Search results for "Microbial"
showing 10 items of 2041 documents
Study of microbial dynamics for the control of Kombucha production
2021
Kombucha is a fermented beverage obtained from the transformation of sugared tea infusion through the activity of a consortium of yeasts and bacteria, during which a cellulosic biofilm is formed. The study of microbial interaction that occur in this matrix aims at improving the control over the production process at industrial scale. The methodology used in this work is mainly based on the isolation and selection of yeasts and acetic acid bacteria from a determined kombucha consortium. The selected microorganisms are then used to inoculate monocultures and cocultures in sugared black tea. Different parameters were followed at the microbiological level (population counts, composition in gene…
Ecology of N2O reducing bacteria in arable soils
2016
Nitrous oxide (N2O) is an important greenhouse gas (GHG) and the main ozone depleting substance. Agricultural soils are the main anthropogenic-induced source of this GHG. The concentration of N2O in the atmosphere is steadily increasing, but we still lack knowledge on the factors controlling its production and consumption in soils. The reduction of N2O to N2 by microorganisms harboring the N2O reductase gene (nosZ) is the only known biological process able to consume this GHG. Recent studies revealed a previously unknown clade of N2O-reducers which was shown to be important to the N2O sink capacity of soils. This thesis seeks to gain a greater understanding on the ecology of N2O-reducers in…
Search for biological signature of the degradation of chlordecone in soil of the French West Indies
2015
The use of chlordecone (CLD) to eradicate the weevil populations in the banana plantations in the French West Indies (Guadeloupe and Martinique) between 1972 and 1993 led to the contamination of the soil and the environment. This very hydrophobic organochlorine insecticide persists in the soil where it slowly transfers not only to the water resources but also to terrestrial and aquatic biota (plants, animals, fishes, shellfishes). Deemed “non-degradable”, CLD is resistant to photolysis, hydrolysis and biodegradation. To date, there is no method to remediate the 20,000 hectares of polluted soil with this insecticide. Given the extent of CLD pollution, biological decontamination processes app…
Microbial diversity and structure are drivers of the biological barrier effect against Listeria monocytogenes in soil
2013
International audience; Understanding the ecology of pathogenic organisms is important in order to monitor their transmission in the environment and the related health hazards. We investigated the relationship between soil microbial diversity and the barrier effect against Listeria monocytogenes invasion. By using a dilution-to-extinction approach, we analysed the consequence of eroding microbial diversity on L. monocytogenes population dynamics under standardised conditions of abiotic parameters and microbial abundance in soil microcosms. We demonstrated that highly diverse soil microbial communities act as a biological barrier against L. monocytogenes invasion and that phylogenetic compos…
Ecological role of mycotoxins produced by Fusarium graminearum : consequences of the presence of deoxynivalenol (DON) in crop residues on the soil mi…
2012
Fusarium graminearum is a plant pathogenic fungus, causing devastating disease “Fusarium head blight” (FHB) in cereals including wheat and maize. It also contaminates the grains with mycotoxins including deoxynivalenol (DON) which are toxic to human and animals. This disease has resulted in the serious losses in grain yield and quality. We established through a first bibliographic review that during off season fungus survives saprophytically on the crop residues (ecological habitat) and serves as primary inoculum for the next season crop. However, we noticed also that the literature was poor about the role mycotoxins could play in the establishment of F. graminearum in such a habitat. The m…
Biogeography of soil microbial communities: a review and a description of the ongoing french national initiative
2010
International audience; Microbial biogeography is the study of the distribution of microbial diversity on large scales of space and time. This science aims at understanding biodiversity regulation and its link with ecosystem biological functioning, goods and services such as maintenance of productivity, of soil and atmospheric quality, and of soil health. Although the initial concept dates from the early 20th century (Beijerinck (1913) De infusies en de ontdekking der backterien, in: Jaarboek van de Knoniklijke Akademie van Wetenschappen, Muller, Amsterdam), only recently have an increasing number of studies have investigated the biogeographical patterns of soil microbial diversity. A such …
Influence de différentes pratiques agricoles sur la qualité et la santé des sols : étude de cas sur des vergers slovènes irrigués ou en agriculture b…
2011
Underestimation of soil properties and poor understanding of soil conditions can have many negative consequences, which results in quality or quantity of yield, soil degradation or even environmental pollution. According to importance of agricultural practices, our study focused on their impact on soil quality and health. The research took place from November 2003 to October 2007 in apple orchards in north-eastern Slovenia where two frequent agricultural practices were investigated: (i) drip irrigation on Calcaric Cambisol and its effects on structural stability and microbial biomass at Gačnik experimental station and (ii) combination of organic fertiliser (Campo guano) and liming in organi…
Methods for studying root colonization by introduced beneficial bacteria
2003
e-Book; Some free-living rhizobacteria are considered as potential biocontrol and plant growth-promoting agents. Successful application of beneficial bacteria as microbial inoculants requires their presence and activity at the appropriate level, but even more, at the right time and place. Various markers are described in the literature to differentiate introduced bacteria from indigenous microflora and to visualize them. These markers are presented together with the methods currently applied to quantify bacterial densities and to characterize the distribution of introduced bacteria. The methods to quantify bacterial densities are either based on bacterial cultivation or not. Different types…
DIAGSOL : development of a new functional marker of exposure to herbicides B-triketones in an agricultural soil
2020
Numerous herbicides target an enzyme found not only in weeds but also in « non-target organisms » such as microorganisms. This proof-of-concept study aims to use microbial gene encoding the targeted enzyme or the targeted enzyme itself as a marker for herbicide exposure in soils. The hppd gene and the encoded enzyme (HPPD; 4-hydroxyphenylpyruvate dioxygenase), targeted by B-triketone herbicides, are the subject of this study. In silico analyses reveal that the hppd gene is spread out in all bacterial phyla. Primers specific to this gene were designed. This primer pair is used to measure the abundance, the composition and the diversity of the hppd bacterial community in soil microcosms expos…
Réponse des interactions plante-sol aux régimes de précipitations
2018
Water availability governs terrestrial nutrient cycles by impacting the functioning of both plants and of soil microorganisms. The predicted changes in precipitation patterns (i.e. the magnitude and frequency of precipitation events) associated with climate change, will thus likely have important consequences on ecosystem functioning. Dry and seasonally dry ecosystems are particularly vulnerable to changes in precipitation patterns, as they are already constrained to a large extent by water availability. However, more mesic systems may also experience dry periods that may impact plant-soil functions. In this thesis, experiments in soil-only systems and plant-soil systems were used to gain i…