Analyzing life-history traits and lipid storage using CARS microscopy for assessing effects of copper on the fitness of Caenorhabditis elegans

Application of Caenorhabditis elegans in Lipid Metabolism Research

Over the last decade, the development and prevalence of obesity have posed a serious public health risk, which has prompted studies on the regulation of adiposity. With the ease of genetic manipulation, the diversity of the methods for characterizing body fat levels, and the observability of feeding behavior, Caenorhabditis elegans (C. elegans) is considered an excellent model for exploring energy homeostasis and the regulation of the cellular fat storage. In addition, the homology with mammals in the genes related to the lipid metabolism allows many aspects of lipid modulation by the regulators of the central nervous system to be conserved in this ideal model organism. In recent years, as the complex network of genes that maintain an energy balance has been gradually expanded and refined, the regulatory mechanisms of lipid storage have become clearer. Furthermore, the development of methods and devices to assess the lipid levels has become a powerful tool for studies in lipid droplet biology and the regulation of the nematode lipid metabolism. Herein, based on the rapid progress of C. elegans lipid metabolism-related studies, this review outlined the lipid metabolic processes, the major signaling pathways of fat storage regulation, and the primary experimental methods to assess the lipid content in nematodes. Therefore, this model system holds great promise for facilitating the understanding, management, and therapies of human obesity and other metabolism-related diseases.

Phenotype Identification of HeLa Cells Knockout CDK6 Gene Based on Label-Free Raman Imaging

Identifying cell phenotypes is essential for understanding the function of biological macromolecules and molecular biology. We developed a noninvasive, label-free, single-cell Raman imaging analysis platform to distinguish between the cell phenotypes of the HeLa cell wild type (WT) and cyclin-dependent kinase 6 (CDK6) gene knockout (KO) type. Via large-scale Raman spectral and imaging analysis, two phenotypes of the HeLa cells were distinguished by their intrinsic biochemical profiles. A significant difference was found between the two cell lines: large lipid droplets formed in the knockout HeLa cells but were not observed in the WT cells, which was confirmed by Oil Red O staining. The band ratio of the Raman spectrum of saturated/unsaturated fatty acids was identified as the Raman spectral marker for HeLa cell WT or gene knockout type differentiation. The interaction between organelles involved in lipid metabolism was revealed by Raman imaging and Lorentz fitting, where the distribution intensity of the mitochondria and the endoplasmic reticulum membrane decreased. At the same time, lysosomes increased after the CDK6 gene knockout. The parameters obtained from Raman spectroscopy are based on hierarchical cluster analysis and one-way ANOVA, enabling highly accurate cell classification.

Polystyrene microbeads influence lipid storage distribution in C. elegans as revealed by coherent anti-Stokes Raman scattering (CARS) microscopy

The exposure of Caenorhabditis elegans to polystyrene (PS) beads of a wide range of sizes impedes feeding, by reducing food consumption, and has been linked to inhibitory effects on the reproductive capacity of this nematode, as determined in standardized toxicity tests. Lipid storage provides energy for longevity, growth, and reproduction and may influence the organismal response to stress, including the food deprivation resulting from microplastics exposure. However, the effects of microplastics on energy storage have not been investigated in detail. In this study, C. elegans was exposed to ingestible sizes of PS beads in a standardized toxicity test (96 h) and in a multigeneration test (∼21 days), after which lipid storage was quantitatively analyzed in individual adults using coherent anti-Stokes Raman scattering (CARS) microscopy. The results showed that lipid storage distribution in C. elegans was altered when worms were exposed to microplastics in form of PS beads. For example, when exposed to 0.1-μm PS beads, the lipid droplet count was 93% higher, the droplets were up to 56% larger, and the area of the nematode body covered by lipids was up to 79% higher than in unexposed nematodes. The measured values tended to increase as PS bead sizes decreased. Cultivating the nematodes for 96 h under restricted food conditions in the absence of beads reproduced the altered lipid storage and suggested that it was triggered by food deprivation, including that induced by the dilutional effects of PS bead exposure. Our study demonstrates the utility of CARS microscopy to comprehensively image the smaller microplastics (<10 μm) ingested by nematodes and possibly other biota in investigations of the effects at the level of the individual organism.

An Overview of Studies on Meiofaunal Traits of the Littoral Zone of Lakes

We carried out an overview of the studies on the traits of the meiofauna of the littoral zone of lakes to investigate the question relating to the Raunkiaeran shortfall (lack of knowledge on biological traits). For this purpose, we selected a series of keywords associated with response and effect traits (feeding habits, locomotion and substrate relation, body size, shape and mass, life history, reproductive strategy, respiration and thermal tolerance) and we counted the relative frequency of occurrence in a set of scientific papers retrieved from Web of Science. The results showed that, except for the traits related to diet and feeding habits, the Raunkiaeran shortfall is very pronounced for all meiofaunal taxa of the littoral zone of lakes, especially for those related to soft-bodied organisms. The reason behind this deficiency concerns many aspects ranging from the high taxonomic expertise required to the intrinsic difficulties of observing organisms of such a small size. The relationship with temperature has not been sufficiently explored and formalized in any of the examined traits; this research aspect needs to be rapidly addressed since the prospects of climate change impacts on lake littorals are expected to be particularly severe.

Bacterial degradation of distillery wastewater pollutants and their metabolites characterization and its toxicity evaluation by using Caenorhabditis elegans as terrestrial test models

Distillery wastewater has significant amount of coloring compounds and organic substances even after the secondary treatment process, which poses many severe environmental and health threats. However, the recalcitrant coloured compounds have not yet been clearly identified. In this study, two bacterial strains DS3 and DS5 capable to decolorize distillery wastewater (DWW) pollutants were isolated and characterized as Staphylococcus saprophyticus (MF182113) and Alcaligenaceae sp. (MF182114), respectively. Results showed that mixed bacterial culture was found more effective decolorizing 71.83% DWW compared to axenic culture DS3 and DS5 resulting only 47.94% and 50.67% decolorization, respectively. The FT-IR and LC-MS/MS analysis of untreated DWW showed the presence of many recalcitrant compounds having different functional groups, but after bacterial treatment, most of compounds get diminished and the toxicity of DWW was reduced significantly. Further, the Nile red staining of Caenorhabditis elegans exposed to untreated and bacteria treated DWW for evaluation of toxicity assay and results revealed that the worms exposed to untreated DWW showed sharp reduction in total fat content having more profound effects, suggesting the diminished nAchR signaling as compare to bacterial treated DWW. Hence, this study revealed that inadequate disposal of untreated DWW may cause transfer of toxic substances into the environment and receiving water bodies.

The effect of metal mixture composition on toxicity to C. elegans at individual and population levels

The toxicity of zinc (Zn), copper (Cu), and cadmium (Cd) to the nematode Caenorhabditis elegans was characterised under single metal and mixture scenarios at different organisational levels. The effects on population size and body length were investigated at two concentrations corresponding to the 24 h LC5 and LC20 levels. Metal toxicity was dependent on metal concentration, exposure time and mixture composition. Populations exposed to LC20 levels of Cd, ZnCu, CuCd and ZnCuCd plummeted, while for all LC5 concentrations, population size continued to increase, albeit that single metals were less harmful than mixtures. Combinations of the LC20 concentration of Cd with a range of Zn concentrations showed concentration dependent mitigating effects on population size and antagonistic effects on mortality. By combining effects at different organisational levels, more insight into metal toxicity was obtained. Metal effects were more evident on population size than on body length or mortality, suggesting that population size could be considered as a sensitive endpoint. Furthermore, our observations of ZnCd mixture effects at the individual and population levels are consistent with literature data on the dose-dependent expression of the cdf-2 gene, which is involved in mediation of Zn and Cd toxicity.