TL;DR
The findings address an existing knowledge gap and highlight the potential dualistic nature of S. sepilia SMBL8, both as a beneficial industrial bacterium and an opportunistic pathogen, facilitated by metabolic versatility and genomic plasticity.
Flacherie is a major bacterial disease compromising silkworm health and cocoon productivity; however, the diversity and genomic features of larva-associated pathogens remain poorly characterized. In the present study, we isolated and characterized a Gram-negative bacterium, designated as Pseudomonas boreofloridensis strain RAC1, from the hemolymph of silkworm larvae with flacherie symptoms. The isolate exhibited clear swimming motility, indicating an active flagellar system. Biochemical profiling using the VITEK-2 platform revealed broad metabolic capabilities, including utilization of multiple organic acids and amino-acids, related enzymatic activities, highlighting its adaptability under nutrient-variable host conditions. Chemotaxonomic analysis using fatty acid methyl ester (FAME) profiling further supported its identity within the genus Pseudomonas. Whole-genome sequencing showed a 4.49 Mb GC-rich genome encoding diverse functional pathways related to central metabolism, aromatic compound degradation, and carbohydrate-active enzymes, suggesting strong ecological flexibility. Importantly, genomic screening identified virulence-associated gene and multiple antimicrobial resistance determinants, dominated by efflux pumps and outer membrane permeability factors. In addition, strain RAC1 contained several mobile genetic elements and three prophage regions, reflecting a highly plastic genome. Pangenome analysis across related Pseudomonas strains indicated an open pangenome, driven largely by accessory and cloud genes. Overall, P. boreofloridensis RAC1 represents a multidrug-resistant and genomically dynamic strain encoding virulence-associated genes and resistance genes. These genomic features suggest adaptive potential in host-associated environments and require further experimental investigation to evaluate its role in silkworm larval disease.
Pseudomonas sp. MUP55, isolated from rainfall water in Western Australia, was characterized by polyphasic taxonomy and functional assays. Whole-genome and 16S rRNA phylogeny placed Pseudomonas sp. MUP55 in the Pseudomonas fluorescens species group. Massetolide A/D was identified as the leading candidate bioactive compound(s), consistent with its biosynthetic gene cluster, GNPS library matching, and loss of activity in regulatory mutants. The strain showed broad-spectrum antimicrobial activity against bacterial (Escherichia coli and Xanthomonas campestris) and fungal (Fusarium oxysporum and Rhizoctonia solani) plant pathogens. GacA regulates Massetolide production: a P58L mutation abolished synthesis and reduced biocontrol efficacy. Metabolomic and transcriptomic analysis of a ΔpvfC mutant revealed that the pvf cluster regulates specialized metabolism while also contributing to secreted growth-inhibitory activity. The pvf cluster differentially regulates dual siderophore systems and uncouples the co-regulated small RNAs rsmY and rsmZ in the Gac/Rsm cascade. Deletion of pvfC partially reduced the growth-inhibitory activity of Pseudomonas sp. MUP55 supernatants against bacterial pathogens, indicating that pvfC also influences secreted antimicrobial activity beyond its global regulatory role. These findings establish Pseudomonas sp. MUP55 as a taxonomically novel, mechanistically characterized biocontrol agent with potential for sustainable agriculture.
An integrated omics study provides foundational insights into the endophytic potential and genomic distinctiveness of AwOcstreb1, isolated from halophytic rice, and opens new avenues for exploring A. welwitschiae for sustainable agriculture and fungal biology.
Genomic and phenotypic results supported the potentials of BGI-N8 and BGI-N9 as candidate probiotic strains with distinct complementary strengths in glycolipid regulation, providing a theoretical basis for their synergistic application.
Genome analysis revealed a complete C5–C20 isoprenoid biosynthesis pathway and multiple biosynthetic gene clusters, including terpene-associated clusters with low similarity to previously characterized pathways, indicating the presence of biosynthetic potential distinct from previously characterized pathways.
The spoilage bacterium Aeromonas veronii poses increasing risks to the safety of edible bivalves, yet the regulatory mechanisms of its key spoilage factors remain largely unknown. In this study, a foodborne pathogen A. veronii GL2 was isolated from edible Hyriopsis cumingii and its genomic sequencing was conducted, in which the mRNA level of metalloprotease-encoded gene htpX was significantly upregulated under thermal processing. A htpX-defected mutant (ΔhtpX) was then constructed to investigate its role in virulence and spoilage potentials. Although htpX deficiency did not affect growth or proteolytic activity, it remarkably impaired biofilm formation, hemolytic activity and stress tolerance. In the hemolymph model of H. cumingii, ΔhtpX exhibited lower survival rates in supernatant and decreased cytotoxicity toward hemocytes. Further detection of virulence demonstrated that ΔhtpX exhibited an 18.5-fold higher LD50 value than GL2, and reduced bacterial loads in edible portions (foot, adductor muscle). Besides, the spoilage potentials of ΔhtpX were markedly attenuated, in which decreased bacterial proliferation further suppressed the levels of TCA-soluble peptide, TVB-N and pH. In conclusion, these results reveal htpX as a novel determinant linking protein quality control to spoilage and virulence in A. veronii, and provide a novel target for developing control strategies against A. veronii contamination in aquatic products.
