Methods to evaluate nodulation competitiveness between Sinorhizobium meliloti strains using melanin production as a marker.
Three methods to evaluate the relative ability of different strains of Sinorhizobium meliloti to occupy nodules formed on alfalfa after co-inoculation were compare in this study. Results obtained using the three methods of evaluation together, provided insight into the relative nodulation competitiveness between two given sinorhizobial strains. A simple visual phenotypic marker, i.e., melanin production was used to distinguish individual strains in a given assay. As such, melanin producing strains were compared with melanin non-producing strains throughout this study. Method 1 required the use of an ELISA plate, took 35 min for the analysis of 40 nodules, and allowed strain identification by melanin production 2 days after nodule harvest. Method 2 required 3 h for the analysis of 40 nodules, used an ELISA plate, growth of bacteria on Petri dishes, and melanin production was analysed after 48 h of cell culture. Finally, method 3 involved the whole nodulated plant root, required less material than the above methods, and results were obtained after 24 h. Only method 2 was useful in determining if both a melanin producing strain and a melanin non-producing strain had occupied an individual nodule. Each of the three methods represented a rapid way of studying strain competition for field studies, using a natural trait as a marker.
Castro
S
S
División de Bioquímica, Instituto de Investigaciones Biológicas Clemente Estable, Avda. Italia 3318, CP 11600, Montevideo, Uruguay. scs@iibce.edu.uy
Carrera
I
I
Martínez-Drets
G
G
D001431:Bacteriological Techniques; D004797:Enzyme-Linked Immunosorbent Assay; D000455:Medicago sativa / Q000382:microbiology*; D008543:Melanins / Q000032:analysis*; D018517:Plant Roots / Q000382:microbiology; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000302:isolation & purification*; D012967:Sodium Dodecyl Sulfate
D008543:Melanins; D012967:Sodium Dodecyl Sulfate