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Coagulation/flocculation is a major phenomenon occurring during industrial and municipal water treatment to remove suspended particles. Common coagulants are metal salts, whereas flocculants are synthetic organic polymers. Those materials are appreciated for their high performance, low cost, ease of use, availability and efficiency. Nonetheless, their use has induced environmental health issues such as water pollution by metals and production of large amounts of sludges. As a consequence, alternative coagulants and flocculants, named biocoagulants and bioflocculants due to their biological origin and biodegradability, have been recently developed for water and wastewater treatment. In particular, chitosan and chitosan-based products have found applications as bioflocculants for the removal of particulate and dissolved pollutants by direct bioflocculation. Direct flocculation is done with water-soluble, ionic organic polymers without classical metal-based coagulants, thus limiting water pollution. Chitosan is a partially deacetylated polysaccharide obtained from chitin, a biopolymer extracted from shellfish sources. This polysaccharide exhibits a variety of physicochemical and functional properties resulting in numerous practical applications. Key findings show that chitosan removed more than 90% of solids and more than 95% of residual oil from palm oil mill effluents. Chitosan reduced efficiently the turbidity of agricultural wastewater and of seawater, below 0.4 NTU for the latter. 99% turbidity removal and 97% phosphate removal were observed over a wide pH range using 3-chloro-2-hydroxypropyl trimethylammonium chloride grafted onto carboxymethyl chitosan. Chitosan also removed 99% Microcystis aeruginosa cells and more than 50% of microcystins. Here, we review advantages and drawbacks of chitosan as bioflocculant. Then, we present examples in water and wastewater treatment, sludge dewatering and post-treatment of sanitary landfill leachate.

The digestive tract is the first organ affected by the ingestion of foodborne bacteria. While commensal bacteria become resident, opportunistic or virulent bacteria are eliminated from the gut by the local innate immune system. Here we characterize a new mechanism of defense, independent of the immune system, in Drosophila melanogaster. We observed strong contractions of longitudinal visceral muscle fibers for the first 2 hours following bacterial ingestion. We showed that these visceral muscle contractions are induced by immune reactive oxygen species (ROS) that accumulate in the lumen and depend on the ROS-sensing TRPA1 receptor. We then demonstrate that both ROS and TRPA1 are required in a subset of anterior enteroendocrine cells for the release of the DH31 neuropeptide which activates its receptor in the neighboring visceral muscles. The resulting contractions of the visceral muscles favors quick expulsion of the bacteria, limiting their presence in the gut. Our results unveil a precocious mechanism of defense against ingested opportunistic bacteria, whether they are Gram-positive like Bacillus thuringiensis or Gram-negative like Erwinia carotovora carotovora. Finally, we found that the human homolog of DH31, CGRP, has a conserved function in Drosophila.

This study focuses on the enzymatic hydrolysis of hemoglobin, the main component of cruor that gives blood its red color in mammals. The antibacterial and antioxidant potentials of human hemoglobin hydrolysates were evaluated in comparison to bovine hemoglobin. The results showed strong antimicrobial activity of the peptide hydrolysates against six bacterial strains, independent of the initial substrate concentration level. The hydrolysates also showed strong antioxidant activity, as measured by four different tests. In addition, the antimicrobial and antioxidant activities of the human and bovine hemoglobin hydrolysates showed little or no significant difference, with only the concentration level being the determining factor in their activity. The results of the mass spectrometry study showed the presence of a number of bioactive peptides, the majority of which have characteristics similar to those mentioned in the literature. New bioactive peptides were also identified in human hemoglobin, such as the antibacterial peptides PTTKTYFPHF (α37-46), FPTTKTYFPH (α36-45), TSKYR (α137-141), and STVLTSKYR (α133-141), as well as the antioxidant TSKYR (α137-141). According to these findings, human hemoglobin represents a promising source of bioactive peptides beneficial to the food or pharmaceutical industries.

Drought episodes decrease plant growth and productivity, which in turn cause high economic losses. Plants naturally sense and respond to water stress by activating specific signalling pathways leading to physiological and developmental adaptations. Genetically engineering genes that belong to these pathways might improve the drought tolerance of plants. The abscisic acid (ABA)-responsive element binding protein 1/ABRE binding factor (AREB1/ABF2) is a key positive regulator of the drought stress response. We investigated whether the CRISPR activation (CRISPRa) system that targets AREB1 might contribute to improve drought stress tolerance in Arabidopsis. Arabidopsis histone acetyltransferase 1(AtHAT1) promotes gene expression activation by switching chromatin to a relaxed state. Stable transgenic plants expressing chimeric dCas9(HAT) were first generated. Then, we showed that the CRISPRa dCas9(HAT) mechanism increased the promoter activity controlling the beta-glucuronidase (GUS) reporter gene. To activate the endogenous promoter of AREB1, the CRISPRa dCas9(HAT) system was set up, and resultant plants showed a dwarf phenotype. Our qRT-PCR experiments indicated that both AREB1 and RD29A, a gene positively regulated by AREB1, exhibited higher gene expression than the control plants. The plants generated here showed higher chlorophyll content and faster stomatal aperture under water deficit, in addition to a better survival rate after drought stress. Altogether, we report that CRISPRa dCas9(HAT) is a valuable biotechnological tool to improve drought stress tolerance through the positive regulation of AREB1.

Meloidogyne graminicola (Mg), commonly known as the rice root-knot nematode, is a highly destructive pest that inflicts significant damage on rice crops worldwide. Mg is thought to reproduce primarily by meiotic parthenogenesis, but its success across diverse habitats and hosts raises important questions about its adaptation mechanisms, particularly those driving the evolution of its virulence. Documenting the origin of the pathogen, its reproductive strategies and other evolutionary processes shaping its genome are thus crucial to understand its recent, rapid expansion. In this study, we first improved gene annotations of the Mg genome to enhance identification of potential secreted parasitism genes. Next, comparative genomics analyses of 13 Mg isolates from diverse geographic locations revealed evolutionary changes in the genome, including single nucleotide variations (SNVs), loss of heterozygosity (LoH), and copy number variations (CNVs). These events affected a substantial number of genes, including those coding for secreted proteins, suggesting their roles in nematode adaptation. LoH, the reduction of linkage disequilibrium between SNPs with distance as well as the 4-gamete test all provide evidence for meiotic recombination, supporting some sexual reproduction in Mg. Clustering of populations, based on LoH profiles and SNVs, allowed the definition of groups of isolates not correlating with current geographic distribution. The low sequence divergence at the genome level and the lack of clear phylogeographic structure among isolates support the hypothesis of a recent, widespread dissemination of the parasite, especially across Southeast Asia. Overall, our study supports a dual reproductive mode (sexual/asexual) in Mg, which offers an evolutionary advantage by balancing clonal proliferation in favorable conditions with occasional sexual reproduction allowing generation of new allelic combinations in adverse environments.

Root-knot nematodes (genus Meloidogyne) are plant parasitic species that cause huge economic loss in the agricultural industry and affect the prosperity of communities in developing countries. Control methods against these plant pests are sparse and the current preferred method is deployment of plant cultivars bearing resistance genes against Meloidogyne species. However, some species such as M. enterolobii are not controlled by the resistance genes deployed in the most important crop plants cultivated in Europe. The recent identification of this species in Europe is thus a major concern. Like the other most damaging Meloidogyne species (e.g. M. incognita, M. arenaria and M. javanica), M. enterolobii reproduces by obligatory mitotic parthenogenesis. Genomic singularities such as a duplicated genome structure and a relatively high proportion of transposable elements have previously been described in the above mentioned mitotic parthenogenetic Meloidogyne. To gain a better understanding of the genomic and evolutionary background we sequenced the genome of M. enterolobii using high coverage short and long read technologies. The information contained in the long reads helped produce a highly contiguous genome assembly of M. enterolobii, thus enabling us to perform high quality annotations of coding and non-coding genes, and transposable elements. The genome assembly and annotation reveals a genome structure similar to the ones described in the other mitotic parthenogenetic Meloidogyne, described as recent hybrids. Most of the genome is present in 3 different copies that show high divergence. Because most of the genes belong to these duplicated regions only few gene losses took place, which suggest a recent polyploidization. The most likely hypothesis to reconcile high divergence between genome copies despite few gene losses and translocations is also a recent hybrid origin. Consistent with this hypothesis, we found an abundance of transposable elements at least as high as the one observed in the mitotic parthenogenetic nematodes M. incognita and M. javanica.