LUMINESCENCE BASED DETECTION OF ERWINIA-CAROTOVORA SUBSP CAROTOVORA IN SOIL

Light output from luminescent strains of Erwinia carotovora subsp. carotovora, constitutively expressing the luciferase genes, was used for specific estimation of bacterial biomass, in liquid culture and in soil. In liquid culture, the lower detection limit was ca 100 cfu ml-1. For cells inoculated into soil, the sensitivity of detection was reduced. When light output was measured directly from 1 g of soil, the lower detection limit was ca 10(6) cfu g-1 of soil, while measuring light from a soil suspension increased the sensitivity to 10(4) cfu g-1 of soil. Measurements of light output were obtained within 5 min of sampling. Luminometry, therefore, offers great potential as a rapid, non-extractive, method for the specific detection and enumeration of genetically-modified microorganisms in soil.