (2018)   Complete Genome Sequence of Bradyrhizobium ottawaense OO99T, an Efficient Nitrogen-Fixing Symbiont of Soybean. Microbiology Resource Announcements 7 (21), e01477-18. https://doi.org/10.1128/MRA.01477-18

54. Tchagang C, Xu R, Overy D, Blackwell B, Chabot D, Hubbard K, Doumbou C, Bromfield ESP, Tambong J (2018). Diversity of bacteria associated with corn roots inoculated with Canadian woodland soils, and description of Pseudomonas aylmerense sp. nov. Heliyon 4 (8), e007614: e00761. https://doi.org/10.1016/j.heliyon.2018.e00761

53. Magazine Article [Report on Eden Bromfield’s research on the isolation, discovery and characterization of novel symbiotic bacteria (Bradyrhizobium spp.) with potential as elite soybean inoculants adapted to Canadian conditions)]:

King, C (2018). Going Native with Nitrogen Fixation. Top Crop Manager, 44: 5-6. https://www.topcropmanager.com/going-native-with-nitrogen-fixation-21468/

52. Bromfield ESP, Cloutier S, Tambong J, Tran Thi TV (2017). Soybeans inoculated with root zone soils of Canadian native legumes harbour diverse and novel Bradyrhizobium spp. that possess agricultural potential. Systematic and Applied Microbiology 40: 440-447. https://doi.org/10.1016/j.syapm.2017.07.007

51. Tambong JT, Xu R and Bromfield ESP (2016). Pseudomonas canadensis sp. nov., a biological control agent isolated from a field plot under long-term mineral fertilization. International Journal of Systematic and Evolutionary Microbiology 67 (4), 889. https://doi.org/10.1099/ijsem.0.001698

50. Tchagang CF, Xu R, Mehrtash S, Rahimi S, Sidibé A, Li X, Bromfield ESP, Tambong JT. (2016). Draft genome sequences of two novel Pseudomonas strains exhibiting differential hypersensitivity reactions on tobacco and corn seedlings. Genome Announcements 4(5): e01057-16. https://doi.org/10.1128/genomeA.01057-16

49. Adam Z, Chen Q, Xu R, Diange R, Bromfield E.S.P, and Tambong JT (2015). Draft Genome Sequence of Pseudomonas simiae Strain 2-36, an in vitro antagonist of Rhizoctonia solani and Gaeumannomyces graminis. Genome Announcements 3(1): e01534-14. https://doi.org/10.1128/genomeA.01534-14. https://doi.org/10.1128/genomeA.01534-14

48. Yu, X., Cloutier, S., Tambong, JT and Bromfield, ESP (2014). Bradyrhizobium ottawaense sp. nov., a symbiotic nitrogen fixing bacterium from root nodules of soybeans in Canada. International Journal of Systematic and Evolutionary Microbiology 64: 3202–3207. https://doi.org/10.1099/ijs.0.065540-0

47. Adam, Z., Tambong, J.T., Lewis, C.T., Lévesque C.A., Chen, W., Bromfield, E.S.P., Khan, I.U.H, and Xu, R (2014) Draft genome sequence of Pantoea ananatis strain LMG 2665T, a bacterial pathogen of Pineapple fruitlets Genome announcements 2(3): e00489-14. https://doi.org/10.1128/genomeA.00489-14

46. Tang J, Bromfield ESP, Rodrigue N, Cloutier S. and Tambong JT (2012). Microevolution of symbiotic Bradyrhizobium populations associated with soybeans in east North America. Ecology and Evolution 2: 2943–2961. https://doi.org/10.1002/ece3.404

45. Tang J, Zheng A, Bromfield ESP, Zhu J, Li S, Wang S, Deng Q and Li P (2011). 16S rRNA gene sequence analysis of halophilic and halotolerant bacteria isolated from a hypersaline pond in Sichuan, China. Annals Microbiology 61 (2), 375-381. https://doi.org/10.1007/s13213-010-0137-x

44. Bromfield ESP, Tambong J T, Cloutier S, Prévost D, Laguerre G, van Berkum P, Tran Thi T V, Assabgui R and Barran LR (2010). Ensifer, Phyllobacterium and Rhizobium species occupy nodules of Medicago sativa (alfalfa) and Melilotus alba (sweet clover) grown at a Canadian site without a history of cultivation. Microbiology 156: 505-520. https://doi.org/10.1099/mic.0.034058-0

43. Tambong, J. T., Xu R, and Bromfield, E. S. P (2009) Intercistronic heterogeneity of the 16S–23S rRNA spacer region among Pseudomonas strains isolated from subterranean seeds of hog peanut (Amphicarpa bracteata). Microbiology 155:2630-2640. https://doi.org/10.1099/mic.0.028274-0

42. Prevost D and Bromfield ESP (2003) Diversity of symbiotic rhizobia resident in Canadian soils. Canadian Journal of Soil Science 83:311-319. https://doi.org/10.4141/S01-066

41. Barran LR, Bromfield ESP, and Brown DCW (2002) Identification and cloning of the bacterial nodulation specificity gene in the Sinorhizobium meliloti - Medicago laciniata symbiosis. Canadian Journal of Microbiology 48: 765-771. https://doi.org/10.1139/w02-072

40. Barran LR, Ritchot N and Bromfield ESP (2001) A cryptic plasmid, pRm1132f, from Sinorhizobium meliloti replicates by a Rolling Circle Mechanism. Journal of Bacteriology 183: 2704-2708. https://doi.org/10.1128/JB.183.8.2704-2708.2001

39. Bromfield, E. S. P., Butler G. and Barran, L. R (2001) Temporal effects on the composition of a population of Sinorhizobium meliloti associated with Medicago sativa and Melilotus alba. Canadian Journal of Microbiology 47: 567-573.

38. Barran LR and Bromfield ESP (2001). Diversity and dynamics of Sinorhizobium meliloti populations. CIFN Twentieth Anniversary (Mexico) Special Issue. Delgado, G. H. (Editor) 94-97.

37. Prevost D. and Bromfield ESP (2001). Diversity of rhizobia in Canadian agricultural soils.

In: Soil Biodiversity: Issues for Canadian Agriculture. Fox C.A. and Topp E (Editors). Research Branch, Agriculture and Agri-Food Canada. 12pp.

36. LR Barran, ESP Bromfield and DCW Brown (2000) Genetic factor of S. meliloti USDA 1170 containing nodulation efficiency factor. Patent WO2000022138A1. https://patents.google.com/patent/WO2000022138A1/

35. DCW Brown, LR Barran and ESP Bromfield (2000) Hybrid alfalfa (Medicago sativa). Patent WO2000021358A1. https://patents.google.com/patent/WO2000021358A1

34. Bromfield E S P, Behara A M P, Singh, R S. and Barran, L R (1998) Genetic variation in local populations of Sinorhizobium meliloti. Soil Biology and Biochemistry 30:1707-1716. https://doi.org/10.1016/S0038-0717(98)00017-0

33. Barran L. R, Bromfield E. S. P. and Whitwill, S. T (1997) Improved medium for isolating Rhizobium meliloti from soil. Soil Biology and Biochemistry 29:1591-1593. https://doi.org/10.1016/S0038-0717(97)00042-4

32. Barran, L.R. and Bromfield, E.S.P (1997) Competition among rhizobia for nodulation of legumes.  In: Biotechnology and the Improvement of Forage Legumes. Eds. McKersie, B.D. and D.C.W. Brown. CAB International, U.K. pp. 343-375 [Book chapter]

31. Froissard, D, Bromfield, ESP, Whitwill, ST and Barran, LR (1995) Construction and properties of cloning vectors based on a 7.2 kb Rhizobium meliloti cryptic plasmid. Plasmid 33: 226-231.  https://doi.org/10.1006/plas.1995.1024

30. Bromfield, E.S.P, Barran L.R. and Wheatcroft R (1995) Relative genetic structure of a  field population of Rhizobium meliloti isolated directly from soil and from nodules of alfalfa (Medicago sativa) and sweet clover (Melilotus alba). Molecular Ecology 4:183-188. https://doi.org/10.1111/j.1365-294X.1995.tb00207.x

29. Barran, L.R., Bromfield, E.S.P., Laberge S and Wheatcroft R (1994) Insertion sequence (IS) hybridization supports classification of Rhizobium meliloti by phage typing. Molecular Ecology 3: 267-270. https://doi.org/10.1111/j.1365-294X.1994.tb00061.x

28. Bromfield, E.S.P., Wheatcroft R and L.R. Barran (1994) Medium for direct isolation of Rhizobium meliloti from soils.  Soil Biology and Biochemistry 26: 423-428. https://doi.org/10.1016/0038-0717(94)90173-2

27. Barran, L.R. and Bromfield E.S.P (1993) Does siderophore production influence the relative abundance of Rhizobium meliloti in two field populations? Canadian Journal of Microbiology 39: 348-351. https://doi.org/10.1139/m93-049

26. Rastogi, V., Bromfield E.S.P., Whitwill S.T and Barran L.R (1992) A cryptic plasmid of indigenous Rhizobium meliloti possesses reiterated nodC and nif E genes and undergoes DNA rearrangement.  Canadian Journal of Microbiology 38: 563-568. https://doi.org/10.1139/m92-092

25. Prévost, D and Bromfield, ESP (1991) Effect of low root temperature on symbiotic nitrogen fixation and competitive nodulation of Onobrychis viciifolia (sainfoin) by strains of arctic and temperate rhizobia. Biology and Fertility of Soils 12: 161-164. https://doi.org/10.1007/BF00337195

24. Barran, L.R., Bromfield, E.S.P., Rastogi, V., Whitwill S.T and Wheatcroft R. (1991) Transposition and copy number of insertion sequence ISRm1 are not correlated with symbiotic performance of Rhizobium meliloti from two field sites. Canadian Journal of Microbiology 37: 576-579. https://doi.org/10.1139/m91-097

23. Bromfield, E.S.P. and Barran L.R (1990) Promiscuous nodulation of Phaseolus vulgaris, Macroptilium atropurpureum and Leucaena leucocephela by indigenous Rhizobium meliloti. Canadian Journal of Microbiology 36: 369-372. https://doi.org/10.1139/m90-065

22. Chan, Y-K., Barran L.R and Bromfield E.S.P (1989) Denitrification activity of phage types representative of two populations of indigenous Rhizobium meliloti. Canadian Journal of Microbiology 35: 737-740. https://doi.org/10.1139/m89-120

21. Bromfield, E.S.P., Barran L.R and Prévost D (1989) Is frequency of occurrence of indigenous Rhizobium meliloti in nodules of field grown plants related to intrinsic competitiveness? Soil Biology and Biochemistry 21(4): 607-609. https://doi.org/10.1016/0038-0717(89)90137-5

20. Barran, L.R. and Bromfield E.S.P (1988) Symbiotic gene probes hybridize to cryptic plasmids of indigenous Rhizobium meliloti. Canadian Journal of Microbiology 34: 703-707. https://doi.org/10.1139/m88-119

19. Thurman, N. P. and Bromfield, E. S. P (1988) Effect of variation within and between Medicago and Melilotus species on the composition and dynamics of indigenous populations of Rhizobium meliloti. Soil Biology and Biochemistry 20: 31-38. https://doi.org/10.1016/0038-0717(88)90123-X

18. Bromfield, E.S.P.,Thurman N.P., Whitwill, S.T and L.R. Barran (1987) Plasmids and symbiotic effectiveness of representative phage types from two indigenous populations of Rhizobium meliloti. Journal of General Microbiology.133: 3457-3466. https://doi.org/10.1099/00221287-133-12-3457

17. Lewis, D.M., Bromfield E.S.P and L.R. Barran (1987) Effect of rifampin resistance on nodulating competitiveness of Rhizobium meliloti. Canadian Journal of Microbiology 33: 343-345. https://doi.org/10.1139/m87-059

16. Bromfield, E.S.P., Sinha I.B and Wolynetz, M.S (1986). Influence of location, host cultivar and inoculation on the composition of naturalized populations of Rhizobium meliloti in Medicago sativa nodules. Applied and Environmental Microbiology 51:1077-1084. https://doi.org/10.1128/aem.51.5.1077-1084.1986

15. Bromfield, E.S.P., Lewis D.M and L.R. Barran (1985) Cryptic plasmid and rifampin resistance in Rhizobium meliloti influencing nodulation competitiveness. Journal of Bacteriology 164: 410-413. https://doi.org/10.1128/jb.164.1.410-413.1985

14. Bromfield, E.S.P (1984) Variation in preference for Rhizobium meliloti within and between Medicago sativa cultivars grown in soil. Applied and Environmental Microbiology 48: 1231-1236. https://doi.org/10.1128/aem.48.6.1231-1236.1984

13. Bromfield, E.S.P (1984) The preference for strains of Rhizobium meliloti by cultivars of Medicago sativa grown on agar. Canadian Journal of Microbiology.30: 1179-1183. https://doi.org/10.1139/m84-184

12. Sinha, R, Bromfield, E.S.P and Peterson, E (1984) Application of immuno-diffusion to the identification of Rhizobium meliloti competing for nodulation on Medicago sativa. Antonie van Leeuwenhoek. 50:155-160. https://doi.org/10.1007/BF00400176

11. Bromfield, ESP and Kumar Rao, JVDK. (1983). Studies on fast and slow growing Rhizobium spp. nodulating Cajanus cajan and Cicer arietinum. Annals of Applied Biology.102: 485-493. https://doi.org/10.1111/j.1744-7348.1983.tb02719.x

10. Bromfield, E.S.P., Stein, M. and White, R.P. (1982). Identification of Rhizobium strains on antibiotic concentration gradients. Annals of Applied Biology 101: 269-277. https://doi.org/10.1111/j.1744-7348.1982.tb00822.x

9. Stein, M, Bromfield, ESP and Dye, M (1982). An assessment of a method based on intrinsic antibiotic resistance for identifying Rhizobium strains. Annals of Applied Biology 101: 1261-1267. https://doi.org/10.1111/j.1744-7348.1982.tb00821.x  

8. Bromfield, ESP and Roughley, RJ (1980). Characterization of rhizobia isolated from nodules of locally adapted Glycine max grown in Nigeria. Annals of Applied Biology 95: 185-190. https://doi.org/10.1111/j.1744-7348.1980.tb04737.x

7. Bromfield, E.S.P. and Jones, D.G. (1980). A strain marker in Rhizobium trifolii based on the absorption of congo-red. Microbiological Research, 135: 290-295 (formerly: Zentralblatt für Bakteriologie, Parasitenkunde, Infektionskrankheiten und Hygiene.).

6. Bromfield, E.S.P. and Jones, D.G. (1980). Studies on double strain occupancy of nodules and the competitive ability of Rhizobium trifolii on red and white clover grown in soil and agar. Annals Applied Biology 94: 51-59. https://doi.org/10.1111/j.1744-7348.1980.tb03895.x

5. Bromfield, E.S.P. and Jones, D.G. (1980). Studies on acid tolerance of Rhizobium trifolii in culture and soil. Journal Applied Bacteriology 48: 253-264. https://doi.org/10.1111/j.1365-2672.1980.tb01224.x

4. Bromfield, E.S.P. and Ayanaba, A (1980) The efficacy of soybean inoculation on acid soil in tropical Africa.  Plant and Soil. 54: 95-106. https://doi.org/10.1007/BF02182002

3. Roughley, R.J., Bromfield, E.S.P., Pulver, E.L. and Day, J.M. (1980). Competition between species of Rhizobium for nodulation of Glycine max. Soil Biology and Biochemistry.12: 467- 470. https://doi.org/10.1016/0038-0717(80)90081-4

2. Bromfield, E.S.P. and Jones, D.G. (1979). The competitive ability and symbiotic effectiveness of doubly labelled antibiotic resistant mutants of Rhizobium trifolii. Annals Applied Biology 91: 211-219. https://doi.org/10.1111/j.1744-7348.1979.tb06492.x

1. Jones, D.G. and Bromfield, E.S.P (1978). A study of the competitive ability of streptomycin and spectinomycin mutants of Rhizobium trifolii using various marker techniques. Annals Applied Biology 88: 448-450. https://doi.org/10.1111/j.1744-7348.1978.tb00738.x