Effect of root exudates and bacterial metabolic activity on conjugal gene transfer in the rhizosphere of a marsh plant
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Effect of root exudates and bacterial metabolic activity on conjugal gene transfer in the rhizosphere of a marsh plant. / Kroer, Niels; Barkay, Tamar; Sørensen, Søren; Weber, David.
In: FEMS Microbiology Ecology, Vol. 25, No. 4, 1998, p. 375-384.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Effect of root exudates and bacterial metabolic activity on conjugal gene transfer in the rhizosphere of a marsh plant
AU - Kroer, Niels
AU - Barkay, Tamar
AU - Sørensen, Søren
AU - Weber, David
PY - 1998
Y1 - 1998
N2 - Genetic exchange between bacteria in natural habitats is believed to be strongly influenced by availability of growth substrates and growth rate. To test this hypothesis, conjugal transfer of an RP4 derivative between Pseudomonas fluorescens and Serratia sp. was studied in a simple sand/plant microcosm and was related to availability of root exudates and bacterial metabolic activity. The presence of the plant (Echinochlora crusgalli) greatly stimulated transfer. Average transfer ratios (T/D·R) were 8.9 x 10- 11 in the rhizosphere and 5.5 x 10-15 in sand unaffected by the plant root. The bacteria used root exudates as growth substrate and depending on cell density, the metabolic activity ([3H]leucine uptake) of the cells was higher in the rhizosphere than in the sand (around 1.0 x 10-2 and 0.5 x 10-2 fmol leucine CFU-1 h-1, respectively). Thus, an apparent correlation between metabolic activity and transfer was observed. Additional experiments, however, suggested that there was no causal relationship between the two. When incubated in a sand microcosm containing root exudates, the metabolic activity of the bacteria increased while conjugal transfer ratios remained constant. Hence, contrary to the accepted view, root exudates and metabolic activity did not appear to be responsible for the stimulation of conjugal transfer in the rhizosphere.
AB - Genetic exchange between bacteria in natural habitats is believed to be strongly influenced by availability of growth substrates and growth rate. To test this hypothesis, conjugal transfer of an RP4 derivative between Pseudomonas fluorescens and Serratia sp. was studied in a simple sand/plant microcosm and was related to availability of root exudates and bacterial metabolic activity. The presence of the plant (Echinochlora crusgalli) greatly stimulated transfer. Average transfer ratios (T/D·R) were 8.9 x 10- 11 in the rhizosphere and 5.5 x 10-15 in sand unaffected by the plant root. The bacteria used root exudates as growth substrate and depending on cell density, the metabolic activity ([3H]leucine uptake) of the cells was higher in the rhizosphere than in the sand (around 1.0 x 10-2 and 0.5 x 10-2 fmol leucine CFU-1 h-1, respectively). Thus, an apparent correlation between metabolic activity and transfer was observed. Additional experiments, however, suggested that there was no causal relationship between the two. When incubated in a sand microcosm containing root exudates, the metabolic activity of the bacteria increased while conjugal transfer ratios remained constant. Hence, contrary to the accepted view, root exudates and metabolic activity did not appear to be responsible for the stimulation of conjugal transfer in the rhizosphere.
KW - Conjugation
KW - Metabolic activity
KW - Rhizosphere
KW - Root exudate
U2 - 10.1016/S0168-6496(98)00007-5
DO - 10.1016/S0168-6496(98)00007-5
M3 - Journal article
AN - SCOPUS:0031979341
VL - 25
SP - 375
EP - 384
JO - F E M S Microbiology Reviews
JF - F E M S Microbiology Reviews
SN - 0168-6445
IS - 4
ER -
ID: 214688890