Multiple signaling systems target a core set of transition metal homeostasis genes using similar binding motifs

Bacterial response to metals can require complex regulation. We report an overlapping regulation for copper and zinc resistance genes in the denitrifying bacterium, Pseudomonas stutzeri RCH2, by three two‐component regulatory proteins CopR1, CopR2 and CzcR. We conducted genome‐wide evaluations to identify gene targets of two paralogous regulators, CopR1 and CopR2, annotated for copper signaling, and compared the results with the gene targets for CzcR, implicated in zinc signaling. We discovered that the CopRs and CzcR have largely common targets, and crossregulate a core set of P. stutzeri copper and zinc responsive genes. We established that this crossregulation is enabled by a conserved binding motif in the upstream regulatory regions of the target genes. The crossregulation is physiologically relevant as these regulators synergistically and antagonistically target multicopper oxidases, metal efflux and sequestration systems. CopR1 and CopR2 upregulate two cop operons encoding copper tolerance genes, while all three regulators downregulate a putative copper chaperone, Psest_1595. CzcR also upregulated the oprD gene and the CzcIABC Zn²⁺ efflux system, while CopR1 and CopR2 downregulated these genes. Our study suggests that crossregulation of copper and zinc homeostasis can be advantageous, and in P. stutzeri this is enabled by shared binding motifs for multiple response regulators.     

Peculiarities of the Seasonal Biology of Ectoparasites of the Genus <Emphasis Type="Italic">Spinturnix</Emphasis> von Heyden, 1826 (Mesostigmata: Gamasina: Spinturnicidae) in the Boreal Zone of the Palearctic Region

The most complete data on the peculiarities of seasonal biology of gamasid mites of the genus Spinturnix, which are ectoparasites of bats of the boreal zone of the Old World, are presented. Data on the dynamics of the sex and age structure of superpopulations of parasites throughout the year are presented; the infestation of various bat species is analyzed, and the factors affecting it are discussed. The main differences between the life cycles of the boreal and subboreal Spinturnicidae mites were revealed.     

DNA synthesis in the nuclei of stimulated NIH 3T3 cells in heterodikaryons obtained by the fusion of these cells with resting cells treated with cycloheximide

Serum-deprived (0.2%) resting NIH 3T3 mouse fibroblasts preincubated with cycloheximide (7.5 micrograms/ml) were fused with stimulated cells taken 10 hours after changing the medium to the one containing 10% serum, and DNA synthesis was investigated in nuclei of heterodikaryons, homodikaryons, and monokaryons, using radioautography with double-labeling technique. Preincubation of resting cells with the inhibitor of protein synthesis cycloheximide for 4, 3, 2, but not for 1 or 0.5 hours abolishes their ability to suppress DNA synthesis in stimulated nuclei in heterodikaryons. Three hours after the removal of cycloheximide from the media, the resting cells acquire once again the inhibitory effect towards the entry of stimulated nuclei into the S-period. The data suggest that the resting cells may produce a labile endogenous inhibitor of cell proliferation, and support the idea on the active metabolic processes occurring in the resting cells.     

The use of cross-linking platinum reagents in the study of tRNA and mRNA interaction with ribosomes

The use of some bifunctional Pt(II)-containing cross-linking reagents for investigation of structural organization of ribosomal tRNA- and mRNA-binding centres is demonstrated for various types of [70S ribosome.mRNA-tRNA] complexes. It is shown that treatment of the complexes [70S ribosome.Ac[14C]Phe-tRNA(Phe).poly(U)], [70S ribosome.3'-32pCp-tRNA(Phe).poly(U)] and [70S ribosome.f[35S]Met-tRNA(fMet).AUGU6] with Pt(II)-derivatives results in covalent attachment of tRNA to ribosome. AcPhe-tRNA(Phe) and 3'-pCp-tRNA(Phe) bound at the P site were found to be cross-linked preferentially to 30S subunit. fMet-tRNA(fMet) within the 70S initiation complex is cross-linked to both ribosome subunits approximately in the same extent, which exceeds two-fold the level of the tRNA(Phe) cross-linking. All used tRNA species were cross-linked in the comparable degree both to rRNA and proteins of both subunits in all types of the complexes studied. 32pAUGU6 cross-links exclusively to 30S subunit (to 16S RNA only) within [70S ribosome.32pAUGU6.fMet-tRNA(fMet)] complex. In the absence of fMet-tRNAfMet the level of the cross-linking is 4-fold lower.     

Differences in 23 S rRNA-protein neighbourhood in Escherichia coli 70 S ribosomes and 70 S initiation complex. Probing by bifunctional Pt(II)-containing reagent

rRNA-protein cross-links in free E. coli 35S-labeled 70 S ribosomes and in the initiation complex 35S-labeled 70 S ribosome.AUGU6.fMet-tRNA(fMet) were studied with the aid of a new type of binuclear Pt(II) compound - dichlorotetra-ammine(1,6-hexamethylenediaminediplatinum++ +) dichloride. The use of this reagent allowed us to reveal differences in the rRNA-protein neighbourhood in free 70 S ribosomes and in the initiation complex. Proteins L3, L6, L23 and L25 were shown to cross-link to 23 S rRNA only in the initiation complex, whereas proteins L1, L13, L14, L16, L17, L18, L22, L28 and S1 did so in both free ribosomes and the complex. 16 S rRNA was found to be cross-linked preferentially to a single protein, S1, in both states of the ribosomes.     

Reovirus intermediate subviral particles constitute a strategy to infect intestinal epithelial cells by exploiting TGF‐β dependent pro‐survival signaling

Intestinal epithelial cells (IECs) constitute the primary barrier that separates us from the outside environment. These cells, lining the surface of the intestinal tract, represent a major challenge that enteric pathogens have to face. How IECs respond to viral infection and whether enteric viruses have developed strategies to subvert IECs innate immune response remains poorly characterized. Using mammalian reovirus (MRV) as a model enteric virus, we found that the intermediate subviral particles (ISVPs), which are formed in the gut during the natural course of infection by proteolytic digestion of the reovirus virion, trigger reduced innate antiviral immune response in IECs. On the contrary, infection of IECs by virions induces a strong antiviral immune response that leads to cellular death. Additionally, we determined that virions can be sensed by both TLR and RLR pathways while ISVPs are sensed by RLR pathways only. Interestingly, we found that ISVP infected cells secrete TGF‐β acting as a pro‐survival factor that protects IECs against virion induced cellular death. We propose that ISVPs represent a reovirus strategy to initiate primary infection of the gut by subverting IECs innate immune system and by counteracting cellular‐death pathways.     

Molecular evolution of cytochrome c oxidase: rate variation among subunit VIa isoforms

Cytochrome c oxidase (COX) consists of 13 subunits, 3 encoded in the mitochondrial genome and 10 in the nucleus. Little is known of the role of the nuclear-encoded subunits, some of which exhibit tissue-specific isoforms. Subunit VIa is unique in having tissue-specific isoforms in all mammalian species examined. We examined relative evolutionary rates for the COX6A heart (H) and liver (L) isoform genes along the length of the molecule, specifically in relation to the tissue-specific function(s) of the two isoforms. Nonsynonymous (amino acid replacement) substitutions in the COX6AH gene occurred more frequently than in the ubiquitously expressed COX6AL gene. Maximum-parsimony analysis and sequence divergences from reconstructed ancestral sequences revealed that after the ancestral COX6A gene duplicated to yield the genes for the H and L isoforms, the sequences encoding the mitochondrial matrix region of the COX VIa protein experienced an elevated rate of nonsynonymous substitutions relative to synonymous substitutions. This is expected for relaxed selective constraints after gene duplication followed by purifying selection to preserve the replacements with tissue-specific functions.      

不同施肥处理对‘赤霞珠’葡萄根际土壤养分和真菌群落的影响

【背景】宁夏贺兰山东麓葡萄产区忽视有机肥的施用,果树枝条焚烧污染环境,造成土壤养分缺失,土壤质量下降。【目的】为解决长期施用化肥对土壤造成的一系列问题,通过大田试验研究施肥及喷施不同浓度菌剂对土壤理化性质、真菌群落组成及多样性的影响,为酿酒葡萄可持续健康发展提供科学依据。【方法】以‘赤霞珠’葡萄根际土壤为试验对象,采用Illumina MiSeq高通量测序技术,测定并分析根际土壤理化性质、真菌群落组成和多样性在7个处理[常规施肥(CK)、蚯蚓粪+腐熟枝条+100倍菌剂(T1)、蚯蚓粪+腐熟枝条+200倍菌剂(T2)、蚯蚓粪+腐熟枝条+300倍菌剂(T3)、蚯蚓粪+未腐熟枝条+100倍菌剂(A1)、蚯蚓粪+未腐熟枝条+200倍菌剂(A2)和蚯蚓粪+未腐熟枝条+300倍菌剂(A3)]的变化。【结果】相较于CK,葡萄根际土壤理化性质差异明显,施肥处理增加了土壤有机质含量,土壤pH含量无明显变化,改良了土壤结构,活化了土壤有效养分。相较于CK,各处理真菌分类操作单元(operational taxonomic unit, OTU)数均降低,A2处理根际土壤丰富度及多样性均显著增加。真菌群落组成...     

黑线毛足鼠年龄和种群密度与肝毛细线虫感染率的关系

2004—2005年,在内蒙古锡林郭勒盟阿巴嘎旗和东乌珠穆沁旗研究了肝毛细线虫病对黑线毛足鼠种群感染情况,分析肝毛细线虫对黑线毛足鼠的感染率与鼠体年龄以及种群密度的关系。结果表明,黑线毛足鼠达到一定的年龄(或体质量)才可感染肝毛细线虫病,最低感染个体体质量为14.6g。肝毛细线虫对低龄鼠的感染检出率比较低,而对成体鼠感染检出率较高,其感染率和感染度均随着个体年龄的增长而增高(感染率与年龄:r=0.97,P<0.05;感染度与年龄:r=0.93,P<0.05)。此外,黑线毛足鼠体质量与肝毛细线虫感染率和感染度也存在显著的相关关系(感染率与体质量:r=0.99,P<0.05;感染度与体质量:r=0.95,P<0.05),黑线毛足鼠的种群密度则对肝毛细线虫的感染率(r=0.27,P>0.05)和平均感染度(r=0.41,P>0.05)没有明显的影响,其感染率可能与地区不同有关。     

A modular treatment of molecular traffic through the active site of cholinesterase

We present a model for the molecular traffic of ligands, substrates, and products through the active site of cholinesterases (ChEs). First, we describe a common treatment of the diffusion to a buried active site of cationic and neutral species. We then explain the specificity of ChEs for cationic ligands and substrates by introducing two additional components to this common treatment. The first module is a surface trap for cationic species at the entrance to the active-site gorge that operates through local, short-range electrostatic interactions and is independent of ionic strength. The second module is an ionic-strength-dependent steering mechanism generated by long-range electrostatic interactions arising from the overall distribution of charges in ChEs. Our calculations show that diffusion of charged ligands relative to neutral isosteric analogs is enhanced approximately 10-fold by the surface trap, while electrostatic steering contributes only a 1.5- to 2-fold rate enhancement at physiological salt concentration. We model clearance of cationic products from the active-site gorge as analogous to the escape of a particle from a one-dimensional well in the presence of a linear electrostatic potential. We evaluate the potential inside the gorge and provide evidence that while contributing to the steering of cationic species toward the active site, it does not appreciably retard their clearance. This optimal fine-tuning of global and local electrostatic interactions endows ChEs with maximum catalytic efficiency and specificity for a positively charged substrate, while at the same time not hindering clearance of the positively charged products.