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On page 1 showing 1 ~ 20 papers out of 34 papers

Natural Extracellular Electron Transfer Between Semiconducting Minerals and Electroactive Bacterial Communities Occurred on the Rock Varnish.

  • Guiping Ren‎ et al.
  • Frontiers in microbiology‎
  • 2019‎

Rock varnish is a thin coating enriched with manganese (Mn) and iron (Fe) oxides. The mineral composition and formation of rock varnish elicit considerable attention from geologists and microbiologists. However, limited research has been devoted to the semiconducting properties of these Fe/Mn oxides in varnish and relatively little attention is paid to the mineral-microbe interaction under sunlight. In this study, the mineral composition and the bacterial communities on varnish from the Gobi Desert in Xinjiang, China were analyzed. Results of principal components analysis and t-test indicated that more electroactive genera such as Acinetobacter, Staphylococcus, Dietzia, and Pseudomonas gathered on varnish bacterial communities than on substrate rock and surrounding soils. We then explored the culture of varnish, substrate and soil samples in media and the extracellular electron transfer (EET) between bacterial communities and mineral electrodes under light/dark conditions for the first time. Orthogonal electrochemical experiments demonstrated that the most remarkable photocurrent density of 6.1 ± 0.4 μA/cm2 was observed between varnish electrode and varnish microflora. Finally, based on Raman and 16S rRNA gene-sequencing results, coculture system of birnessite and Pseudomonas (the major Mn oxide and a common electroactive bacterium in varnish) was established to study underlying mechanism. A steadily growing photocurrent (205 μA at 100 h) under light was observed with a stable birnessite after 110 h. However, only 47 μA was generated in the dark control and birnessite was reduced to Mn2+ in 13 h, suggesting that birnessite helped deliver electrons instead of serving as an electron acceptor under light. Our study demonstrated that electroactive bacterial communities were positively correlated with Fe/Mn semiconducting minerals in varnish, and diversified EET process occurred on varnish under sunlight. Overall, these phenomena may influence bacterial-community structure in natural environments over time.


Diversity of Cultivable Protease-Producing Bacteria in Laizhou Bay Sediments, Bohai Sea, China.

  • Yan Li‎ et al.
  • Frontiers in microbiology‎
  • 2017‎

Protease-producing bacteria are widespread in ocean sediments and play important roles in degrading sedimentary nitrogenous organic materials. However, the diversity of the bacteria and the proteases involved in such processes remain largely unknown especially for communities in enclosed sea bays. Here, we investigated the diversity of the extracellular protease-producing bacteria and their protease types in Laizhou Bay. A total of 121 bacterial isolates were obtained from sediment samples in 7 sites and their protease types were characterized. The abundance of cultivable protease-producing bacteria was about 104 CFU g-1 of sediment. Phylogenetic analysis based on 16S rRNA gene sequences suggest that the isolates belonged to 17 genera from 4 phyla including Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes, and mainly dominated by the genera Pseudoalteromonas (40.5%), Bacillus (36.3%), and Photobacterium (5.8%). The diversity and community structure varied among different sampling sites but no significant correlation was observed with soil sediment's characteristics. Enzyme activity and inhibition tests further revealed that all isolates secreted proteases that were inhibited by serine and/or metalloprotease inhibitors, and a smaller proportion was inhibited by inhibitors of cysteine and/or aspartic proteases. Furthermore, all isolates effectively degraded casein and/or gelatin with only a few that could hydrolyze elastin, suggesting that the bacteria were producing different kinds of serine proteases or metalloproteases. This study provided novel insights on the community structure of cultivable protease-producing bacteria near the Yellow River estuary of an enclosed sea bay.


Emergence of NDM-1- and CTX-M-3-Producing Raoultella ornithinolytica in Human Gut Microbiota.

  • Shuang Wang‎ et al.
  • Frontiers in microbiology‎
  • 2019‎

Raoultella ornithinolytica is an opportunistic pathogen of the Enterobacteriaceae family and has been implicated in nosocomial infections in recent years. The aim of this study was to characterize a carbapenemase-producing R. ornithinolytica isolate and three extended-spectrum β-lactamase (ESBL)-producing R. ornithinolytica isolates from stool samples of adults in a rural area of Shandong Province, China. The species were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and 16S rDNA sequence analysis. Antimicrobial susceptibility test showed that all four isolates were multidrug-resistant (MDR). The whole genome sequence (WGS) of these isolates was determined using an Illumina HiSeq platform, which revealed MDR-related genes. The S1 nuclease-pulsed-field gel electrophoresis (S1-PFGE) was used to characterize the plasmids carried by the R. ornithinolytica isolates. The bla NDM-1 and bla CTX-M-3 genes were probed using Southern blotting, which confirmed the location of both genes on the same plasmid with molecular weight of 336.5-398.4 kb. The transferability of bla NDM-1 and bla CTX-M was also confirmed by conjugation assays. Finally, BLAST analysis of both genes showed that mobile genetic elements were associated with the spread of drug resistance genes. Taken together, we report the presence of conjugative bla NDM-1 and bla CTX-M plasmids in R. ornithinolytica isolates from healthy humans, which indicate the possibility of inter-species transfer of drug resistance genes. To the best of our knowledge, this is the first study to isolate and characterize carbapenemase-producing R. ornithinolytica and ESBL-producing R. ornithinolytica isolates from healthy human hosts.


Ectopic Colonization and Immune Landscapes of Periodontitis Microbiota in Germ-Free Mice With Streptozotocin-Induced Type 1 Diabetes Mellitus.

  • Xin Shen‎ et al.
  • Frontiers in microbiology‎
  • 2022‎

A two-way relationship between diabetes and periodontitis has been discussed recently. Periodontitis microbiota might affect the immune homeostasis of diabetes, but the molecular mechanism of their interactions is still not clear. The aims of this study were to clarify the possible immune regulatory effects of periodontitis microbiota on diabetes and the correlation between immunomodulation and ectopic colonization. A model of germ-free mice with streptozotocin-induced type 1 diabetes mellitus (T1D), which was orally inoculated with mixed saliva samples for 2 weeks, was used in this study. Those mice were randomly divided into two groups, namely, SP (where the T1D mice were orally inoculated with mixed saliva samples from periodontitis patients) and SH (where the T1D mice were orally inoculated with mixed saliva samples from healthy subjects). Ectopic colonization of saliva microbiota was assessed using culture-dependent method and Sanger sequencing, and the composition of gut microbiota was analyzed using 16S rRNA gene sequencing. Changes in 15 types of immune cells and six cytokines either from the small intestine or spleen were detected by multicolor flow cytometry. The correlation between gut microbiota and immune cells was evaluated by redundancy analysis. Although periodontitis microbiota minorly colonized the lungs, spleens, and blood system, they predominantly colonized the gut, which was mainly invaded by Klebsiella. SH and SP differed in beta diversity of the gut bacterial community. Compared to SH, microbial alteration in small intestine occurred with an increase of Lacticaseibacillus, Bacillus, Agathobacter, Bacteroides, and a decrease of Raoultella in SP. More types of immune cells were disordered in the spleen than in the small intestine by periodontitis microbiota, mainly with a dramatical increase in the proportion of macrophages, plasmacytoid dendritic cells (pDCs), monocytes, group 3 innate lymphoid cells, CD4-CD8- T cells and Th17 cells, as well as a decline of αβT cells in SP. Cytokines of IFNγ, IL17, and IL22 produced by CD4 + T cells as well as IL22 produced by ILCs of small intestine rose in numbers, and the intestinal and splenic pDCs were positively regulated by gut bacterial community in SP. In conclusion, periodontitis microbiota invasion leads to ectopic colonization of the extra-oral sites and immune cells infiltration, which might cause local or systemic inflammation. Those cells are considered to act as a "bridge" between T1D and periodontitis.


Emergence of IncX3 Plasmid-Harboring bla NDM- 5 Dominated by Escherichia coli ST48 in a Goose Farm in Jiangsu, China.

  • Ziyi Liu‎ et al.
  • Frontiers in microbiology‎
  • 2019‎

Twelve carbapenem-resistant Escherichia coli strains were obtained from goose farms in Jiangsu, China. These isolates were resistant to multiple antimicrobials, and positive for the bla NDM- 5. The carbapenem-resistance of all strains mediated by bla NDM- 5 were successfully conjugated to E. coli J53. S1-PFGE and WGS results showed bla NDM- 5 was located on IncX3 conjugative plasmids with a size of ca. 46 kb. All bla NDM- 5-bearing IncX3 plasmids shared the same genetic context almost identical to pNDM_MGR194-bla NDM- 5 and pNDM-QD28-bla NDM- 5 reported in India and China, respectively. The twelve strains belonged to three STs, in which the dominant type of E. coli isolated from breeding goose farm carrying bla NDM- 5 was ST48. The emergence of bla NDM- 5-bearing strains in goose farms and the clonal transmission of E. coli within the breeding goose farm highlighted the potential reservoir of carbapenemase genes in waterfowl farming system, which may further contaminate environments and pose a threat to public health. Comprehensive surveillance of carbapenem-resistant bacteria in goose farms warrants further study to evaluate the underlying risks.


Biodiversity and Geographic Distribution of Rhizobia Nodulating With Vigna minima.

  • Guohua Liu‎ et al.
  • Frontiers in microbiology‎
  • 2021‎

Vigna minima is a climbing annual plant widely distributed in barren wilderness, grass land, and shrub bush of China and other countries such as Japan. However, the rhizobia nodulating with this plant has never been systematically studied. In order to reveal the biodiversity of nodulating rhizobia symbiosis with V. minima, a total of 874 rhizobium isolates were obtained from root nodules of the plant spread in 11 sampling sites of Shandong Peninsula, China, and they were designated as 41 haplotypes in the genus Bradyrhizobium based upon recA sequence analyses. By multilocus sequence analysis (MLSA) of five housekeeping genes (dnaK, glnII, gyrB, recA, and rpoB), the 41 strains representing different recA haplotypes were classified into nine defined species and nine novel genospecies. Bradyrhizobium elkanii, Bradyrhizobium ferriligni, and Bradyrhizobium pachyrhizi were the predominant and universally distributed groups. The phylogeny of symbiotic genes of nodC and nifH showed similar topology and phylogenetic relationships, in which all the representative strains were classified into two clades grouped with strains nodulating with Vigna spp., demonstrating that Vigna spp. shared common nodulating groups in the natural environment. All the representative strains formed nodules with V. minima in a nodulation test performed in green house conditions. The correlation between V. minima nodulating rhizobia and soil characteristics analyzed by CANOCO indicates that available nitrogen, total nitrogen, and organic carbon in the soil samples were the main factors affecting the distribution of rhizobia isolated in this study. This study systematically uncovered the biodiversity and distribution characteristics of V. minima nodulating rhizobia for the first time, which provided novel information for the formation of the corresponding rhizobium community.


Identification of Enantiomeric Byproducts During Microalgae-Mediated Transformation of Metoprolol by MS/MS Spectrum Based Networking.

  • Min Lv‎ et al.
  • Frontiers in microbiology‎
  • 2018‎

Metoprolol (MPL) is a chiral β-blocker ubiquitously detected in various environments due to its low to moderate removal in wastewater treatment plants. This study was conducted to test the potential of using microalgae to degrade emerging contaminant MPL and to characterize the enantiomeric enrichment during MPL degradation by microalgae. The results showed that PO43-- P, NO3-- N and MPL could be simultaneously removed in the synthetic effluent by the targeted microalgae species, indicating microalgae were promising in wastewater treatment. Stereoselectivity was observed during MPL degradation by microalgae, with R-form enrichment. A marginal linear relationship between MPL degradation and enantiomeric enrichment was observed, implying that the enantiomeric tool, used as a quantitative indicator of biodegradation, could possibly be applied in MPL degradation by microalgae. An efficient liquid chromatograph tandem high resolution mass spectrometry (LC-HRMS/MS) chiral analytical method was developed to identify transformation products (TPs). The results showed that MS/MS spectral similarity networking could be used as a powerful tool to quickly identify unknown TPs. A total of 6 pairs of chiral TPs were identified, among which two new TPs of MPL including hydroxy{4-[2-hydroxy-3-(isopropylamino)propoxy]phenyl}acetic acid (α-HMPLA) and 4-[2-Hydroxy-3-(isopropylamino)propoxy]benzaldehyde (DMPLD) were firstly reported, and proposed transformation pathways of MPL by microalgae were given. Considering the paired TPs detected and that the degradation of the two enantiomers followed first order kinetics, the two enantiomers likely had the same degradation mechanism.


TLR3 Regulated Poly I:C-Induced Neutrophil Extracellular Traps and Acute Lung Injury Partly Through p38 MAP Kinase.

  • Tingting Gan‎ et al.
  • Frontiers in microbiology‎
  • 2018‎

Acute lung injury (ALI) is the leading cause of morbidity and mortality in critically ill patients. Neutrophil extracellular traps (NETs) have been well documented in the ALI model of bacterial infection. In the present study, we demonstrated that poly I:C could induce pulmonary NETs. Upon poly I:C intratracheal inoculation, neutrophil infiltration in the bronchoalveolar lavage fluid (BALF) was significantly increased. Furthermore, the inflammatory cytokines IL-1β, IL-6, and TNF-α in the lung were also significantly elevated. Neutrophil depletion abolished NETs and decreased both neutrophil infiltration and IL-1β in the lung. As expected, DNase I, an inhibitor of MPO and NADPH, decreased pulmonary inflammation and NETs. Blocking of the poly I:C receptor TLR3 reduced lung inflammation and NETs. The MAPK kinase inhibitor p38 diminished the formation of NETs and restored the expression of the tight junction protein claudin-5 in the mouse lung when challenged with poly I:C. In summary, poly I:C induced the formation of pulmonary NETs and ALI, which may be associated with the activation of p38 MAPK and the decreased expression of claudin-5.


An Exogenous Surfactant-Producing Bacillus subtilis Facilitates Indigenous Microbial Enhanced Oil Recovery.

  • Peike Gao‎ et al.
  • Frontiers in microbiology‎
  • 2016‎

This study used an exogenous lipopeptide-producing Bacillus subtilis to strengthen the indigenous microbial enhanced oil recovery (IMEOR) process in a water-flooded reservoir in the laboratory. The microbial processes and driving mechanisms were investigated in terms of the changes in oil properties and the interplay between the exogenous B. subtilis and indigenous microbial populations. The exogenous B. subtilis is a lipopeptide producer, with a short growth cycle and no oil-degrading ability. The B. subtilis facilitates the IMEOR process through improving oil emulsification and accelerating microbial growth with oil as the carbon source. Microbial community studies using quantitative PCR and high-throughput sequencing revealed that the exogenous B. subtilis could live together with reservoir microbial populations, and did not exert an observable inhibitory effect on the indigenous microbial populations during nutrient stimulation. Core-flooding tests showed that the combined exogenous and indigenous microbial flooding increased oil displacement efficiency by 16.71%, compared with 7.59% in the control where only nutrients were added, demonstrating the application potential in enhanced oil recovery in water-flooded reservoirs, in particular, for reservoirs where IMEOR treatment cannot effectively improve oil recovery.


Differential Proteomic Profiles of Pleurotus ostreatus in Response to Lignocellulosic Components Provide Insights into Divergent Adaptive Mechanisms.

  • Qiuyun Xiao‎ et al.
  • Frontiers in microbiology‎
  • 2017‎

Pleurotus ostreatus is a white rot fungus that grows on lignocellulosic biomass by metabolizing the main constituents. Extracellular enzymes play a key role in this process. During the hydrolysis of lignocellulose, potentially toxic molecules are released from lignin, and the molecules are derived from hemicellulose or cellulose that trigger various responses in fungus, thereby influencing mycelial growth. In order to characterize the mechanism underlying the response of P. ostreatus to lignin, we conducted a comparative proteomic analysis of P. ostreatus grown on different lignocellulose substrates. In this work, the mycelium proteome of P. ostreatus grown in liquid minimal medium with lignin, xylan, and carboxymethyl cellulose (CMC) was analyzed using the complementary two-dimensional gel electrophoresis (2-DE) approach; 115 proteins were identified, most of which were classified into five types according to their function. Proteins with an antioxidant function that play a role in the stress response were upregulated in response to lignin. Most proteins involving in carbohydrate and energy metabolism were less abundant in lignin. Xylan and CMC may enhanced the process of carbohydrate metabolism by regulating the level of expression of various carbohydrate metabolism-related proteins. The change of protein expression level was related to the adaptability of P. ostreatus to lignocellulose. These findings provide novel insights into the mechanisms underlying the response of white-rot fungus to lignocellulose.


Soybean continuous cropping affects yield by changing soil chemical properties and microbial community richness.

  • Yan Li‎ et al.
  • Frontiers in microbiology‎
  • 2022‎

In agroecosystems, different cropping patterns cause changes in soil physicochemical properties and thus in microbial communities, which in turn affect crop yields. In this study, the yields of soybean continuous cropping for 5 years (C5), 10 years (C10), and 20 years (C20) and of soybean-corn rotational cropping (R) treatments were determined, and samples of the tillage layer soil were collected. High-throughput sequencing technology was used to analyze the diversity and composition of the soil bacterial and fungal communities. The factors influencing microbial communities, along with the effects of these communities and those of soil chemical indexes on yield, were further evaluated. The results showed that the community richness index of bacteria was higher in C20 than in R and that of fungi was highest in C5. The differences in the bacterial and fungal communities diversity indexes were not significant among the different continuous cropping treatments, respectively. The soil microbial community composition of all continuous cropping treatments differed significantly from R. The dominant bacterial phylum was Actinobacteriota and the dominant fungal phylum was Ascomycota. The relative abundance of Fusarium did not differ significantly among the continuous cropping treatments, while that of the plant pathogen fungi Lectera sp., Plectosphaerella sp., and Volutella sp. increased with continuous cropping years. Soil pH, SOM, N, and TP had significant effects on both bacterial and fungal communities, and TK and C/N had highly significant effects on fungal communities. The yield of C5 was significantly lower than that of R, and the differences in yield between C10, C20, and R were not significant. TN, TP, and pH had significant effects on yield, and fungal community abundance had a greater negative effect on yield than bacterial community abundance.


Emergence of Carbapenem- and Tigecycline-Resistant Proteus cibarius of Animal Origin.

  • Yan Li‎ et al.
  • Frontiers in microbiology‎
  • 2020‎

The emergence of tet(X) and carbapenemase genes in Enterobacterales pose significant challenges to the treatment of infectious diseases. Convergence of these two categories of genes in an individual pathogen would deteriorate the antimicrobial resistance (AMR) crisis furthermore. Here, tigecycline-resistant Enterobacterales strains were isolated and detected with carbapenemase genes, characterized by antimicrobial susceptibility testing, PCR, conjugation assay, whole genome sequencing, and bioinformatics analysis. Three tigecycline-resistant isolates consisting of one plasmid-mediated tet(X4)-bearing Escherichia fergusonii and two chromosomal tet(X6)-bearing Proteus cibarius were recovered from chicken feces. The tet(X4) was located on a conjugative IncX1 plasmid pHNCF11W-tetX4 encoding the identical structure as reported tet(X4)-bearing IncX1 plasmids in Escherichia coli. Among two P. cibarius strains, tet(X6) was located on two similar chromosomal MDR regions with genetic contexts IS26-aac(3)-IVa-aph(4)-Ia-ISEc59-tnpA-tet(X6)-orf-orf-ISCR2-virD2-floR-ISCR2-glmM-sul2 and IS26-aac(3)-IVa-aph(4)-Ia-ISEc59-tnpA-tet(X6)-orf-orf-ISCR2-glmM-sul2. Apart from tet(X6), P. cibarius HNCF44W harbored a novel transposon Tn6450b positive for bla NDM- 1 on a conjugative plasmid. This study probed the genomic basis of three tet(X)-bearing, tigecycline-resistant strains, one of which coharbored bla NDM- 1 and tet(X6), and identified P. cibarius as the important reservoir of tet(X6) variants. Emergence of P. cibarius encoding both bla NDM- 1 and tet(X6) reveals a potential public health risk.


Notch Signaling Ligand Jagged1 Enhances Macrophage-Mediated Response to Helicobacter pylori.

  • Junjie Wen‎ et al.
  • Frontiers in microbiology‎
  • 2021‎

Helicobacter pylori (H. pylori) is one of the gram-negative bacteria that mainly colonize the stomach mucosa and cause many gastrointestinal diseases, such as gastritis, peptic ulcer, and gastric cancer. Macrophages play a key role in eradicating H. pylori. Recent data have shown that Notch signaling could modulate the activation and bactericidal activities of macrophages. However, the role of Notch signaling in macrophages against H. pylori remains unclear. In the present study, in the co-culture model of macrophages with H. pylori, the inhibition of Notch signaling using γ-secretase decreased the expression of inducible nitric oxide synthase (iNOS) and its product, nitric oxide (NO), and downregulated the secretion of pro-inflammatory cytokine and attenuated phagocytosis and bactericidal activities of macrophages to H. pylori. Furthermore, we identified that Jagged1, one of Notch signaling ligands, was both upregulated in mRNA and protein level in activated macrophages induced by H. pylori. Clinical specimens showed that the number of Jagged1+ macrophages in the stomach mucosa from H. pylori-infected patients was significantly higher than that in healthy control. The overexpression of Jagged1 promoted bactericidal activities of macrophages against H. pylori and siRNA-Jagged1 presented the opposite effect. Besides, the addition of exogenous rJagged1 facilitated the pro-inflammatory mediators of macrophages against H. pylori, but the treatment of anti-Jagged1 neutralizing antibody attenuated it. Taken together, these results suggest that Jagged1 is a promoting molecule for macrophages against H. pylori, which will provide insight for exploring Jagged1 as a novel therapeutic target for the control of H. pylori infection.


Long non-coding RNA expression in PBMCs of patients with active pulmonary tuberculosis.

  • Guoli Li‎ et al.
  • Frontiers in microbiology‎
  • 2023‎

Mycobacterium tuberculosis (Mtb) infection is the primary cause of the chronic infectious illness tuberculosis (TB). Long non-coding RNAs (lncRNAs) are functional RNA molecules that cannot be translated into proteins and play a crucial role in regulating the immune system's innate and adaptive responses. It has been demonstrated that the dysregulation of lncRNA expression is associated with various human diseases. However, the mechanism underlying the involvement of so many lncRNAs in the immune response to TB infection remains unclear. The objective of our current study was to identify a number of significantly differentially expressed lncRNAs in peripheral blood mononuclear cells (PBMCs) from TB patients and to select the most indicative lncRNAs as potential biomarkers for active pulmonary tuberculosis.


Genome Sequencing of Streptomyces atratus SCSIOZH16 and Activation Production of Nocardamine via Metabolic Engineering.

  • Yan Li‎ et al.
  • Frontiers in microbiology‎
  • 2018‎

The Actinomycetes are metabolically flexible microorganisms capable of producing a wide range of interesting compounds, including but by no means limited to, siderophores which have high affinity for ferric iron. In this study, we report the complete genome sequence of marine-derived Streptomyces atratus ZH16 and the activation of an embedded siderophore gene cluster via the application of metabolic engineering methods. The S. atratus ZH16 genome reveals that this strain has the potential to produce 26 categories of natural products (NPs) barring the ilamycins. Our activation studies revealed S. atratus SCSIO ZH16 to be a promising source of the production of nocardamine-type (desferrioxamine) compounds which are important in treating acute iron intoxication and performing ecological remediation. We conclude that metabolic engineering provides a highly effective strategy by which to discover drug-like compounds and new NPs in the genomic era.


Metagenomic Study Suggests That the Gut Microbiota of the Giant Panda (Ailuropoda melanoleuca) May Not Be Specialized for Fiber Fermentation.

  • Wei Guo‎ et al.
  • Frontiers in microbiology‎
  • 2018‎

Bamboo-eating giant panda (Ailuropoda melanoleuca) is an enigmatic species, which possesses a carnivore-like short and simple gastrointestinal tract (GIT). Despite the remarkable studies on giant panda, its diet adaptability status continues to be a matter of debate. To resolve this puzzle, we investigated the functional potential of the giant panda gut microbiome using shotgun metagenomic sequencing of fecal samples. We also compared our data with similar data from other animal species representing herbivores, carnivores, and omnivores from current and earlier studies. We found that the giant panda hosts a bear-like gut microbiota distinct from those of herbivores indicated by the metabolic potential of the microbiome in the gut of giant pandas and other mammals. Furthermore, the relative abundance of genes involved in cellulose- and hemicellulose-digestion, and enrichment of enzymes associated with pathways of amino acid degradation and biosynthetic reactions in giant pandas echoed a carnivore-like microbiome. Most significantly, the enzyme assay of the giant panda's feces indicated the lowest cellulase and xylanase activity among major herbivores, shown by an in-vitro experimental assay of enzyme activity for cellulose and hemicellulose-degradation. All of our results consistently indicate that the giant panda is not specialized to digest cellulose and hemicellulose from its bamboo diet, making the giant panda a good mammalian model to study the unusual link between the gut microbiome and diet. The increased food intake of the giant pandas might be a strategy to compensate for the gut microbiome functions, highlighting a strong need of conservation of the native bamboo forest both in high- and low-altitude ranges to meet the great demand of bamboo diet of giant pandas.


Biocontrol of Bacterial Fruit Blotch by Bacillus subtilis 9407 via Surfactin-Mediated Antibacterial Activity and Colonization.

  • Haiyan Fan‎ et al.
  • Frontiers in microbiology‎
  • 2017‎

In this study, Bacillus subtilis 9407 showed a strong antibacterial activity against Acidovorax citrulli in vitro and 61.7% biocontrol efficacy on melon seedlings 4 days post inoculation under greenhouse conditions. To understand the biocontrol mechanism of B. subtilis 9407, identify the primary antibacterial compound and determine its role in controlling bacterial fruit blotch (BFB), a srfAB deletion mutant (ΔsrfAB) was constructed. The ΔsrfAB which was deficient in production of surfactin, not only showed almost no ability to inhibit growth of A. citrulli but also decreased biofilm formation and reduced swarming motility. Colonization assay demonstrated that B. subtilis 9407 could conlonize on melon roots and leaves in a large population, while ΔsrfAB showed a four- to ten-fold reduction in colonization of melon roots and leaves. Furthermore, a biocontrol assay showed that ΔsrfAB lost the biocontrol efficacy. In summary, our results indicated that surfactin, which consists of C13- to C16-surfactin A was the primary antibacterial compound of B. subtilis 9407, and it played a major role in biofilm formation, swarming motility, colonization and suppressing BFB. We propose that the biocontrol activity of B. subtilis 9407 is the results of the coordinated action of surfactin-mediated antibacterial activity and colonization. This study reveals for the first time that the use of a B. subtilis strain as a potential biological control agent could efficiently control BFB by producing surfactin.


Bacterial Profiling and Dynamic Succession Analysis of Phlebopus portentosus Casing Soil Using MiSeq Sequencing.

  • Rui-Heng Yang‎ et al.
  • Frontiers in microbiology‎
  • 2019‎

Phlebopus portentosus (Berk. and Broome) Boedijin is a popular edible mushroom found in China and Thailand. To date, P. portentosus is the only species in the order Boletales that can be successfully cultivated worldwide. The use of a casing layer or casing soil overlaying the substrate is a crucial step in the production of this mushroom. In this study, bacterial profiling and dynamic succession analyses of casing soil during the cultivation of P. portentosus were performed. One hundred and fifty samples were collected, and MiSeq sequencing of the V3-V4 region of the 16S rRNA gene was conducted. After performing a decontamination procedure, only 38 samples were retained, including 6 casing soil-originated samples (OS), 6 casing soil samples (FHCS) and 5 upper substrate samples (FHCU) from the period of complete colonization by mycelia; 6 casing soil samples (PCS) and 5 upper substrate samples (PCU) from the primordium period; and 6 casing soil samples (FCS) and 4 upper substrate samples (FCU) from fruit body period. The results revealed that bacterial diversity increased sharply from the hyphal to the primordium stage and then decreased during harvesting. The non-metric multidimensional scaling (NMDS) ordination and analysis of similarities (ANOSIM) analysis suggested that the community composition during different stages was significantly different in casing soil. The most abundant phyla in all of the samples were Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Saccharibacteria, and Bacteroidetes. Burkholderia was the most abundant genus in all the samples except the OS samples. The relative abundance of Burkholderia in the FHCS samples (55.79%) decreased to 35.14% in the PCS samples and then increased to 45.60% in the FCS samples. The abundances of Acidobacterium, Rhizobium, Acidisphaera, Bradyrhizobium, and Bacillus increased from the FHCS to PCS samples. The linear discriminant analysis (LDA) effect size (LEfSe) suggested that Acidobacterium and Acidisphaera are micromarkers for PCS, whereas Bradyrhizobium, Roseiarcus, and Pseudolabrys were associated with fruit body stages. The network analyses resulted in 23 edges, including 4 negative and 19 positive edges. Extensive mutualistic interactions may occur among casing soil bacteria. Furthermore, these bacteria play important roles in mycelial elongation, primordium formations, and the production of increased yields.


Genomic Investigation of Antimicrobial-Resistant Salmonella enterica Isolates From Dead Chick Embryos in China.

  • Mohammed Elbediwi‎ et al.
  • Frontiers in microbiology‎
  • 2021‎

Salmonella spp. is recognized as an important zoonotic pathogen. The emergence of antimicrobial resistance in Salmonella enterica poses a great public health concern worldwide. While the knowledge on the incidence and the characterization of different S. enterica serovars causing chick embryo death remains obscure in China. In this study, we obtained 45 S. enterica isolates from 2,139 dead chick embryo samples collected from 28 breeding chicken hatcheries in Henan province. The antimicrobial susceptibility assay was performed by the broth microdilution method and the results showed that 31/45 (68.8%) isolates were multidrug-resistant (≥3 antimicrobial classes). Besides the highest resistance rate was observed in the aminoglycoside class, all the isolates were susceptible to chloramphenicol, azithromycin, and imipenem. Furthermore, genomic characterization revealed that S. Enteritidis (33.33%; 15/45) was a frequent serovar that harbored a higher number of virulence factors compared to other serovars. Importantly, genes encoding β-lactamases were identified in three serovars (Thompson, Enteritidis, and Kottbus), whereas plasmid-mediated quinolone resistance genes (qnrB4) were detected in certain isolates of S. Thompson and the two S. Kottbus isolates. All the examined isolates harbored the typical virulence factors from Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2). Additionally, a correlation analysis between the antimicrobial resistance genes, phenotype, and plasmids was conducted among Salmonella isolates. It showed strong positive correlations (r < 0.6) between the different antimicrobial-resistant genes belonging to certain antimicrobial classes. Besides, IncF plasmid showed a strong negative correlation (r > -0.6) with IncHI2 and IncHI2A plasmids. Together, our study demonstrated antimicrobial-resistant S. enterica circulating in breeding chicken hatcheries in Henan province, highlighting the advanced approach, by using genomic characterization and statistical analysis, in conducting the routine monitoring of the emerging antimicrobial-resistant pathogens. Our findings also proposed that the day-old breeder chicks trading could be one of the potential pathways for the dissemination of multidrug-resistant S. enterica serovars.


Hydrated lime promoted the polysaccharide content and affected the transcriptomes of Lentinula edodes during brown film formation.

  • Yan Li‎ et al.
  • Frontiers in microbiology‎
  • 2023‎

Brown film formation, a unique developmental stage in the life cycle of Lentinula edodes, is essential for the subsequent development of fruiting bodies in L. edodes cultivation. The pH of mushroom growth substrates are usually adjusted with hydrated lime, yet the effects of hydrated lime on cultivating L. edodes and the molecular mechanisms associated with the effects have not been studied systemically. We cultivated L. edodes on substrates supplemented with 0% (CK), 1% (T1), 3% (T2), and 5% (T3) hydrated lime (Ca (OH)2), and applied transcriptomics and qRT-PCR to study gene expression on the brown film formation stage. Hydrated lime increased polysaccharide contents in L. edodes, especially in T2, where the 5.3% polysaccharide content was approximately 1.5 times higher than in the CK. The addition of hydrated lime in the substrate promoted laccase, lignin peroxidase and manganese peroxidase activities, implying that hydrated lime improved the ability of L. edodes to decompose lignin and provide nutrition for its growth and development. Among the annotated 9,913 genes, compared to the control, 47 genes were up-regulated and 52 genes down-regulated in T1; 73 genes were up-regulated and 44 were down-regulated in T2; and 125 genes were up-regulated and 65 genes were down-regulated in T3. Differentially expressed genes (DEGs) were enriched in the amino acid metabolism, lipid metabolism and carbohydrate metabolism related pathways. The carbohydrate-active enzyme genes up-regulated in the hydrated lime treatments were mostly glycosyl hydrolase genes. The results will facilitate future optimization of L. edodes cultivation techniques and possibly shortening the production cycle.


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