Isolation and characterization of two homolog phages infecting Pseudomonas aeruginosa.

Bacteriophages (phages) are capable of infecting specific bacteria, and therefore can be used as a biological control agent to control bacteria-induced animal, plant, and human diseases. In this study, two homolog phages (named PPAY and PPAT) that infect Pseudomonas aeruginosa PAO1 were isolated and characterized. The results of the phage plaque assay showed that PPAT plaques were transparent dots, while the PPAY plaques were translucent dots with a halo. Transmission electron microscopy results showed that PPAT (65 nm) and PPAY (60 nm) strains are similar in size and have an icosahedral head and a short tail. Therefore, these belong to the short-tailed phage family Podoviridae. One-step growth curves revealed the latent period of 20 min and burst time of 30 min for PPAT and PPAY. The burst size of PPAT (953 PFUs/infected cell) was higher than that of PPAY (457 PFUs/infected cell). Also, the adsorption rate constant of PPAT (5.97 × 10-7 ml/min) was higher than that of PPAY (1.32 × 10-7 ml/min) at 5 min. Whole-genome sequencing of phages was carried out using the Illumina HiSeq platform. The genomes of PPAT and PPAY have 54,888 and 50,154 bp, respectively. Only 17 of the 352 predicted ORFs of PPAT could be matched to homologous genes of known function. Likewise, among the 351 predicted ORFs of PPAY, only 18 ORFs could be matched to genes of established functions. Homology and evolutionary analysis indicated that PPAT and PPAY are closely related to PA11. The presence of tail fiber proteins in PPAY but not in PPAT may have contributed to the halo effect of its plaque spots. In all, PPAT and PPAY, newly discovered P. aeruginosa phages, showed growth inhibitory effects on bacteria and can be used for research and clinical purposes.

Cadmium induces the thymus apoptosis of pigs through ROS-dependent PTEN/PI3K/AKT signaling pathway.

Cadmium (Cd) is a transition metal that is toxic to living organisms in the environment and endangers living organisms. To explore whether Cd induces apoptosis in pig thymus and its possible mechanism, the role Cd induction of the PTEN/PI3K/Akt pathway in apoptosis of thymus cells was studied in pigs. We found that Cd exposure (the feed is treated with Cd) significantly increased Cd accumulation in the thymus of pigs. The TUNEL assay confirmed the typical apoptotic characteristics of thymus in Cd group. Moreover, in the Cd group, the activities of antioxidant indices decreased significantly, while the levels of oxidative stress indexes increased significantly, and the mRNA levels of GSH, CAT, Gpx1, GST, SOD1, and SOD2 decreased obviously. Moreover, the mRNA and protein levels of PTEN/PI3K/AKT and apoptosis-related genes were detected by qPCR and western blotting. The results show that the expressions of PI3K and AKT decreased, while the expression of PTEN increased, indicating that pathway activated. With the PTEN/PI3K/AKT pathway regulating, Bcl-2 expression decreased. Conversely, the mRNA and protein expression of apoptosis-related genes were up-regulated. In conclusion, accumulation of Cd in the pigs caused oxidative damage to immune tissues. In addition, Cd-induced oxidative stress activates the PTEN/PI3K/AKT pathway, inducing apoptosis in the thymus of pigs.

MicroRNA-294 Regulates Apoptosis of the Porcine Cerebellum Caused by Selenium Deficiency via Targeting iNOS.

Deficiency of the essential trace element selenium (Se) can lead to cell apoptosis, and various microRNAs (miRNAs) are known to participate in the regulation of apoptosis by regulating their target genes. In this study, we explore the effect of Se deficiency on porcine cerebellar cell apoptosis and the role of miRNA in this process. After constructing a low-Se pig model, we observed the porcine cerebellum through an electron microscope and observed obvious characteristics of apoptosis. Moreover, it was found that the expression of miR-294 in Se-deficient pigs was significantly lower than that in the control group. Through bioinformatics, qRT-PCR, western blot analysis, and other experimental techniques, we further confirmed that inducible nitric oxide synthase (iNOS) is one of the target genes of miR-294. Our experimental results show that Se deficiency can reduce the expression of miR-294 and increase both the expression of iNOS and the nitric oxide (NO) content (P < 0.01). The expression of heat shock proteins (HSPs, such as HSP70, HSP90, HSP60, HSP40, and HSP27) and mitochondrial pathway-related indicators, such as Bcl2-associated X protein (Bax), cytochrome C (Cyt-C), and cysteinyl aspartate-specific proteinases (caspase 3, caspase 7, and caspase 8), was upregulated (P < 0.05), and the expression of B cell lymphoma-2 (Bcl-2) was downregulated (P < 0.05). In summary, we believe that Se deficiency can lead to abnormal expression of miR-294 and HSPs; moreover, the mitochondrial apoptosis pathway is activated, which significantly enhances apoptosis of cerebellar cells in Se-deficient pigs. These results enrich the biological effects of Se deficiency.

Immunosuppressive effects of arsenic in broiler chicks exposed to Newcastle disease virus.

To assess the effects of prolonged exposure to arsenic (As, as arsenate) on host immune competence overall and resistance to Newcastle disease (ND) viral infection in particular, a study was carried out in broiler chicks. At 7 days of age, chicks were assigned to groups that would undergo varying vaccination, challenge, and/or As exposures; Group 1 was a control; Group 2 was to receive Newcastle disease virus (NDV) only; two groups (Groups 3, 4) were to be given As daily (50 mg/kg, by gavage) from Days 7-35 of the experiment. All groups underwent normal vaccination on Days 5, 23, and 32 against live NDV (B1 type, LaSota strain); two groups (Groups 2, 4) were challenged with field-isolated NDV at Day 24. At Days 14, 21, 28, and 35 of age, subsets of chicks in each group were evaluated. The results showed feed intake and weight gain were lower in As-treated and NDV-challenged chicks. In As-treated chicks, absolute and relative spleen weights were significantly greater, whereas those of the thymus significantly lower, over the entire 35-day period. Effects on bursa weights (absolute, relative) were only significantly reduced through Day 21. Antibody titers against ND were significantly reduced (vs. control) over the whole 35 days in birds that received As alone, but only significantly depressed through the first 21 days in birds that received As + NDV; thereafter, titers were significantly greater (in parallel with effects in birds that received NDV alone). In contrast, antibody responses to T-dependent antigen (Sheep red blood cells [SRBC]) were significantly lower in As only- and As + NDV-treated chicks throughout the study period. Among birds exposed to As (alone or with NDV), in situ phagocytic activity was elevated and cutaneous sensitivity responses decreased during the period from Day 28 to Day 35. NDV alone had spurious effects on phagocytic activity but did cause significant reductions in cutaneous sensitivity responses. It was concluded that arsenic decreased immunity in broiler chicks, thereby making them prone to ND.

The EPS characteristics of sludge in an aerobic granule membrane bioreactor.

The relationship between extracellular polymerase substances (EPS) and sludge characteristic were investigated by extraction and analysis of EPS in different size biomass and membrane fouling in an aerobic granule membrane bioreactor (GMBR). The results indicated that the contents of EPS, polysaccharides and proteins in large granules (particle diameter, d>0.45mm) were significantly lower than that in small granules (d<0.45mm) and flocculent sludge. In addition, the content of EPS in membrane fouling was more than that in suspended biomass. For flocculent sludge, the sedimentation and filtering performance decreased markedly as increasing EPS content. However, for granular sludge, there was no significant correlation between EPS content and sludge characteristics. Furthermore, application of aerobic granule can improve sludge filtering properties and delay the process of membrane fouling, as a result of better morphological structure and lower EPS content.