Progress on phage genomics of Pseudomonas spp.

Pseudomonas spp. are one of the most important ecological flora on the earth, widely distributed in freshwater, soil and other ecological environments. Pseudomonas phages are viruses hosted by Pseudomonas spp., which not only affect the survival and evolution of the hosts, but also play important roles in biomass circulation and energy flow. With the rapid development of genome sequencing technologies, the whole genome sequences of many Pseudomonas phages have been completed. As of July 2020, 247 Pseudomonas phage genomes were deposited in GenBank, accounting for 2.45% of the total 10,069 viral genomes. The genome sizes of Pseudomonas bacteriophages and the genetic contents are different, and the similarity between genomes is low, so the study on Pseudomonas bacteriophage genomes is relatively less. In this review, we summarize the characteristics, genetic diversity, and functional genes of Pseudomonas bacteriophages genomes in order to provide a reference for understanding the antagonistic coevolution of bacteria and phages and the genetic evolution of phages.

[Analyzing the function of different expression genes in the brain of rat exposure to methylmercury using genomics technology].

OBJECTIVE: Analyzing the function of different expression genes in the brain of rat exposure to methylmercury. METHODS: The experimental group of rats were treated with 0.5 mg/kg weight of methylmercury via hypodermic injection. The different expression genes were scanned by using cDNA microarray, and the function genes were analyzed using genomics technology. RESULTS: The gene expression profiles showed that there were 303 genes, in which 170 were upregulated and 133 were downregulated, were differential expressed in the experimental group. Further analysis by bioinformatic technique disclosed that the differentially expressed genes were involved in many biological processes, which included immuno-response and detoxifcation, transfer and expression of genetic information, cell signalling, neurotransduction, cell proliferation and cell differentiation, apoptosis, etc. Cell signaling gene and neurotransduction gene had an very obvious change in the exposure group. CONCLUSION: The signaling pathway was the target by which methylmercury exerted the neurotoxic effects.

Rice from mercury contaminated areas in Guizhou Province induces c-jun expression in rat brain.

OBJECTIVE: Mercury (Hg), as one of the priority pollutants and also a hot topic of frontier environmental research in many countries, has been paid higher attention in the world since the middle of the last century. Guizhou Province (at N24 degrees 30'-29 degrees 13', E103 degrees 1'-109 degrees 30', 1 100 m above the sea level, with subtropical humid climate) in southwest China is an important mercury production center. It has been found that the mercury content in most media of aquatics, soil, atmosphere and in biomass of corns, plants and animals, is higher than the national standard. The present study aims to explore the influence of mercury pollution on the health of local citizens. METHODS: The effect of rice from two mercury polluted experimental plots of Guizhou Province on the expression of c-jun mRNA in rat brain and c-jun protein in cortex, hippocampus and ependyma was observed using reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemical methods. RESULTS: The results showed that the mercury polluted rice induced expression of c-jun mRNA and its protein significantly. Selenium can reduce Hg uptake, an antagonism between selenium and mercury on the expression of c-jun mRNA and c-jun protein. CONCLUSION: c-jun participates in the toxicity process of brain injury by mercury polluted rice, the expression of c-jun mRNA in brain, and c-jun protein in rat cortex and hippocampus can predict neurotoxicity of mercury polluted rice. People should be advised to be cautious in eating any kind of Hg-polluted foods. To reveal the relationship between c-jun induction and apoptosis, further examinations are required.

Neurotransmitter level changes in domestic ducks (Shaoxing duck) growing up in typical mercury contaminated area in China.

The neurotransmitter level changes of ducks exposed 8-month in a mercury-polluted site (Wanshan, China) and a reference site (Shanghai, China) were examined. Chemical analyses showed both higher mercury and selenium concentrations in the organ of Wanshan ducks. An increased content of acetylcholine (ACh) in brain and blood and a decreased activity of acetylcholinesterase (AChE) in blood were observed. Moreover, there was an increasing trend for nitric oxide synthase (NOS) activity and nitric oxide(NO) production in duck brain, but a reduction of NOS activity in duck serum. The possible explanations were due to the interactive effect of selenium accumulation and the sublethal exposure level of mercury in Wanshan area. The present study showed that AChE and NOS were sensitive to mercury contamination of real circumstance, suggesting that these two indexes have the potential to be biomarkers in assessment of health effects by mercury contamination.

Development of a new polyclonal antibody for the determination of polychlorinated biphenyls in indoor air by ic-ELISA.

A new polyclonal antibody (pAb) was prepared and used for the determination of polychlorinated biphenyls (PCBs) in air samples to promote the application of immunoassay technology in the determination of PCBs. Three PCB congeners immunogen mixture was used to stimulate immune responses in rabbits. The specific pAb to PCBs was obtained and used to develop an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA). A standard curve for Aroclor 1248 was prepared using concentrations ranging from 0.1 to 100 µg L(-1). The average IC50 value was 16.21 µg L(-1) and the limit of detection at 10% inhibition (IC90) was 0.069 µg L(-1). The entire procedure was then evaluated using spiked air samples. The recoveries of Aroclor 1248 at various spiking levels in the air samples ranged from 84 to 113%, with relative standard deviations of 3 to 6%. Under optimum conditions, the cross-reactivity profiles of the assays were obtained using three selected congeners, four Aroclor products, and other structurally related compounds of PCBs. The assays were found to be highly specific for PCB congeners and Aroclors 1248 and 1242. The air samples were then analyzed using gas chromatography coupled with high-resolution mass spectrometry to confirm the ic-ELISA results. The attained results demonstrated that the proposed method was an effective and inexpensive technique for the PCBs determination in air samples.

[Transthyretin-binding activity of hexabromocyclododecanes (HBCDs) and its thyroid hormone disrupting effects after developmental exposure].

In vivo and in vitro research approaches were carried out to survey the potential health risk of environmental exposure by hexabromocyclododecanes (HBCDs). Transthyretin-binding assay was designed to test for the potency of HBCDs to compete with thyroxine (T4) for binding to the transport protein. The results showed that the binding of 25I-T4 and T4 was only slightly inhabited even at the highest competitive concentration of HBCDs (75.08%, 80 micromol x L(-1)), indicating the marginally interfere potency of HBCDs in the transportation of T4. Sprague-Dawley rats of 3-days old were exposed to 0.2 mg/kg and 1 mg/kg HBCDs for 21 d to examine the thyroid hormones (THs) disrupting effects of HBCDs after developmental exposure. Compared with the controls, levels of total 3,3',5-triiodothyronine (TT3), free 3,3',5-triiodothyronine (FT3), increased significantly (p < 0.05, p < 0.05) in low- and high-dose exposures, thyroid stimulating hormone (TSH) also increased slightly while the total thyroxine (TT4), free thyroxine (FT4) had a decline about two-fold inversely. Combined both the in vivo and in vitro results, the possible mode of action of HBCDs on THs disruption may through the synergy or substitution effect of T3. The findings support further investigation of the potential THs disrupting effects of HBCDs on public health, especially on children during brain development.

[Construction of promoter probe vector for a cold-adapted bacterium, Acinetobacter sp. DWC6].

In order to build a protein expression system in a cold-adapted bacterium Acinetobacter sp. DWC6, a promoter probe vector was constructed based on the plasmid pBR322. A fragment containing the promoter of the beta-lactamase gene (the ampicillin resistance gene) in pBR322 was eliminated and replaced by a fragment comprizing a kanamycin resistance gene amplified from pJRD215. DNA fragment harboring in the Acinetobacter species specific ori was also inserted into the plasmid pBR322 to construct a promoter probe vector named pBAP1, which could replicate both in E. coli and in Acinetobacter sp. DWC6. The promoter selection library was constructed by randomly inserting genomic DNA fragment of Acinetobacter sp. DWC6 at upstream of reported gene, and target promoters were screened from genomic library on ampicillin selection plates. The function of pBAP1 and isolated promoters were determined by detection of the ampicillin sensitivity and the expression level of beta-lactamase in the host cell.

[Effect of chronic exposure by mercury contaminated rice on neurotransmitter level changes in rat brain].

In order to survey the potential health risk of environmental exposure by mercury, Sprague-Dawley rats were reared by mercury contaminated rice from mercury mining area. The changes of neurotransmitter acetylcholine (ACh) and acetylcholinesterase (AChE) in rat brain were examined at different times. The results show that the mercury-contaminated rice significantly increase the content of ACh in rat brain after exposure for 7 days. ACh maintained at a high level even after exposure for 30 days, but decreased significantly after exposure for 90 days. The changes of AChE represented an inverse trend compared with that of ACh. The coexisting selenium in rice exhibited antagonistic effects on both mercury accumulation and toxicity. The findings suggested that neurotoxic effects of environmental mercury contamination had been significantly represented after chronically dietary exposure. Further studies are needed to examine the relationship between the neurotransmitter level changes and the Alzheimer's Disease (AD).

[Analyzing differentially expressed genes in the brain of rat exposed to mercury chloride using cDNA microarray].

This study is to determine differentially expressed genes in the brain of rat exposed to mercury chloride and investigate the molecular mechanism of mercury neurotoxicity using cDNA microarray. The experimental group of rats were treated with 0.5 mg/kg weight of mercury chloride via hypodermic injection. The differentially expressed genes in rat brains after I h of injection were scanned by the cDNA microarray. The gene expression profiles show that there are 742 genes, in which 562 are upregulated and 180 are downregulated. Further analysis by bioinformatic technique disclosed that the differentially expressed genes were involved in many biological processes, which included immuno-response and detoxifcation, transfer and expression of genetic information, cell signalling, neurotransduction, cell proliferation and cell differentiation, apoptosis, etc. The result of analysis indicated these genes might be related to the neurotoxicity of mercury. The investigation of differentially expressed genes using cDNA microarray provides a new approach to further disclose the neurotoxic mechanism of mercury.

[Induction of free radicals after dietary exposure by mercury contaminated rice and protective effect of coexisting selenium].

Sprague-Dawley rats were reared by environmental mercury contaminated rice to survey the potential health risk of Wanshan mercury mining area. Electron spin resonance (ESR) was introduced to detect the species and the intensities of free radicals, using spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The results showed that the mercury-contaminated rice significantly increased the levels of free radicals and MDA in rat brain at 7 days (p < 0.05). ESR spectrums showed that the principal spin adducts resulted from the trapping of alkyl free radical (alphaH = 22.7 x 10(-4)T +/- 1.6 x 10(-4)T, alphaN = 15.5 x 10(-4)T +/- 0.5 x 10(-4)T), and hydroxyl radical. Levels of free radicals and MDA increased slowly until after 90-day exposure period (83%, 100%). Element correlation analysis showed high correlations of mercury and selenium in the brain of rat fed with Wanshan rice, suggesting that the coexisting selenium in rice exhibited antagonistic effects on both mercury accumulation and toxicity. The slight increases of free radicals in rat brain at 7, 20 and 30-day exposure periods should be related with the scavenger effect of Se.