COMPARATIVE-ANALYSIS OF ANTIBIOTIC-RESISTANCE - IMMUNOFLUORESCENT COLONY STAINING, AND A TRANSGENIC MARKER (BIOLUMINESCENCE) FOR MONITORINGTHE ENVIRONMENTAL FATE OF A RHIZOBACTERIUM

Field releases of the mild-type plant growth-promoting rhizobacterium Pseudomonas fluorescens 89B-27, its bioluminescent derivative GEM-8 (8 9B-27::Tn4431), and a spontaneous rifampin-resistant variant (R34) wer e established on cucumber in 1994 and 1995 to examine the efficiency o f these marker systems for estimating the wild-type population, Seed a nd root samples were taken 0, 7, 14, 21 or 28, 35 or 42, and 70 days a fter planting in each year and processed for enumeration by spiral pla ting or immunofluorescent colony staining (IFC), In both Sears, the po pulations of 89B-27. R34, and GEM-8, as measured by IFC, were not sign ificantly different (P > 0.05) from each other at each sampling time, However, the populations of R34 and GEM-8, as measured by spiral plati ng and differentiation based on their respective phenotypes, were sign ificantly lower (P < 0.05) than the wild-type populations and their IF C-determined populations, These data indicate that traditional marker systems may underestimate populations and hence the survival and colon ization of genetically marked bacteria.