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Melanin production by Rhizobium strains
M T Cubo1, A M Buendia-Claveria, J E Beringer
1Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080 Seville, Spain, and Department of Microbiology, University of Bristol, The Medical School, University Walk, Bristol, BS8 1TD, United Kingdom.
Applied and Environmental Microbiology
|July 1, 1988
Summary
Melanin production was identified in several Rhizobium strains, including R. leguminosarum and R. meliloti, but not in Bradyrhizobium. The genes responsible for melanin synthesis (mel genes) were found to be plasmid-borne in these Rhizobium species.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Melanin production is a characteristic observed in some bacteria.
- The genetic basis and location of melanin production in Rhizobium and Bradyrhizobium species are not fully understood.
Purpose of the Study:
- To screen Rhizobium and Bradyrhizobium strains for melanin production.
- To investigate the genetic location of melanin production (mel genes) in producer strains.
Main Methods:
- Screening of various Rhizobium and Bradyrhizobium strains for pigment production.
- Plasmid analysis and gene mapping in selected strains.
Main Results:
- Melanin production was detected in strains of Rhizobium leguminosarum (biovars viceae, trifolii, phaseoli), Rhizobium meliloti, and Rhizobium fredii.
- No melanin production was observed in 19 Bradyrhizobium strains.
- Melanin production and nod genes were found to be plasmid-borne in R. leguminosarum biovar trifolii RS24.
- Melanin synthesis (mel) genes were located on symbiotic plasmids in R. leguminosarum biovar phaseoli CFN42 and R. meliloti GR015.
- Melanin production in R. fredii USDA 205 correlated with its smallest indigenous plasmid.
Conclusions:
- Melanin production is strain-specific within the Rhizobium genus, with Bradyrhizobium strains lacking this trait.
- The genetic determinants for melanin production in Rhizobium are primarily located on plasmids, often the symbiotic plasmid, suggesting a link between symbiosis and pigment production.