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[
Curr Biol,
2019]
Extremophiles have much to reveal about the biology of resilience, yet their study is limited by sampling and culturing difficulties [1-3]. The broad success and small size of nematodes make them advantageous for tackling these problems [4-6]. We investigated the arsenic-rich, alkaline, and hypersaline Mono Lake (CA, US) [7-9] for extremophile nematodes. Though Mono Lake has previously been described to contain only two animal species (brine shrimp and alkali flies) in its water and sediments [10], we report the discovery of eight nematode species from the lake, including microbe grazers, parasites, and predators. Thus, nematodes are the dominant animals of Mono Lake in species richness. Phylogenetic analysis suggests that the nematodes originated from multiple colonization events, which is striking, given the young history of extreme conditions at Mono Lake [7, 11]. One species, Auanema sp., is new, culturable, and survives 500 times the human lethal dose of arsenic. Comparisons to two non-extremophile sister species [12] reveal that arsenic resistance is a common feature of the genus and a preadaptive trait that likely allowed Auanema to inhabit Mono Lake. This preadaptation may be partly explained by a variant in the gene
dbt-1 shared with some Caenorhabditiselegans natural populations and known to confer arsenic resistance [13]. Our findings expand Mono Lake's ecosystem from two known animal species to ten, and they provide a new system for studying arsenic resistance. The dominance of nematodes in Mono Lake and other extreme environments and our findings of preadaptation to arsenic raise the intriguing possibility that nematodes are widely pre-adapted to be extremophiles.
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[
Freshwater Biology,
2001]
1 . We investigated the effect of refractory dissolved organic matter (refractory DOM: fulvic acids (FAs) and ultrafiltrates (UFs)), isolated from five different sources, on the reproduction of the bacterivorous nematode Caenorhabditis elegans. Nematodes were exposed to DOM (0.5-64 mg L-1 dissolved organic carbon) during a whole life cycle (72 h). At the end of the test, the number of offspring per worm was determined. 2. We also studied the effect of refractory DOM on abundance, cell size, and activity of the bacteria (Escherichia coli) that were used as a food source for the nematodes, to assess possible indirect effects of DOM via the food organisms. 3. The effects of DOM on the reproduction of C. elegans varied, depending on the origin and concentration of DOM. FAs isolated from a soil leachate and from the effluent of a waste water plant, as well as UFs from a humic lake and from a marsh, stimulated the reproduction of C. elegans. FAs from ground water had no effect, while FAs from a humic lake inhibited the reproduction of the nematodes. All effects occurred at ecologically relevant DOM concentrations and showed clear dose-response relationships. 4. Neither bacterial abundance nor cell size were influenced by refractory DOM. Bacterial activity was unaffected by four types of DOM. Only FAs from the humic lake caused a significant decrease in bacterial activity over 72 h. 5. The negative effect of FAs from the humic lake on nematode reproduction may be a consequence of a lower bacterial activity in this treatment. The positive effects of refractory DOM, however, could not be related to bacterial parameters. Therefore, we assume that the DOM directly influenced the reproduction of C. elegans. We speculate that refractory DOM can potentially be an additional carbon source or a source of trace nutrients influencing the reproduction of C. elegans. Adsorption of refractory DOM on bacterial cells, serving as food for the nematodes, may have been an important factor for the availability of DOM for C. elegans.
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[
Zootaxa,
2022]
Rhagovelia medinae sp. nov., of the hambletoni group (angustipes complex), and R. utria sp. nov., of the hirtipes group (robusta complex), are described, illustrated, and compared with similar congeners. Based on the examination of type specimens, six new synonymies are proposed: R. elegans Uhler, 1894 = R. pediformis Padilla-Gil, 2010, syn. nov.; R. cauca Polhemus, 1997 = R. azulita Padilla-Gil, 2009, syn. nov., R. huila Padilla-Gil, 2009, syn. nov., R. oporapa Padilla-Gil, 2009, syn. nov, R. quilichaensis Padilla-Gil, 2011, syn. nov.; and R. gaigei, Drake Hussey, 1947 = R. victoria Padilla-Gil, 2012 syn. nov. The first record from Colombia is presented for R. trailii (White, 1879), and the distributions of the following species are extended in the country: R. cali Polhemus, 1997, R. castanea Gould, 1931, R. cauca Polhemus, 1997, R. gaigei Drake Hussey, 1957, R. elegans Uhler, 1894, R. femoralis Champion, 1898, R. malkini Polhemus, 1997, R. perija Polhemus, 1997, R. sinuata Gould, 1931, R. venezuelana Polhemus, 1997, R. williamsi Gould, 1931, and R. zeteki Drake, 1953.
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[
J Biol Chem,
1990]
The nematode Caenorhabditis elegans (C. elegans) expresses the regulatory subunit (R) of cAMP-dependent protein kinase at a level similar to the levels determined for R subunits in mammalian tissues. Approximately 60% of the C. elegans cAMP-binding protein is tightly associated with particulate structures by noncovalent interactions. Ionic detergents or 7 M urea solubilize particulate R. Solubilized and cytosolic R subunits have apparent Mr values of 52,000 and pI values of 5.5. cDNA and genomic DNA encoding a unique C. elegans R subunit were cloned and sequenced. The derived amino acid sequence contains 375 residues; carboxyl-terminal residues 145-375 are 69% identical with mammalian RI. However, residues 44-145 are markedly divergent from the corresponding regions of all other R sequences. This region might provide sufficient structural diversity to adapt a single R subunit for multiple functional roles in C. elegans. Antibodies directed against two epitopes in the deduced amino acid sequence of C. elegans R avidly bound nematode cytosolic and particulate R subunits on Western blots and precipitated dissociated R subunits and R2C2 complexes from solution. Immunofluorescence analysis revealed that the tip of the head, which contains chemosensory and mechanosensory neurons, and the pharyngeal nerve ring were enriched in R. The R subunit concentration is low during early embryogenesis in C. elegans. A sharp increase (approximately 6-fold) in R content begins several hours before the nematodes hatch and peaks during the first larval stage. Developmental regulation of R expression occurs at translational and/or post-translational levels. The 8-kilobase pair C. elegans R gene is divided into 8 exons by introns ranging from 46 to 4300 base pairs. The 5'-flanking region has no TATA box and contains preferred and minor transcription start sites.
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[
Am J Trop Med Hyg,
1985]
This study of onchocercal nodules reveals an intimate relationship between the cuticle of Onchocerca volvulus and the capillaries of the host. Perfusion of blood vessels with India ink and other special techniques reveal a proliferation of capillaries around the worms and communication between small vessels and the spaces around the worms. The space around the worm is continuous with the central fibrin lake. These findings, together with the fact that the worm's gut contains hemosiderin, suggest that the worm subverts the vascular reaction and causes within the nodule a controlled hemorrhage that serves the worm's nutritional needs. We believe this explains, in part, how worms survive in fibrous nodules for many years.
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[
Nat Commun,
2021]
R-bodies are long, extendable protein polymers formed in the cytoplasm of some bacteria; they are best known for their role in killing of paramecia by bacterial endosymbionts. Pseudomonas aeruginosa PA14, an opportunistic pathogen of diverse hosts, contains genes (referred to as the reb cluster) with potential to confer production of R-bodies and that have been implicated in virulence. Here, we show that products of the PA14 reb cluster associate with R-bodies and control stochastic expression of R-body structural genes.PA14 expresses reb genes during colonization of plant and nematode hosts, and R-body production is required for full virulence in nematodes. Analyses of nematode ribosome content and immune response indicate that P. aeruginosa R-bodies act via a mechanism involving ribosome cleavage and translational inhibition. Our observations provide insight into the biology of R-body production and its consequences during P. aeruginosa infection.
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[
Dev Biol,
2024]
While the nervous system of bilaterian animals is mainly left-right (L-R) symmetric at the anatomical level, some molecular and functional L-R asymmetries exist. However, the extent of these molecular asymmetries and their functional consequences remain poorly characterized. C. elegans allows to study L-R asymmetries in the nervous system with single-neuron resolution. We have previously shown that a neural bHLH transcription factor, HLH-16/Olig, is L-R asymmetrically expressed in the AIY neuron lineage and regulates AIY axon projections in a L-R asymmetric manner. Here, by combining a candidate approach and single-cell RNA sequencing data analysis, we identify the ephrin protein EFN-2 and the Flamingo protein FMI-1 as downstream targets of HLH-16 that are L-R asymmetrically expressed in the AIY lineage. We show that EFN-2 and FMI-1 collaborate in the L-R asymmetric regulation of axonal growth. EFN-2 may act via a non-canonical receptor of the L1CAM family, SAX-7. Our study reveals novel molecular L-R asymmetries in the C. elegans nervous system and their functional consequences.
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[
Commun Integr Biol,
2011]
The development of bilateral symmetry during the evolution of species probably 600 million years ago brought about several important innovations: It fostered efficient locomotion, streamlining and favored the development of a central nervous system through cephalization. However, to increase their functional capacities, many organisms exhibit chirality by breaking their superficial left-right (l-r) symmetry, which manifests in the lateralization of the nervous system or the l-r asymmetry of internal organs. In most bilateria, the mechanisms that maintain consistent l-r asymmetry throughout development are poorly understood. This review highlights insights into mechanisms that couple early embryonic l-r symmetry breaking to subsequent l-r patterning in the roundworm Caenorhabditis elegans. A recently identified strategy for l-r patterning in the early C. elegans embryo is discussed, the spatial separation of midline and anteroposterior axis, which relies on a rotational cellular rearrangement and non-canonical Wnt signaling. Evidence for a general relevance of rotational/torsional rearrangements during organismal l-r patterning and for non-canonical Wnt signaling/planar cell polarity as a common signaling mechanism to maintain l-r asymmetry is presented.
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[
J Biol Chem,
2007]
The biological methyl donor, S adenosylmethionine (AdoMet), can exist in two diastereoisomeric states with respect to its sulfonium ion. The "S" configuration, (S,S)AdoMet, is the only form that is produced enzymatically as well as the only form used in almost all biological methylation reactions. Under physiological conditions, however, the sulfonium ion can spontaneously racemize to the "R" form, producing (R,S)AdoMet. As of yet, (R,S)AdoMet has no known physiological function and may inhibit cellular reactions. In this study, two enzymes have been found in Saccharomyces cerevisiae that are capable of recognizing (R,S)AdoMet and using it to methylate homocysteine to form methionine. These enzymes are the products of the SAM4 and MHT1 genes, previously identified as homocysteine methyltransferases dependent upon AdoMet and S-methylmethionine respectively. We find here that Sam4 recognizes both (S,S) and (R,S)AdoMet, but its activity is much higher with the R,S form. Mht1 reacts with only the R,S form of AdoMet while no activity is seen with the S,S form. R,S-specific homocysteine methyltransferase activity is also shown here to occur in extracts of Arabidopsis thaliana, Drosophila melanogaster, and Caenorhabditis elegans, but has not been detected in several tissue extracts of Mus musculus. Such activity may function to prevent the accumulation of (R,S)AdoMet in these organisms.
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[
Mol Cell,
2013]
R loops are transcription byproducts that constitute athreat to genome integrity. Here we show that R loops are tightly linked to histone H3 S10 phosphorylation (H3S10P), a mark of chromatin condensation.Chromatin immunoprecipitation (ChIP)-on-chip (ChIP-chip) analyses reveal H3S10P accumulation at centromeres, pericentromeric chromatin, and a large number of active open reading frames (ORFs) in R-loop-accumulating yeast cells, better observed in G1. Histone H3S10 plays a key role in maintaining genome stability, as scored by ectopic recombination and plasmid loss, Rad52 foci, and Rad53 checkpoint activation. H3S10P coincides with the presence of DNA-RNA hybrids, is suppressed by ribonucleaseH overexpression, and causes reduced accessibility of restriction endonucleases, implying a tight connection between R loops, H3S10P, and chromatin compaction. Such histone modifications were also observed in R-loop-accumulating Caenorhabditis elegans and HeLa cells. We therefore provide a role of RNA in chromatin structure essential to understand how R loops modulate genome dynamics.