Ferriphaselus amnicola GF-20 is the first Fe-oxidizing bacterium isolated from the continental subsurface. It was isolated from groundwater circulating at 20 m depth in the fractured-rock catchment ...observatory of Guidel-Ploemeur (France). Strain GF-20 is a neutrophilic, iron- and thiosulfate-oxidizer and grows autotrophically. The strain shows a preference for low oxygen concentrations, which suggests an adaptation to the limiting oxygen conditions of the subsurface. It produces extracellular stalks and dreads when grown with Fe(II) but does not secrete any structure when grown with thiosulfate. Phylogenetic analyses and genome comparisons revealed that strain GF-20 is affiliated with the species Ferriphaselus amnicola and is strikingly similar to Ferriphaselus amnicola strain OYT1 which was isolated from a groundwater seep in Japan. Based on the phenotypic and phylogenetic characteristics, we propose that GF-20 represents a new strain within the species Ferriphaselus amnicola.
Dans cet article, nous étudions les facteurs individuels expliquant la détention d’actions sous ses différentes formes, et leurs évolutions suite à la crise financière. Il existe trois principaux ...modes d’investissement dans les actions : acheter des titres en direct ; les acheter par l’intermédiaire de fonds communs de placement ; et enfin souscrire une assurance-vie liée à des fonds (contrats en unité de compte). Ces trois canaux n’impliquent pas les mêmes comportements. En effet, outre les caractéristiques de risque et de rendement, ils diffèrent par leurs coûts de transaction, leurs frais de gestion et leur fiscalité. En conséquence, il n’y a pas de raison a priori de considérer que les décisions de choix de portefeuille des ménages sur ces différents supports sont équivalentes et correspondent aux mêmes caractéristiques des individus. Les données suggèrent que la baisse régulière du taux d’actionnaires observée en France pendant la crise concerne aussi bien la détention directe qu’indirecte d’actions. Seule échappe à cette baisse la détention des contrats d’assurance-vie. Leur diffusion, croissante entre 2004 et 2014, ne peut cependant expliquer la moindre détention des autres produits-actions (pas d’effet de substitution). Les estimations économétriques permettent d’affiner l’analyse et d’identifier les caractéristiques spécifiques des actionnaires en fonction du support choisi : ceux qui investissent directement dans des actions sont plus riches, plus éduqués et relativement moins averses au risque ; ceux qui détiennent des fonds communs de placement sont un peu plus riches mais aussi plus averses au risque que les actionnaires en direct et ne sont pas plus éduqués ; enfin, pour les investissements en actions sur des contrats d’assurance-vie, la position dans le cycle de vie et la catégorie sociale jouent un rôle important, de même qu’une aversion au risque modérée et une préférence faible pour le présent. Les épargnants qui investissent dans des contrats d’assurance-vie le font davantage par prévoyance (financement de leur retraite par exemple) et ne recherchent pas forcément un rendement à court terme de leurs placements. L’information joue aussi un rôle prépondérant : la détention d’actions par les parents influence les décisions d’investissement des enfants. Enfin, une décomposition économétrique (Oaxaca-Blinder) permet de séparer les effets dus à l’évolution des caractéristiques de la population des effets dus aux changements des comportements sur la diminution du nombre d’actionnaires. Le fait que plus des deux tiers de l’effet global ne puisse pas être expliqué par les changements socio-démographiques met en évidence le fort impact de la crise sur les investissements en actions des ménages. Classification JEL: G11; E21; D14; C35
The flux of methane, a potent greenhouse gas, from the seabed is largely controlled by anaerobic oxidation of methane (AOM) coupled to sulfate reduction (S-AOM) in the sulfate methane transition ...(SMT). S-AOM is estimated to oxidize 90% of the methane produced in marine sediments and is mediated by a consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria. An additional methane sink, i.e., iron oxide coupled AOM (Fe-AOM), has been suggested to be active in the methanic zone of marine sediments. Geochemical signatures below the SMT such as high dissolved iron, low to undetectable sulfate and high methane concentrations, together with the presence of iron oxides are taken as prerequisites for this process. So far, Fe-AOM has neither been proven in marine sediments nor have the governing key microorganisms been identified. Here, using a multidisciplinary approach, we show that Fe-AOM occurs in iron oxide-rich methanic sediments of the Helgoland Mud Area (North Sea). When sulfate reduction was inhibited, different iron oxides facilitated AOM in long-term sediment slurry incubations but manganese oxide did not. Especially magnetite triggered substantial Fe-AOM activity and caused an enrichment of ANME-2a archaea. Methane oxidation rates of 0.095 ± 0.03 nmol cm
d
attributable to Fe-AOM were obtained in short-term radiotracer experiments. The decoupling of AOM from sulfate reduction in the methanic zone further corroborated that AOM was iron oxide-driven below the SMT. Thus, our findings prove that Fe-AOM occurs in methanic marine sediments containing mineral-bound ferric iron and is a previously overlooked but likely important component in the global methane budget. This process has the potential to sustain microbial life in the deep biosphere.
A Lewis superacidic bis(borane) C
6
F
4
{B(C
6
F
5
)
2
}
2
was reacted with tungsten N
2
-complexes W(N
2
)
2
(R
2
PCH
2
CH
2
PR
2
)
2
(R = Ph or Et), affording zwitterionic boryldiazenido W(
ii
) ...complexes
trans
-W(L)(R
2
PCH
2
CH
2
PR
2
)
2
(N
2
{B(C
6
F
5
)
2
(C
6
F
4
B(C
6
F
5
)
3
}) (L = ø, N
2
or THF). These compounds feature only one N-B linkage of the covalent type, as a result of intramolecular boron-to-boron C
6
F
5
transfer. Complex
trans
-W(THF)(Et
2
PCH
2
CH
2
PEt
2
)
2
(N
2
{B(C
6
F
5
)
2
C
6
F
4
B(C
6
F
5
)
3
}) (
5
) was shown to split H
2
, leading to a seven-coordinate complex W(H)
2
(Et
2
PCH
2
CH
2
PEt
2
)
2
(N
2
{B(C
6
F
5
)
2
}
2
C
6
F
4
) (
7
). Interestingly, hydride storage at the metal triggers backward C
6
F
5
transfer. This reverts the bis(boron) moiety to its bis(borane) state, now doubly binding the distal N, with structural parameters and DFT computations pointing to dative N→B bonding. By comparison with an N
2
complex W(H)
2
(Et
2
PCH
2
CH
2
PEt
2
)
2
(N
2
{B(C
6
F
5
)
3
} (
10
) differing only in the Lewis acid (LA), namely B(C
6
F
5
)
3
, coordinated to the distal N, we demonstrate that two-fold LA coordination imparts strong N
2
activation up to the diazene-diide (N
2
2−
) state. To the best of our knowledge, this is the first example of a neutral LA coordination that induces reduction of N
2
.
The first two-fold Lewis acid adduct of a terminal N
2
ligand was prepared by employing a bis(borane). The influence of double coordination is benchmarked against the adduct of a related, non-chelating Lewis acid.
A Lewis superacidic bis(borane) C
F
{B(C
F
)
}
was reacted with tungsten N
-complexes W(N
)
(R
PCH
CH
PR
)
(R = Ph or Et), affording zwitterionic boryldiazenido W(ii) complexes
-W(L)(R
PCH
CH
PR
)
...(N
{B(C
F
)
(C
F
B(C
F
)
}) (L = ø, N
or THF). These compounds feature only one N-B linkage of the covalent type, as a result of intramolecular boron-to-boron C
F
transfer. Complex
-W(THF)(Et
PCH
CH
PEt
)
(N
{B(C
F
)
C
F
B(C
F
)
}) (5) was shown to split H
, leading to a seven-coordinate complex W(H)
(Et
PCH
CH
PEt
)
(N
{B(C
F
)
}
C
F
) (7). Interestingly, hydride storage at the metal triggers backward C
F
transfer. This reverts the bis(boron) moiety to its bis(borane) state, now doubly binding the distal N, with structural parameters and DFT computations pointing to dative N→B bonding. By comparison with an N
complex W(H)
(Et
PCH
CH
PEt
)
(N
{B(C
F
)
} (10) differing only in the Lewis acid (LA), namely B(C
F
)
, coordinated to the distal N, we demonstrate that two-fold LA coordination imparts strong N
activation up to the diazene-diide (N
) state. To the best of our knowledge, this is the first example of a neutral LA coordination that induces reduction of N
.
•3-hydroxy fatty acids analysed in soils from two contrasting altitudinal transects.•Distribution of 3-hydroxy fatty acids correlated with air temperature and soil pH.•Promising pH and temperature ...proxies in terrestrial environments.
Three hydroxy (3-OH) fatty acids (FAs), containing 10 to 18 C and a hydroxyl group in third position are characteristic components of Gram-negative bacteria. These compounds were used previously to detect and quantify Gram-negative bacterial communities in various types of samples, from terrestrial, aquatic and atmospheric environments. The relative abundance of 3-OH FAs in soils was recently shown to vary with mean annual air temperature (MAAT) and pH in soils from Mt. Shennongjia (China). In the current study, the concentrations and abundances of 3-OH FAs were determined in soils from altitudinal transects under tropical and temperate climates: Mt. Rungwe (SW Tanzania) and Mt. Majella (Central Italy), respectively. The aim was to (i) examine and compare the distributions of 3-OH FAs in soils from different climatic zones and (ii) to investigate the potential of 3-OH FAs as temperature and pH proxies. When combined with previously published data, a moderate correlation (R2 0.62) between the summed iso and anteiso to the total amount of normal 3-OH FAs (RIAN index) and pH was obtained. We show that Gram-negative bacteria respond in the same way to temperature variations in soils from different latitudes, with a relative increase of the anteiso to normal 3-OH FA ratios of the C15 and C17 compounds (RAN15 and RAN17 indices, respectively) with decreasing temperature. Nevertheless, the intercepts of the relationships between RAN15 and MAAT are mountain-dependent, suggesting that regional calibrations may be required to use RAN15 as a temperature proxy. In contrast with RAN15, the statistical similarity of the local relationships between RAN17 and MAAT leads to a combined calibration (R2 0.60, residual mean error 5.1 °C) covering a wide range of temperature (ca. 0–25 °C). As 3-OH FAs seem well-preserved in sedimentary archives, this strengthens the potential of these compounds as a temperature and pH proxy for paleoreconstructions in terrestrial settings.
Planktonic archaea include predominantly Marine Group I Thaumarchaeota (MG I) and Marine Group II Euryarchaeota (MG II), which play important roles in the oceanic carbon cycle. MG I produce specific ...lipids called isoprenoid glycerol dibiphytanyl glycerol tetraethers (GDGTs), which are being used in the sea surface temperature proxy named TEX86. Although MG II may be the most abundant planktonic archaeal group in surface water, their lipid composition remains poorly characterized because of the lack of cultured representatives. Circumstantial evidence from previous studies of marine suspended particulate matter suggests that MG II may produce both GDGTs and archaeol-based lipids. In this study, integration of the 16S rRNA gene quantification and sequencing and lipid analysis demonstrated that MG II contributed significantly to thepool of archaeal tetraether lipids in samples collected from MG II-dominated surface waters of the Northwestern Pacific Ocean (NWPO). The archaeal lipid composition in MG II-dominated NWPO waters differed significantly from that of known MG I cultures, containing relatively more 2G-OH-, 2G- and 1G- GDGTs, especially in their acyclic form. Lipid composition in NWPO waters was also markedly different from MG I-dominated surface water samples collected in the East China Sea. GDGTs from MG II-dominated samples seemed to respond to temperature similarly to GDGTs from the MG I-dominated samples, which calls for further study using pure cultures to determine the exact impact of MG II on GDGT-based proxies.
The first example of a formal 1,3-B-H bond addition across the M-N≡N unit of an end-on dinitrogen complex has been achieved. The use of Piers' borane HB(C
F
)
was essential to observe this reactivity ...and it plays a triple role in this transformation: 1) electrophilic N
-borylation agent, 2) Lewis acid in a frustrated Lewis pair-type B-H bond activation, and 3) hydride shuttle to the metal center. This chemistry is supported by NMR spectroscopy and solid-state characterization of products and intermediates. The combination of chelate effect and strong σ donation in the diphosphine ligand 1,2-bis(diethylphosphino)ethane was mandatory to avoid phosphine dissociation that otherwise led to complexes where borylation of N
occurred without hydride transfer.
One of the most distinctive characteristics of archaea is their unique lipids. While the general nature of archaeal lipids has been linked to their tolerance to extreme conditions, little is known ...about the diversity of lipidic structures archaea are able to synthesize, which hinders the elucidation of the physicochemical properties of their cell membrane. In an effort to widen the known lipid repertoire of the piezophilic and hyperthermophilic model archaeon
Thermococcus barophilus
, we comprehensively characterized its intact polar lipid (IPL), core lipid (CL), and polar head group compositions using a combination of cutting-edge liquid chromatography and mass spectrometric ionization systems. We tentatively identified 82 different IPLs based on five distinct CLs and 10 polar head group derivatives of phosphatidylhexoses, including compounds reported here for the first time, e.g., di-N-acetylhexosamine phosphatidylhexose-bearing lipids. Despite having extended the knowledge on the lipidome, our results also indicate that the majority of
T. barophilus
lipids remain inaccessible to current analytical procedures and that improvements in lipid extraction and analysis are still required. This expanded yet incomplete lipidome nonetheless opens new avenues for understanding the physiology, physicochemical properties, and organization of the membrane in this archaeon as well as other archaea.
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