Search results for "microorganism"
showing 10 items of 449 documents
Production of volatile compounds in liquid cultures by six strains of coryneform bacteria
1992
The aromatic profiles of four strains of Brevibacterium linens, one strain of Brevibacterium sp. and one strain of Microbacterium sp. were determined with some pure cultures of these microorganisms in standard trypcase soy liquid medium, which enabled four of these six strains to produce flavour compounds of ripened cheese. Thirty-two flavour compounds were identified by gas chromatography and mass spectrometry. The identified flavour compounds included the following: fatty acids, alcohols, methylketones, sulphur compounds, aromatic compounds and a pyrazine. Some important differences were found among the six strains studied. The four strains of B. linens had similar flavour profiles. Their…
Biomethylation of Heavy Metals in Soil and Terrestrial Invertebrates
2009
Heavy metals play a prominent role in the lives of all organisms. They can be essential, as in the cases of iron, manganese, nickel and copper, which are needed to obtain proper enzyme conformation and reactivity. Some heavy metals are toxic to organisms, such as mercury or cadmium. Often, these metals are rarely accessible in their inorganic form. After biological transformation into organometallic compounds, they exhibit increased toxicity and penetration into animal tissue is facilitated. The alkylation mechanisms of metals (especially mercury) performed by aquatic microorganisms have been well documented. The organometallic food chain from fish to humans has also been investigated. Howe…
Effect of high-pressure processing on carotenoids profile, colour, microbial and enzymatic stability of cloudy carrot juice
2019
Abstract The objective of this work was to assess the impact of high-pressure processing (HPP) on the carotenoid profile, colour as well as the microbial and enzymatic stability of cloudy carrot juice. The predominant carotenoids in the fresh juices were by far the provitamin A carotenoids β-carotene and α-carotene. Others were ζ-carotene, phytofluene, phytoene and lutein. HPP at 300 MPa in three cycles caused the highest carotenoids degradation (41%) whereas the lowest degradation (26%) was achieved at 600 MPa. The highest inactivation of POD (31%) and PPO (57%) was achieved with 600 MPa and 300 MPa applied in three cycles, respectively what indicates that POD is more responsible for carot…
Influence of Initial Water Content on the Wettability of Autoclaved Soils
2010
Autoclaving is a commonly used practice to destroy microbial activity in soils but is thought to have a limited effect on other soil properties. Small changes in chemical composition have been reported, but there have been no previous reports of any alteration of physical properties. This study, however, showed that autoclaving can cause a major change in soil hydraulic properties. For samples with intermediate water contents (10-35% v/v), it caused severe or extreme water repellency in three of four soil types tested, although no effect for initially low or high water contents was found. These findings have important implications for any experimental work involving soil autoclaving as a pr…
Réponses des cellules de Nicotiana tabacum à des molécules microbiennes : évènements de signalisation précoce, influence de la dynamique membranaire …
2018
In their natural environment plants are in close interaction with beneficial, neutral, or pathogenic microbes, which are highly dependent on carbon resources exuded by plant roots. Sugar transport, which is a key process of plant physiology, is essential to support the fate of plant-microbe interactions. During evolution, plants have acquired the ability to perceive microbial molecules, initiating specific signal transduction cascades and leading to adapted response for microbe lifestyles (avirulent, virulent, or benefic). Plant survival will depend on the nature of the induced mechanisms. My PhD work, carried out on a simplified experimental system, contributes to the understanding of mech…
Infecciones por clamidias
2007
Las clamidias son un grupo peculiar de bacterias, cuyo ciclo vital transcurre en parte en el interior de las células. Tienen la propiedad de adherirse a determinados epitelios, en los que pueden acabar produciendo infecciones. Existen tres especies patógenas para el hombre: Chlamydia trachomatis, que produce infecciones fundamentalmente en los epitelios genital y urinario, y C. psittaci y C. pneumoniae, que producen fundamentalmente infecciones respiratorias. A las dos últimas se les clasifica en la actualidad en un género diferente, el de las Chlamydophilas.
Boronic Acids of Pharmaceutical Importance Affect the Growth and Photosynthetic Apparatus of Cyanobacteria in a Dose-Dependent Manner
2020
The dynamic increase in the commercial application of antimicrobial derivatives of boronic acids, and potential impact of their presence in aquatic systems, supports the necessity to study the toxicity of these substances towards microorganisms of crucial meaning in the environment. One example of the mentioned derivatives is tavaborole (5-fluoro-substituted benzoxaborole), a pharmaceutical agent with antifungal activity. Cyanobacteria were used as model organisms, which are photoautotrophic prokaryotes, as representative aquatic bacteria and photoautotrophs associated with the plant kingdom. To the best of our knowledge, we investigated this issue for the first time. In order to recognize …
Modulation of the growth and metabolic response of cyanobacteria by the multifaceted activity of naringenin
2017
The interactions between the plant-derived bioflavonoid, naringenin, and prokaryotic microalgae representatives (cyanobacteria), were investigated with respect to its influence on the growth and metabolic response of these microorganisms. To achieve reliable results, the growth of cyanobacteria was determined based on measurements of chlorophyll content, morphological changes were assessed through microscopic observations, and the chemical response of cells was determined using liquid and gas chromatography (HPLC; GC-FID). The results show that micromolar levels of naringenin stimulated the growth of cyanobacteria. Increased growth was observed for halophilic strains at naringenin concentra…
Naphthalene production by microorganisms associated with termites: Evidence from a microcosm experiment
2009
Abstract There have been several reports published which suggest that it is possible that the polycyclic aromatic hydrocarbons (PAHs) naphthalene (NAPH), phenanthrene (PHEN) and perylene (PERY) in tropical environments have a biological source. This source might be related to the activity of termites or their associated microorganisms. We aimed to provide direct evidence for the biological production of NAPH, PHEN and PERY by conducting microcosm experiments in the State of Tocantins, Brazil, in which termite nests (with or without termites) were placed in an enclosed environment in which we controlled all PAH fluxes and monitored changes of PAH stocks. The experiments were carried out with…
Aerobic granular sludge treating high strength citrus wastewater: Analysis of pH and organic loading rate effect on kinetics, performance and stabili…
2017
Abstract In the present paper, the feasibility of citrus wastewater treatment with aerobic granular sludge sequencing batch reactors (AGSBR) was investigated. Two AGSBRs (named R1 and R2, respectively) were operated for 90 days under different organic loading rates (OLR) and pH in two experimental periods. The OLR ranged approximately between 3.0 kg TCOD m−3d−1 and 7 kg TCOD m−3d−1 during Period I, whereas between 7 kg TCOD m−3d−1 and 15 kg TCOD m−3d−1 during Period II. pH was maintained at 7.0 and 5.5 in R1 and R2, respectively. The results revealed that under high OLR and unbalanced feast/famine regime (Period I), the development of fast-growing microorganisms (fungi and filamentous bacte…