Tepidibacter aestuarii sp. nov., isolated from the Bach Dang Estuary, Haiphong, Vietnam.

A mesophilic, anaerobic, endospore-forming, fermentative bacterium designated strain 8C15bT was isolated from bank sediment of the Bach Dang Estuary, Haiphong, Vietnam. The Bach Dang Estuary, where Haiphong harbour is located, is subject to strong anthropogenic influence, resulting in high concentrations of black carbon and heavy metals. Strain 8C15bT grew optimally at 30 °C, pH 7.5 and with 2.5 % (w/v) NaCl. The main cellular fatty acids consisted of iso-C15 : 0 (51 %), iso-C15:1 ω7c (32 %) and iso-C13 : 0 (5 %). Genomic considerations of strain 8C15bT and comparisons with the phylogenetically closest strains of the genus Tepidibacter provide evidence that Tepidibacter thalassicus SC562T (=DSM 15285T), Tepidibacter formicigenes DV1184T (=DSM 15518T), Tepidibacter mesophilus B1T (=JCM 16806T) and strain 8C15bT could be differentiated at the species level. We propose the name Tepidibacter aestuarii sp. nov. for the type strain 8C15bT (=JCM 35983T=KCTC 25692T). Finally, the nickel-tolerance properties of strain 8C15bT are highlighted in this study.

Guanosine tetraphosphate (ppGpp) accumulation inhibits chloroplast gene expression and promotes super grana formation in the moss Physcomitrium (Physcomitrella) patens.

The nucleotides guanosine tetraphosphate and pentaphosphate (or (p)ppGpp) are implicated in the regulation of chloroplast function in plants. (p)ppGpp signalling is best understood in the model vascular plant Arabidopsis thaliana in which it acts to regulate plastid gene expression to influence photosynthesis, plant development and immunity. However, little information is known about the conservation or diversity of (p)ppGpp signalling in other land plants. We studied the function of ppGpp in the moss Physcomitrium (previously Physcomitrella) patens using an inducible system for triggering ppGpp accumulation. We used this approach to investigate the effects of ppGpp on chloroplast function, photosynthesis and growth. We demonstrate that ppGpp accumulation causes a dramatic drop in photosynthetic capacity by inhibiting chloroplast gene expression. This was accompanied by the unexpected reorganisation of the thylakoid system into super grana. Surprisingly, these changes did not affect gametophore growth, suggesting that bryophytes and vascular plants may have different tolerances to defects in photosynthesis. Our findings point to the existence of both highly conserved and more specific targets of (p)ppGpp signalling in the land plants that may reflect different growth strategies.

Body plan innovation in treehoppers through the evolution of an extra wing-like appendage.

Body plans, which characterize the anatomical organization of animal groups of high taxonomic rank, often evolve by the reduction or loss of appendages (limbs in vertebrates and legs and wings in insects, for example). In contrast, the addition of new features is extremely rare and is thought to be heavily constrained, although the nature of the constraints remains elusive. Here we show that the treehopper (Membracidae) 'helmet' is actually an appendage, a wing serial homologue on the first thoracic segment. This innovation in the insect body plan is an unprecedented situation in 250 Myr of insect evolution. We provide evidence suggesting that the helmet arose by escaping the ancestral repression of wing formation imparted by a member of the Hox gene family, which sculpts the number and pattern of appendages along the body axis. Moreover, we propose that the exceptional morphological diversification of the helmet was possible because, in contrast to the wings, it escaped the stringent functional requirements imposed by flight. This example illustrates how complex morphological structures can arise by the expression of ancestral developmental potentials and fuel the morphological diversification of an evolutionary lineage.

M1BP is an essential transcriptional activator of oxidative metabolism during Drosophila development.

Oxidative metabolism is the predominant energy source for aerobic muscle contraction in adult animals. How the cellular and molecular components that support aerobic muscle physiology are put in place during development through their transcriptional regulation is not well understood. Using the Drosophila flight muscle model, we show that the formation of mitochondria cristae harbouring the respiratory chain is concomitant with a large-scale transcriptional upregulation of genes linked with oxidative phosphorylation (OXPHOS) during specific stages of flight muscle development. We further demonstrate using high-resolution imaging, transcriptomic and biochemical analyses that Motif-1-binding protein (M1BP) transcriptionally regulates the expression of genes encoding critical components for OXPHOS complex assembly and integrity. In the absence of M1BP function, the quantity of assembled mitochondrial respiratory complexes is reduced and OXPHOS proteins aggregate in the mitochondrial matrix, triggering a strong protein quality control response. This results in isolation of the aggregate from the rest of the matrix by multiple layers of the inner mitochondrial membrane, representing a previously undocumented mitochondrial stress response mechanism. Together, this study provides mechanistic insight into the transcriptional regulation of oxidative metabolism during Drosophila development and identifies M1BP as a critical player in this process.

Control of ciliogenesis by FOR20, a novel centrosome and pericentriolar satellite protein.

Cilia and flagella are evolutionary conserved organelles that generate fluid movement and locomotion, and play roles in chemosensation, mechanosensation and intracellular signalling. In complex organisms, cilia are highly diversified, which allows them to perform various functions; however, they retain a 9+0 or 9+2 microtubules structure connected to a basal body. Here, we describe FOR20 (FOP-related protein of 20 kDa), a previously uncharacterized and highly conserved protein that is required for normal formation of a primary cilium. FOR20 is found in PCM1-enriched pericentriolar satellites and centrosomes. FOR20 contains a Lis1-homology domain that promotes self-interaction and is required for its satellite localization. Inhibition of FOR20 expression in RPE1 cells decreases the percentage of ciliated cells and the length of the cilium on ciliated cells. It also modifies satellite distribution, as judged by PCM1 staining, and displaces PCM1 from a detergent-insoluble to a detergent-soluble fraction. The subcellular distribution of satellites is dependent on both microtubule integrity and molecular motor activities. Our results suggest that FOR20 could be involved in regulating the interaction of PCM1 satellites with microtubules and motors. The role of FOR20 in primary cilium formation could therefore be linked to its function in regulating pericentriolar satellites. A role for FOR20 at the basal body itself is also discussed.

Flumequine-loaded titanate nanotubes as antibacterial agents for aquaculture farms.

Flumequine (FLUM), a quinolone-derived antibiotic is one of the most prescribed drugs in aquaculture farms. However, its intensive use becomes worrisome because of its environmental risks and the emergence of FLUM-resistant bacteria. To overcome these problems we propose in this study the encapsulation and the delivery of FLUM by titanate nanotubes (TiNTs). Optimal FLUM loading was reached by suspending the dehydrated powder nanomaterials (FLUM : TiNTs ratio = 1 : 5) in ethanol. The drug entrapment efficiency was calculated to be 80% approximately with a sustained release in PBS at 37 °C up to 5 days. Then FLUM@TiNTs was evaluated for both its in vitro drug release and antimicrobial activity against Escherichia coli (E. coli). Spectacularly high antibacterial activity compared to those of free FLUM antibiotic was obtained confirming the efficiency of TiNTs to protect FLUM from rapid degradation and transformation within bacteria improving thereby its antibacterial effect. Indeed FLUM@TiNTs was efficient to decrease gradually the bacterial viability to reach ≈5% after 5 days versus ≈75% with free FLUM. Finally, the ex vivo permeation experiments on sea bass (Dicentrachus labrax) intestine shows that TiNTs act to increase the intestinal permeation of FLUM during the experiment. Indeed the encapsulated FLUM flux increased 12 fold (1.46 µg cm2 h-1) compared to the free antibiotic (0.18 µg cm2 h-1). Thanks to its physical properties (diameter 10 nm, tubular shape…) and its high stability in the simulated intestinal medium, TiNTs are easy internalized by enterocytes, thus involving an endocytosis mechanism, and then improve intestinal permeation of FLUM. Taken together, FLUM@TiNTs hold potential as an effective approach for enhancing the antimicrobial activity of FLUM and pave the way not only for future pharmacokinetic studies in the treatment and targeting of fish infections but also for instating of novel strategies that overcome the challenges associated with the abusive use of antibiotics in fish farming.

Assessment of Pharmacokinetics, Toxicity, and Biodistribution of a High Dose of Titanate Nanotubes Following Intravenous Injection in Mice: A Promising Nanosystem of Medical Interest.

Titanate nanotubes (TiNTs) produced by the static hydrothermal process present a promising nanosystem for nanomedicine. However, the behavior of these nanotubes in vivo is not yet clarified. In this work, for the first time, we investigated the toxicity of these materials, their pharmacokinetic profile, and their biodistribution in mice. A high dose of TiNTs (45 mg/kg) was intravenously injected in mice and monitored from 6 h to 45 days. The histological examination of organs and the analysis of liver and kidney function markers and then the inflammatory response were in agreement with a long-term innocuity of these nanomaterials. The parameters of pharmacokinetics revealed the rapid clarification of TiNTs from the bloodstream after 6 h of the intravenous injection which then mainly accumulated in the liver and spleen, and their degradation and clearance in these tissues were relatively slow (>4 weeks). Interestingly, an important property of these materials is their slow dissolution under the lysosome acid environment, rendering them biodegradable. It is noteworthy that TiNTs were directly eliminated in urine and bile ducts without obvious toxicity in mice. Altogether, all these typical in vivo tests studying the TiNT pharmacokinetics, toxicity, and biodistribution are supporting the use of these biocompatible nanomaterials in the biomedical field, especially as a nanocarrier-based drug delivery system.

Sensory inputs stimulate progenitor cell proliferation in an adult insect brain.

Although most brain neurons are produced during embryonic and early postnatal development, recent studies clearly demonstrated in a wide range of species from invertebrates to humans that new neurons are added to specific brain structures throughout adult life. Hormones, neurotransmitters, and growth factors as well as environmental conditions modulate this neurogenesis. In this study, we address the role of sensory inputs in the regulation of adult neural progenitor cell proliferation in an insect model. In some insect species, adult neurogenesis occurs in the mushroom bodies, the main sensory integrative centers of the brain, receiving multimodal information and often considered as the analog of the vertebrate hippocampus. We recently showed that rearing adult crickets in enriched sensory and social conditions enhanced neuroblast proliferation in the mushroom bodies. Here, by manipulating hormonal levels and affecting olfactory and/or visual inputs, we show that environmental regulation of neurogenesis is in direct response to olfactory and visual stimuli rather than being mediated via hormonal control. Experiments of unilateral sensory deprivation reveal that neuroblast proliferation can be inhibited in one brain hemisphere only. These results, obtained in a relatively simple brain, emphasize the role of sensory inputs on stem cell division.

Deciphering the adaptation strategies of Desulfovibrio piezophilus to hydrostatic pressure through metabolic and transcriptional analyses.

Desulfovibrio piezophilus strain C1TLV30(T) is a mesophilic piezophilic sulfate-reducer isolated from Wood Falls at 1700 m depth in the Mediterranean Sea. In this study, we analysed the effect of the hydrostatic pressure on this deep-sea living bacterium at the physiologic and transcriptomic levels. Our results showed that lactate oxidation and energy metabolism were affected by the hydrostatic pressure. Especially, acetyl-CoA oxidation pathway and energy conservation through hydrogen and formate recycling would be more important when the hydrostatic pressure is above (26 MPa) than below (0.1 MPa) the optimal one (10 MPa). This work underlines also the role of the amino acid glutamate as a piezolyte for the Desulfovibrio genus. The transcriptomic analysis revealed 146 differentially expressed genes emphasizing energy production and conversion, amino acid transport and metabolism and cell motility and signal transduction mechanisms as hydrostatic pressure responding processes. This dataset allowed us to identify a sequence motif upstream of a subset of differentially expressed genes as putative pressure-dependent regulatory element.

Suppression of adult neurogenesis impairs olfactory learning and memory in an adult insect.

Although adult neurogenesis has now been demonstrated in many different species, the functional role of newborn neurons still remains unclear. In the house cricket, a cluster of neuroblasts, located in the main associative center of the insect brain, keeps producing new interneurons throughout the animal's life. Here we address the functional significance of adult neurogenesis by specific suppression of neuroblast proliferation using gamma irradiation of the insect's head and by examining the impact on the insect's learning ability. Forty gray irradiation performed on the first day of adult life massively suppressed neuroblasts and their progeny without inducing any noticeable side effect. We developed a new operant conditioning paradigm especially designed for crickets: the "escape paradigm." Using olfactory cues, visual cues, or both, crickets had to choose between two holes, one allowing them to escape and the other leading to a trap. Crickets lacking adult neurogenesis exhibited delayed learning when olfactory cues alone were used. Furthermore, retention 24 hr after conditioning was strongly impaired in irradiated crickets. By contrast, when visual cues instead of olfactory ones were provided, performance of irradiated insects was only slightly affected; when both olfactory and visual cues were present, their performance was not different from that of controls. From these results, it can be postulated that newborn neurons participate in the processing of olfactory information required for complex operant conditioning.

Development of cricket mushroom bodies.

Mushroom bodies are recognized as a multimodal integrator for sensorial stimuli. The present study analyzes cricket mushroom body development from embryogenesis to adulthood. In the house cricket, Kenyon cells were born from a group of neuroblasts located at the apex of mushroom bodies. Our results demonstrate the sequential generation of Kenyon cells: The more external they are, the earlier they were produced. BrdU treatment on day 8 (57% stage) of embryonic life results, at the adult stage, in the labelling of the large Kenyon cells at the periphery of the mushroom body cortex. These cells have specific projections into the posterior calyx, the gamma lobe, and an enlargement at the inner part of the vertical lobe; they represent a part of mushroom bodies of strictly embryonic origin. The small Kenyon cells were formed from day 9 (65% stage) of the embryonic stage onward, and new interneurons are produced throughout the entire life of the insect. They send their projections into the anterior calyx and into the vertical and medial lobes. Mushroom body development of Acheta should be considered as a primitive template, and cross-taxonomic comparisons of the mushroom body development underscore the precocious origin of the gamma lobe. As a result of continuous neurogenesis, cricket mushroom bodies undergo remodeling throughout life, laying the foundation for future studies of the functional role of this developmental plasticity.

Hormonal and sensory inputs regulate distinct neuroblast cell cycle properties in adult cricket brain.

From invertebrates to humans, it has been demonstrated that new neurons are added to specific brain structures throughout adult life. In the house cricket, adult neurogenesis occurs in the mushroom bodies, the main sensory integrative center of the brain, often considered an analogue of vertebrate hippocampus. We have previously shown that this neurogenesis can be modulated by hormones through the polyamine pathway and by environmental conditions through sensory inputs and the nitric oxide pathway. Environment-induced neurogenesis is independent of juvenile hormone levels, so we addressed the roles of sensory inputs and hormones in the control of neuroblast proliferation. Here, by using double labelling of cells specifically in S phase (5-bromo-2'-deoxyuridine) together with labelling of mitotically active cells in any phase (proliferating cell nuclear antigen), we show that juvenile hormone acts on progenitor cell proliferation by inducing quiescent neuroblasts to enter the cell cycle, whereas sensory inputs act by shortening the cell cycle. Thus, in the adult house cricket, regulation of neuroblast proliferation by hormonal and environmental cues occurs through two independent modes of action.

A novel role for polyamines in adult neurogenesis in rodent brain.

Although neurogenesis in the adult is known to be regulated by various internal cues such as hormones, growth factors and cell-adherence molecules, downstream elements underlying their action at the cellular level still remain unclear. We previously showed in an insect model that polyamines (putrescine, spermidine and spermine) play specific roles in adult brain neurogenesis. Here, we demonstrate their involvement in the regulation of secondary neurogenesis in the rodent brain. Using neurosphere assays, we show that putrescine addition stimulates neural progenitor proliferation. Furthermore, in vivo depletion of putrescine by specific and irreversible inhibition of ornithine decarboxylase, the first key enzyme of the polyamine synthesis pathway, induces a consistent decrease in neural progenitor cell proliferation in the two neurogenic areas, the dentate gyrus and the subventricular zone. The present study reveals common mechanisms underlying birth of new neurons in vertebrate and invertebrate species.

Effect of hormones and growth factors on the proliferation of adult cricket neural progenitor cells in vitro.

In the adult cricket brain, a cluster of neuroblasts produces new interneurons that integrate into the mushroom body (MB), the main associative structure for multisensory information of the insect brain. In previous study we showed the antagonist role of the two morphogenetic hormones, juvenile hormone (JH) and ecdysone, on the regulation of adult MB neurogenesis in vivo. In order to examine whether these hormones act directly on neural progenitor cells, we developed an organotypic culture of MB cortices. Cell proliferation was assessed by 5-bromo, 2'-deoxyuridine (BrdU) incorporation. We showed that JH increased mushroom body neuroblast (MBNb) proliferation, confirming the mitogenic effect of JH observed in vivo. By contrast, ecdysone did not affect the amount of BrdU-labeled nuclei, suggesting that the inhibitory effect observed in vivo probably proceeded from an indirect pathway. We then examined the role of growth factors known to stimulate neural stem cell/progenitor cell proliferation in vertebrates. As shown by calcium imaging, MBNb only expressed functional receptors for insulin whereas mature interneurons responded to IGF-I and bFGF. Both insulin (10 microg/ml) and IGF-I (10 ng/ml) enhanced MB progenitor cell proliferation in culture, although the insulin effect was more pronounced. This effect was abolished when an inhibitor of polyamine biosynthesis was present in the medium, suggesting a link between polyamines and the insulin signaling pathway. By contrast, bFGF (20-200 ng/ml) failed to stimulate MBNb proliferation. Our results point to conserved and divergent mechanisms between vertebrates and invertebrates in the regulation of adult neural progenitor cell proliferation.