In situ survival of plasmid-bearing and plasmidless Pseudomonas aeruginosa in pristine tropical waters.
Two rare wild-type strains of Pseudomonas aeruginosa were mixed in membrane diffusion chambers and then introduced into a natural freshwater environment for 72 h. The plasmid-containing strain (R serotype 15) and the plasmidless strain (H serotype 5) had initial bacterial densities of 2 x 10(5) cells per ml. Samples collected from the chambers were analyzed for viable and direct counts and for acquired-resistance frequencies. Suspected transconjugant-to-donor ratios ranged from 0.5 to 1.3; transfer percentages ranged from 13 to 70%. [3H]thymidine uptake indicated DNA synthesis in both strains as well as in transconjugants. These studies indicate that rare wild-type bacterial strains with large plasmid loads can survive as well as can bacteria with low plasmid loads when exposed to the in situ conditions of a tropical freshwater habitat. These results also suggest that genetic modification of indigenous microbiota through conjugation or transformation is feasible when rare wild-type strains or genetically engineered microorganisms are released in large numbers in tropical aquatic ecosystems.
Cruz-Cruz
N E
NE
Department of Biology, College of Natural Sciences, University of Puerto Rico, Río Piedras 00931.
Toranzos
G A
GA
Ahearn
D G
DG
Hazen
T C
TC
D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000096:biosynthesis; D005455:Fluorescent Antibody Technique; D005618:Fresh Water; D010957:Plasmids; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000254:growth & development*; D011647:Puerto Rico; D014329:Tropical Climate; D014871:Water Microbiology
D004269:DNA, Bacterial