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Natural products (NPs) are a consistent source of antimicrobial metabolites and pesticide leads and are largely produced by Pseudomonads-like soil-dwelling microorganisms. Herein we report the isolation of Pseudomonas mosselii strain 923 from rice rhizosphere soils of paddy fields; this strain specifically inhibited the growth of rice bacterial pathogens Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc) and the fungal pathogen Magnaporthe oryzae. The antimicrobial compound produced by P. mosselii 923 was purified and identified as pseudoiodinine using HRMS, NMR and single-crystal X-ray diffraction. Genome-wide random mutagenesis, transcriptome analysis and biochemical assays were used to define the pseudoiodinine biosynthetic cluster as a seven-gene operon, which was designated psdABCDEFG. Pseudoiodinine biosynthesis is proposed to initiate from GTP, which is converted into 2,5-diamino-6-(5-phospho-d-ribosylamino) pyrimidin-4(3H)-one by PsdD and converted to 5-amino-6-(5-phospho-d-ribitylamino) uracil by PsdG, followed by cyclization with glycine by PsdC/PsdE and an unknown ring contraction and two methylation reactions by PsdA and PsdF. Transposon mutagenesis indicated that pseudoiodinine biosynthesis is mediated by the global regulator GacA. Further regulation is mediated by two noncoding small RNAs, rsmY and rsmZ, that positively regulate pseudoiodinine transcription, and the carbon storage regulators CsrA2 and CsrA3, which negatively regulate expression. A 22.4-fold increase in pseudoiodinine production was achieved by optimizing the media used for fermentation, overexpressing the biosynthetic operon, and removing the CsrA binding sites. Use of P. mosselii strain 923 and purified pseudoiodinine in planta revealed that both of them inhibited X. oryzae without affecting the rice host, suggesting that pseudoiodinine can be used to control plant diseases.

Background The study aimed to investigate the differences of different Akkermansia muciniphila (A.muciniphila) genotypes on metabolic protective effects in mice with high-fat diet and explore possible mechanisms. Methods Male C57BL/6 mice were randomly divided into 6 groups, including high-fat diet (HFD)+ A.muciniphila I/II/PBS group, normal chow diet (NCD)+A.muciniphila I/ II /PBS group, respectively. Dietary intervention and A.muciniphila gavage were performed simultaneously. Blood glucose and lipid metabolism, brown adipose morphology and activities, and intestinal barrier function were examined after the mice were sacrificed. Results A.muciniphila gavage improved the impaired glucose tolerance, hyperlipidemia and liver steatosis in HFD mice, and that A.muciniphila II was not as effective as A.muciniphila I. This phenomenon might be because A.muciniphila I intervention significantly inhibited brown adipose tissue whitening and inflammation induced by HFD, by repairing the intestinal barrier and relieving endotoxemia. A.muciniphila II did not display the same results as A.muciniphila I in HFD mice, but had stronger effects in the NCD mice. Conclusions This study mainly reveals the distinct functions of different A.muciniphila genotypes on diet-induced obesity, suggesting that different A.muciniphila genotypes may play inequitable roles in pathological conditions through distinct action pathways.