Oxalate production at different initial Pb²+ concentrations and the influence of oxalate during solid-state fermentation of straw with Phanerochaete chrysosporium

The production of oxalate at different initial Pb²⁺ concentrations during solid-state fermentation of straw with Phanerochaete chrysosporium was investigated. It was found that the maximal peak value of oxalate concentration (22.84 mM) was detected at the initial Pb²⁺ concentration of 200 mg kg⁻¹ dry straw, while the minimum (15.89 mM) at the concentration of 600 mg Pb²⁺ kg⁻¹ dry straw, and at moderate concentration of Pb²⁺ the capability of oxalic acid secretion was enhanced. In addition, it was also found that more oxalic acid accumulation went together with better Pb²⁺ passivation effect and higher manganese peroxidase (MnP) activity. The present findings will improve the understandings of the interactions of heavy metals with white-rot fungi and the role of oxalate in lignin degradation system, which could provide useful references for more efficient treatment of Pb-contaminated lignocellulosic waste.     

Analysis of pSC138, the multidrug resistance plasmid of Salmonella enterica serotype Choleraesuis SC-B67

Salmonella enterica serotype Choleraesuis (S. Choleraesuis) usually causes systemic infections in man and needs antimicrobial treatment. Multidrug resistance (MDR) in S. Choleraesuis is thus a great concern in the treatment of systemic non-typhoid salmonellosis. A large plasmid, pSC138, was identified in 2002 from a S. Choleraesuis strain SC-B67 that was resistant to all antimicrobial agents commonly used to treat salmonellosis, including ciprofloxacin and ceftriaxone. Complete DNA sequence of the plasmid had been determined previously (Chiu et al., 2005). In the present study, the sequence of pSC138 was reannotated in detail and compared with several newly sequenced plasmids. Some transposable elements and drug resistance genes were further delineated. Plasmid pSC138 was 138,742 bp in length and consisted of 177 open reading frames (ORFs). While 134 of the ORFs displayed significant identity levels to other plasmid and prokaryotic sequences, the remaining 43 ORFs have not been previously reported. Mobile elements, including two integrons, seven insertion sequences and eight transposons, and a truncated prophage together encompass at least 66,781 bp (48.1%) of the plasmid genome. The sequence of pSC138 consists of three major regions: a large composite transposable region Tn6088 with a Tn21-like backbone inserted by a variety of integrons or transposable elements; a transfer/maintenance region that contains a conserved ISEcp1-mediated transposon-like element Tn6092, carrying an AmpC gene, bla(CMY-2), that confers the ceftriaxone resistance; and a Rep_3 type of replication region. Another seven bacteremic strains of S. Choleraesuis that expressed the same MDR phenotype were identified during 2003-2008. The same Rep_3 type replicase and the bla(CMY-2)-containing, ISEcp1-mediated transposon-like element were found in the MDR isolates, suggesting a successful preservation and dissemination of the MDR plasmid. Comparison of pSC138 with other recently published plasmids revealed a high identity level between partial sequences of pSC138 and plasmids of the same or different incompatibility groups. The large MDR region found in pSC138 may provide a niche for the future evolution of the plasmid by acquisition of relevant resistance genes through the panoply of mobile elements and illegitimate recombination events.     

Adenosine kinase regulation of cardiomyocyte hypertrophy

There is evidence that extracellular adenosine can attenuate cardiac hypertrophy, but the mechanism by which this occurs is not clear. Here we investigated the role of adenosine receptors and adenosine metabolism in attenuation of cardiomyocyte hypertrophy. Phenylephrine (PE) caused hypertrophy of neonatal rat cardiomyocytes with increases of cell surface area, protein synthesis, and atrial natriuretic peptide (ANP) expression. These responses were attenuated by 5 μM 2-chloroadenosine (CADO; adenosine deaminase resistant adenosine analog) or 10 μM adenosine. While antagonism of adenosine receptors partially blocked the reduction of ANP expression produced by CADO, it did not restore cell size or protein synthesis. In support of a role for intracellular adenosine metabolism in regulating hypertrophy, the adenosine kinase (AK) inhibitors iodotubercidin and ABT-702 completely reversed the attenuation of cell size, protein synthesis, and expression of ANP by CADO or ADO. Examination of PE-induced phosphosignaling pathways revealed that CADO treatment did not reduce AKT(Ser??3) phosphorylation but did attenuate sustained phosphorylation of Raf(Ser33?) (24-48 h), mTOR(Ser2???) (24-48 h), p70S6k(Thr3??) (2.5-48 h), and ERK(Thr2?2/Tyr2??) (48 h). Inhibition of AK restored activation of these enzymes in the presence of CADO. Using dominant negative and constitutively active Raf adenoviruses, we found that Raf activation is necessary and sufficient for PE-induced mTORC1 signaling and cardiomyocyte hypertrophy. CADO treatment still blocked p70S6k(Thr3??) phosphorylation and hypertrophy downstream of constitutively active Raf, however, despite a high level phosphorylation of ERK(Thr202/Tyr204) and AKT(Ser??3). Reduction of Raf-induced p70S6k(Thr3??) phosphorylation and hypertrophy by CADO was reversed by inhibiting AK. Together, these results identify AK as an important mediator of adenosine attenuation of cardiomyocyte hypertrophy, which acts, at least in part, through inhibition of Raf signaling to mTOR/p70S6k.     

Protective effects of activated vitamin D receptor on radiation‐induced intestinal injury

Radiation‐induced intestinal injury (RIII) is a common complication after radiation therapy in patients with pelvic, abdominal, or retroperitoneal tumours. Recently, in the model of DSS (Dextran Sulfate Sodium Salt) ‐induced intestinal inflammatory injury, it has been found in the study that transgenic mice expressing hVDR in IEC (Intestinal Epithelial Cell) manifest highly anti‐injury properties in colitis, suggesting that activated VDR in the epithelial cells of intestine may inhibit colitis by protecting the mucosal epithelial barrier. In this study, we investigated the effect of the expression and regulation of VDR on the protection of RIII, and the radiosensitivity in vitro experiments, and explored the initial mechanism of VDR in regulating radiosensitivity of IEC. As a result, we found that the expression of VDR in intestinal tissues and cells in mice can be induced by ionizing radiation. VDR agonists are able to prolong the average survival time of mice after radiation and reduce the radiation‐induced intestinal injury. For lack of vitamin D, the radiosensitivity of intestinal epithelial cells in mice increased, which can be reduced by VDR activation. Ensuing VDR activation, the radiation‐induced intestinal stem cells damage is decreased, and the regeneration and differentiation of intestinal stem cells is promoted as well. Finally, on the basis of sequencing analysis, we validated and found that VDR may target the HIF/PDK1 pathway to mitigate RIII. We concluded that agonism or upregulation of VDR expression attenuates radiation‐induced intestinal damage in mice and promotes the repair of epithelial damage in intestinal stem cells.     

Countrywide Survey for MERS-Coronavirus Antibodies in Dromedaries and Humans in Pakistan

Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is a zoonotic pathogen capable of causing severe respiratory disease in humans. Although dromedary camels are considered as a major reservoir host, the MERS-CoV infection dynamics in camels are not fully understood. Through surveillance in Pakistan, nasal (n = 776) and serum (n = 1050)samples were collected from camels between November 2015 and February 2018. Samples were collected from animal markets, free-roaming herds and abattoirs. An in-house ELISA was developed to detect IgG against MERS-CoV. A total of 794 camels were found seropositive for MERS-CoV. Prevalence increased with the age and the highest seroprevalence was recorded in camels aged [ 10 years (81.37%) followed by those aged 3.1–10 years (78.65%) and B 3 years (58.19%).Higher prevalence was observed in female (78.13%) as compared to male (70.70%). Of the camel nasal swabs, 22 were found to be positive by RT-qPCR though with high Ct values. Moreover, 2,409 human serum samples were also collected from four provinces of Pakistan during 2016–2017. Among the sampled population, 840 humans were camel herders.Although we found a high rate of MERS-CoV antibody positive dromedaries (75.62%) in Pakistan, no neutralizing antibodies were detected in humans with and without contact to camels.     

Cloning, sequencing and expression of a dextransucrase gene (dexYG) from Leuconostoc mesenteroides

The gene dexYG encoding the dextransucrase from an industrial strain of Leuconostoc mesenteroides 0326 was isolated by PCR. The nucleotide sequence of the dexYG gene consists of an open reading frame (ORF) of 4,584 bp, coding for a 1,527 aa protein with a Mr of 170 kDa. The results were analysed by a BLAST similarity search of the GenBank database, which revealed the amino acid sequence was similiar to dsrD derived from L. mesenteroides Lcc4. The dexYG gene was subcloned into the plasmid pET28a(+) and was expressed in E. coli BL21 (DE3) by IPTG induction. The pH value was one of the main reasons which caused the degradation of enzyme activity in the later stage of induction. The highest activity was reached 36 U/ml after 5 h induction in medium at pH 6.0. Biotransformation yield of the enzyme reached 65% and the molecular weight of transformed dextran was more than 68 kDa in 2 h.