Papers by Fabrice Martin-Laurent
Environmental controls of 2-methyl-4-chlorophenoxyacetic acid (MCPA) degradation are poorly under... more Environmental controls of 2-methyl-4-chlorophenoxyacetic acid (MCPA) degradation are poorly understood. We investigated whether microbial MCPA degraders are stimulated by (maize) litter and whether this process depends on concentrations of MCPA and litter. In a microcosm experiment, different amounts of litter (0, 10 and 20 g kg−1) were added to soils exposed to three levels of the herbicide (0, 5 and 30 mg kg−1). The treated soils were incubated at 20 °C for 6 weeks, and samples were taken after 1, 3 and 6 weeks of incubation. In soils with 5 mg kg−1 MCPA, about 50 % of the MCPA was dissipated within 1 week of the incubation. Almost complete dissipation of the herbicide had occurred by the end of the incubation with no differences between the three litter amendments. At the higher concentration (30 mg kg−1), MCPA endured longer in the soil, with only 31 % of the initial amount being removed at the end of the experiment in the absence of litter. Litter addition greatly increased the dissipation rate with 70 and 80 % of the herbicide being dissipated in the 10 and 20 g kg−1 litter treatments, respectively. Signs of toxic effects of MCPA on soil bacteria were observed from related phospholipid fatty acid (PLFA) analyses, while fungi showed higher tolerance to the increased MCPA levels. The abundance of bacterial tfdA genes in soil increased with the co-occurrence of litter and high MCPA concentration, indicating the importance of substrate availability in fostering MCPA-degrading bacteria and thereby improving the potential for removal of MCPA in the environment.
Environmental science and pollution research international, Jan 22, 2015
Journal of Hazardous Materials, 2015
Soil organic amendment affects biotic and abiotic processes that control the fate of pesticides, ... more Soil organic amendment affects biotic and abiotic processes that control the fate of pesticides, but the treatment history of the soil is also relevant. These processes were assessed in a multidisciplinary study with the aim of optimizing pesticide mitigation in soils. Soil microcosms pre-treated (E2) or not with diuron (E1) were amended with either winery (W) or olive waste (O) vermicomposts. Herbicide dissipation followed a double first-order model in E1 microcosms, but a single first-order model in E2. Also, diuron persistence was longer in E1 than in E2 (E1-DT50>200 day(-1), E2-DT50<16 day(-1)). The genetic structure of the bacterial community was modified by both diuron exposure and amendment. O-vermicompost increased enzymatic activities in both experiments, but diuron-degrading genetic potential (puhB) was quantified only in E2 microcosms in accordance with reduced diuron persistence. Therefore, O-vermicompost addition favoured the proliferation of diuron degraders, increasing the soil diuron-depuration capability.
Environmental science and pollution research international, Jan 21, 2015
The fifth meeting of INRA's national network of ecotoxicologists took place on 25 to 27 Novem... more The fifth meeting of INRA's national network of ecotoxicologists took place on 25 to 27 November 2014 in Biarritz, France. The main aim of the meeting was to bring together ecotoxicologists from INRA and associated partners, providing them ample opportunity to share and discuss their latest scientific results as well as the national policy of research in ecotoxicology and to precise perspectives for the network.
Environmental science and pollution research international, Jan 31, 2015
The action mode of sulfonylurea herbicides is the inhibition of the acetohydroxyacid synthase (AH... more The action mode of sulfonylurea herbicides is the inhibition of the acetohydroxyacid synthase (AHAS) required for the biosynthesis of amino acids valine and isoleucine in plants. However, this enzyme is also present in a range of non-targeted organisms, among which soil microorganisms are known for their pivotal role in ecosystem functioning. In order to assess microbial toxicity of sulfonylurea herbicide nicosulfuron (NS), a tiered microcosm (Tier I) to field (Tier II) experiment was designed. Soil bacteria harboring AHAS enzyme tolerant to the herbicide nicosulfuron were enumerated, isolated, taxonomically identified, and physiologically characterized. Results suggested that application of nicosulfuron drives the selection towards NS-tolerant bacteria, with increasing levels of exposure inducing an increase in their abundance and diversity in soil. Tolerance to nicosulfuron was shown to be widespread among the microbial community with various bacteria belonging to Firmicutes (Baci...
Environmental Pollution, 2015
Pesticides generate transformation products (TPs) when they are released into the environment. Th... more Pesticides generate transformation products (TPs) when they are released into the environment. These TPs may be of ecotoxicological importance. Past studies have demonstrated how difficult it is to predict the occurrence of pesticide TPs and their environmental risk. The monitoring approaches mostly used in current regulatory frameworks target only known ecotoxicologically relevant TPs. Here, we present a novel combined approach which identifies and categorizes known and unknown pesticide TPs in soil by combining suspect screening time-of-flight mass spectrometry with in silico molecular typology. We used an empirical and theoretical pesticide TP library for compound identification by both non-target and target time-of-flight (tandem) mass spectrometry, followed by structural proposition through a molecular structure correlation program. In silico molecular typology was then used to group TPs according to common molecular descriptors and to indirectly elucidate their environmental parameters by analogy to known pesticide compounds with similar molecular descriptors. This approach was evaluated via the identification of TPs of the triazole fungicide tebuconazole occurring in soil during a field dissipation study. Overall, 22 empirical and 12 yet unknown TPs were detected, and categorized into three groups with defined environmental properties. This approach combining suspect screening time-of-flight mass spectrometry with molecular typology could be extended to other organic pollutants and used to rationalize the choice of TPs to be investigated towards a more comprehensive environmental risk assessment scheme.
Applied microbiology and biotechnology, Jan 25, 2015
The Arthrobacter sp. strain AK-YN10 is an s-triazine pesticide degrading bacterium isolated from ... more The Arthrobacter sp. strain AK-YN10 is an s-triazine pesticide degrading bacterium isolated from a sugarcane field in Central India with history of repeated atrazine use. AK-YN10 was shown to degrade 99 % of atrazine in 30 h from media supplemented with 1000 mg L(-1) of the herbicide. Draft genome sequencing revealed similarity to pAO1, TC1, and TC2 catabolic plasmids of the Arthrobacter taxon. Plasmid profiling analyses revealed the presence of four catabolic plasmids. The trzN, atzB, and atzC atrazine-degrading genes were located on a plasmid of approximately 113 kb.The flagellar operon found in the AK-YN10 draft genome suggests motility, an interesting trait for a bioremediation agent, and was homologous to that of Arthrobacter chlorophenolicus. The multiple s-triazines degradation property of this isolate makes it a good candidate for bioremediation of soils contaminated by s-triazine pesticides.
A microcosm approach was designed to link the abundances of bacteria and fungi to microhabitat fu... more A microcosm approach was designed to link the abundances of bacteria and fungi to microhabitat functions of soil microbiota. In microcosms, we used MCPA (2-methyl-4-chlorophenoxyacetic acid) as a model organic substance due to its well-known degradation pathways (tfdA genes) and due to the availability of primers targeting the tfdA gene encoding the enzyme responsible for the first step in degradation of this compound. We used maize litter to create a well-defined soil-litter interface (detritusphere). We studied microbial degradation, microbial abundance of degraders, adsorption, desorption and transport of MCPA along a gradient of decreasing availability of dissolved organic matter. Isotopic data ( 14 CO 2 , 14 C mic , 14 C-DOC, 14 C org , 14 C-MCPA, 14 C in the leachate) and molecular data (tfdA, 16S rDNA and 18S rDNA sequence copy numbers) were used as input variables for a mechanistic model. We showed that the quantification of the abundance of genes encoding specific functions of soil microbial communities helps to clarify the regulation of degradation of complex organic compounds at a biogeochemical interface.
Environmental science and pollution research international, Jan 7, 2015
Environmental controls of 2-methyl-4-chlorophenoxyacetic acid (MCPA) degradation are poorly under... more Environmental controls of 2-methyl-4-chlorophenoxyacetic acid (MCPA) degradation are poorly understood. We investigated whether microbial MCPA degraders are stimulated by (maize) litter and whether this process depends on concentrations of MCPA and litter. In a microcosm experiment, different amounts of litter (0, 10 and 20 g kg(-1)) were added to soils exposed to three levels of the herbicide (0, 5 and 30 mg kg(-1)). The treated soils were incubated at 20 °C for 6 weeks, and samples were taken after 1, 3 and 6 weeks of incubation. In soils with 5 mg kg(-1) MCPA, about 50 % of the MCPA was dissipated within 1 week of the incubation. Almost complete dissipation of the herbicide had occurred by the end of the incubation with no differences between the three litter amendments. At the higher concentration (30 mg kg(-1)), MCPA endured longer in the soil, with only 31 % of the initial amount being removed at the end of the experiment in the absence of litter. Litter addition greatly incre...
Applied Microbiology and Biotechnology, 2004
The kinetic resolution of racemic sulfoxides by dimethyl sulfoxide (DMSO) reductases was investig... more The kinetic resolution of racemic sulfoxides by dimethyl sulfoxide (DMSO) reductases was investigated with a range of microorganisms. Three bacterial isolates (provisionally identified as Citrobacter braakii, Klebsiella sp. and Serratia sp.) expressing DMSO reductase activity were isolated from environmental samples by anaerobic enrichment with DMSO as terminal electron acceptor. The organisms reduced a diverse range of racemic sulfoxides to yield either residual enantiomer depending upon the strain used. C. braakii DMSO-11 exhibited wide substrate specificity that included dialkyl, diaryl and alkylaryl sulfoxides, and was unique in its ability to reduce the thiosulfinate 1,4-dihydrobenzo-2, 3-dithian-2-oxide. DMSO reductase was purified from the periplasmic fraction of C. braakii DMSO-11 and was used to demonstrate unequivocally that the DMSO reductase was responsible for enantiospecific reductive resolution of racemic sulfoxides.
Environmental Science and Pollution Research, 2014
Your article is protected by copyright and all rights are held exclusively by Springer-Verlag Ber... more Your article is protected by copyright and all rights are held exclusively by Springer-Verlag Berlin Heidelberg. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Environmental Pollution, 2013
The impact of a multiple contamination by polycyclic aromatic hydrocarbons (PAHs) was studied on ... more The impact of a multiple contamination by polycyclic aromatic hydrocarbons (PAHs) was studied on permanent grassland soil, historically presenting low contamination (i.e. less than 1 mg kg À1 ). Soil microcosms were spiked at 300 mg kg À1 with either single or a mixture of seven PAHs. While total dissipation of the phenanthrene was reached in under 90 days, only 60% of the PAH mixture were dissipated after 90 days. Interestingly, after 30 days, the abundance of the GammaProteobacteria class (assessed by qPCR) become significantly higher in microcosms spiked with the PAH mixture. In addition, the specific abundance of the cultivable Pseudomonas spp., which belong to the GammaProteobacteria class, increased earlier and transiently (after 8 days) in the microcosms spiked with the PAH mixture. Consequently, we propose to use the GammaProteobacteria as a bioindicator to detect the impact on the bacterial community of a multiple contamination by PAHs in agricultural soils.
Soil Biology and Biochemistry, 2013
Environmental Pollution, 2007
Catabolic processes providing alternative sources of electron for the mitochondrial electron tran... more Catabolic processes providing alternative sources of electron for the mitochondrial electron transport chain are progressively emerging as important players in plants for stress responses, nutritional switch responses and growth and development. In this context, xenobiotics, such as the herbicide atrazine, which are at the crossroads of xenobiotic action, photosystem homeostasis and ROS dynamics, are likely to be useful for understanding the regulation of these catabolic processes. Transcriptomic analysis of atrazine effects on Arabidopsis under different conditions of carbon status reveals that atrazine significantly upregulates the genes involved in leucine catabolism, in contrast to partial regulatory effects on the genes involved in valine, isoleucine and lysine catabolic pathways. These effects on amino acid catabolism gene expression are associated with regulatory effects on genes involved in proteolytic processes and in alternative carbon mitochondrial respiration. Genes involved in leucine catabolism are activated by atrazine in the presence of exogenous sucrose, thus indicating that atrazine-associated signals can override sucrose repression. There may be a link between these effects and atrazine-related increase in hydrogen peroxide, which is involved in retrograde signalling. However, comparison with studies of reactive oxygen species modifications indicate that atrazine regulation of branched chain amino acid catabolism differs from reactive oxygen species signalling, including hydrogen peroxide, thus suggesting complex signalling pathways between photosystem functioning and leucine catabolism.
FEMS Microbiology Ecology, 2000
In the last 10 years, accelerated mineralization of Atrazine (2-chloro-ethylamino-6-isopropylamin... more In the last 10 years, accelerated mineralization of Atrazine (2-chloro-ethylamino-6-isopropylamino-s-triazine) has been evidenced in agricultural soils repeatedly treated with this herbicide. Here, we report on the interaction between earthworms, considered as soil engineers, and the Atrazine-degrading community.
Soil Biology & Biochemistry, 2008
Earthworms, because they change soil physical and chemical properties, are efficient engineers th... more Earthworms, because they change soil physical and chemical properties, are efficient engineers that act on soil microbial community and activity. Thus they may drive pollutant biodegradation in soil such as atrazine mineralization. We hypothesized that earthworms modify the abundance of indigenous soil bacteria and the fate and activity of atrazine-degraders in the soil they engineer by bioturbation. Two bacterial strains
Chemosphere, 2009
The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was found to ... more The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was found to be rapidly mineralized by a bacterial culture isolated from an agricultural soil regularly exposed to IPU. Molecular analysis of the bacterial culture by DNA fingerprinting, cloning and sequencing of the 16S rRNA genes revealed that it consisted of six different members among whom the dominant was related to Sphingomonas sp. Six bacterial strains belonging to genera Ancylobacter, Pseudomonas, Stenotrophomonas, Methylobacterium, Variovorax and Agrobacterium were isolated from the IPU-degrading culture. None of these were able to degrade IPU in pure culture and only the intact culture sustained the ability to mineralize IPU. The composition of the culture appeared stable suggesting that yet unknown interactions are involved in the IPU mineralization. IPU degradation involved the transitory accumulation of three known IPU metabolites 3-(4-isopropylphenyl)-1-methylurea, 3-(4-isopropylphenyl)-urea, and 4-isopropylaniline and their further degradation. Thus, it indicates a metabolic pathway initiated by two successive N-demethylations, followed by cleavage of the urea side chain. This culture did not degrade other structurally related phenylurea herbicides. The degrading activity of the bacterial culture was deeply influenced by the pH, being completely inhibited at pH 5.5 and optimal at pH 7.5.
Biodegradation, 2011
The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was found to ... more The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was found to be rapidly mineralized in an agricultural soil in France that had been periodically exposed to IPU. Enrichment cultures from samples of this soil isolated a bacterial strain able to mineralize IPU. 16S rRNA sequence analysis showed that this strain belonged to the phylogeny of the genus Sphingomonas (96% similarity with Sphingomonas sp. JEM-14, AB219361) and was designated Sphingomonas sp. strain SH. From this strain, a partial sequence of a 1,2-dioxygenase (catA) gene coding for an enzyme degrading catechol putatively formed during IPU mineralization was amplified. Phylogenetic analysis revealed that the catA sequence was related to Sphingomonas spp. and showed a lack of congruence between the catA and 16S rRNA based phylogenies, implying horizontal gene transfer of the catA gene cluster between soil microbiota. The IPU degrading ability of strain SH was strongly influenced by pH with maximum degradation taking place at pH 7.5. SH was only able to mineralize IPU and its known metabolites including 4-isopropylaniline and it could not degrade other structurally related phenylurea herbicides such as diuron, linuron, monolinuron and chlorotoluron or their aniline derivatives. These observations suggest that the catabolic abilities of the strain SH are highly specific to the metabolism of IPU.
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Papers by Fabrice Martin-Laurent