Complete genome sequence of C130_2, a novel myovirus infecting pathogenic Escherichia coli and Shigella strains

Molecular Characteristics of Novel Phage vB_ShiP-A7 Infecting Multidrug-Resistant Shigella flexneri and Escherichia coli, and Its Bactericidal Effect in vitro and in vivo

In recent years, increasing evidence has shown that bacteriophages (phages) can inhibit infection caused by multidrug-resistant (MDR) bacteria. Here, we isolated a new phage, named vB_ShiP-A7, using MDR Shigella flexneri as the host. vB_ShiP-A7 is a novel member of Podoviridae, with a latency period of approximately 35 min and a burst size of approximately 100 phage particles/cell. The adsorption rate constant of phage vB_ShiP-A7 to its host S. flexneri was 1.405 × 10^–8 mL/min. The vB_ShiP-A7 genome is a linear double-stranded DNA composed of 40,058 bp with 177 bp terminal repeats, encoding 43 putative open reading frames. Comparative genomic analysis demonstrated that the genome sequence of vB_ShiP-A7 is closely related to 15 different phages, which can infect different strains. Mass spectrometry analysis revealed that 12 known proteins and 6 hypothetical proteins exist in the particles of phage vB_ShiP-A7. Our results confirmed that the genome of vB_ShiP-A7 is free of lysogen-related genes, bacterial virulence genes, and antibiotic resistance genes. vB_ShiP-A7 can significantly disrupt the growth of some MDR clinical strains of S. flexneri and Escherichia coli in liquid culture and biofilms in vitro. In addition, vB_ShiP-A7 can reduce the load of S. flexneri by approximately 3–10 folds in an infection model of mice. Therefore, vB_ShiP-A7 is a stable novel phage with the potential to treat infections caused by MDR strains of S. flexneri and E. coli.

Exploring the Remarkable Diversity of Culturable Escherichia coli Phages in the Danish Wastewater Environment

Phages drive bacterial diversity, profoundly influencing microbial communities, from microbiomes to the drivers of global biogeochemical cycling. Aiming to broaden our understanding of Escherichiacoli (MG1655, K-12) phages, we screened 188 Danish wastewater samples and isolated 136 phages. Ninety-two of these have genomic sequences with less than 95% similarity to known phages, while most map to existing genera several represent novel lineages. The isolated phages are highly diverse, estimated to represent roughly one-third of the true diversity of culturable virulent dsDNA Escherichia phages in Danish wastewater, yet almost half (40%) are not represented in metagenomic databases, emphasising the importance of isolating phages to uncover diversity. Seven viral families, Myoviridae, Siphoviridae, Podoviridae,Drexlerviridae,Chaseviridae,Autographviridae, and Microviridae, are represented in the dataset. Their genomes vary drastically in length from 5.3 kb to 170.8 kb, with a guanine and cytosine (GC) content ranging from 35.3% to 60.0%. Hence, even for a model host bacterium, substantial diversity remains to be uncovered. These results expand and underline the range of coliphage diversity and demonstrate how far we are from fully disclosing phage diversity and ecology.

Isolation and Characterization of a Novel myovirus Infecting Shigella dysenteriae from the Aeration Tank Water

The genome sequence, morphology, and genetic features of a novel phage, named SSE1, is reported here. Phage SSE1 that infects Shigella dysenteriae (China General Microbiological Culture Collection Center number: 1.1869) was isolated from the aeration tank water of a sewage treatment plant. SSE1 showed morphological features associated with those of phages in Myoviridae. The whole genome sequence of phage SSE1 is composed of 169,744 bp with the GC content of 37.51%. The double-stranded DNA of SSE1 contains 270 open reading frameworks (ORFs). Phylogenetically, phage SSE1 showed a stronger homology (whole genome and terminase large subunit protein sequence) to Escherichia phages than other Shigella phages in the NCBI database, but SSE1 did not infect Escherichia stains. This indicates that phage SSE1 should be a novel phage infecting Shigella dysenteriae. Besides, the result of this study provided a new idea for phage therapy. SSE1 may become a candidate for potential therapy against Shigella dysenteriae infection in clinical applications.

Effect of Modified Xijiao Dihuang Decoction () on Intestinal Flora and Th17/Treg in Rats with Radiation Enteritis

OBJECTIVE

To observe the effect of Modified Xijiao Dihuang Decoction (, MXDD) on rats with radiation enteritis, and explore its action mechanism.

METHODS

Thirty female Sprague Dawley rats were divided into the control, model, dexamethasone (DXM), golden bifid (GB) and MXDD groups using random number table, 6 rats in each group. Except the control group, the other rats were developed into radiation enteritis model by exposing to a single ⁶⁰Co-γ ray at a dose of 11 Gy. The rats in the DXM, GB and MXDD groups were treated with DXM (1.425 mg/kg), GB (0.8 g/kg) and MXDD (36.0 g/kg) for 3 days, respectively. Body weight and diarrhea condition of rats were evaluated daily. On day 3, the feces of rats were collected for intestinal flora detection and the small intestinal tissues were also collected. Bacterial species annotation, alpha and beta diversities as well as composition of intestinal flora were detected and compared. The protein and mRNA expressions of interleukin 17 (IL-17), retinoid-related orphan nuclear receptor gamma t (ROR-γt) and forkhead/ winged helix transcription factor p3 (FoxP3) were determined by Western blot and polymerase chain reaction, respectively. The abundance and diversity of intestinal flora as well as the proportion at the phylum and genus levels were assayed by 16S rRNA metagenome sequencing. Correlation between intestinal flora and Th17/Treg was analyzed by heatmap method.

RESULTS

On day 1 to 3 after radiation, compared with the control group, the body weight in model group was decreased (P<0.05 or P<0.01). Compared with the model group, MXDD could alleviate weight loss and diarrhea caused by irradiation. At the phylum level, MXDD cause a significant increase in Firmicutes, and a decrease in Proteobacteria (P<0.05 or P<0.01). At the genus level, MXDD reduced the proportion of Escherichia Shigella (P<0.01). In addition, IL-17 and FoxP3 mRNA and protein expression levels were down-regulated and ROR-γt was up-regulated by MXDD treatment (P<0.05). Besides, Firmicutes and Lactobacillus were positively correlated with FoxP3 (r=0.73, 0.79, respectively; P<0.01), negatively correlated with IL-17 (r=0.66, 0.64, respectively; P<0.01 or P<0.05) and ROR-γt (r0.73, 0.81, respectively; P<0.01). Proteobacteria and Escherichia Shigella both had positive correlation with IL-17 (r 0.77, 0.57, respectively; P<0.01 or P<0.05 ) and ROR-γt (r=0.94, 0.79, respectively; P<0.01) and negative correlation with FoxP3 (r0.74, 0.65; P<0.01).

CONCLUSION

MXDD could improve the survival status of irradiated rats by regulating the richness, diversity and composition of intestinal flora, and restoring the balance of Th17/Treg.