The analysis by Denaturing Gradient Gel Electrophoresis (DGGE) of the PCR-amplified V3 region of 16S rRNA gene was previously shown to detect and differentiate a large number of human and animal ...mycoplasmas. In this study, we further assessed the suitability of the technique for epidemiological surveillance of mycoplasmas belonging to the 'Mycoplasma mycoides' cluster, a phylogenetic group that includes major ruminant pathogens. The V3 region of 16S rRNA genes from approx. 50 field strains was amplified and analysed by DGGE. Detection and identification results were compared with the ones obtained by antigenic testing and sequence analysis. The DGGE technique is robust and valuable as a first-line test, but the patterns obtained for strains belonging to the 'M. mycoides' cluster were too variable within a taxon and in contrast too conserved between taxa to allow an unequivocal identification of isolates without further analysis. Issues raised by the quest for a single universal test able to detect and identify any mycoplasma in one clinical sample are thoroughly documented.
In Erwinia chrysanthemi 3937, pectate lyase activity mainly results from the cumulative action of five major isoenzymes, PelA to PelE. Comparison of their amino acid sequences revealed two families, ...PelB-C and PelA-D-E. Molecular cloning permitted expression of the different pel genes in Escherichia coli and the isolation of each Pel independently from the other isoenzymes. We used similar experimental conditions to overproduce and purify the five Pels in a one-step chromatography method. We analyzed some of the basic enzymatic properties of these five isoenzymes. PelA has a low specific activity compared to the other four enzymes. PelB and PelC have a high affinity for their substrate: about 10-fold higher than the enzymes of the PelA-D-E group. The optimum pH is more alkaline for PelB and PelC (about 9.2) than for PelA, PelD, and PelE (from 8 to 8.8). Below pH 7, activity was negligible for PelB and PelC, while PelA, PelD, and PelE retained 25 to 30% of their activities. The temperature optima were determined to be 50 degrees C for PelD and PelE, 55 degrees C for PelA, and 60 degrees C for PelB and PelC. Enzymes of the PelB-C group are more stable than those of the PelA-D-E group. Use of substrates presenting various degrees of methylation revealed that PelA, PelD, and PelE are active only for very low levels of methylation, while PelB and PelC are more active on partially methylated pectins (up to 22% for PelC and up to 45% for PelB). Pectate lyases have an absolute requirement for Ca2+ ions. For the five isoenzymes, maximal activity was obtained at a Ca2+ concentration of 0.1 mM. None of the tested cations (Ba2+, Co2+, Cu2+, Mg2+, Mn2+, Sr2+, Zn2+) can substitute for Ca2+. At a high concentration (1 mM), most of the divalent cations inhibited pectate lyase activity. In addition, we demonstrated that two compounds present in plant tissues, epicatechin and salicylic acid, inhibit the pectate lyases at a concentration of 0.2 mM
The antimicrobial susceptibility was determined for 50
Streptococcus uberis, 42
S. dysgalactiae subsp.
dysgalactiae and eight
S. agalactiae strains isolated from cow mastitis. Only 27% of the strains ...were susceptible to all antimicrobial compounds tested. Resistance to tetracycline was most frequent (particularly for
S. dysgalactiae strains), then macrolide and/or lincomycin resistance. High level resistance to streptomycin and kanamycin was detected. All
S. dysgalactiae and
S. agalactiae strains were susceptible to β-lactams but 44% of the
S. uberis strains showed an elevated penicillin G MIC. All strains were susceptible to chloramphenicol and rifampicin.
Contagious agalactia (CA) is a disease caused equally by four
species, in single or mixed infections. Clinical signs are multiple, including mastitis, arthritis, keratoconjunctivitis, pneumonia, and ...septicemia, non-specific, and expressed differently depending whether sheep or goats are affected, on causative mycoplasmas as well as type of husbandry. CA has been reported worldwide and its geographic distribution maps to that of small ruminant breeding areas. However, as current diagnostic tests are expensive and difficult to implement, it is certainly underdiagnosed and prevalence data are only available for a few countries. CA control relies on vaccines, chemotherapy and good herd management practices. It requires long-term commitment but is often unsuccessful, with frequent clinical relapses. The persistence of the etiological agents, despite their overall susceptibility to antimicrobials, comes from their genetic plasticity and capacity to escape the host immune response. The existence of asymptomatic carriers and the numerous sources of infections contribute to rapid spread of the disease and complicate the control and prevention efforts. Here we review all these aspects in order to highlight recent progress made and identify gaps in knowledge or tools needed for better disease management. Discussion also underlines the detrimental effect of contagious agalactia on small ruminant welfare.
•N cycling was compared in Eucalyptus (100E), Acacia mangium (100A) and mixed-species plantations (50A50E).•Atmospheric N fixation in 50A50E and 100A was 250 and 400 kg N ha−1 rotation−1, ...respectively.•N contents in litterfall and soil N mineralization rates were 60% higher in 100A than in 100E.•Soil C and N stocks were dependent on soil texture but not influenced by tree species.
Mixing N-fixing trees with eucalypts is an attractive option to improve the long-term soil N status in fast-growing plantations established in tropical soils. A randomized block design was replicated at four sites in Brazil to compare the biogeochemical cycles in mono-specific stands of Eucalyptus (100E) and Acacia mangium (100A) with mixed-species plantations in a proportion of 1:1 (50A50E). Our study aimed to assess the effects of introducing A. mangium trees in Eucalyptus plantations on atmospheric N2 fixation, N cycling and soil organic matter stocks. Litterfall and soil N mineralization were measured over the last two years of the rotation (4–6 years after planting). Aboveground N accumulation in the trees and C and N stocks in the forest floor and in the top soil were intensively sampled at harvesting age. N2 fixation rates were estimated using the natural abundance of 15N as well as by the difference between total N stocks in 100A and 50A50E relative to 100E (accretion method).
While the 15N natural abundance method was unsuitable, the accretion method showed consistently across the four sites that atmospheric N fixation reached about 250 and 400 kg N ha−1 rotation−1 in 50A50E and 100A, respectively. Except at one site with high mortality, N contents within trees at harvesting were approximately 40% higher in 100A than in 100E. Mean N contents in litterfall and N mineralization rates were about 60% higher in 100A than in 100E, with intermediate values in 50A50E. The amounts of N in litterfall were much more dependent on soil N mineralization rates for acacia trees than for eucalypt trees. Soil C and N stocks were dependent on soil texture but not influenced by tree species. N budgets over a 6-year rotation were enhanced by about 65 kg N ha−1 yr−1 in 100A and 40 kg N ha−1 yr−1 in 50A50E relative to monospecific eucalypt plantations. Introducing N-fixing trees in eucalypt plantations might therefore contribute to reducing the need for mineral N fertilization in the long-term.
The chlorophyll-b-less chlorina-f2 barley mutant is deficient in the major as well as some minor light-harvesting chlorophyll-protein complexes of photosystem II (LHCII). Although the LHCII ...deficiency had relatively minor repercussions on the leaf photosynthetic performances, the responses of photosystem II (PSII) to elevated temperatures and to bright light were markedly modified. The chlorina-f2 mutation noticeably reduced the thermostability of PSII, with thermal denaturation of PSII starting at about 35 degrees C and 38.5 degrees C in chlorina-f2 and in the wild type, respectively. The increased susceptibility of PSII to heat stress in chlorina-f2 leaves was due to the weakness of its electron donor side, with moderate heat stress causing detachment of the 33-kD extrinsic PSII protein from the oxygen-evolving complex. Prolonged dark adaptation of chlorina-f2 leaves was also observed to inhibit the PSII donor side. However, weak illumination slowly reversed the dark-induced inhibition of PSII in chlorina-f2 and cancelled the difference in PSII thermostability observed between chlorina-f2 and wild-type leaves. The mutant was more sensitive to photoinhibition than the wild type, with strong light stress impairing the PSII donor side in chlorina-f2 but not in the wild type. This difference was not observed in anaerobiosis or in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, diuron. The acceptor side of PSII was only slightly affected by the mutation and/or the aforementioned stress conditions. Taken together, our results indicate that LHCII stabilize the PSII complexes and maintain the water-oxidizing system in a functional state under varying environmental conditions
We proposed to study and quantify the anteroposterior component, on top of the lateral one, of the body sway induced by different configurations of galvanic vestibular stimulation (GVS) in order to ...advance the understanding of the orientation of the response. Four stimulation configurations were used in two separate experiments: monaural, binaural, and opposite double monaural in the first experiment (11 subjects); monaural and double monaural in the second (13 subjects). The postural response of the subjects, standing with their eyes closed, to the stimulus (0.6 mA, 4 s) was assessed by measuring the displacement of the center of pressure (CoP) using a force platform. As usual, binaural GVS induced a strictly lateral deviation of the center of pressure. The opposite double monaural condition induced a similar lateral sway to that obtained in the binaural mode, although with a very different stimulation configuration. Monaural GVS induced an oblique, stereotyped deviation in each subject. The anteroposterior component comprised a forward deviation when the anode was on the forehead and a backward deviation when the anode was on the mastoid. The lateral component, directed towards the anode as in the binaural design, was twice as large in the binaural than in the monaural mode. The second experiment showed that double monaural stimulation elicited an anteroposterior deviation (backwards when the anode was on the mastoids and forwards when it was on the forehead) that was equivalent to the addition of two complementary monaural configurations. The present results show that monaural stimulation activates one side of the vestibular apparatus and induces reproducible, stereotyped deviations of the CoP in both the anteroposterior and lateral plane. Secondly, binaural GVS appears to result from the addition of two complementary monaural stimulations. Lateral components of the response to each stimulation, being in the same direction, are summed, whilst anteroposterior components, being in opposite directions, cancel each other out. The opposite happens when both labyrinths are polarized in the same way, as in the double monaural configuration. We suggest that the orientation of the response to GVS is a function of the imbalance between right and left vestibular polarization, rather than a function of the actual position of the electrodes.
Since echinocandins are recommended as first line therapy for invasive candidiasis, detection of resistance, mainly due to alteration in FKS protein, is of main interest. EUCAST AFST recommends ...testing both MIC of anidulafungin and micafungin, and breakpoints (BPs) have been proposed to detect echinocandin-resistant isolates. We analyzed MIC distribution for all three available echinocandins of 2,787 clinical yeast isolates corresponding to 5 common and 16 rare yeast species, using the standardized EUCAST method for anidulafungin and modified for caspofungin and micafungin (AM3-MIC). In our database, 64 isolates of common pathogenic species were resistant to anidulafungin, according to the EUCAST BP, and/or to caspofungin, using our previously published threshold (AM3-MIC ≥ 0.5 mg/L). Among these 64 isolates, 50 exhibited 21 different FKS mutations. We analyzed the capacity of caspofungin AM3-MIC and anidulafungin MIC determination in detecting isolates with FKS mutation. They were always identified using caspofungin AM3-MIC and the local threshold while some isolates were misclassified using anidulafungin MIC and EUCAST threshold. However, both methods misclassified four wild-type C. glabrata as resistant. Based on a large data set from a single center, the use of AM3-MIC testing for caspofungin looks promising in identifying non-wild-type C. albicans, C. tropicalis and P. kudiravzevii isolates, but additional multicenter comparison is mandatory to conclude on the possible superiority of AM3-MIC testing compared to the EUCAST method.
•Ammonia fluxes were measured following slurry application in a wheat crop.•Dynamics of emission potentials were measured in soil, litter, cuticle, and apoplast.•Ammonia was mainly emitted from the ...soil surface during a short period.•Decrease of ammonia emission was probably due to the surface drying.•Leaving plant compartments (roots, leaves) had low evolution of their emission potential.
Ammonia exchanges between the atmosphere and terrestrial ecosystems are composed of several pathways including exchange with the soil, the litter, the plant surfaces (cuticle) and through the stomata. In this study, the fate of nitrogen in the different pools (soil and plant) was analyzed with the aim of determining the sources and sink of atmospheric ammonia after slurry application on a wheat canopy. To do this, we measured ammonia exchanges between a winter wheat canopy and the atmosphere following cattle slurry application with a trailing hose. From 12 March to 8 April in Grignon near Paris, France, the ammonia fluxes ranged from an emission peak of 54,300 NH3 ngm−2s−1 on the day of slurry application (with a median during the first 24h of 5990 NH3 ngm−2s−1) to a deposition flux of −600 NH3 ngm−2s−1 (with a median during the last period of −16 NH3 ngm−2s−1). The ammonia compensation points were evaluated for apoplasm, foliar bulk, root bulk and litter bulk tissue, as well as for soil surface. Ammonia emission potentials defined by the ratios between the concentration in NH4+ and H+ for each N ecosystem pool were in the same order of magnitude for the plant decomposed in apoplastic liquid, green leaf bulk tissue and cuticle, respectively, averaging at 73, 160 and 120; in green leaf bulk tissues, the emission potential decreased gradually from 230 to 78 during the period after slurry application, while in the dead leaf bulk tissues considered as litter, the emission potential reached a maximum of 50,200 after application stabilized at around 20000. The dynamic of the emission potential for roots was similar to the ammonium concentration in the first two centimeters of the soil, with a maximum of 820 reached two days after application and a minimum of 44 reached three weeks later. The surfatm-NH3 model interpreted the emission and deposition fluxes by testing soil surface resistance. We conclude that emission of the first day application was driven by climatic conditions and ammonia concentration at the soil surface, with no surface resistance and with only soil surface emission potential. On the next three days, the ammonia emission originated from the soil surface with the growth of a dry surface layer inducing surface resistance and regulated by slurry infiltration. The following days need a more detailed description of soil surface processes and the integration of vegetation exchanges (stomatal and cuticle pathways), particularly in the last period, in order to explain the ammonia deposition.
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