Search

Sand production has been a shared problem in the development of weakly-cemented sandstone oil reservoirs. Sanding simulation and prediction are of utmost importance for the production optimization of this type of reservoir. For a long time, research on sand production has been centered on “what is produced from the formation,” such as the size and rate of produced sand. However, “what is left inside the formation,” which is the structural change of the rock after sanding, is also another intriguing and important topic for the management of sand-prone reservoirs. Some related studies have been carried out, and they have proposed that wormhole-like pore throat will appear after sand production, but the precise morphological description and formation mechanism are still lacking. A series of sanding simulation experiments are performed to deepen the understanding of the sanding cavity pattern and its mechanism. The experiments are carried out using a visual sanding simulation apparatus. Through this, the complex wormhole sand production patterns are found and classified into single-branch wormhole cavity patterns and multi-branch wormhole cavity patterns. The extension processes of those different patterns are also demonstrated. Besides, this work discusses the change in the reservoir flowability performance in wormhole sanding mode, and the near-well flowability might be improved by actively inducing weakly-cemented sandstone to create a bigger aperture wormhole sanding pattern. Through the visual microscopic system, the sand competitive detachment mechanism that induces wormhole extending is revealed, along with the cavities concurrent extension mechanism that induces multi-branch wormhole extending. Moreover, this work discusses the microscopic detachment forms which help explain the sand-produced rate from weakly-cemented sandstone. This work enhances and creates a novel understanding of the sanding patterns and mechanisms in weakly-cemented heterogeneous reservoirs, which is beneficial to providing direct guidance for sand production prediction and sand control optimization.

ABSTRACTApplication of bone marrow-derived mesenchymal stem cell-derived exosomes (BMSC-exos) in cancer treatment has been widely studied. Here, we elaborated the function of BMSC-exos containing microRNA-187 (miR-187) in prostate cancer. Differentially expressed miRs and genes were screened with microarray analysis. The relationship between CD276 and miR-187 in prostate cancer was evaluated. Following miR-187 mimic/inhibitor or CD276 overexpression transfection, their actions in prostate cancer cell biological processes were analyzed. Prostate cancer cells were then exposed to BMSC-exos that were treated with either miR-187 mimic/inhibitor or CD276 overexpression for pinpointing the in vitro and in vivo effects of exosomal miR-187. miR-187 was poorly expressed while CD276 was significantly upregulated in prostate cancer. Additionally, restoring miR-187 inhibited the prostate cancer cell malignant properties by targeting CD276. Upregulation of miR-187 led to declines in CD276 expression and the JAK3-STAT3-Slug signaling pathway. Next, BMSC-exos carrying miR-187 contributed to repressed cell malignant features as well as limited tumorigenicity and tumor metastasis. Collectively, this study demonstrated that BMSC-derived exosomal miR-187 restrained prostate cancer by reducing CD276/JAK3-STAT3-Slug axis.

Aim:The aim of this study was to access the effect of HmsA, a 65-nt small regulatory RNA encoded by the pPCP1 plasmid, on Yersinia pestisvirulence. Materials & methods:Survival and the competition index were determined in mice infected with wild-type Y. pestisand an hmsAdeletion mutant. RNA-seq was used to identify HmsA-regulated genes. Results:HmsA deletion enhanced Y. pestisvirulence. However, there was no overlap between 18 upregulated genes associated with pathogenicity and potential direct HmsA targets, based on gene expression screening after HmsA-pulse overexpression. Conclusion:HmsA inhibits Y. pestisvirulence, but this effect may be mediated by indirect effects on pathogenesis, iron homeostasis and/or other cellular processes.

Chemical stabilization is a viable solution for controlling the sand migration and production issues encountered in unconsolidated sandstone reservoirs. With numerous sand stabilizers available, screening the appropriate reagent and clarifying its utilization are crucial for enhancing sand control efficiency. This paper explores the impact of chemical sand stabilization on the expansion and diversification of sand production patterns and provides an experimental evaluation approach from an engineering standpoint. The evaluation experiments show that the sanding patterns may shift from collapse to a stabilized sanding cavity as the stabilizer content increases, and may remain relatively steady despite the increased flow rate under a high content of chemical sand stabilizer. Nevertheless, chemical stabilization has limited power to control unconsolidated sandstone, particularly in the early stages of fluid flushing when adequate support could not be provided, resulting in explosive sand production. Furthermore, their lifetime of efficacy in engineering applications is still insufficient. Based on the evaluation results, research on the construction method of mechanical-chemical sand control and parameter optimization including treatment range, dosage, and extrusion rate was established. The chemical stabilization screening method and mechanical-chemical design method presented in this work have been proven to be feasible through the successful application in the Gudong oilfield. The combination of chemical stabilization and squeeze gravel pack technology provides dual benefits of blocking coming sand near well and stabilizing weekly cemented sand far well, particularly for wells with extensive sanding history. It has a fair chance of helping with the engineering of sand management and production enhancement for unconsolidated sandstone reservoirs.

Graphical Abstract

Humans have profoundly affected the ocean environment but little is known about anthropogenic effects on the distribution of microbes. Vibrio parahaemolyticusis found in warm coastal waters and causes gastroenteritis in humans and economically significant disease in shrimps. Based on data from 1103 genomes of environmental and clinical isolates, we show that V. parahaemolyticusis divided into four diverse populations, VppUS1, VppUS2, VppX and VppAsia. The first two are largely restricted to the US and Northern Europe, while the others are found worldwide, with VppAsia making up the great majority of isolates in the seas around Asia. Patterns of diversity within and between the populations are consistent with them having arisen by progressive divergence via genetic drift during geographical isolation. However, we find that there is substantial overlap in their current distribution. These observations can be reconciled without requiring genetic barriers to exchange between populations if long-range dispersal has increased dramatically in the recent past. We found that VppAsia isolates from the US have an average of 1.01% more shared ancestry with VppUS1 and VppUS2 isolates than VppAsia isolates from Asia itself. Based on time calibrated trees of divergence within epidemic lineages, we estimate that recombination affects about 0.017% of the genome per year, implying that the genetic mixture has taken place within the last few decades. These results suggest that human activity, such as shipping, aquatic products trade and increased human migration between continents, are responsible for the change of distribution pattern of this species.

Humans have profoundly affected the ocean environment but little is known about anthropogenic effects on the distribution of microbes. Vibrio parahaemolyticusis found in warm coastal waters and causes gastroenteritis in humans and economically significant disease in shrimps. Based on data from 1103 genomes of environmental and clinical isolates, we show that V. parahaemolyticusis divided into four diverse populations, VppUS1, VppUS2, VppX and VppAsia. The first two are largely restricted to the US and Northern Europe, while the others are found worldwide, with VppAsia making up the great majority of isolates in the seas around Asia. Patterns of diversity within and between the populations are consistent with them having arisen by progressive divergence via genetic drift during geographical isolation. However, we find that there is substantial overlap in their current distribution. These observations can be reconciled without requiring genetic barriers to exchange between populations if long-range dispersal has increased dramatically in the recent past. We found that VppAsia isolates from the US have an average of 1.01% more shared ancestry with VppUS1 and VppUS2 isolates than VppAsia isolates from Asia itself. Based on time calibrated trees of divergence within epidemic lineages, we estimate that recombination affects about 0.017% of the genome per year, implying that the genetic mixture has taken place within the last few decades. These results suggest that human activity, such as shipping, aquatic products trade and increased human migration between continents, are responsible for the change of distribution pattern of this species.

Aim:Determination of the virulence regulatory network controlled by the ATP-dependent Lon protease in Salmonella entericaserovar Typhimurium. Materials & methods:The effect of Lon on S.Typhimurium virulence genes expression was investigated by RNA sequencing, and virulence-associated phenotypes between the wild-type and lonmutant were compared. Results:SPI-1, SPI-4, SPI-9and flagellar genes were activated, while SPI-2genes were repressed in the lonmutant. Accordingly, the lonmutant exhibited increased adhesion to and invasion of epithelial cells, increased motility and decreased replication in macrophages. The activation of SPI-2genes by Lon partially accounts for the replication defect of the mutant. Conclusion:A wide range of virulence regulatory functions are governed by Lon in S. entericaser. Typhimurium.

Sand production is a troublesome problem in the petroleum industry, especially in relation to weakly consolidated formations. In this work, a visual experimental apparatus, which allows sand particles to be observed, has been constructed to simulate sand production in weakly consolidated sandstone core. The experimental apparatus can accommodate sandstone core flakes as a reactor. The experiment aims to investigate the microscopic sand production mechanism of the weakly consolidated sandstone reservoir under the influence of high water cut, high clay content and polymer aging blockage. Core flakes were produced using simulated formation sands with median particle sizes of 160 μm and uniformity coefficients of 2.5, 4.6, 7.3 and 12.6, as well as clay (content 5%, 10%, 20%, 30%, respectively) and aged polymers in the wells. A total of 17 sets of experimental tests were carried out with water injection. The visual experimental results show that sand morphology presents complex wormhole. Morphology is particularly affected by core strength and heterogeneity. Based on dynamic differential pressure of experimental results, most sand production process is divided into two obvious stages, that is, the cavities formation stage of sharp sand production and the stable sand production stage. Analysis of sensitive factors revealed that the sand production rate is strongly influenced by the core strength and related to clay content, formation heterogeneity and production program. The volumetric sand production ratio decreases with the increase of core strength, with the volumetric sand production ratio (VSPR) reaching up to 0.24%. It is found that about 38% clay (1–3.91 μm) was produced in the initial stage of low flow, which is particularly evident in cores with high clay content. Moreover, for weakly consolidated reservoir, the particle competition peeling mechanism of wormhole front is proposed, and the strengthening bonding effect of aging polymer and the pore blockage effect of fine clay are clarified. The findings could contribute to better understanding of the mechanisms underlying sand production in weakly consolidated sandstone reservoirs, which also provide a solid evidence base for accurate sand production prediction and more targeted sand control.

The immune response of brain cells to invading bacteria in vivoand the mechanism used by pathogenic bacteria to escape brain immune surveillance remain largely unknown. It is believed that microglia eliminate bacteria by phagocytosis based on in vitrodata. Here we find that a small percentage of microglia in the brain engulf neonatal meningitis-causing Escherichia coli(NMEC), but more microglia are activated to produce tumor necrosis factor alpha (TNFα), which activates astrocytes to secrete complement component 3 (C3) involved in anti-bacterial activity. To evade anti-bacterial activity of the immune system, NMEC senses low concentration of threonine in cerebrospinal fluid (CSF) to down-modulate the expression of flagellin and reduce microglial TNFα and astrocyte C3 production. Our findings may help develop strategies for bacterial meningitis treatment.

Bacterial pathogens have evolved various mechanisms to modulate host immune responses for successful infection. In this study, RNA-sequencing technology was used to analyze the responses of human monocytes THP1 to Yersinia pestisinfection. Over 6000 genes were differentially expressed over the 12 h infection. Kinetic responses of pathogen recognition receptor signaling pathways, apoptosis, antigen processing, and presentation pathway and coagulation system were analyzed in detail. Among them, RIG-I-like receptor (RLR) signaling pathway, which was established for antiviral defense, was significantly affected. Mice lacking MAVS, the adaptor of the RLR signaling pathway, were less sensitive to infection and exhibited lower IFN-β production, higher Th1-type cytokines IFN-γ and IL-12 production, and lower Th2-type cytokines IL-4 and IL-13 production in the serum compared with wild-type mice. Moreover, infection of pathogenic bacteria other than Y. pestisalso altered the expression of the RLR pathway, suggesting that the response of RLR pathway to bacterial infection is a universal mechanism.

ABSTRACTArtificially passive immunization has been demonstrated to be effective against Yersinia pestisinfection in animals. However, maternal antibodies' protective efficacy against plague has not yet been demonstrated. Here, we evaluated the kinetics, protective efficacy, and transmission modes of maternal antibodies, using mice immunized with plague subunit vaccine SV1 (20 µg of F1 and 10 µg of rV270). The results showed that the rV270- and F1-specific antibodies could be detected in the sera of newborn mice (NM) until 10 and 14 weeks of age, respectively. There was no antibody titer difference between the parturient mice immunized with SV1 (PM-S) and the caesarean-section newborns (CSN) from the PM-S or between the lactating mice immunized by SV1 (LM-S) and the cross-fostered mice (CFM) during 3 weeks of lactation. The NM had a 72% protection against 4,800 CFU Y. pestisstrain 141 challenge at 6 weeks of age, whereas at 14 weeks of age, NM all succumbed to 5,700 CFU of Y. pestischallenge. After 7 weeks of age, CFM had an 84% protection against 5,000 CFU of Y. pestischallenge. These results indicated that maternal antibodies induced by the plague subunit vaccine in mother mice can be transferred to NM by both placenta and lactation. Passive antibodies from the immunized mothers could persist for 3 months and provide early protection for NM. The degree of early protection is dependent on levels of the passively acquired antibody. The results indicate that passive immunization should be an effective countermeasure against plague during its epidemics.

ABSTRACTThe spread of the blaNDM-1gene is gaining worldwide attentions. This gene is usually carried by large plasmids and has been discovered in diverse bacteria since it was originally found in Klebsiella pneumoniae. Here we report the complete sequences of a blaNDM-1-bearing plasmid, pNDM-BJ01, and its variant, pNDM-BJ02, isolated from clinical Acinetobacter lwoffiistrains. The plasmid pNDM-BJ01 is 47.3 kb in size and cannot be classified into any known plasmid incompatibility group, thus representing a novel plasmid with an unknown maintenance mechanism. This plasmid contains both a blaNDM-1gene and a type IV secretion system (T4SS) gene cluster. The T4SS is assigned to the P-type T4SS group, which usually encode a short, rigid pilus, and the blaNDM-1gene is located within a composite transposon flanked by two insertion elements of ISAba125. Plasmid pNDM-BJ02 is nearly identical to pNDM-BJ01 except that one copy of the ISAba125element is missing, and it is therefore regarded as a variant of pNDM-BJ01. Sequence alignment indicated that this blaNDM-1-containing composite transposon, which can also be captured by other mobile elements, was probably a product of multiple recombination events and can move as a whole by transposition.

A protein microarray representing 149 Yersinia pestis proteins was developed to profile antibody responses in EV76-immunized rabbits. Antibodies to 50 proteins were detected. There are 11 proteins besides F1 and V antigens to which the predominant antibody response occurred, and these proteins show promise for further evaluation as candidates for subunit vaccines and/or diagnostic antigens.

ABSTRACTA protein microarray representing 149 Yersinia pestisproteins was developed to profile antibody responses in EV76-immunized rabbits. Antibodies to 50 proteins were detected. There are 11 proteins besides F1 and V antigens to which the predominant antibody response occurred, and these proteins show promise for further evaluation as candidates for subunit vaccines and/or diagnostic antigens.

Yersinia pestis, the etiologic agent of plague, must acclimatize itself to temperature shifts between the temperature (26 C) for flea blockage and the body temperature (37 C) of warm‐blooded hosts during its life cycle. Here a whole‐genome DNA microarray was used to investigate transcriptional regulation upon the upshift of growth temperature from 26 to 37 C in a chemically defined medium. Four hundred and one genes were regulated differentially under the two temperatures. About 39% of these genes were up‐regulated at 37 C, whereas 61% were down‐regulated. Temperature‐induced changes occurred at the level of transcription of genes encoding proven or predicted virulence factors, regulators, metabolism‐associated proteins, prophages, and hypothetical proteins. Strikingly, many gene clusters displayed a co‐transcription pattern in response to temperature upshift. Our data provided a genome‐wide profile of gene transcription induced by temperature shift and should shed light on the pathogenicity and host‐microbe interaction of this deadly pathogen.

Polymerase chain reaction (PCR) amplification of DNA‐based unique markers, the signature sequences, is ideal for rapid detection and identification of pathogens. We described the discovery of twenty‐eight signature genes of Yersinia pestisby DNA microarray‐based comparative genome hybridization in conjunction with PCR validation. Three pairs of Y. pestis‐specific primers designed from signature genes were demonstrated to have the expected specificity to this target bacterium, without cross‐reaction with the closely related Y. pseudotuberculosisor a large collection of genomic DNAs from other organisms.

A magnetic capture‐hybridization method was developed for purification of bacterial messenger RNA (mRNA) from total RNA by removing 5S, 16S and 23S ribosomal RNAs (rRNA). The quality of mRNA was evaluated by A260nm/A280nmvalue, denatured gel electrophoresis and RT‐PCR. The results showed that highly purified and intact mRNA was obtained by this method. The magnetic capture‐hybridization is a rapid and simple method for bacterial mRNA purification and has promising potential for improving studies using bacterial mRNA.

Plague is a zoonotic disease that primarily infects rodents viafleabite. Transmission from flea to host niches requires rapid adaption of Yersinia pestisto the outer environments to establish infection. Here, quantitative proteome and secretome analyses of Y. pestisgrown under conditions mimicking the two typical niches, i.e., the mammalian host (Mh) and the flea vector (Fv), were performed to understand the adaption strategies of this deadly pathogen. A secretome of Y. pestiscontaining 308 proteins has been identified using TMT-labeling mass spectrometry analysis. Although some proteins are known to be secreted, such as the type III secretion substrates, PsaA and F1 antigen, most of them were found to be secretory proteins for the first time. Comparative proteomic analysis showed that membrane proteins, chaperonins and stress response proteins are significantly upregulated under the Mh condition, among which the previously uncharacterized proteins YP_3416∼YP_3418 are remarkable because they cannot only be secreted but also translocated into HeLa cells by Y. pestis. We further demonstrated that the purified YP_3416 and YP_3418 exhibited E3 ubiquitin ligase activity in in vitroubiquitination assay and yp_3416∼3418deletion mutant of Y. pestisshowed significant virulence attenuation in mice. Taken together, our results represent the first Y. pestissecretome, which will promote the better understanding of Y. pestispathogenesis, as well as the development of new strategies for treatment and prevention of plague.

ABSTRACTDifferent assays were used to analyze 1,621 serum specimens collected from military recruits from the People's Republic of China in 2002 for severe acute respiratory syndrome (SARS) coronavirus antibodies. The results demonstrated that the subjects either had rarely been exposed to the virus before the 2003 SARS outbreak or had not been exposed but the nucleocapsid protein cross-reacted with other antibodies in humans.

ABSTRACTRecent studies revealed that acetylation is a widely used protein modification in prokaryotic organisms. The major protein acetylation acetyltransferase YfiQ and the sirtuin-like deacetylase CobB have been found to be involved in basic physiological processes, such as primary metabolism, chemotaxis, and stress responses, in Escherichia coliand Salmonella. However, little is known about protein acetylation modifications in Yersinia pestis, a lethal pathogen responsible for millions of human deaths in three worldwide pandemics. Here we found that Yp_0659and Yp_1760of Y. pestisencode the major protein acetylation acetyltransferase YfiQ and the sirtuin-like deacetylase CobB, respectively, which can acetylate and deacetylate PhoP enzymatically in vitro. Protein acetylation impairment in cobBand yfiQmutants greatly decreased bacterial tolerance to cold, hot, high-salt, and acidic environments. Our comparative transcriptomic data revealed that the strongly decreased tolerance to stress stimuli was probably related to downregulation of the genes encoding the heat shock proteins (HtpG, HslV, HslR, and IbpA), cold shock proteins (CspC and CspA1), and acid resistance proteins (HdeB and AdiA). We found that the reversible acetylation mediated by CobB and YfiQ conferred attenuation of virulence, probably partially due to the decreased expression of the psaABCDEFoperon, which encodes Psa fimbriae that play a key role in virulence of Y. pestis. This is the first report, to our knowledge, on the roles of protein acetylation modification in stress responses, biofilm formation, and virulence of Y. pestis.

ABSTRACTPathogenic yersiniae harbor a type III secretion system (T3SS) that injects Yersiniaouter protein (Yop) into host cells. YopK has been shown to control Yop translocation and prevent inflammasome recognition of the T3SS by the innate immune system. Here, we demonstrate that YopK inhibits bacterial adherence to host cells by binding to the extracellular matrix adaptor protein matrilin-2 (MATN2). YopK binds to MATN2, and deleting amino acids 91 to 124 disrupts binding of YopK to MATN2. A yopKnull mutant exhibits a hyperadhesive phenotype, which could be responsible for the established Yop hypertranslocation phenotype of yopKmutants. Expression of YopK, but not YopKΔ91–124, in a yopKmutant restored the wild-type phenotypes of adhesion and Yop translocation, suggesting that binding to MATN2 might be essential for YopK to inhibit bacterial adhesion and negatively regulate Yop translocation. A green fluorescent protein (GFP)-YopK fusion specifically binds to the endogenous MATN2 on the surface of HeLa cells, whereas GFP-YopKΔ91–124cannot. Addition of purified YopK protein during infection decreased adhesion of Y. pestisto HeLa cells, while YopKΔ91–124protein showed no effect. Taking these results together, we propose a model that the T3SS-secreted YopK hinders bacterial adhesion to HeLa cells by binding to MATN2, which is ubiquitously exposed on eukaryotic cells.