Search results for "bacteria."
showing 10 items of 4757 documents
Polar accumulation of the metabolic sensory histidine kinases DcuS and CitA in Escherichia coli
2008
Signal transduction in prokaryotes is frequently accomplished by two-component regulatory systems in which a histidine protein kinase is the sensory component. Many of these sensory kinases control metabolic processes that do not show an obvious requirement for inhomogeneous distribution within bacterial cells. Here, the sensory kinases DcuS and CitA, two histidine kinases of Escherichia coli, were investigated. Both are membrane-integral and involved in the regulation of carboxylate metabolism. The two-component sensors were fused with yellow fluorescent protein (YFP) and live images of immobilized cells were obtained by confocal laser fluorescence microscopy. The fluorescence of the fusio…
Efficient, non-toxic anion transport by synthetic carriers in cells and epithelia.
2016
Transmembrane anion transporters (anionophores) have potential for new modes of biological activity, including therapeutic applications. In particular they might replace the activity of defective anion channels in conditions such as cystic fibrosis. However, data on the biological effects of anionophores are scarce, and it remains uncertain whether such molecules are fundamentally toxic. Here, we report a biological study of an extensive series of powerful anion carriers. Fifteen anionophores were assayed in single cells by monitoring anion transport in real time through fluorescence emission from halide-sensitive yellow fluorescent protein. A bis-(p-nitrophenyl)ureidodecalin shows especial…
Distinct Clones of Yersinia pestis Caused the Black Death
2010
From AD 1347 to AD 1353, the Black Death killed tens of millions of people in Europe, leaving misery and devastation in its wake, with successive epidemics ravaging the continent until the 18th century. The etiology of this disease has remained highly controversial, ranging from claims based on genetics and the historical descriptions of symptoms that it was caused by Yersinia pestis to conclusions that it must have been caused by other pathogens. It has also been disputed whether plague had the same etiology in northern and southern Europe. Here we identified DNA and protein signatures specific for Y. pestis in human skeletons from mass graves in northern, central and southern Europe that …
Immunomodulatory effects of dietary β-1,3-glucan from Euglena gracilis in rainbow trout (Oncorhynchus mykiss) immersion vaccinated against Yersinia r…
2012
Abstract Potential immunostimulatory effects of orally administered β-glucan were investigated in combination with immersion vaccination against enteric redmouth disease caused by Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss). A linear, unbranched and pure (purity ≥98%) β-1,3-glucan (syn. paramylon) from the alga Euglena gracilis was applied at an inclusion level of 1% β-glucan in feed administered at a rate of 1% biomass day−1 for 84 consecutive days. Fish were vaccinated after two weeks of experimental feeding and bath challenged with live Y. ruckeri six weeks post-vaccination. Blood and head kidney were sampled at day 0, 13 (1 day pre-vaccination), 15, 55, 59 (day 3 post-challe…
Comparative efficacy of Zataria multiflora Boiss., Origanum compactum and Eugenia caryophyllus essential oils against E. coli O157:H7, feline caliciv…
2013
Abstract Ready-to-eat salads using baby-leaf and multi-leaf mixes are one of the most promising developments in the fresh-cut food industry. There is great interest in developing novel decontamination treatments, which are both safe for consumers and more efficient against foodborne pathogens. In this study, emulsions of essential oils (EOs) from Origanum compactum (oregano), Eugenia caryophyllus (clove), and Zataria multiflora Boiss (zataria) were applied by spray (0.8 ml) after the sanitizing washing step. The aim was to investigate their ability to control the growth of potentially cross-contaminating pathogens and endogenous microbiota in commercial baby leaves, processed in a fresh-cut…
Kinetic modelling of the Zymomonas mobilis Entner-Doudoroff pathway: insights into control and functionality.
2013
Zymomonas mobilis, an ethanol-producing bacterium, possesses the Entner-Doudoroff (E-D) pathway, pyruvate decarboxylase and two alcohol dehydrogenase isoenzymes for the fermentative production of ethanol and carbon dioxide from glucose. Using available kinetic parameters, we have developed a kinetic model that incorporates the enzymic reactions of the E-D pathway, both alcohol dehydrogenases, transport reactions and reactions related to ATP metabolism. After optimizing the reaction parameters within likely physiological limits, the resulting kinetic model was capable of simulating glycolysis in vivo and in cell-free extracts with good agreement with the fluxes and steady-state intermediate …
The presence of conifer resin decreases the use of the immune system in wood ants.
2008
5 pages; International audience; 1. Wood ants ( Formica paralugubris ) incorporate large amounts of solidified conifer resin into their nest, which reduces the density of many bacteria and fungi and protects the ants against some detrimental micro-organisms. By inducing an environment unfavourable to pathogens, the presence of resin may allow workers to reduce the use of their immune system. 2. The present study tested the hypothesis that the presence of resin decreases the immune activity of wood ants. Specifically, three components of the humoral immune defences of workers kept in resin-rich and resin-free experimental nests (antibacterial, lytic, and prophenoloxidase activities) were com…
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,…