Bacterial Respiration and Growth Rates Affect the Feeding Preferences, Brood Size and Lifespan of Caenorhabditis elegans

Combination of a membrane bioreactor with a rotating biological contactor holding several diverse metazoans can reduce excess sludge with fouling mitigation

In a membrane bioreactor (MBR) system, in situ sludge reduction techniques induce membrane fouling. To address this challenge, we incorporated a rotating mesh carrier, which can adsorb organic matter and provide a habitat for metazoans, into the anoxic tank of a conventional anoxic/oxic-MBR (A/O-MBR) system, termed rotating biological contactor-MBR (RBC-MBR), and evaluated treatment performance. Over 151 days, lab-scale RBC-MBR and A/O-MBR were used to treat municipal sewage. Both reactors showed similar COD and NH4+ removal rates. However, RBC-MBR reduced excess sludge by approximately 45 % compared with A/O-MBR. Microscopic observation and 18S rRNA gene-based microbial analysis revealed the persistence of microfauna and metazoans (oligochaetes, nematodes, and rotifers) in RBC, which are typically absent in activated sludge. Additionally, the metazoan's population in the RBC-MBR membrane tank was two-fold that of A/O-MBR, indicating enhanced sludge reduction through predation. Despite these reductions, the increase in transmembrane pressure was similar between RBC-MBR and A/O-MBR, suggesting that sludge holding by RBC mesh media degrade fouling substances, such as proteins and polysaccharides and improves sludge filterability, resulting in membrane fouling mitigation. Microbial communities in both reactors were similar, indicating that the installation of RBC did not alter the microbial community of sludge. Network analysis suggested potential symbiotic or prey-predator relationships between bacteria and metazoans. This study reveals that RBC-MBR effectively reduced the excess sludge while mitigating membrane fouling, highlighting one of the promising technology for applying metazoan predation into MBR.

Pesticides in sediments from Magdalena River, Colombia, are linked to reproductive toxicity on Caenorhabditis elegans

Pesticides are prevalent pollutants found in river sediments in agricultural regions worldwide, leading to environmental pollution and toxic effects on biota. In this study, twenty sediment samples were collected from the Magdalena River in Colombia and analyzed for forty pesticides. Methanolic extracts of the sediments were used to expose Caenorhabditis elegans for 24 h, evaluating the effects on its reproduction. The most abundant pesticides found in Magdalena River sediments were atrazine, bromacil, DDE, and chlorpyrifos. The concentrations of DDE and the sum of DDD, DDE, and DDT were above the Threshold Effect Concentration (TEC) values for freshwater sediments, indicating potential effects on aquatic organisms. The ratios of DDT/(DDE + DDD) and DDD/DDE suggest historical contributions of DDT and degradation under aerobic conditions. Several sampling sites displayed a moderate toxicity risk to biota, as calculated by the sediment quality guideline quotient (SQGQ). Nematode brood size was reduced by up to 37% after sediment extract exposure. The presence of chlordane, DDT-related compounds, and chlorpyrifos in Magdalena River sediments was associated with reproductive toxicity among C. elegans.

Methods to extract and study the biological effects of murine gut microbiota using Caenorhabditis elegans as a screening host

Gut microbiota has been established as a main regulator of health. However, how changes in gut microbiota are directly associated with physiological and cellular alterations has been difficult to tackle on a large-scale basis, notably because of the cost and labor-extensive resources required for rigorous experiments in mammals. In the present study, we used the nematode Caenorhabditis elegans as a model organism to elucidate microbiota-host interactions. We developed a method to extract gut microbiota (MCB) from murine feces, and tested its potential as food source for and its impact on C. elegans biology compared to the standard bacterial diet Escherichia coli OP50. Although less preferred than OP50, MCB was not avoided but had a lower energy density (triglycerides and glucose). Consistently, MCB-fed worms exhibited smaller body length and size, lower fertility, and lower fat content than OP50-fed worms, but had a longer mean lifespan, which resembles the effects of calorie restriction in mammals. However, these outcomes were altered when bacteria were inactivated, suggesting an important role of symbiosis of MCB beyond nutrient source. Taken together, our findings support the effectiveness of gut MCB processing to test its effects in C. elegans. More work comparing MCB of differently treated mice or humans is required to further validate relevance to mammals before large-scale screening assays.

Lacticaseibacillus rhamnosus Probio-M9 extends the lifespan of Caenorhabditis elegans

Probiotics have been characterized as useful for maintaining the balance of host gut flora and conferring health effects, but few studies have focused on their potential for delaying aging in the host. Here we show that Lacticaseibacillus rhamnosus Probio-M9 (Probio-M9), a healthy breast milk probiotic, enhances the locomotor ability and slows the decline in muscle function of the model organism Caenorhabditis elegans. Live Probio-M9 significantly extends the lifespan of C. elegans in a dietary restriction-independent manner. By screening various aging-related mutants of C. elegans, we find that Probio-M9 extends lifespan via p38 cascade and daf-2 signaling pathways, independent on daf-16 but dependent on skn-1. Probio-M9 protects and repairs damaged mitochondria by activating mitochondrial unfolded protein response. The significant increase of amino acids, sphingolipid, galactose and fatty acids in bacterial metabolites might be involved in extending the lifespan of C. elegans. We reveal that Probio-M9 as a dietary supplementation had the potential to delay aging in C. elegans and also provide new methods and insights for further analyzing probiotics in improving host health and delaying the occurrence of age-related chronic diseases.

C. elegans PEZO-1 is a mechanosensitive ion channel involved in food sensation

PIEZO channels are force sensors essential for physiological processes, including baroreception and proprioception. The Caenorhabditis elegans genome encodes an orthologue gene of the Piezo family, pezo-1, which is expressed in several tissues, including the pharynx. This myogenic pump is an essential component of the C. elegans alimentary canal, whose contraction and relaxation are modulated by mechanical stimulation elicited by food content. Whether pezo-1 encodes a mechanosensitive ion channel and contributes to pharyngeal function remains unknown. Here, we leverage genome editing, genetics, microfluidics, and electropharyngeogram recording to establish that pezo-1 is expressed in the pharynx, including in a proprioceptive-like neuron, and regulates pharyngeal function. Knockout (KO) and gain-of-function (GOF) mutants reveal that pezo-1 is involved in fine-tuning pharyngeal pumping frequency, as well as sensing osmolarity and food mechanical properties. Using pressure-clamp experiments in primary C. elegans embryo cultures, we determine that pezo-1 KO cells do not display mechanosensitive currents, whereas cells expressing wild-type or GOF PEZO-1 exhibit mechanosensitivity. Moreover, infecting the Spodoptera frugiperda cell line with a baculovirus containing the G-isoform of pezo-1 (among the longest isoforms) demonstrates that pezo-1 encodes a mechanosensitive channel. Our findings reveal that pezo-1 is a mechanosensitive ion channel that regulates food sensation in worms.

Anti-aging potency correlates with metabolites from in vitro fermentation of edible fungal polysaccharides using human fecal intestinal microflora

Aging is a natural process in which the structural integrity of an organism declines over time.

Organic Bioelectronics for In Vitro Systems

Bioelectronics have made strides in improving clinical diagnostics and precision medicine. The potential of bioelectronics for bidirectional interfacing with biology through continuous, label-free monitoring on one side and precise control of biological activity on the other has extended their application scope to in vitro systems. The advent of microfluidics and the considerable advances in reliability and complexity of in vitro models promise to eventually significantly reduce or replace animal studies, currently the gold standard in drug discovery and toxicology testing. Bioelectronics are anticipated to play a major role in this transition offering a much needed technology to push forward the drug discovery paradigm. Organic electronic materials, notably conjugated polymers, having demonstrated technological maturity in fields such as solar cells and light emitting diodes given their outstanding characteristics and versatility in processing, are the obvious route forward for bioelectronics due to their biomimetic nature, among other merits. This review highlights the advances in conjugated polymers for interfacing with biological tissue in vitro, aiming ultimately to develop next generation in vitro systems. We showcase in vitro interfacing across multiple length scales, involving biological models of varying complexity, from cell components to complex 3D cell cultures. The state of the art, the possibilities, and the challenges of conjugated polymers toward clinical translation of in vitro systems are also discussed throughout.

Assessment on chronic and transgenerational toxicity of methamphetamine to Caenorhabditis elegans and associated aquatic risk through toxicity indicator sensitivity distribution (TISD) analysis

Evidence about the adverse effects of methamphetamine (METH) on invertebrates is scarce. Hence, C. elegans, a representative invertebrate model, was exposed to METH at environmental levels to estimate chronic and transgenerational toxicity. The results of chronic exposure were integrated into an underlying toxicity framework of METH in invertebrates (e.g., benthos) at environmentally relevant concentrations. The induction of cellular oxidative damage-induced apoptosis and fluctuation of ecologically important traits (i.e., feeding and locomotion) might be attributed by the activation of the longevity regulating pathway regulated by DAF-16/FOXO, and detoxification by CYP family enzymes. The adverse effects to the organism level included impaired viability and decreased fecundity. The results from transgenerational exposure elucidated the cumulative METH-induced damage in invertebrates. Finally, a new risk assessment method named toxicity indicator sensitivity distribution (TISD) analysis was proposed by combining multiple toxicity indicator test data (EC_x) to derive the hazardous concentration for 10% indicators (C₁₀) of one species. The risk quotient (RQ) values calculated by measured environmental concentrations and C₁₀ in southern China, southeastern Australia, and the western US crossed the alarm line (RQ = 5), suggesting a need for long-term monitoring.

Cultivation of Caenorhabditis elegans on new cheap monoxenic media without peptone

The study of species biodiversity within the Caenorhabditis genus of nematodes would be facilitated by the isolation of as many species as possible. So far, over 50 species have been found, usually associated with decaying vegetation or soil samples, with many from Africa, South America and Southeast Asia. Scientists based in these regions can contribute to Caenorhabditis sampling and their proximity would allow intensive sampling, which would be useful for understanding the natural history of these species. However, severely limited research budgets are often a constraint for these local scientists. In this study, we aimed to find a more economical, alternative growth media to rear Caenorhabditis and related species. We tested 25 media permutations using cheaper substitutes for the reagents found in the standard nematode growth media (NGM) and found three media combinations that performed comparably to NGM with respect to the reproduction and longevity of C. elegans. These new media should facilitate the isolation and characterization of Caenorhabditis and other free-living nematodes for the researchers in the poorer regions such as Africa, South America, and Southeast Asia where nematode diversity appears high.

An alternative food source for metabolism and longevity studies in Caenorhabditis elegans

Caenorhabditis elegans is an instrumental research model used to advance our knowledge in areas including development, metabolism, and aging. However, research on metabolism and/or other measures of health/aging are confounded by the nematode's food source in the lab, live E. coli bacteria. Commonly used treatments, including ultraviolet irradiation and antibiotics, are successful in preventing bacterial replication, but the bacteria can remain metabolically active. The purpose of this study is to develop a metabolically inactive food source for the worms that will allow us to minimize the confounding effects of bacterial metabolism on worm metabolism and aging. Our strategy is to use a paraformaldehyde (PFA) treated E. coli food source and to determine its effects on worm health, metabolism and longevity. We initially determine the lowest possible concentrations of PFA necessary to rapidly and reproducibly kill bacteria. We then measure various aspects of worm behavior, healthspan and longevity, including growth rate, food attraction, brood size, lifespan and metabolic assessments, such as oxygen consumption and metabolomics. Our resulting data show that worms eat and grow well on these bacteria and support the use of 0.5% PFA-killed bacteria as a nematode food source for metabolic, drug, and longevity experiments.

A three-dimensional habitat for C. elegans environmental enrichment

As we learn more about the importance of gene-environment interactions and the effects of environmental enrichment, it becomes evident that minimalistic laboratory conditions can affect gene expression patterns and behaviors of model organisms. In the laboratory, Caenorhabditis elegans is generally cultured on two-dimensional, homogeneous agar plates abundantly covered with axenic bacteria culture as a food source. However, in the wild, this nematode thrives in rotting fruits and plant stems feeding on bacteria and small eukaryotes. This contrast in habitat complexity suggests that studying C. elegans in enriched laboratory conditions can deepen our understanding of its fundamental traits and behaviors. Here, we developed a protocol to create three-dimensional habitable scaffolds for trans-generational culture of C. elegans in the laboratory. Using decellularization and sterilization of fruit tissue, we created an axenic environment that can be navigated throughout and where the microbial environment can be strictly controlled. C. elegans were maintained over generations on this habitat, and showed a clear behavioral bias for the enriched environment. As an initial assessment of behavioral variations, we found that dauer populations in scaffolds exhibit high-frequency, complex nictation behavior including group towering and jumping behavior.

The Use of Plant Growth-Promoting Bacteria to Prevent Nematode Damage to Plants

Simple Summary

It has been estimated that 100 g of bulk soil can host about 2000–4000 nematodes and this amount is increased 5-fold in the rhizosphere. A certain number of these nematodes are pathogenic for plants and cause yield and economic losses. Application of chemical nematicides is the most common method used to reduce nematode populations, but these chemicals can have a negative impact on both the environment and human health. Therefore, other more environmentally friendly methods of suppression of plant-parasitic nematodes have been proposed. Among them, the use of plant beneficial soil bacteria, behaving as biocontrol agents against nematodes, represent a potential alternative to chemicals.

Abstract

Plant-parasitic nematodes have been estimated to annually cause around US $173 billion in damage to plant crops worldwide. Moreover, with global climate change, it has been suggested that the damage to crops from nematodes is likely to increase in the future. Currently, a variety of potentially dangerous and toxic chemical agents are used to limit the damage to crops by plant-parasitic nematodes. As an alternative to chemicals and a more environmentally friendly means of decreasing nematode damage to plants, researchers have begun to examine the possible use of various soil bacteria, including plant growth-promoting bacteria (PGPB). Here, the current literature on some of the major mechanisms employed by these soil bacteria is examined. It is expected that within the next 5–10 years, as scientists continue to elaborate the mechanisms used by these bacteria, biocontrol soil bacteria will gradually replace the use of chemicals as nematicides.

Anti-fat effect and mechanism of polysaccharide-enriched extract from Cyclocarya paliurus (Batal.) Iljinskaja in Caenorhabditis elegans

Obesity is a global epidemic. The polysaccharide extract from Cyclocarya paliurus have good performance in safely alleviating the fat accumulation of C. elegans, which is expected to be developed into an effective natural anti-obesity product.

Wrapping culture plates with Parafilm M® increases Caenorhabditis elegans growth

OBJECTIVE

Parafilm M® is a moisture-resistant thermoplastic commonly used to seal Nematode Growth Media (NGM) agar plates on which the nematode Caenorhabditis elegans is cultured. This practice reduces media dehydration and microbial contamination. However, the effects on C. elegans individuals of placing this barrier between the external environment and the interior of the NGM plate are currently unknown. Our research aims to determine if this common practice engenders developmental changes, such as growth, that could subsequently and unintentionally alter experimental data. We compared the larval growth over 48 h of animals cultured on Parafilm-wrapped and unwrapped control NGM plates.

RESULTS

Wrapping culture plates with Parafilm significantly accelerated and increased larval growth, with a 0.87 μm/h increase in growth rate (~ 6%) and a 37.90 μm increase in the change in growth (Δgrowth; ~ 5%) over 48 h. Therefore, C. elegans investigators should be aware that wrapping their experimental cultures with Parafilm may result in statistically detectable changes in worm growth and possibly other developmental processes.

Characterization of aminopeptidase encoding gene anp-1 and its association with development in Caenorhabditis elegans

Background

Aminopeptidases play important roles in various biological processes in nematodes including growth, development and reproduction. Although the aminopeptidases have been shown to regulate reproduction in Caenorhabditis elegans (C. elegans), the role of aminopeptidases in development and aging has not been reported. This study focused on the function of aminopeptidase AlaNyl aminopeptidase 1 (ANP-1) on development in C. elegans.

Methods

In the present study, we reported the identification of ANP-1 in C. elegans along with sequence analysis and its functional expression and characterization. The phenotype changes were observed when anp-1 mutated. Then, differential expression genes (DEGs) between wild type strain (N2) and anp-1 deletion strain (RB804) were identified using transcriptome sequencing method. Finally, DEGs were verified by qRT-PCR assay.

Results

Our observations suggested that anp-1 mutation induced small body size in the L4/young adult stage of C. elegans, however, there was no difference between N2 and RB804 in adult stage. Moreover, deletion of anp-1 resulted in shortening lifespan and laying fewer eggs. DEGs (184 genes) were observed between N2 groups and RB804 groups by transcriptome sequencing. According to GO annotations and KEGG enrichment analysis, these DEGs play vital roles in development regulation in C. elegans. These data demonstrate ANP-1 participates in development and aging of C. elegans and will considerably contribute to the existing knowledge of aminopeptidase function in C. elegans.

Whey: The Soil Bio-Community Enhancer That Selectively Controls Root-Knot Nematodes

To date, it is mandatory for ecofriendly pest-management tools to be used in agriculture. Whey is a dairy-processing waste, a plant and soil chemical and fungicidal basic substance. The beneficial effect of whey on soil microorganisms, enzymatic activities, and free-living nematodes-combined with its toxic activity on the plant parasites-forms root knot nematodes. In this study, this finding is reported for the first time. A drip-irrigating tomato plant combined with whey in water at 3.125% (v/w) and 6.25% (v/w) dose dependently promoted Gram+ and Gram- bacteria, actinomycetes, and fungi biomass. Respectively, whey treatment and duration augmented the bacterial feeding nematodes along with the soil enzymatic activities, e.g., alkaline phosphatase, dehydrogenase, and urease. The counterpart for these soil organisms' and enzymes' functionality is the decomposition of organic matter, nutrient mineralization and cycling. Additionally, whey applied at 6.25% (v/w) every 10 days in a field experiment exhibited an efficacy of 70% on root knot nematodes. It is calculated that the EC_50/3d value paralyzes in vitro Meloidogyne javanica, which was 3.2% (v/v). Conclusively, the soil application of whey could be a sustainable and ecofriendly method to combat the root knot nematodes and additionally to enhance soil biotic components.

Interplay between mitochondria and diet mediates pathogen and stress resistance in Caenorhabditis elegans

Diet is a crucial determinant of organismal biology; interactions between the host, its diet, and its microbiota are critical to determining the health of an organism. A variety of genetic and biochemical means were used to assay stress sensitivity in C. elegans reared on two standard laboratory diets: E. coli OP50, the most commonly used food for C. elegans, or E. coli HT115, which is typically used for RNAi-mediated gene knockdown. We demonstrated that the relatively subtle shift to a diet of E. coli HT115 had a dramatic impact on C. elegans's survival after exposure to pathogenic or abiotic stresses. Interestingly, this was independent of canonical host defense pathways. Instead the change arises from improvements in mitochondrial health, likely due to alleviation of a vitamin B12 deficiency exhibited by worms reared on an E. coli OP50 diet. Increasing B12 availability, by feeding on E. coli HT115, supplementing E. coli OP50 with exogenous vitamin B12, or overexpression of the B12 transporter, improved mitochondrial homeostasis and increased resistance. Loss of the methylmalonyl-CoA mutase gene mmcm-1/MUT, which requires vitamin B12 as a cofactor, abolished these improvements, establishing a genetic basis for the E. coli OP50-incurred sensitivity. Our study forges a mechanistic link between a dietary deficiency (nutrition/microbiota) and a physiological consequence (host sensitivity), using the host-microbiota-diet framework.

Structural characterization of peptides fromLocusta migratoria manilensis(Meyen, 1835) and anti-aging effect inCaenorhabditis elegans

Locusts are a kind of agricultural pest rich in protein and widely eaten by people, yet, the nutritional and antioxidant activities of locust peptide have never been explored. In the current study, the locust peptides (LPs) were isolated from the Locusta migratoria manilensis (Meyen, 1835) and the anti-aging effects on Caenorhabditis elegans (C. elegans) were evaluated. The mean lifespan of C. elegans was significantly extended using LPs with a concentration of 1.0 mg mL⁻¹. Out of the 23 peptides, LP-1, a pentapeptide with The-Phe-Lys-His-Gly sequence, with a concentration of 2.5 mg mL⁻¹ significantly extended the lifespan of the worms by 23.5%. Additionally, LP-1 was observed to be a strong free radical-scavenger which can improve the survival of the C. elegans under oxidative stress, thermal stress and UV radiation. Furthermore, the LP-1 can up-regulate the expression of the transcription factor DAF-16 and jnk-1, suggesting that LP-1 may promote the C. elegans lifespan and stress resistance through a JNK-1-DAF-16 pathway. This study will be significant for the development of locusts and improvement of functional insect peptide production.

Locusts are a kind of agricultural pest rich in protein and widely eaten by people, yet, the nutritional and antioxidant activities of locust peptide have never been explored.

Identification of attractive odorants released by preferred bacterial food found in the natural habitats of C. elegans

Food choice is critical for survival because organisms must choose food that is edible and nutritious and avoid pathogenic food. Many organisms, including the nematode C. elegans, use olfaction to detect and distinguish among food sources. C. elegans exhibits innate preferences for the odors of different bacterial species. However, little is known about the preferences of C. elegans for bacterial strains isolated from their natural environment as well as the attractive volatile compounds released by preferred natural bacteria isolates. We tested food odor preferences of C. elegans for non-pathogenic bacteria found in their natural habitats. We found that C. elegans showed a preference for the odor of six of the eight tested bacterial isolates over its standard food source, E. coli HB101. Using solid-phase microextraction and gas chromatography coupled with mass spectrometry, we found that four of six attractive bacterial isolates (Alcaligenes sp. JUb4, Providenica sp. JUb5, Providencia sp. JUb39, and Flavobacteria sp. JUb43) released isoamyl alcohol, a well-studied C. elegans attractant, while both non-attractive isolates (Raoultella sp. JUb38 and Acinetobacter sp. JUb68) released very low or non-detectable amounts of isoamyl alcohol. In conclusion, we find that isoamyl alcohol is likely an ethologically relevant odor that is released by some attractive bacterial isolates in the natural environment of C. elegans.

Combination of Metabolomic and Proteomic Analysis Revealed Different Features among Lactobacillus delbrueckii Subspecies bulgaricus and lactis Strains While In Vivo Testing in the Model Organism Caenorhabditis elegans Highlighted Probiotic Properties

Lactobacillus delbrueckii represents a technologically relevant member of lactic acid bacteria, since the two subspecies bulgaricus and lactis are widely associated with fermented dairy products. In the present work, we report the characterization of two commercial strains belonging to L. delbrueckii subspecies bulgaricus, lactis and a novel strain previously isolated from a traditional fermented fresh cheese. A phenomic approach was performed by combining metabolomic and proteomic analysis of the three strains, which were subsequently supplemented as food source to the model organism Caenorhabditis elegans, with the final aim to evaluate their possible probiotic effects. Restriction analysis of 16S ribosomal DNA revealed that the novel foodborne strain belonged to L. delbrueckii subspecies lactis. Proteomic and metabolomic approaches showed differences in folate, aminoacid and sugar metabolic pathways among the three strains. Moreover, evaluation of C. elegans lifespan, larval development, brood size, and bacterial colonization capacity demonstrated that L. delbrueckii subsp. bulgaricus diet exerted beneficial effects on nematodes. On the other hand, both L. delbrueckii subsp. lactis strains affected lifespan and larval development. We have characterized three strains belonging to L. delbrueckii subspecies bulgaricus and lactis highlighting their divergent origin. In particular, the two closely related isolates L. delbrueckii subspecies lactis display different galactose metabolic capabilities. Moreover, the L. delbrueckii subspecies bulgaricus strain demonstrated potential probiotic features. Combination of omic platforms coupled with in vivo screening in the simple model organism C. elegans is a powerful tool to characterize industrially relevant bacterial isolates.

Control of Germline Stem Cell Lineages by Diet and Physiology

Tight coupling of reproduction to environmental factors and physiological status is key to long-term species survival. In particular, highly conserved pathways modulate germline stem cell lineages according to nutrient availability. This chapter focuses on recent in vivo studies in genetic model organisms that shed light on how diet-dependent signals control the proliferation, maintenance, and survival of adult germline stem cells and their progeny. These signaling pathways can operate intrinsically in the germ line, modulate the niche, or act through intermediate organs to influence stem cells and their differentiating progeny. In addition to illustrating the extent of dietary regulation of reproduction, findings from these studies have implications for fertility during aging or disease states.