Search results for "Soil microbiology"
showing 10 items of 213 documents
Effects of sewage sludge addition to Norway spruce seedlings on nitrogen availability and soil fauna in clear-cut areas
2012
Anaerobically digested and composted sewage sludge (CSS) has been suggested to be a slow-release fertilizer in forestry and an alternative to quick-release inorganic fertilizers. The effects of CSS with or without added carbohydrate on inorganic nitrogen availability and on soil animals were tested in two Norway spruce plantations. Half of the seedlings were individually fertilized with CSS, and the rest were left as controls. Solid sucrose was added to half of the fertilized and untreated seedlings. Soil samples were taken in the autumn in the first and the second year after the treatments. CSS increased soil NH4-N (2100%), the proportion of soil NO3-N, and the N concentration of spruce ne…
Pythium stipitatumsp. nov. isolated from soil and plant debris taken in France, Tunisia, Turkey, and India
2009
Pythium stipitatum is a slow-growing oomycete and has been isolated from soil samples and plant materials from France, Tunisia, Turkey and India. Its morphological characteristics are reminiscent of those of Pythium ramificatum, discovered in Algeria by the corresponding author. Unfortunately, the Algerian isolate was not deposited in any culture collection and ultimately got lost. Those were the days when molecular description of fungi was not a fashion; hence, no molecular characteristics of the Algerian isolates were deposited to the GenBank. Moreover, its coralloid antheridial branches made it an easy prey to be considered as synonymous to Pythium minus. Because there are no living stra…
Characterization of field isolates of Trichoderma antagonistic against Rhizoctonia solani.
2010
The aim of the present study was to characterize sixteen isolates of Trichoderma originating from a field of sugar beet where disease patches caused by Rhizoctonia solani were observed. Use of both molecular and morphological characteristics gave consistent identification of the isolates. Production of water-soluble and volatile inhibitors, mycoparasitism and induced systemic resistance in plant host were investigated using in vitro and in vivo tests in both sterilized and natural soils. This functional approach revealed the intra-specific diversity as well as biocontrol potential of the different isolates. Different antagonistic mechanisms were evident for different strains. The most antag…
Importance of dispersal and thermal environment for mycorrhizal communities: lessons from Yellowstone National Park
2011
International audience; The relative importance of dispersal and niche restrictions remains a controversial topic in community ecology, especially for microorganisms that are often assumed to be ubiquitous. We investigated the impact of these factors for the community assembly of the root-symbiont arbuscular mycorrhizal fungi (AMF) by sampling roots from geothermal and nonthermal grasslands in Yellowstone National Park (YNP), followed by sequencing and RFLP of AMF ribosomal DNA. With the exception of an apparent generalist RFLP type closely related to Glomus intraradices, a distance-based redundancy analysis indicated that the AMF community composition correlated with soil pH or pH-driven c…
Seasonal fluctuations and long-term persistence of pathogenic populations of Agrobacterium spp. in soils.
2002
ABSTRACT Short- and long-term persistence of pathogenic (i.e., tumor forming) agrobacteria in soil was investigated in six nursery plots with a history of high crown gall incidence. No pathogenic Agrobacterium strains were isolated in soil samples taken in fall and winter in any plots, but such strains were isolated from both bulk soils and weed rhizospheres (over 0.5 × 10 5 pathogenic CFU/g of bulk soil or rhizosphere) in three out of six plots in spring and summer. PCR amplifications of a vir sequence from DNA extracted from soil confirmed the presence of Ti plasmids in summer and their absence in fall and winter. The results indicate that strains that harbor a Ti plasmid had an unforesee…
Acyl-homoserine lactone production is more common among plant-associated Pseudomonas spp. than among soilborne Pseudomonas spp.
2001
ABSTRACT A total of 137 soilborne and plant-associated bacterial strains belonging to different Pseudomonas species were tested for their ability to synthesize N -acyl-homoserine lactones (NAHL). Fifty-four strains synthesized NAHL. Interestingly, NAHL production appears to be more common among plant-associated than among soilborne Pseudomonas spp. Indeed, 40% of the analyzed Pseudomonas syringae strains produced NAHL which were identified most often as the short-chain NAHL, N -hexanoyl- l -homoserine lactone, N -(3-oxo-hexanoyl)-homoserine lactone, and N -(3-oxo-octanoyl)- l -homoserine lactone (no absolute correlation between genomospecies of P. syringae and their ability to produce NAHL …
Depth matters : Effects of precipitation regime on soil microbial activity upon rewetting of a plant-soil system
2018
International audience; Climate change is predicted to affect not only the amount but also the temporal distribution of rain. Changes in frequency and amplitude of rain events, i.e. precipitation patterns, result in different water conditions with soil depth, and likely affect plant growth and shape plant and soil microbial activity. Here, we used 18O stable isotope probing (SIP) to investigate bacterial and fungal communities that actively grew or not upon rewetting, at three different depths in plant-soil mesocosms previously subjected to frequent or infrequent watering for 12 weeks (equal total water input). Phylogenetic marker genes for bacteria and fungi were sequenced after rewetting,…
Determinants of the distribution of nitrogen-cycling microbial communities at the landscape-scale
2010
Little information is available regarding the landscape-scale distribution of microbial communities and its environmental determinants. However, a landscape perspective is needed to understand the relative importance of local and regional factors and land management for the microbial communities. In this manuscript, we investigated the distribution of functional microbial communities involved in N-cycling and of the total bacterial and crenarchaeal communities over 107 sites using a grid with a 16 km lag distance within Burgundy, a 31 500 km2 region in France. After quantifying the abundances of the total bacterial, crenarchaeal, nitrate-reducing, denitrifying and ammonia-oxidizing communit…
Effect of cropping cycles and repeated herbicide applications on the degradation of diclofop-methyl, bentazone, diuron, isoproturon and pendimethalin…
2002
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. In wheat-planted soils, diclofop-methyl application resulted in persistent increase of the amount of microbial biomass. Bentazone did not show accelerated degradation even af…
Monitoring of atrazine treatment on soil bacterial, fungal and atrazine-degrading communities by quantitative competitive PCR
2003
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. In addition, comparison of atzC QC-PCR results wit…