Conjugal transfer at natural population densities in a microcosm simulating an estuarine environment

Abstract

Estuarine microcosmswere used to follow conjugal transfer of a broad host range IncPl plasmid from a Pseudomonas putidu donor to indigenous bacteria. Donor cells were added at a concentration similar to the natural abundance of bacteria in the water column (lo6 cells ml-'). Transfer was not detected in any of the test microcosms (calculated limit of detection of lo-' and 10m4 transconjugants donor-' in water column and sediment, respectively), with the exception of transfer to an isogenic recipient (added at lo5 cells ml-'1 in sediments of controls that had been inoculated with both donors and recipients. The same plasmid was transferred with high efficiencies (10-l to 10m3) to a variety of recipients in filter and broth matings. These results suggest that if conjugal gene transfer occurred, it was at efficiencies that were not detectable in estuarine microcosms simulating natural population densities.

Ecotoxicological risk assessment of hospital wastewater: a proposed framework for raw effluents discharging into urban sewer network

“…The development of resistance to antimicrobial agents by many bacterial pathogens has compromised traditional therapeutic regimens, making treatment of infections more difficult [4]. Three factors have contributed to the development and spread of resistance: mutation in common genes that extend their spectrum of resistance, transfer of resistance genes among diverse microorganisms, and increase in selective pressures that enhance the development of resistant organisms [4,[20][21][22][23][24].…”

Using microcosms to study gene transfer in aquatic habitats

“…Habitats investigated in this way (Table 1) include river water and epilithon [13, 14, 19–21], lake water [16, 17, 22], marine water and sediment [23–33], estuarine water and sediment [34], drinking water [35] and wastewater [36, 37]. A typical example is the beaker microcosm used by Bale et al [13–15] and Hill et al [20] to investigate gene transfer in river epilithon.…”

Effect of root exudates and bacterial metabolic activity on conjugal gene transfer in the rhizosphere of a marsh plant

“…Gene transfer by conjugation has been shown to occur in a wide variety of laboratory systems simulating diverse environmental habitats such as soil [3^7], sea water [8,9], freshwater [10], sediments [8,11], bio¢lms [12] and sludge [13]. However, our own studies have shown infrequent spread of a plasmid by conjugation, when natural population densities were employed, in microcosms simulating the water column and bulk sediment of an aquatic ecosystem [8]. Hence, we hypothesized that in aquatic environments, conjugal gene transfer is localized to habitats de¢ned by high bacterial densities and availability of growth substrates.…”