title: Surfactants expressed by soil pseudomonads alter local soil-water distribution, suggesting a hydrological role for these compounds.
abstract: Several biological roles have been demonstrated for surfactants expressed by soil and rhizosphere Pseudomonas spp., but the impact of these powerful surface-active agents on the local soil-water distribution within the partially saturated soil pore network has not been examined. To investigate this potential hydrological role, the liquid surface tension (γ)-reducing activities (LSTRA) of 72 pseudomonads isolated from a sandy loam soil by tensiometry of culture supernatants were characterized. Of these, 67% exhibited LSTRA, reducing γ to a minimum (γ(Min)) of 24 mN m(-1) established by individual distribution identification analysis. Soil microcosms were then used to examine the impact of surfactant expression on the local soil-water distribution. The volumetric water content (θ) of soil microcosms was significantly lowered (0.78 ×) by Pseudomonas fluorescens SBW25 expressing the surfactant viscosin compared with a surfactant-deficient mutant (P<0.002). Six of 15 soil pseudomonad isolates examined were found to have a similar impact on θ when compared with sterile microcosms (P<0.05). These findings indicate that surfactant-expressing pseudomonads could modify the local soil-water distributions and that surfactants may therefore play a significant hydrological role in soils, in addition to their recognized biological activities.
authors.affiliation: The SIMBIOS Centre and the School of Contemporary Sciences, University of Abertay Dundee, Dundee, UK.
authors.forename: Joanna
authors.initials: J
authors.lastname: Fechtner
authors.forename: Anna
authors.initials: A
authors.lastname: Koza
authors.forename: Patricia Dello
authors.initials: PD
authors.lastname: Sterpaio
authors.forename: Simona M
authors.initials: SM
authors.lastname: Hapca
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Spiers
mesh_terms: D011549:Pseudomonas / Q000235:genetics / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*; D013500:Surface Tension; D013501:Surface-Active Agents / Q000032:analysis / Q000378:metabolism*; D058438:Water Cycle
chemical_list: D012987:Soil; D012989:Soil Pollutants; D013501:Surface-Active Agents