Corn stover induces extracellular laccase activity in Didymosphaeria sp. (syn. = Paraconiothyrium sp.) and exhibits increased in vitro ruminal digestibility when treated with this fungal species

Dynamic Gut Microbiota of Apolygus lucorum Across Different Life Stages Reveals Potential Pathogenic Bacteria for Facilitating the Pest Management

Insect's gut microbiota has diverse effects on their fitness, and a comprehensive understanding of gut microbiota functions requires analyzing its diversity. Apolygus lucorum is a highly destructive pest that threatens many economically important crops in China. This study investigated the gut microbiota of A. lucorum across its life cycle using both culture-dependent and culture-independent methods. A total of 87 gut bacterial isolates were identified, belonging to 4 phyla, 27 families, and 45 genera, while Miseq sequencing detected 91 amplicon sequence variants (ASVs) assigned to 5 phyla, 28 families, and 39 genera. Proteobacteria and Firmicutes were the predominant phyla, with Staphylococcus and Serratia as the major genera. There were significant differences in the relative abundance of these genera between the nymph and adult stages. Staphylococcus was significantly more abundant in nymphs than it in adults, while Serratia was significantly more abundant in sexually mature adults than in other developmental stages. Notably, Serratia is a common opportunistic pathogen in many insects. Injecting the gut-dominant isolate Serratia marcescens verified its high pathogenicity. Additionally, immune indicators of the bug at different developmental stages supported the hypothesis that Serratia is a pathogen of A. lucorum. This study provides a foundation for understanding the role of gut bacteria in the life history of A. lucorum and developing new pest control strategies based on microbes.

Microbial gut diversity in four grasshopper species and its correlation with cellulose digestibility

Grasshoppers are common pests, and their intestinal microbes have coevolved with them. These microorganisms have varied community structures, and they participate in the nutritional absorption and metabolism of grasshoppers. Here, we describe the gut microbiota diversity of four species of grasshoppers, Oxya chinensis, Pararcyptera microptera meridionalis, Gastrimargus marmoratus, and Calliptamus abbreviatus. We constructed a 16S rDNA gene library and analyzed the digestibility of cellulose and hemicellulose in grasshoppers using moss black phenol and anthrone colorimetry. The grasshopper with the highest microbial diversity in the gut among the four species was Oxya chinensis, and there were no significant differences in gut microbial diversity between the two geographic collections of Oxya chinensis. The most dominant phyla of the four grasshopper gut microorganisms were Proteobacteria, Bacteroidetes, and Firmicutes, and the most dominant genus was Enterobacter. The gut microbiota features of the four grasshoppers were correlated with their cellulose and hemicellulose digestibility. There was a significant positive correlation with cellulose digestibility for Pantoea. A significant negative correlation was found with cellulose digestibility for Acinetobacter, Enterococcus, Citrobacter, Serratia. A significant negative correlation was found with hemicellulose digestibility for Pantoea. This study contributes to the understanding of the structural composition of different species of grasshoppers gut microbiota, which may be useful for developing grasshopper digestive tracts as bioreactors for cellulose decomposition, improving the decomposition and utilization of agricultural straw, producing clean biomass energy, and processing biologically derived products.

Analysis of Intestinal Microbial Diversity of Four Species of Grasshoppers and Determination of Cellulose Digestibility

Simple Summary

Grasshoppers are typical phytophagous pests, which prefer eating monocotyledons with more cellulose and hemicellulose. Due to its large appetite and high utilization rate, the intestinal contents of grasshoppers have the potential to be developed into a bioreactor, which can be applied to improve straw utilization efficiency in the future. The digestive tract of grasshoppers is a complex ecosystem, inhabited by a large number of microorganisms. The existence of these microorganisms enables grasshoppers to have high decomposition and utilization of plant fibers. However, there are few reports on the microflora structure and diversity of the digestive tract of grasshoppers. In this study, the diversity of symbiotic bacteria in the intestinal tract of four species of grasshoppers, namely Acrida cinerea, Trilophidia annulata, Atractomorpha sinensis and Sphingonotus mongolicus, was studied by using the method of constructing a 16S rRNA gene library and Illumina Miseq sequencing technology. At the same time, the digestibility of cellulose and hemicellulose of the four species of grasshoppers were determined and the relationship between digestibility and intestinal microbial diversity was analyzed. This study provided basic data for the development of the digestible bioreactor of cellulose and hemicellulose, which may provide a new idea for degrading straw.

Abstract

Grasshoppers (Insecta, Orthoptera, Acridoidea) are a large group of agricultural and animal husbandry pests. They have a large food intake with high utilization of plants fibers. However, the composition of the grasshopper gut microbial community, especially the relationship between gut microbial community and cellulose digestibility, remains unclear. In this research, 16S rRNA gene sequences were used to determine the intestinal microbial diversity of Acrida cinerea, Trilophidia annulata, Atractomorpha sinensis and Sphingonotus mongolicus, and Spearman correlation analysis was performed between the intestinal microbes of grasshoppers and the digestibility of cellulose and hemicellulose. The results showed that Proteobacteria was the dominant phylum and Klebsiella was the dominant genus in the guts of the four species of grasshoppers; there was no significant difference in the species composition of the gut microbes of the four species of grasshoppers. Spearman correlation analysis showed that Brevibacterium and Stenotrophomonas were significantly correlated with cellulose digestibility. Brevibacterium, Clavibacter, Microbacterium and Stenotrophomonas were significantly associated with hemicellulose digestibility. Our results confirmed that the gut microbes of grasshoppers were correlated with the digestibility of cellulose and hemicellulose, and indicated that grasshoppers may have the potential to develop into bioreactors, which can be applied to improve straw utilization efficiency in the future.

The genus Paraconiothyrium: species concepts, biological functions, and secondary metabolites

The genus Paraconiothyrium has worldwide distribution with diverse host habitats and exhibits potential utilisation as biocontrol agent, bioreactor and antibiotic producer. In this review, we firstly comprehensively summarise the current taxonomic status of Paraconiothyrium species, including their category names, morphological features, habitats, and multigene phylogenetic relationships. Some Paraconiothyrium species possess vital biological functions and potential applications in medicine, agriculture, industry, and environmental protection. A total of 147 secondary metabolites have been reported so far from Paraconiothyrium, among which 95 are novel. This paper serves to provide an overview of their diverse structures with chemical classification and biological activities. To date, 27 species of Paraconiothyrium have been documented; however, only seven have been investigated for their secondary metabolites or biological functions. Our review is expected to draw more attention to this genus for providing a taxonomic reference, discovering extensive biological functions, and searching in-depth for new bioactive natural products.

Solid State Fermentation as a Tool to Stabilize and Improve Nutritive Value of Fruit and Vegetable Discards: Effect on Nutritional Composition, In Vitro Ruminal Fermentation and Organic Matter Digestibility

Simple Summary

A huge quantity of fruits and vegetables are wasted every year, having a negative impact in both the economy and the environment. Valorizing them as animals’ feeds would contribute to reduce feeding cost and, at the same time, would be in the interest of prevention of resource wastage and better economy of the processing plants. The aim of this study was, on the one side, to transform fruit and vegetable discards using solid state fermentation (SSF) to a stabilized product enriched in protein and, on the other side, to evaluate its suitability for ruminants feeding by determining the in vitro organic matter digestibility, fermentation characteristics and methane production of the control and the fermented product. As a result, it was found that SSF reduced the organic matter and reducing sugar content of the fermented product, while crude protein and fiber fractions were increased. In conclusion, SSF led to a stabilized feed ingredient enriched in protein, but at the expense of digestibility reduction.

Abstract

This research aimed to evaluate in vitro organic matter digestibility, fermentation characteristics and methane production of fruit and vegetable discards processed by solid state fermentation (SSF) by Rhizopus sp. Mixtures were composed of approximately 28% citric fruits, 35% other fruits and 37% vegetables. Fruit and vegetables were processed and fermented to obtain a stabilized product. Nutritional characterization and in vitro ruminal fermentation tests were performed to determine the effect of fungal bioconversion on digestibility, end products and gas production kinetics. Results indicate that SSF reduced organic matter and reducing sugars, while it increased crude protein and neutral detergent fiber, acid detergent fiber and neutral detergent insoluble protein. The in vitro gas production showed that SSF led to a reduction of the organic matter digestibility (p < 0.001), short chain fatty acids (SCFA; p = 0.003) and CH₄ (p = 0.002). SSF reduced the gas production from the insoluble fraction (p = 0.001), without modifying the production rate (p = 0.676) or the lag time (p = 0.574). Regarding SCFA profile, SSF increased acetic (p = 0.020) and decreased propionic (p = 0.004) and butyric (p = 0.006) acids proportions, increasing acetic to propionic (p = 0.008) and acetic plus butyric to propionic (p = 0.011) ratios. SSF succeeded in obtaining a stabilized material enriched in protein, but at the expense of a reduction of protein availability and organic matter digestibility. These changes should be considered before including them in a ruminant’s rations.

Enhanced Biogas Production by Ligninolytic Strain Enterobacter hormaechei KA3 for Anaerobic Digestion of Corn Straw

Lignin-feeding insect gut is a natural ligninolytic microbial bank for the sustainable conversion of crop straw to biogas. However, limited studies have been done on highly efficient microbes. Here, an efficient ligninolytic strain Enterobacter hormaechei KA3 was isolated from the gut microbiomes of lignin-feeding Hypomeces squamosus Fabricius, and its effects on lignin degradation and anaerobic digestion were investigated. No research has been reported. Results showed that strain KA3 had better lignin-degrading ability for corn straw with a higher lignin-degrading rate (32.05%) and lignin peroxidase activity (585.2 U/L). Furthermore, the highest cumulative biogas yield (59.19 L/kg-VS) and methane yield (14.76 L/kg-VS) were obtained for KA3 inoculation, which increased by 20% and 31%, respectively, compared to CK. Higher removal rates of COD, TS, and vs. of 41.6%, 43.11%, and 66.59% were also found. Moreover, microbial community diversity increased as digestion time prolonged in TG, and bacteria were more diverse than archaea. The dominant genus taxon, for methanogens, was Methanosate in TG, while in CK was Methanosarcina. For bacteria, dominant taxa were similar for all groups, which were Solibacillus and Clostridium. Therefore, strain KA3 improved the methane conversion of the substrate. This study could provide a new microbial resource and practical application base for lignin degradation.