title: Preservation of Rhizobium viability and symbiotic infectivity by suspension in water.
abstract: Three Rhizobium japonicum strains and two slow-growing cowpea-type Rhizobium strains were found to remain viable and able to rapidly modulate their respective hosts after being stored in purified water at ambient temperatures for periods of 1 year and longer. Three fast-growing Rhizobium species did not remain viable under the same water storage conditions. After dilution of slow-growing Rhizobium strains with water to 10(3) to 10(5) cells ml-1, the bacteria multiplied until the viable cell count reached levels of between 10(6) and 10(7) cells ml-1. The viable cell count subsequently remained fairly constant. When the rhizobia were diluted to 10(7) cells ml-1, they did not multiply, but full viability was maintained. If the rhizobia were washed and suspended at 10(9) cells ml-1, viability slowly declined to 10(7) cells ml-1 during 9 months of storage. Scanning electron microscopy showed that no major morphological changes took place during storage. Preservation of slow-growing rhizobia in water suspensions could provide a simple and inexpensive alternative to current methods for the preservation of rhizobia for legume inoculation.
mesh_terms: D001431:Bacteriological Techniques; D007887:Fabaceae / Q000382:microbiology*; D008855:Microscopy, Electron, Scanning; D010935:Plant Diseases; D010946:Plants, Medicinal; D011309:Preservation, Biological / Q000379:methods; D012231:Rhizobium / Q000166:cytology / Q000502:physiology*; D013025:Glycine max / Q000382:microbiology; D013559:Symbiosis; D013696:Temperature; D013997:Time Factors; D014871:Water Microbiology