The gut microbiota has been linked to cardiovascular diseases. However, the composition and functional capacity of the gut microbiome in relation to cardiovascular diseases have not been systematically examined. Here, we perform a metagenome-wide association study on stools from 218 individuals with atherosclerotic cardiovascular disease (ACVD) and 187 healthy controls. The ACVD gut microbiome deviates from the healthy status by increased abundance of Enterobacteriaceae and Streptococcus spp. and, functionally, in the potential for metabolism or transport of several molecules important for cardiovascular health. Although drug treatment represents a confounding factor, ACVD status, and not current drug use, is the major distinguishing feature in this cohort. We identify common themes by comparison with gut microbiome data associated with other cardiometabolic diseases (obesity and type 2 diabetes), with liver cirrhosis, and rheumatoid arthritis. Our data represent a comprehensive resource for further investigations on the role of the gut microbiome in promoting or preventing ACVD as well as other related diseases.

EfeB/YcdB is a member of the dye-decolorizing peroxidase (DyP) protein family. A recent study has shown that this protein can extract iron from heme without breaking the tetrapyrrole ring. We report the crystal structure of EfeB from Escherichia coli O157 bound to heme at 1.95 Å resolution. The EfeB monomer contains two domains. The heme molecule is located in a large hydrophobic pocket in the C-terminal domain. A long loop connecting the two domains extensively interacts with the heme, which is a distinctive structural feature of EfeB homologues. A large tunnel formed by this loop and the ␤-sheet of C-terminal domain provides a potential cofactor/substrate binding site. Biochemical data show that the production of protoporphyrin IX (PPIX) is closely related to the peroxidation activity. The mutant D235N keeps nearly the same activity of guaiacol peroxidase as the wild-type protein, whereas the corresponding mutation in the classic DyP protein family completely abolished the peroxidation activity. These results suggest that EfeB is a unique member of the DyP protein family. In addition, dramatically enhanced fluorescence excitation and emission of EfeB-PPIX was observed, implying this protein may be used as a red color fluorescence marker.

Myxobacterial predation on bacteria has been investigated for several decades. However, their predation on fungi has received less attention. Here, we show that a novel outer membrane β-1,6-glucanase GluM from Corallococcus sp. strain EGB is essential for initial sensing and efficient decomposition of fungi during predation. GluM belongs to an unstudied family of outer membrane β-barrel proteins with potent specific activity up to 24,000 U/mg, whose homologs extensively exist in myxobacteria. GluM was able to digest fungal cell walls efficiently and restrict Magnaporthe oryzae infection of rice plants. Genetic complementation with gluM restored the fungal predation ability of Myxococcus xanthus CL1001, which was abolished by the disruption of gluM homolog oar. The inability to prey on fungi with cell walls that lack β-1,6-glucans indicates that β-1,6-glucans are targeted by GluM. Our results demonstrate that GluM confers myxobacteria with the ability to feed on fungi, and provide new insights for understanding predator-prey interactions. Considering the attack mode of GluM, we suggest that β-1,6-glucan is a promising target for the development of novel broad-spectrum antifungal agents.

Mulberry fruits with high concentrations of anthocyanins are favored by consumers because of their good taste, bright color, and high nutritional value. However, neither the regulatory mechanism controlling flavonoid biosynthesis in mulberry nor the molecular basis of different mulberry fruit colors is fully understood. Here, we report that a flavonoid homeostasis network comprising activation and feedback regulation mechanisms determines mulberry fruit color. In vitro and in vivo assays showed that MYBA-bHLH3-TTG1 regulates the biosynthesis of anthocyanins, while TT2L1 and TT2L2 work with bHLH3 or GL3 and form a MYB-bHLH-WD40 (MBW) complex with TTG1 to regulate proanthocyanidin (PA) synthesis. Functional and expression analyses showed that bHLH3 is a key regulator of the regulatory network controlling mulberry fruit coloration and that MYB4 is activated by MBW complexes and participates in negative feedback control of the regulatory network to balance the accumulation of anthocyanins and proanthocyanidins. Our research demonstrates that the interaction between bHLH3 and MYB4 in the homeostasis regulatory network ensures that the fruits accumulate desirable flavonoids and that this network is stable in pigmentrich mulberry fruits. However, the abnormal expression of bHLH3 disrupts the balance of the network and redirects flavonoid metabolic flux in pale-colored fruits, resulting in differences in the levels and proportions of anthocyanins, flavones, and flavonols among differently colored mulberry fruits (red, yellow, and white). The results of our study reveal the molecular basis of the diversity of mulberry fruit colors.