title: Photodegradation of soil organic matter and its effect on gram-negative bacterial growth.
abstract: To learn more about the role of the reactive oxygen species (ROS) in the production of bioavailable products of the dissolved organic matter, we investigate here the effect of the photolysis (lambda(exc) > 320 nm) of a soil extract (SE) on the growth of bacteria isolated from the same soil as used for obtaining the extract. Comparative experiments with Aldrich humic acid (AHA) as substrate were performed. The photodegradation of the SE was evaluated with different techniques-UV-visible absorption spectroscopy, fluorescence excitation emission matrices (EEM) and Fourier transform infrared spectroscopy (FTIR). Known ROS scavengers were employed to study the effect of photochemically produced ROS on the photodegradation of the substrates. To evaluate the effect of irradiation on the bioavailability of the SE and AHA, photolyzed and nonphotolyzed substrates were added to different culture media and the growth of Pseudomonas sp. isolated from the soil and a strain of Escherichia coli were studied. The different results obtained were assigned to the dissimilar metabolisms of both bacteria.
authors.affiliation: Instituto de Investigaciones Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina.
authors.forename: Gabriela N
authors.initials: GN
authors.lastname: Bosio
authors.forename: Pedro David
authors.initials: PD
authors.lastname: Gara
authors.forename: Fernando S García
authors.initials: FS
authors.lastname: Einschlag
authors.forename: Mónica C
authors.initials: MC
authors.lastname: Gonzalez
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Del Panno
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Mártire
mesh_terms: D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development*; D006812:Humic Substances / Q000528:radiation effects*; D009930:Organic Chemicals / Q000737:chemistry / Q000494:pharmacology / Q000528:radiation effects*; D010777:Photochemistry; D010782:Photolysis / Q000528:radiation effects; D011549:Pseudomonas / Q000187:drug effects* / Q000254:growth & development*; D017382:Reactive Oxygen Species / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D012988:Soil Microbiology; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D006812:Humic Substances; D009930:Organic Chemicals; D017382:Reactive Oxygen Species