A Study of the Gut Bacterial Community of Reticulitermes virginicus Exposed to Chitosan Treatment

Chitosan-based insecticide formulations for insect pest control management: A review of current trends and challenges

Future agricultural practices necessitate green alternatives to replace hazardous insecticides while distinguishing between pests and beneficial insects. Chitosan, as a biological macromolecule derived from chitin, is biodegradable and exhibits low toxicity to non-target organisms, making it a sustainable alternative to synthetic pesticides. This review identifies chitosan-derivatives for insecticidal activity and highlights its efficacy including genotoxicity, defense mechanism, and disruption of insect's exoskeleton at different concentrations against several insect pests. Similarly, synergistic effects of chitosan in combination with natural extracts, essential oils, and plant-derived compounds, enhances insecticidal action against various pests was evaluated. The chitosan-based insecticide formulations (CHIF) in the form of emulsions, microcapsules, and nanoparticles showed efficient insecticide action on the targeted pests with less environmental impact. The current challenges associated with the field-trial application were also recognized, by optimizing potent CHIF-formulation parameters, scaling-up process, and regulatory hurdles addressed alongside potential solutions. These findings will provide insight into achieving the EU mission of reducing chemical pesticides by 50 %.

Understanding the Role of Free-Living Bacteria in the Gut of the Lower Termite Coptotermes gestroi Based on Metagenomic DNA Analysis

Termites' digestive systems, particularly in lower termites with the presence of protozoa, are unique ecological niches that shelter a diverse microbiota with a variety of functions for the host and the environment. In 2012, the metagenomic DNA (5.4 Gb) of the prokaryotes that freely live in the gut of the lower termite Coptotermes gestroi were sequenced. A total of 125,431 genes were predicted and analyzed in order to mine lignocellulolytic genes. however, the overall picture of the structure, diversity, and function of the prokaryotic gut microbiota was not investigated. In the present study, these 125,431 genes were taxonomically classified by MEGAN and functionally annotated by the Kyoto Encyclopedia of Genes and Genomes (KEGG) and by the Carbohydrate-Active enZYmes (CAZy) and HMMER databases. As a result, 95,751 bacterial genes were classified into 35 phyla. The structure of the bacteria, typified by a high ratio of Firmicutes to Bacterioidetes, was distinct from the structure of the entirety of the bacteria in the lower or higher termites' guts. The archaea (533 genes) were distributed into 4 phyla, 10 classes, 15 orders, 21 families, 47 genera, and 61 species. Although freely living in the guts, the prokaryotic community was formed, developed, and adapted to exhibit unique interactions in order to perform mutual roles of benefit to their hosts. Methanobacteriales, accounting for 61% of the archaea symbionts, seem to play an important role in methanogenesis. Concomitantly, bacterial methanotrophs in the gut utilize methane and combine with other bacterial groups, including potential lignocellulolytic degraders, acetogens, sulfur bacteria, and nitrogen-recycling bacteria, to efficiently convert wood with little nitrogen into acetates via certain pathway modules specified by prokaryotes that freely live in the gut. This forms an important energy source for the termites. Furthermore, bacteria carry 2223 genes involved in the biosynthesis of 17 antibiotic groups. The gut bacteria also possess genes for the degradation of 18 toxic aromatic compounds, of which four are commercial pesticides against termites commonly used for the preservation of wooden constructions. Eight of the eighteen pathways were the first to be reported from the termite gut. Overall, this study sheds light on the roles of the freely living bacteria and archaea in the C. gestroi gut, providing evidence that the gut microbiome acts as the second host genome, contributing both nutrients and immunity to support the host's existence, growth, and development.

Research Progresses on the Function and Detection Methods of Insect Gut Microbes

The insect gut is home to an extensive array of microbes that play a crucial role in the digestion and absorption of nutrients, as well as in the protection against pathogenic microorganisms. The variety of these gut microbes is impacted by factors such as age, diet, pesticides, antibiotics, sex, and caste. Increasing evidence indicates that disturbances in the gut microbiota can lead to compromised insect health, and that its diversity has a far-reaching impact on the host's health. In recent years, the use of molecular biology techniques to conduct rapid, qualitative, and quantitative research on the host intestinal microbial diversity has become a major focus, thanks to the advancement of metagenomics and bioinformatics technologies. This paper reviews the main functions, influencing factors, and detection methods of insect gut microbes, in order to provide a reference and theoretical basis for better research utilization of gut microbes and management of harmful insects.