Search results for "Soil microbiology"
showing 10 items of 213 documents
Investigation of the roles of AgrA and σB regulators in Listeria monocytogenes adaptation to roots and soil
2020
ABSTRACT Little is known about the regulatory mechanisms that ensure the survival of the food-borne bacterial pathogen Listeria monocytogenes in the telluric environment and on roots. Earlier studies have suggested a regulatory overlap between the Agr cell–cell communication system and the general stress response regulator σB. Here, we investigated the contribution of these two systems to root colonisation and survival in sterilised and biotic soil. The ability to colonise the roots of the grass Festuca arundinacea was significantly compromised in the double mutant (∆agrA∆sigB). In sterile soil at 25°C, a significant defect was observed in the double mutant, suggesting some synergy between …
LisRK is required for optimal fitness ofListeria monocytogenesin soil
2020
ABSTRACTListeria monocytogenes is a food-borne pathogen responsible for the disease listeriosis. It is ubiquitously found in the environment and soil is one of its natural habitats. Listeria monocytogenes is highly capable of coping with various stressful conditions. We hypothesized that stress-responsive two-component systems such as LisRK might contribute to the adaptation of L. monocytogenes to the soil environment. Indeed, investigations of the population dynamics of wild-type and mutant strains suggest an important role of LisRK for optimal fitness of L. monocytogenes in sterile soil. Results from non-sterile soil showed that the parental strain was capable of surviving longer than mut…
Sex-specific interaction between arbuscular mycorrhizal and dark septate fungi in the dioecious plant Antennaria dioica (Asteraceae).
2012
Male and female plants of dioecious species often differ in their resource demands and this has been linked to secondary sexual dimorphism, including sex-specific interactions with other organisms such as herbivores and pollinators. However, little is known about the interaction between dioecious plants and fungal root endophytes. Plants may be simultaneously colonised by arbuscular mycorrhizal (AM) and dark septate (DS) fungi. While it is well established that AM mutualism involves reciprocal transfer of photosynthates and mineral nutrients between roots of host plants and these fungi, the role of DS fungi remains controversial. Here, we report the temporal and spatial variation in AM and …
Molecular analysis of the nitrate-reducing community from unplanted and maize-planted soils
2002
ABSTRACT Microorganisms that use nitrate as an alternative terminal electron acceptor play an important role in the global nitrogen cycle. The diversity of the nitrate-reducing community in soil and the influence of the maize roots on the structure of this community were studied. The narG gene encoding the membrane bound nitrate reductase was selected as a functional marker for the nitrate-reducing community. The use of narG is of special interest because the phylogeny of the narG gene closely reflects the 16S ribosomal DNA phylogeny. Therefore, targeting the narG gene provided for the first time a unique insight into the taxonomic composition of the nitrate-reducing community in planted an…
ITS region of the rDNA of Pythium longandrum, a new species; its taxonomy and its comparison with related species.
2001
Pythium longandrum (F-73.0) was isolated, from soil samples taken in Lille in northern France. Morphologically the fungus resembles closely Pythium rostratum, however its antheridial characters are unique. The oogonia of this species are provided with hypogynous and monoclinous antheridia. The antheridial cells are inflated and are probably the largest and longest for the genus. The internal transcribed spacer region of its nuclear ribosomal DNA indicates that it is entirely different from all other species of Pythium. This new species is characterized by its spherical to elongated sporangia, smooth-walled oogonia and hypogynous to monoclinous antheridia bearing long antheridial cells close…
Pythium campanulatumsp. nov., isolated from the rhizosphere of maize, its taxonomy, ITS region of rDNA, and comparison with related species
2003
Pythium campanulatum sp. nov. was isolated from some soil samples taken in the rhizosphere of maize (Zea mays) in north-eastern India. This species is characterized by the absence of zoospores and sporangia, antheridial branches wrapping around the oogonia leaving one to two campanulate antheridial cells after fertilization, and aplerotic oospores. The ITS region of its rDNA is comprised of 922 bases. This oomycete is closely related to Pythium orthogonon, Pythium nunn and Pythium toruloides. However, it has its own characteristic features and is completely devoid of zoospores. Taxonomic description of this new species and its comparison with related oomycetes, together with the sequence of…
Pythium glomeratum, a new species isolated from agricultural soil taken in north-eastern France, its ITS region and its comparison with related speci…
2003
Pythium glomeratum sp. nov. is described here. It was isolated from soil samples taken in the northern France in 1992, was wrongly identified as Pythium heterothallicum and was kept aside. Recently, the ITS region of the rDNA of this oomycete was amplified and sequenced. The differences between the sequence and a more detailed study of the morphological characters of these two species, revealed that both are related but different species. P. glomeratum is characterized by the presence of branched antheridia that wrap around the oogonia, aplerotic to almost plerotic oospores, and the lack of zoosporangia and zoospores. Taxonomical description of this new species, its comparison with related …
A new species of Pythium isolated from a vineyard in France.
2006
Pythium apiculatum sp. nov. is a new oomycete characterized by the presence of both ornamented and smooth-walled oogonia. The ornamentations are blunt, and at times, bent. The oomycete was isolated from soil samples taken in a vineyard in the Burgundian region of France. Morphologically, it resembles some species having ornamented oogonia like Pythium radiosum, Pythium echinulatum, and resembles, also the species having smooth-walled oogonia like Pythium hypogynum and Pythium acrogynum. However, the oomycete has its own distinguishing characteristics which, when combined with molecular features, enables us to describe it as a new species. The taxonomic description of this new oomycete, its …
Genetic characterization of the nitrate reducing community based on narG nucleotide sequence analysis.
2003
The ability of facultative anerobes to respire nitrate has been ascribed mainly to the activity of a membrane-bound nitrate reductase encoded by the narGHJI operon. Respiratory nitrate reduction is the first step of the denitrification pathway, which is considered as an important soil process since it contributes to the global cycling of nitrogen. In this study, we employed direct PCR, cloning, and sequencing of narG gene fragments to determine the diversity of nitrate-reducing bacteria occurring in soil and in the maize rhizosphere. Libraries containing 727 clones in total were screened by restriction fragment analysis. Phylogenetic analysis of 128 narG sequences separated the clone famili…
Retama species growing in different ecological-climatic areas of northeastern Algeria have a narrow range of rhizobia that form a novel phylogenetic …
2009
International audience; Sixty-seven isolates were isolated from nodules collected on roots of Mediterranean shrubby legumes Retama raetam and Retama sphaerocarpa growing in seven ecological-climatic areas of northeastern Algeria. Genetic diversity of the Retama isolates was analyzed based on genotyping by restriction fragment length polymorphism of PCR-amplified fragments of the 16S rRNA gene, the intergenic spacer (IGS) region between the 16S and 23S rRNA genes (IGS), and the symbiotic genes nifH and nodC. Eleven haplotypes assigned to the Bradyrhizobium genus were identified. Significant biogeographical differentiation of the rhizobial populations was found, but one haplotype was predomin…