With the emergence of multidrug-resistant and extensively drug-resistant bacterial pathogens, phage therapy and other alternative or additional therapeutic modalities are receiving resurgent attention. One of the major obstacles in developing effective phage therapies is the evolution of phage resistance in the bacterial host. When Pseudomonas aeruginosa was infected with a phage that uses O-antigen as receptor, phage resistances typically achieved through changing or loss of O-antigen structure. In this study, we showed that dsRNA phage phiYY uses core lipopolysaccharide as receptor and therefore efficiently kills the O-antigen deletion mutants. Furthermore, by phage training, we obtained PaoP5-m1, a derivative of dsDNA phage PaoP5, which is able to infect mutants with truncated O-antigen. We then generated a cocktail by mixing phiYY and PaoP5-m1 with additional three wide host range P. aeruginosa phages. The phage cocktail was effective against a diverse selection of clinical isolates of P. aeruginosa, and in the short-term constrained the appearance of the phage-resistant mutants that had beleaguered the effectiveness of single phage. Resistance to the 5phage cocktail emerges after several days, and requires mutations in both wzy and migA Thus, this study provides an alternative strategy for designing phage cocktail and phage therapy.

Capsaicin (CAP) reduces body weight mainly through activation of transient receptor potential vanilloid 1 (TRPV1) cation channel. However, recent evidence indicates that the gut microbiota influences many physiological processes in host and might provoke obesity. This study determined whether the anti-obesity effect of CAP is related to the changes in gut microbiota. C57BL/6 mice were fed either with high-fat diet (HFD) or HFD with CAP (HFD-CAP) for 9 weeks. We observed a significantly reduced weight gain and improved glucose tolerance in HFD-CAP-fed mice compared with HFD-fed mice. 16S rRNA gene sequencing results showed a decrease of phylum Proteobacteria in HFD-CAP-fed mice. In addition, HFD-CAP-fed mice showed a higher abundance of Akkermansia muciniphila, a mucin-degrading bacterium with beneficial effects on host metabolism. Further studies found that CAP directly up-regulates the expression of Mucin 2 gene Muc2 and antimicrobial protein gene Reg3g in the intestine. These data suggest that the anti-obesity effect of CAP is associated with a modest modulation of the gut microbiota.

The interactions between Bacteriophage (phage) and host bacteria are widespread in nature and influences of phage replication on the host cells are complex and extensive. Here, we investigate genome-wide interactions of Pseudomonas aeruginosa (P. aeruginosa) and its temperate phage PaP3 at five time points during phage infection. Compared to the uninfected host, 38% (2160/5633) genes of phage-infected host were identified as differentially expressed genes (DEGs). Functional analysis of the repressed DEGs revealed infection-stage-dependent pathway communications. Based on gene co-expression analysis, most PaP3 middle genes were predicted to have negative impact on host transcriptional regulators. Sub-network enrichment analysis revealed that adjacent genes of PaP3 interacted with the same host genes and might possess similar functions. Finally, our results suggested that during the whole infection stage, the early genes of PaP3 had stronger regulatory role in host gene expression than middle and late genes, while the host genes involved amino acid metabolism were the most “vulnerable” targets of these phage genes. This work provides the basis for understanding survival mechanisms of parasites and host, and seeking phage gene products that could potentially be used in anti-bacterial infection.

Cadmium (Cd) is widely used in daily life and was recently recognized as a possible source of human toxicity due to its ability to accumulate in organs. Previous studies have shown that Cd exposure may cause testicular toxicity through oxidative stress and an inflammatory effect. Melatonin has been demonstrated to be an effective anti-oxidant and has an anti-inflammatory effect. The aim of the present study was to investigate the toxicological effects of Cd on reproduction in male mice and the potential protective action of melatonin against these adverse effects. Adult male mice were injected intraperitoneally with Cd at a dose of 2 mg/kg body weight per day for seven consecutive days with or without melatonin pretreatment. Sex organ weight, sperm parameters including sperm quality, apoptosis, acrosome integrity, mitochondrial membrane potential, testicular morphology, serum sex hormone, inflammatory status, and oxidative stress were evaluated. The results showed that significant adverse effects were observed in the male reproductive system after Cd exposure, including alterations in sperm parameters, increased DNA damage, and sex hormone disturbance. Acute Cd exposure also significantly increased malondialdehyde (MDA) contents, decreased glutathione (GSH) and superoxide dismutase (SOD) activities, and upregulated levels of the pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-α), and interleukin-1beta (IL-1β), in the testis. In contrast, melatonin pretreatment significantly alleviated these toxic effects, and its mechanism may involve inhibiting MDA level, restoring GSH and SOD activities, and reducing the upregulation of TNF-α and IL-1β. Our data suggest that oxidative stress and inflammation are involved in Cd-induced toxicity in the male reproductive system and that co-administration of melatonin exerts a protective effect against Cd-induced male reproductive toxicity.

Toxin-antitoxin (TA) systems are small genetic modules that are widely distributed in the genomes of bacteria and archaea and have been proposed to fulfill numerous functions. Here, we describe the identification and characterization of a type II TA system, comprising the hicAB locus in the human opportunistic pathogen Pseudomonas aeruginosa. The hicAB locus consists of genes hicA and hicB encoding a toxin and its cognate antitoxin, respectively. BLAST analysis revealed that hicAB is prevalent in approximately 36% of P. aeruginosa strains and locates in the same genomic region. RT-PCR demonstrated that hicAB forms a bicistronic operon that is cotranscribed under normal growth conditions. Overproduction of HicA inhibited the growth of Escherichia coli, and this effect could be counteracted by co-expression of HicB. The Escherichia coli kill/rescue assay showed that the effect of HicA is bacteriostatic, rather than bactericidal. Deletion of hicAB had no effect on the biofilm formation and virulence of P. aeruginosa in a mice infection model. Collectively, this study presents the first characterization of the HicAB system in the opportunistic pathogen P. aeruginosa.

Bacteriophages (phages) are widely distributed in the biosphere and play a key role in modulating microbial ecology in the soil, ocean, and humans. Although the role of DNA bacteriophages is well described, the biology of RNA bacteriophages is poorly understood. More than 1900 phage genomes are currently deposited in NCBI, but only 6 dsRNA bacteriophages and 12 ssRNA bacteriophages genome sequences are reported. The 6 dsRNA bacteriophages were isolated from legume samples or lakes with Pseudomonas syringae as the host. Here, we report the first Pseudomonas aeruginosa phage phiYY with a three-segmented dsRNA genome. phiYY was isolated from hospital sewage in China with the clinical P. aeruginosa strain, PAO38, as a host. Moreover, the dsRNA phage phiYY has a broad host range, which infects 99 out of 233 clinical P. aeruginosa strains isolated from four provinces in China. This work presented a detailed characterization of the dsRNA bacteriophage infecting P. aeruginosa.

The basic biology of bacteriophage–host interactions has attracted increasing attention due to a renewed interest in the therapeutic potential of bacteriophages. In addition, knowledge of the host pathways inhibited by phage may provide clues to novel drug targets. However, the effect of phage on bacterial gene expression and metabolism is still poorly understood. In this study, we tracked phage–host interactions by combining transcriptomic and metabolomic analyses in Pseudomonas aeruginosa infected with a lytic bacteriophage, PaP1. Compared with the uninfected host, 7.1% (399/5655) of the genes of the phage-infected host were differentially expressed genes (DEGs); of those, 354 DEGs were downregulated at the late infection phase. Many of the downregulated DEGs were found in amino acid and energy metabolism pathways. Using metabolomics approach, we then analyzed the changes in metabolite levels in the PaP1-infected host compared to un-infected controls. Thymidine was significantly increased in the host after PaP1 infection, results that were further supported by increased expression of a PaP1-encoded thymidylate synthase gene. Furthermore, the intracellular betaine concentration was drastically reduced, whereas choline increased, presumably due to downregulation of the choline–glycine betaine pathway. Interestingly, the choline–glycine betaine pathway is a potential antimicrobial target; previous studies have shown that betB inhibition results in the depletion of betaine and the accumulation of betaine aldehyde, the combination of which is toxic to P. aeruginosa. These results present a detailed description of an example of phage-directed metabolism in P. aeruginosa. Both phage-encoded auxiliary metabolic genes and phage-directed host gene expression may contribute to the metabolic changes observed in the host.

As a potential alternative to antibiotics, phages can be used to treat multi-drug resistant bacteria. As such, the biological characteristics of phages should be investigated to utilize them as effective antimicrobial agents. In this study, phage PaoP5, a lytic virus that infects Pseudomonas aeruginosa PAO1, was isolated and genomically characterized. PaoP5 comprises an icosahedral head with an apex diameter of 69 nm and a contractile tail with a length of 120 nm. The PaoP5 genome is a linear dsDNA molecule containing 93,464 base pairs (bp) with 49.51% G + C content of 11 tRNA genes and a 1,200 bp terminal redundancy. A total of 176 protein-coding genes were predicted in the PaoP5 genome. Nine PaoP5 structural proteins were identified. Three hypothetical proteins were determined as structural. Comparative genomic analyses revealed that seven new Pseudomonas phages, namely, PaoP5, K8, C11, vB_PaeM_C2-10_Ab02, vB_PaeM_C2-10_Ab08, vB_PaeM_C2-10_Ab10, and vB_PaeM_C2-10_Ab15, were similar to PAK_P1-like viruses. Phylogenetic and pan-genome analyses suggested that the new phages should be assigned to PAK_P1-like viruses, which possess approximately 100 core genes and 150 accessory genes. This work presents a detailed and comparative analysis of PaoP5 to enhance our understanding of phage biology.