Gisèle Laguerre died last night. She was just 55 years old but had been ill for some months. She was such a good colleague and friend over many years, and made important contributions to rhizobial science.
I first met Gisèle more than 20 years ago, when she worked with Noëlle Amarger at INRA in Dijon. We shared an interest in the genetic diversity of Rhizobium leguminosarum at a time when studies of bacterial population genetics were rare. This is not the time for a comprehensive review of her work, but here are a few of her early contributions to our knowledge of rhizobia. It was an exciting time of discovery, and I remember many discussions with Gisèle while this work was in progress. She demonstrated that plasmid profiles could be highly variable and made them into a useful tool for characterising strains (1), enabling her to demonstrate that genetic transfer had occurred (2). In a technically difficult study that has seldom been followed up, she and her student isolated R. leguminosarum directly from soil and demonstrated that many strains did not carry nodulation genes (3-5). She characterised the symbionts of Phaseolus vulgaris in European soils and demonstrated that they were not all R. leguminosarum (6-8). She developed PCR-based methods for characterising strain diversity (9-10). She found a strain of R. leguminosarum that appeared to have the nodulation genes carried in the chromosome (11). She demonstrated variation in host compatibility within R. leguminosarum biovar viciae (12). Those are just a few of her earlier papers, mostly on R. leguminosarum – she continued to publish important work on this species, on other rhizobia, and on other bacteria.
Gisèle has left us far too early, but we still have the wealth of knowledge about rhizobia that she brought us.
(1) Laguerre, G., Mazurier, S.I., and Amarger, N. (1992) Plasmid profiles and restriction fragment length polymorphism of Rhizobium leguminosarum bv viciae in field populations. FEMS Microbiology Ecology 101: 17-26. http://dx.doi.org/10.1016/0378-1097(92)90693-I
(2) Laguerre, G., Geniaux, E., Mazurier, S.I., Casartelli, R.R., and Amarger, N. (1993) Conformity and diversity among field isolates of Rhizobium leguminosarum bv. viciae, bv. trifolii, and bv. phaseoli revealed by DNA hybridization using chromosome and plasmid probes. Canadian Journal of Microbiology 39: 412-419.
(3) Laguerre, G., Bardin, M., and Amarger, N. (1993) Isolation from soil of symbiotic and nonsymbiotic Rhizobium leguminosarum by DNA hybridization. Canadian Journal of Microbiology 39: 1142-1149.
(4) Louvrier, P., Laguerre, G., and Amarger, N. (1995) Semiselective medium for isolation of Rhizobium leguminosarum from soils. Soil Biology & Biochemistry 27: 919-924.
(5) Louvrier, P., Laguerre, G., and Amarger, N. (1996) Distribution of symbiotic genotypes in Rhizobium leguminosarum biovar viciae populations isolated directly from soils. Applied and Environmental Microbiology 62: 4202-4205.
(6) Geniaux, E., Laguerre, G., and Amarger, N. (1993) Comparison of geographically distant populations of rhizobium isolated from root nodules of Phaseolus vulgaris. Molecular Ecology 2: 295-302. http://dx.doi.org/10.1111/j.1365-294X.1993.tb00022.x
(7) Amarger, N., Bours, M., Revoy, F., Allard, M.R., and Laguerre, G. (1994) Rhizobium tropici nodulates field-grown Phaseolus vulgaris in France. Plant and Soil 161: 147-156.
(8) Amarger, N., Macheret, V., and Laguerre, G. (1997) Rhizobium gallicum sp. nov. and Rhizobium giardinii sp. nov., from Phaseolus vulgaris nodules. International Journal of Systematic Bacteriology 47: 996-1006.
(9) Laguerre, G., Allard, M.R., Revoy, F., and Amarger, N. (1994) Rapid identification of rhizobia by Restriction Fragment Length Polymorphism analysis of PCR-amplified 16S ribosomal-RNA genes. Applied and Environmental Microbiology 60: 56-63.
(10) Laguerre, G., Mavingui, P., Allard, M.R., Charnay, M.P., Louvrier, P., Mazurier, S.I. et al. (1996) Typing of rhizobia by PCR DNA fingerprinting and PCR-restriction fragment length polymorphism analysis of chromosomal and symbiotic gene regions: Application to Rhizobium leguminosarum and its different biovars. Applied and Environmental Microbiology 62: 2029-2036.
(11) Mazurier, S.I., and Laguerre, G. (1997) Unusual localization of nod and nif genes in Rhizobium leguminosarum bv. viciae. Canadian Journal of Microbiology 43: 399-402.
(12) Laguerre, G., Louvrier, P., Allard, M.R., and Amarger, N. (2003) Compatibility of rhizobial genotypes within natural populations of Rhizobium leguminosarum biovar viciae for nodulation of host legumes. Applied and Environmental Microbiology 69: 2276-2283.