Endophytes represent a ubiquitous and magical world in plants. Almost all plant species studied by different researchers have been found to harbor one or more endophytes, which protect host plants from pathogen invasion and from adverse environmental conditions. They produce various metabolites that can directly inhibit the growth of pathogens and even promote the growth and development of the host plants. In this review, we focus on the biological control of plant diseases, aiming to elucidate the contribution and key roles of endophytes and their metabolites in this field with the latest research information. Metabolites synthesized by endophytes are part of plant disease management, and the application of endophyte metabolites to induce plant resistance is very promising. Furthermore, multi-omics should be more fully utilized in plant–microbe research, especially in mining novel bioactive metabolites. We believe that the utilization of endophytes and their metabolites for plant disease management is a meaningful and promising research direction that can lead to new breakthroughs in the development of more effective and ecosystem-friendly insecticides and fungicides in modern agriculture.

Background: Probiotics are being considered as valuable microorganisms related to human health. Hu sheep is referred as one of the important sheep breeds in China. Goat milk produced by Hu sheep is characterized with high nutritional value and hypoallergenic in nature. Particularly, this milk contains plenty of milk prebiotic and probiotic bacteria. This study was aimed to scrutinize more bacterial strains from Hu sheep milk with potential probiotic activity. Results: Based on 16S rRNA sequence analysis, pool of forty bacterial strains were identified and evaluated their antimicrobial activities against Staphylococcus aureus, enterohemorrhagic Escherichia coli (EHEC), Salmonella typhimurium, Listeria monocytogenes enterotoxigenic E. coli (ETEC) and Aeromonas caviae. Four out of these isolated strains demonstrated their efficient bacteriostatic ability and potential healthy properties. We also examined the safety aspects of these bacterial candidates including three Lactococcus lactis strains (named as HSM-1, HSM-10, and HSM-18) and one Leuconostoc lactis strain (HSM-14), and were further evaluated via in vitro tests, including antimicrobial activity, cell surface characteristics (hydrophobicity, co-aggregation, and self-aggregation), heat treatment, antibiotic susceptibility, simulated transport tolerance in the gastrointestinal tract, and acid/bile tolerance. The obtained results revealed that HSM-1, HSM-10, HSM-14, and HSM-18 showed high survival rate at different conditions for example low pH, presence of bovine bile and demonstrated high hydrophobicity. Moreover, HSM-14 had an advantage over other strains in terms of gastrointestinal tract tolerance, antimicrobial activities against pathogens, and these results were significantly better than other bacterial candidates. Conclusion: Hu sheep milk as a source of exploration of potential lactic acid bacteria (LAB) probiotics open the new horizon of probiotics usage from unconventional milk sources. The selected LAB strains are excellent probiotic candidates which can be used for animal husbandry in the future. Rationale of the study was to utilize Hu sheep milk as a source of potential probiotic LABs. The study has contributed to the establishment of a complete bacterial resource pool by exploring the Hu sheep milk microflora.

Lactic acid bacteria (LAB) are vital probiotics in the food processing industry, which are widely spread in food additives and products, such as meat, milk, and vegetables. Pediococcus pentosaceus (P. pentosaceus), as a kind of LAB, has numerous probiotic effects, mainly including antioxidant, cholesterol-lowering, and immune effects. Recently, the applications in the probiotic- fermentation products have attracted progressively more attentions. However, it is necessary to screen P. pentosaceus with abundant functions from diverse sources due to the limitation about the source and species of P. pentosaceus. This review summarized the screening methods of P. pentosaceus and the exploration methods of probiotic functions in combination with the case study. The screening methods included primary screening and rescreening including gastric acidity resistance, bile resistance, adhesion, antibacterial effects, etc. The application and development prospects of P. pentosaceus were described in detail, and the shortcomings in the practical application of P. pentosaceus were evaluated to make better application of P. pentosaceus in the future.

Precise and fluent genetic manipulation is still limited to only a few prokaryotes. Ideally the highly advanced technologies available in Escherichia coli could be broadly applied. Our efforts to apply lambda Red technology, widely termed ‘recombineering’, in Photorhabdus and Xenorhabdus yielded only limited success. Consequently we explored the properties of an endogenous Photorhabdus luminescens lambda Red-like operon, Plu2934/Plu2935/Plu2936. Bioinformatic and functional tests indicate that Plu2936 is a 5’-3’ exonuclease equivalent to Redα and Plu2935 is a single strand annealing protein equivalent to Redβ. Plu2934 dramatically enhanced recombineering efficiency. Results from bioinformatic analysis and recombineering assays suggest that Plu2934 may be functionally equivalent to Redγ, which inhibits the major endogenous E. coli nuclease, RecBCD. The recombineering utility of Plu2934/Plu2935/Plu2936 was demonstrated by engineering Photorhabdus and Xenorhabdus genomes, including the activation of the 49-kb non-ribosomal peptide synthase (NRPS) gene cluster plu2670 by insertion of a tetracycline inducible promoter. After tetracycline induction, novel secondary metabolites were identified. Our work unlocks the potential for bioprospecting and functional genomics in the Photorhabdus, Xenorhabdus and related genomes.

Background: In modern animal husbandry, breeders pay increasing attention to improving sow nutrition during pregnancy and lactation to favor the health of neonates. Sow milk is a main food source for piglets during their first three weeks of life, which is not only a rich repository of essential nutrients and a broad range of bioactive compounds, but also an indispensable source of commensal bacteria. Maternal milk microorganisms are important sources of commensal bacteria for the neonatal gut. Bacteria from maternal milk may confer a health benefit on the host.Methods: Sow milk bacteria were isolated using culturomics followed by identification using 16S rRNA gene sequencing. To screen isolates for potential probiotic activity, the functional evaluation was conducted to assess their antagonistic activity against pathogensin vitroand evaluate their resistance against oxidative stress in damagedDrosophilainduced by paraquat. In a piglet feeding trial, a total of 54 newborn suckling piglets were chosen from nine sows and randomly assigned to three treatments with different concentrations of a candidate strain. Multiple approaches were carried out to verify its antioxidant function including western blotting, enzyme activity analysis, metabolomics and 16S rRNA gene amplicon sequencing.Results: The 1240 isolates were screened out from the sow milk microbiota and grouped into 271 bacterial taxa based on a nonredundant set of 16S rRNA gene sequencing. Among 80Pediococcusisolates, a newPediococcus pentosaceusstrain (SMM914) showed the best performance in inhibition ability against swine pathogens and in aDrosophilamodel challenged by paraquat. Pretreatment of piglets with SMM914 induced the Nrf2-Keap1 antioxidant signaling pathway and greatly affected the pathways of amino acid metabolism and lipid metabolism in plasma. In the colon, the relative abundance ofLactobacilluswas significantly increased in the high dose SMM914 group compared with the control group.Conclusion: P. pentosaceusSMM914 is a promising probiotic conferring antioxidant capacity by activating the Nrf2-Keap1 antioxidant signaling pathway in piglets. Our study provided useful resources for better understanding the relationships between the maternal microbiota and offspring.