3K Papers found (0.022 seconds)

Janssen AB et al. (2020) Antimicrob Agents Chemother "Evolution of colistin resistance in the Klebsiella pneumoniae complex follows multiple evolutionary trajectories with variable effects on fitness and virulence characteristics."

Janssen AB, Bengoechea JA, Rogers MRC, van Schaik W, Doorduijn DJ, Willems RJL, Mills G, Rooijakkers SHM, Bonten MJM

[

Antimicrob Agents Chemother,

2020]

The increasing prevalence of multidrug-resistant Klebsiella pneumoniae has led to a resurgence in the use of colistin as last-resort drug. Colistin is a cationic antibiotic that selectively acts on Gram-negative bacteria through electrostatic interactions with anionic phosphate groups of the lipid A moiety of lipopolysaccharides (LPS). Colistin resistance in K. pneumoniae is mediated through loss of these phosphate groups, their modification by cationic groups, and by the hydroxylation of acyl-groups of lipid A. Here, we study the in vitro evolutionary trajectories towards colistin resistance in four clinical K. pneumoniae complex strains and their impact on fitness and virulence characteristics.Through population sequencing during in vitro evolution, we found that colistin resistance develops through a combination of single nucleotide polymorphisms, insertion and deletions, and the integration of insertion sequence elements, affecting genes associated with LPS biosynthesis and modification, and capsule structures. Colistin resistance decreased the maximum growth rate of one K. pneumoniae sensu stricto strain, but not in the other three K. pneumoniae complex strains. Colistin-resistant strains had lipid A modified through hydroxylation, palmitoylation, and L-Ara4N addition. K. pneumoniae sensu stricto strains exhibited cross-resistance to LL-37, in contrast to the K. variicola subsp. variicola strain. Virulence, as determined in a Caenorhabditis elegans survival assay, was increased in two colistin-resistant strains.Our study suggests that nosocomial K. pneumoniae complex strains can rapidly develop colistin resistance through diverse evolutionary trajectories upon exposure to colistin. This effectively shortens the lifespan of this last-resort antibiotic for the treatment of infections with multidrug-resistant Klebsiella.

Yue Z et al. (2024) PNAS Nexus "A leak K⁺ channel TWK-40 sustains the rhythmic motor program."

Boulin T, Mouridi SE, Yu B, Chen L, Yue Z, Meng J, Chitturi J, Li Y, Tian Y, Zhen M, Gao S, Wang Y, Zhang C, Xu Y

[

PNAS Nexus,

2024]

Leak potassium (K+) currents, conducted by two-pore domain K+ (K2P) channels, are critical for the stabilization of the membrane potential. The effect of K2P channels on motor rhythm remains enigmatic. We show here that the K2P TWK-40 contributes to the rhythmic defecation motor program (DMP) in Caenorhabditis elegans. Disrupting TWK-40 suppresses the expulsion defects of nlp-40 and aex-2 mutants. By contrast, a gain-of-function (gf) mutant of twk-40 significantly reduces the expulsion frequency per DMP cycle. In situ whole-cell patch clamping demonstrates that TWK-40 forms an outward current that hyperpolarize the resting membrane potential of dorsorectal ganglion ventral process B (DVB), an excitatory GABAergic motor neuron that activates expulsion muscle contraction. In addition, TWK-40 substantially contributes to the rhythmic activity of DVB. Specifically, DVB Ca2+ oscillations exhibit obvious defects in loss-of-function (lf) mutant of twk-40. Expression of TWK-40(gf) in DVB recapitulates the expulsion deficiency of the twk-40(gf) mutant, and inhibits DVB Ca2+ oscillations in both wild-type and twk-40(lf) animals. Moreover, DVB innervated enteric muscles also exhibit rhythmic Ca2+ defects in twk-40 mutants. In summary, these findings establish TWK-40 as a crucial neuronal stabilizer of DMP, linking leak K2P channels with rhythmic motor activity.

Cochran JP et al. (2024) Nanomaterials (Basel) "Effects of Multiple Stressors, Pristine or Sulfidized Silver Nanomaterials, and a Pathogen on a Model Soil Nematode Caenorhabditis elegans."

Unrine JM, Cochran JP, Ngy P, Tsyusko OV, Matocha CJ

[

Nanomaterials (Basel),

2024]

Previous research using the model soil nematode Caenorhabditis elegans has revealed that silver nanoparticles (AgNP) and their transformed counterpart, sulfidized AgNP (sAgNP), reduce their reproduction and survival. To expand our understanding of the environmental consequences of released NP, we examined the synergistic/antagonistic effects of AgNP and sAgNP along with AgNO3 (ionic control) on C. elegans infected with the pathogen Klebsiella pneumoniae. Individual exposures to each stressor significantly decreased nematode reproduction compared to controls. Combined exposures to equitoxic EC30 concentrations of two stressors, Ag in nanoparticulate (AgNP or sAgNP) or ionic form and the pathogen K. pneumoniae, showed a decline in the reproduction that was not significantly different compared to individual exposures of each of the stressors. The lack of enhanced toxicity after simultaneous combined exposure is partially due to Ag decreasing K. pneumoniae pathogenicity by inhibiting biofilm production outside the nematode and significantly reducing viable pathogens inside the host. Taken together, our results indicate that by hindering the ability of K. pneumoniae to colonize the nematode's intestine, Ag reduces K. pneumoniae pathogenicity regardless of Ag form. These results differ from our previous research where simultaneous exposure to zinc oxide (ZnO) NP and K. pneumoniae led to a reproduction level that was not significantly different from the controls.

Martinez MAQ et al. (2020) Bio Protoc "Auxin-mediated Protein Degradation in Caenorhabditis elegans."

Matus DQ, Martinez MAQ

[

Bio Protoc,

2020]

The auxin-inducible degron (AID) technology was recently adapted for use in the nematode Caenorhabditis elegans. Rapid degradation of C. elegans proteins tagged with an AID is mediated by a plant-specific F-box protein, transport inhibitor response 1 (TIR1), and occurs only in the presence of the phytohormone auxin. The first iteration of this technology elicited protein degradation in C. elegans through a naturally occurring form of auxin, indole-3-acetic acid (IAA). Here, we present a protocol that uses 1-naphthaleneacetic acid, potassium salt (K-NAA), an indole-free synthetic auxin analog. At equal concentration, K-NAA is as effective as IAA in standard nematode growth media (NGM). K-NAA is also effective in physiological buffer (M9), allowing for high-throughput experimentation. The main advantages of K-NAA are twofold: first, its photostability prevents light-induced compound degradation during storage and the production of toxic indole-derivatives during fluorescence microscopy of live cells; and second, its water solubility eliminates the need of using ethanol to dissolve the auxin compound, a solvent that may confound C. elegans lifespan and behavioral assays. In this protocol, we describe our method of degrading C. elegans proteins using K-NAA on solid and in liquid media, as well as our method of analyzing protein degradation.

Jiang L et al. (2019) MethodsX "Inappropriateness of RNAlater to preserve Caenorhabditis elegans for RNA extraction."

Li L, Yu H, Kang P, Jiang L, Xie MY, Gong J, Nie SP

[

MethodsX,

2019]

Caenorhabditis elegans is a well-established laboratory animal model and has been widely used in biological research. However, it is still a challenge to obtain a good amount of quality RNA from a limited number of C. elegans for gene expression studies. To address this issue, the present study has compared different conditions to preserve C. elegans for RNA extraction after the failure of an initial effort to use RNAlater-preserved worms for RNA extraction. The effects of different concentrations of proteinase K, different worm life stages, and different worm numbers on RNA extraction were also investigated. The best results were achieved under the following conditions: 1) adult worms that were either freshly prepared or quickly frozen in liquid nitrogen followed by storage at -80C; 2) disruption of C. elegans with proteinase K (1mg/mL) in a lysis buffer (65C for 10min) prior to extraction with Trizol agent. This method can provide a stable, rapid, and effective means to extract RNA from C. elegans with variable worm numbers from 20 to 200. RNAlater was inappropriate for preserving C. elegans for effective RNA extraction.Proteinase K was verified for lysing a limited number of C. elegans for RNA extraction.

Neve IAA et al. (2019) G3 (Bethesda) "Escherichia coli Metabolite Profiling Leads to the Development of an RNA Interference Strain for Caenorhabditis elegans."

Ye Y, Herman C, Lin CJ, Sivaramakrishnan P, Neve IAA, Han L, Wang MC, Sowa JN

[

G3 (Bethesda),

2019]

The relationship of genotypes to phenotypes can be modified by environmental inputs. Such crucial environmental inputs include metabolic cues derived from microbes living together with animals. Thus, the analysis of genetic effects on animals' physiology can be confounded by variations in the metabolic profile of microbes. Caenorhabditis elegans exposed to distinct bacterial strains and species exhibit phenotypes different at cellular, developmental, and behavioral levels. Here we reported metabolomic profiles of three Escherichia coli strains, B strain OP50, K-12 strain MG1655, and B-K-12 hybrid strain HB101, as well as different mitochondrial and fat storage phenotypes of C. elegans exposed to MG1655 and HB101 versus OP50. We found that these metabolic phenotypes of C. elegans are not correlated with overall metabolic patterning of bacterial strains, but their specific metabolites. In particular, the fat storage phenotype is traced to the betaine level in different bacterial strains. HT115 is another K-12 E. coli strain that is commonly utilized to elicit an RNA interference response, and we showed that C. elegans exposed to OP50 and HT115 exhibit differences in mitochondrial morphology and fat storage levels. We thus generated an RNA interference competent OP50 (iOP50) strain that can robustly and consistently knockdown endogenous C. elegans genes in different tissues. Together, these studies suggest the importance of specific bacterial metabolites in regulating the host's physiology and provide a tool to prevent confounding effects when analyzing genotype-phenotype interactions under different bacterial backgrounds.

Scott E et al. (2019) Front Microbiol "Intra Strain Variation of the Effects of Gram-Negative ESKAPE Pathogens on Intestinal Colonization, Host Viability, and Host Response in the Model Organism Caenorhabditis elegans."

Scott E, O'Connor V, Holden-Dye L, Wand ME

[

Front Microbiol,

2019]

In its native environment of rotting vegetation, the soil nematode Caenorhabditis elegans encounters a range of bacteria. This includes species from the ESKAPE group of pathogens that pose a clinical problem in acquired hospital infections. Here, we investigated three Gram-negative members of the ESKAPE group, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. Pathogenicity profiles as measured by time to kill adult C. elegans showed that P. aeruginosa was the most pathogenic, followed by K. pneumoniae, while C. elegans cultured on A. baumannii exhibited the same survival as those on the standard laboratory food source for C. elegans, Escherichia coli OP50. The pathogenicity was paralleled by a reduction in time that C. elegans resided on the bacterial lawn with the most pathogenic strains triggering an increase in the frequency of food-leaving. Previous reports indicate that gut colonization is a feature of pathogenicity, but we found that the most pathogenic strains were not associated with the highest level of colonization. Indeed, clearance of P. aeruginosa strains from the C. elegans gut was independent of bacterial pathogenicity. We show that this clearance is regulated by neuromodulation as C. elegans mutants in unc-31 and egl-3 have enhanced clearance of P. aeruginosa. Intriguingly this is also not linked to their pathogenicity. It is likely that there is a dynamic balance occurring in the C. elegans intestinal environment between maintaining a healthy, beneficial microbiota and removal of pathogenic bacteria.

Souza ACR et al. (2018) Genes (Basel) "Pathogenesis of the Candida parapsilosis Complex in the Model Host Caenorhabditis elegans."

Colombo AL, Fuchs BB, Jayamani E, Mylonakis E, Souza ACR, Alves VS

[

Genes (Basel),

2018]

Caenorhabditiselegans is a valuable tool as an infection model toward the study of Candida species. In this work, we endeavored to develop a C. elegans-Candidaparapsilosis infection model by using the fungi as a food source. Three species of the C. parapsilosis complex (C.parapsilosis (sensustricto), Candidaorthopsilosis and Candidametapsilosis) caused infection resulting in C. elegans killing. All three strains that comprised the complex significantly diminished the nematode lifespan, indicating the virulence of the pathogens against the host. The infection process included invasion of the intestine and vulva which resulted in organ protrusion and hyphae formation. Importantly, hyphae formation at the vulva opening was not previously reported in C. elegans-Candida infections. Fungal infected worms in the liquid assay were susceptible to fluconazole and caspofungin and could be found to mount an immune response mediated through increased expression of cnc-4, cnc-7, and fipr-22/23. Overall, the C. elegans-C. parapsilosis infection model can be used to model C. parapsilosis host-pathogen interactions.

Crocetti L et al. (2009) Bioorg Med Chem Lett "A thiabendazole sulfonamide shows potent inhibitory activity against mammalian and nematode alpha-carbonic anhydrases."

Scozzafava A, Maresca A, Muhlschlegel FA, Supuran CT, Temperini C, Crocetti L, Hall RA

[

Bioorg Med Chem Lett,

2009]

A sulfonamide derivative of the antihelmintic drug thiabendazole was prepared and investigated for inhibition of the zinc enzyme carbonic anhydrase CA (EC 4.2.1.1). Mammalian isoforms CA I-XIV and the nematode enzyme of Caenorhabditis elegans CAH-4b were included in this study. Thiabendazole-5-sulfonamide was a very effective inhibitor of CAH-4b and CA IX (K(I)s of 6.4-9.5nm) and also inhibited effectively isozymes CA I, II, IV-VII, and XII, with K(I)s in the range of 17.8-73.2nM. The high resolution X-ray crystal structure of its adduct with isozyme II evidenced the structural elements responsible for this potent inhibitory activity.

Bai X et al. (2018) J Gen Physiol "A forward genetic screen identifies chaperone CNX-1 as a conserved biogenesis regulator of ERG K⁺ channels."

Bai X, Kang XL, Yao L, Li K, Cai SQ

[

J Gen Physiol,

2018]

The human ether-a-go-go-related gene (hERG) encodes a voltage-gated potassium channel that controls repolarization of cardiac action potentials. Accumulating evidence suggests that most disease-related hERG mutations reduce the function of the channel by disrupting protein biogenesis of the channel in the endoplasmic reticulum (ER). However, the molecular mechanism underlying the biogenesis of ERG K+ channels is largely unknown. By forward genetic screening, we identified an ER-located chaperone CNX-1, the worm homologue of mammalian chaperone Calnexin, as a critical regulator for the protein biogenesis of UNC-103, the ERG-type K+ channel in Caenorhabditis elegans Loss-of-function mutations of cnx-1 decreased the protein level and current density of the UNC-103 K+ channel and suppressed the behavioral defects caused by a gain-of-function mutation in unc-103 Moreover, CNX-1 facilitated tetrameric assembly of UNC-103 channel subunits in a liposome-assisted cell-free translation system. Further studies showed that CNX-1 act in parallel to DNJ-1, another ER-located chaperone known to regulate maturation of UNC-103 channels, on controlling the protein biogenesis of UNC-103. Importantly, Calnexin interacted with hERG proteins in the ER in HEK293T cells. Deletion of calnexin reduced the expression and current densities of endogenous hERG K+ channels in SH-SY5Y cells. Collectively, we reveal an evolutionarily conserved chaperone CNX-1/Calnexin controlling the biogenesis of ERG-type K+ channels.

load 10 more results