Mutual interactions of E. andrei earthworm and pathogens during the process of vermicomposting

Assessment of microbial flora and pesticidal effect of vermicast generated from Azadirachta indica (neem) for developing a biofertilizer-cum-pesticide as a single package

The soil comprising organic matter, nutrients, serve as substrate for plant growth and various organisms. In areas where there are large plantations, there is a huge leaf litter fall. The leaf litter upon decomposition releases nutrients and helps in nutrient recycling, for which the soil engineers such as earthworms, ants and termites are important key players. In this context, the present study was conducted to assess the characteristics of the vermicast obtained by vermicomposting neem leaf litter in terms of microbial flora, plant growth promoting properties and antagonistic activities of the vermicast against phytopathogens. Vermicomposting of neem leaf litter was done using two epigeic earthworm species Eisenia fetida and Eudrilus eugeniae. The vermicast exhibited antagonistic potential against plant pathogens. Out of the four vermiwash infusions studied, the 75 % formulation reduced the disease incidence against mealybug by 82 % in the tree Neolamarkia cadamba. The result of the study suggests that vermicast made from neem leaf litter may be a potent combination of a biofertilizer and a pesticide.

Changes in the content of emerging pollutants and potentially hazardous substances during vermi/composting of a mixture of sewage sludge and moulded pulp

Processing sewage sludge can be problematic due to its potential environmental toxicity. It may contain high concentrations of pharmaceuticals, polycyclic aromatic hydrocarbons, and heavy metals, as well as pathogenic microorganisms. However, it is a good source of organic matter and rich in microbial communities and enzymatic activity. This study deals with composting and vermicomposting of pre-composted mixtures of two different kinds of sewage sludge blended with moulded pulp in an operating composting plant. Of the total number and concentration of pollutants detected in individual piles, a large percentage of them were reduced by the composting process. The composting 2 process resulted in the greatest reduction in contaminating substances--a total of 19 substances by 4.39-90.4%. Some pharmaceuticals accumulated in earthworm bodies during vermicomposting; a total of 11 substances were detected. Atorvastatin showed the highest percentage reduction in compost 2 (90.4%), vermicompost 1 (65.2%) and vermicompost 2 (97.3%). Both composting and vermicomposting appeared to be effective for removal of heavy metals. A higher content of microbial phospholipid fatty acids (PLFAs) was found in composts than vermicomposts. There was a significant reduction in the content of pathogenic microorganisms in both processes, but the reduction in enterococci was not significant.

New insights into vermiremediation of sewage sludge: The effect of earthworms on micropollutants and vice versa

Vermicomposting represents an environmentally friendly method for the treatment of various types of biowastes, including sewage sludge (SS), as documented in numerous studies. However, there are few papers providing insights into the mechanisms and toxicity effects involved in SS vermicomposting to present a comprehensive overview of the process. In this work, the vermiremediation of SS containing various micropollutants, including pharmaceuticals, personal care products, endocrine disruptors, and per/polyfluoroalkyl substances, was studied. Two SSs originating from different wastewater treatment plants (WWTP1 and WWTP2) were mixed with a bulking agent, moistened straw, at ratios of 0, 25, 50, and 75% SS. Eisenia andrei earthworms were introduced into the mixtures, and after six weeks, the resulting materials were subjected to various types of chemical and toxicological analyses, including conventional assays (mortality, weight) as well as tissue- and cell-level assays, such as malondialdehyde production, cytotoxicity tests and gene expression assays. Through the vermiremediation process significant removal of diclofenac (90%), metoprolol (88%), telmisartan (62%), and triclosan (81%) was achieved. Although the concentrations of micropollutants were substantially different in the original SS samples, the micropollutants vermiaccumulated to a similar extent over the incubation period. The earthworms substantially eliminated the present bacterial populations, especially in the 75% SS treatments, in which the average declines were 90 and 79% for WWTP1 and WWTP2, respectively. To the best of our knowledge, this is the first study to investigate the vermiremediation of such a large group of micropollutants in real SS samples and provide a thorough evaluation of the effect of SS on earthworms at tissue and cellular level.

Problems associated with vermicomposting of dog excrement in practice using Eisenia andrei

One 25-kg dog produces about 500 g of excrement per day. Excrement is a potentially hazardous material, as it may contain pathogenic microorganisms. Our samples were tested for the presence of thermotolerant coliform bacteria, Enterococcus spp., Escherichia coli and Salmonella spp., which are indicators of faecal contamination, as well as for the presence of helminths and their eggs. During the experiment, it was observed whether these microorganisms could be eliminated by vermicomposting. There were two variants of vermicomposting piles: one test pile (with continuous feeding) and one control pile (with a single feeding). The vermicomposting process was run in outdoor conditions in park for 51 weeks using Eisenia andrei earthworms. The vermicomposting of dog excrement with waste from park maintenance (1:2) can produce a good quality fertiliser. During the process of vermicomposting, there was a gradual decrease in the content of pathogenic bacteria. At the end of the vermicomposting process, there were no eggs or adult helminths. The vermicompost was very rich in microorganisms and enzymatic activity. The pH value was slightly alkaline, and the C:N ratio corresponded to value of mature vermicompost.

Bacterial Engulfment Mechanism Is Strongly Conserved in Evolution Between Earthworm and Human Immune Cells

Invertebrates, including earthworms, are applied to study the evolutionarily conserved cellular immune processes. Earthworm immunocytes (so-called coelomocytes) are functionally similar to vertebrate myeloid cells and form the first line of defense against invading pathogens. Hereby, we compared the engulfment mechanisms of THP-1 human monocytic cells, differentiated THP-1 (macrophage-like) cells, and Eisenia andrei coelomocytes towards Escherichia coli and Staphylococcus aureus bacteria applying various endocytosis inhibitors [amantadine, 5-(N-ethyl-N-isopropyl) amiloride, colchicine, cytochalasin B, cytochalasin D, methyl-ß-cyclodextrin, and nystatin]. Subsequently, we investigated the messenger RNA (mRNA) expressions of immune receptor-related molecules (TLR, MyD88, BPI) and the colocalization of lysosomes with engulfed bacteria following uptake inhibition in every cell type. Actin depolymerization by cytochalasin B and D has strongly inhibited the endocytosis of both bacterial strains in the studied cell types, suggesting the conserved role of actin-dependent phagocytosis. Decreased numbers of colocalized lysosomes/bacteria supported these findings. In THP-1 cells TLR expression was increased upon cytochalasin D pretreatment, while this inhibitor caused a dropped LBP/BPI expression in differentiated THP-1 cells and coelomocytes. The obtained data reveal further insights into the evolution of phagocytes in eukaryotes. Earthworm and human phagocytes possess analogous mechanisms for bacterial internalization.

Taxonomic and functional characteristics of aerobic bacteria isolated from the chloragogenous tissue of the earthworm Aporrectodea molleri

Earthworms are considered as a rich microhabitat for the growth and proliferation of diverse soil microorganisms. Hence, earthworms' associated bacteria attracted interest due to their high metabolic profiles and benefits to soil fertility and plant growth. In this study, we aimed to isolate for the first-time aerobic bacteria present in the chloragogenous tissue of the earthworm Apporectodea molleri and test their Plant Growth-Promoting abilities and their resistance to heavy metals (Mn, Zn, Cu, Cd, and Ni). The 16S rRNA gene sequencing revealed the affiliation of the fifteen isolates to six main bacterial genera: Enterobacter, Citrobacter, Aeromonas, Pseudomonas, Bacillus, Terribacillus. These strains displayed different plant growth promoting traits (e.g., indole-3-acetic acid IAA, siderophores, nitrogen fixation, phosphate, and potassium solubilization), in addition, they were able to resist differently to heavy metals. Bacillus strains were most effective as three strains, namely B. subtilis strain TC34; B. circulans strain TC7 and Bacillus sp. strain TC10, were positive to all PGP traits and resisted to all heavy metals. This study illustrates the potential of bacteria from the chloragogenous tissue to exhibit multiple properties, which can be related to the functional feature of this tissue to stock metabolites and neutralize toxic elements.

In Vitro Interactions of TiO2 Nanoparticles with Earthworm Coelomocytes: Immunotoxicity Assessment

Titanium dioxide nanoparticles (TiO₂ NPs) are manufactured worldwide. Once they arrive in the soil environment, they can endanger living organisms. Hence, monitoring and assessing the effects of these nanoparticles is required. We focus on the Eisenia andrei earthworm immune cells exposed to sublethal concentrations of TiO₂ NPs (1, 10, and 100 µg/mL) for 2, 6, and 24 h. TiO₂ NPs at all concentrations did not affect cell viability. Further, TiO₂ NPs did not cause changes in reactive oxygen species (ROS) production, malondialdehyde (MDA) production, and phagocytic activity. Similarly, they did not elicit DNA damage. Overall, we did not detect any toxic effects of TiO₂ NPs at the cellular level. At the gene expression level, slight changes were detected. Metallothionein, fetidin/lysenin, lumbricin and MEK kinase I were upregulated in coelomocytes after exposure to 10 µg/mL TiO₂ NPs for 6 h. Antioxidant enzyme expression was similar in exposed and control cells. TiO₂ NPs were detected on coelomocyte membranes. However, our results do not show any strong effects of these nanoparticles on coelomocytes at both the cellular and molecular levels.

Bacterial community composition of vermicompost-treated tomato rhizospheres

Vermicompost application has been shown to promote plant growth, alter the rhizosphere microbiome, and suppress plant pathogens. These beneficial properties are often attributed to the activity of vermicompost-associated microorganisms. However, little is known about the microbial shifts that occur in the rhizosphere after vermicompost application. To better understand the impact of vermicompost treatments on the assembly of rhizosphere bacterial communities, 16S rDNA communities of vermicompost and rhizospheres of each peat- and soil-grown tomatoes were profiled after conventional fertigation, irrigation without additional nutrients, and addition of three different vermicompost-extracts. The full dataset consisted of 412 identified genera, of which 317 remained following stringent quality filtration. Tomato rhizosphere microbiome responses to treatments were complex and unique between peat and soil growth substrates. Direct colonization of vermicompost-origin taxa into rhizospheres was limited, with genera Photobacterium and Luteimonas colonizing peat rhizospheres, genera Truepera, Phenylobacterium, and Lysinibacillus colonizing soil rhizospheres, and genus Pelagibius appearing in both soil and peat rhizospheres. Further patterns of differential abundance and presence/absence between treatments highlight vermicompost-mediated effects on rhizosphere microbiome assembly as an interplay of rhizosphere medium, direct colonization of vermicompost-origin taxa and vermicompost-induced shifts in the rhizosphere microbial community. This exploratory analysis is intended to provide an initial look at 16S community composition of vermicompost and the effects of vermicompost treatment on the rhizosphere microbiome assembly to highlight interactions of potential merit for subsequent investigations.