Impact of a pesticide cocktail (fenhexamid, folpel, deltamethrin) on the abundance of Glomeromycota in two agricultural soils.

Pesticide contamination of the environment can result from agricultural practices. Persistence of pesticide residues is a threat to the soil biota including plant roots and beneficial microorganisms, which support an important number of soil ecosystem services. Arbuscular mycorrhizal fungi (AMF) are key symbiotic microorganisms contributing to plant nutrition.

Characterization of epiphytic bacterial communities from grapes, leaves, bark and soil of grapevine plants grown, and their relations.

Despite its importance in plant health and crop quality, the diversity of epiphytic bacteria on grape berries and other plant parts, like leaves and bark, remains poorly described, as does the role of telluric bacteria in plant colonization. In this study, we compare the bacterial community size and structure in vineyard soils, as well as on grapevine bark, leaves and berries. Analyses of culturable bacteria revealed differences in the size and structure of the populations in each ecosystem.

Grape berry bacterial microbiota: impact of the ripening process and the farming system.

Wine grapes are a primary source of microbial communities that play a prominent role in the quality of grapes prior to harvesting, as well as in the winemaking process. This study investigated the dynamics and diversity of the epiphytic bacteria on the grape berry surface during maturation. The quantitative and qualitative effects of conventional and organic farming systems on this microbial community were investigated, using both cultivation-dependent and independent approaches.

Diuron mineralisation in a Mediterranean vineyard soil: impact of moisture content and temperature.

Background: The diuron-mineralising ability of the microbiota of a Mediterranean vineyard soil exposed each year to this herbicide was measured. The impact of soil moisture and temperature on this microbial activity was assessed.

Results: The soil microbiota was shown to mineralise diuron.

A fluorescence-based assay for measuring the viable cell concentration of mixed microbial communities in soil.

Microbial cell concentration is a particularly important bioindicator of soil health and a yardstick for determining biological quotients which are likely to gain in ecological significance if they are calculated in relation to the viable, rather than total, microbial density. A dual-staining technique with fluorescent dyes was used for the spectrofluorimetric quantitative determination of the concentration of viable microbial cells present in three different soil types. This is a novel and substantially modified application of the dual-staining procedure implemented in the LIVE/DEAD BacLight viability kit which has never been successfully applied to the quantification of naturally occurring soil microbial communities.

Interactions of earthworms with Atrazine-degrading bacteria in an agricultural soil.

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. The impact of earthworm macrofauna on Atrazine mineralization was assessed in representative soil microsites of earthworm activities (gut contents, casts, burrow linings).

Isolation and characterisation of an isoproturon-mineralising Methylopila sp. TES from French agricultural soil.

Using enrichment culture three isoproturon (IPU) mineralising bacterial isolates were isolated from a French agricultural soil mineralising up to 50% of the initially added 14C-ring labelled IPU within only eight days. These isolates showed similar metabolic (BIOLOG GN) and amplified rDNA restriction (ARDRA) profiles. Partial 16S rDNA sequencing revealed that they were identical and identified as Methylopila sp TES.

Estimation of atrazine-degrading genetic potential and activity in three French agricultural soils.

The impact of organic amendment (sewage sludge or waste water) used to fertilize agricultural soils was estimated on the atrazine-degrading activity, the atrazine-degrading genetic potential and the bacterial community structure of soils continuously cropped with corn. Long-term application of organic amendment did not modify atrazine-mineralizing activity, which was found to essentially depend on the soil type. It also did not modify atrazine-degrading genetic potential estimated by quantitative PCR targeting atzA, B and C genes, which was shown to depend on soil type.

Real-time reverse transcription PCR analysis of expression of atrazine catabolism genes in two bacterial strains isolated from soil.

The level of expression of highly conserved, plasmid-borne, and widely dispersed atrazine catabolic genes (atz) was studied by RT-qPCR in two telluric atrazine-degrading microbes. RT-qPCR assays, based on the use of real-time PCR, were developed in order to quantify atzABCDEF mRNAs in Pseudomonas sp. ADP and atzABC mRNAs in Chelatobacter heintzii.

Monitoring of atrazine treatment on soil bacterial, fungal and atrazine-degrading communities by quantitative competitive PCR.

We report the development of quantitative competitive (QC) PCR assays for quantifying the 16S, 18S ribosomal and atzC genes in nucleic acids directly extracted from soil. QC-PCR assays were standardised, calibrated and evaluated with an experimental study aiming to evaluate the impact of atrazine application on soil microflora. Comparison of QC-PCR 16S and 18S results with those of soil microbial biomass showed that, following atrazine application, the microbial biomass was not affected and that the amount of 16S rDNA gene representing 'bacteria' increased transitorily, while the amount of 18S rDNA gene representing fungi decreased in soil.

Plasmid localisation of atrazine-degrading genes in newly described Chelatobacter and Arthrobacter strains.

Abstract In a previous study, we isolated a collection of atrazine-degrading bacteria from various soils. The aim of this study was to localise the atrazine-degrading genes in these 25 atrazine-degrading strains. In the case of the Gram-negative strains of Chelatobacter heintzii, six to seven plasmids were observed.

Effect of cropping cycles and repeated herbicide applications on the degradation of diclofop-methyl, bentazone, diuron, isoproturon and pendimethalin in soil.

A greenhouse study was conducted to investigate the ability of four crops (wheat, corn, oilseed rape and soybean) to influence the degradation of bentazone, diclofop-methyl, diuron, isoproturon and pendimethalin in soil. The present study showed that microbial biomass-carbon was significantly higher in planted soils than in bulk soil, especially with wheat and corn, after several cropping cycles. The biomass in corn and soybean planted soils was adversely affected by bentazone but recovered after three cropping cycles.