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排序方式: 共有545条查询结果,搜索用时 31 毫秒
71.
Patrick Heritier-Robbins Smruthi Karthikeyan Janet K. Hatt Minjae Kim Markus Huettel Joel E. Kostka Konstantinos T. Konstantinidis Luis M. Rodriguez-R 《The ISME journal》2021,15(11):3418
The specialization-disturbance hypothesis predicts that, in the event of a disturbance, generalists are favored, while specialists are selected against. This hypothesis has not been rigorously tested in microbial systems and it remains unclear to what extent it could explain microbial community succession patterns following perturbations. Previous field observations of Pensacola Beach sands that were impacted by the Deepwater Horizon (DWH) oil spill provided evidence in support of the specialization-disturbance hypothesis. However, ecological drift as well as uncounted environmental fluctuations (e.g., storms) could not be ruled out as confounding factors driving these field results. In this study, the specialization-disturbance hypothesis was tested on beach sands, disturbed by DWH crude oil, ex situ in closed laboratory advective-flow chambers that mimic in situ conditions in saturated beach sediments. The chambers were inoculated with weathered DWH oil and unamended chambers served as controls. The time series of shotgun metagenomic and 16S rRNA gene amplicon sequence data from a two-month long incubation showed that functional diversity significantly increased while taxonomic diversity significantly declined, indicating a decrease in specialist taxa. Thus, results from this laboratory study corroborate field observations, providing verification that the specialization-disturbance hypothesis can explain microbial succession patterns in crude oil impacted beach sands.Subject terms: Microbial ecology, Community ecology 相似文献
72.
Arumugam Karthikeyan 《Symbiosis (Philadelphia, Pa.)》2017,72(2):89-94
Impact of different levels of elevated CO 2 on the activity of Frankia (Nitrogen-fixing actinomycete) in Casuarina equisetifolia rooted stem cuttings has been studied to understand the relationship between C. equisetifolia, Frankia and CO2. The stem cuttings of C. equietifolia were collected and treated with 2000 ppm of Indole Butyric Acid (IBA) for rooting. Thus vegetative propagated rooted stem cuttings of C. equisetifolia were inoculated with Frankia and placed in the Open top chambers (OTC) with elevated CO2 facilities. These planting stocks were maintained in the OTC for 12 months under different levels of elevated CO2 (ambient control, 600 ppm, 900 ppm). After 12 months, the nodule numbers, bio mass, growth, and photosynthesis of C. equisetifolia rooted stem cuttings inoculated with Frankia were improved under 600 ppm of CO2. The rooted stem cuttings of C. equisetifolia inoculated with Frankia showed a higher number of nodules under 900 ppm of CO2 and cuttings without Frankia inoculation exhibited poor growth. Tissue Nitrogen (N) content was also higher under 900 ppm of CO2 than ambient control and 600 ppm levels. The photosynthetic rate was higher (17.8 μ mol CO2 m?2 s?1) in 900 ppm of CO2 than in 600 ppm (13.2 μ mol CO2 m?2 s?1) and ambient control (8.3 μ mol CO2 m?2 s?1). This study showed that Frankia can improve growth, N fixation and photosynthesis of C. equietifolia rooted stem cuttings under extreme elevated CO2 level conditions (900 ppm). 相似文献
73.
Soybean mosaic virus (SMV) is one of the most devastating pathogens for soybeans in China. Among the country-wide 22 strains, SC5 dominates in Huang-Huai and Changjiang valleys. For controlling its damage, the resistance gene was searched through Mendelian inheritance study, gene fine-mapping, and candidate gene analysis combined with qRT-PCR (quantitative real-time polymerase chain reaction) analysis. The parents F1, F2, and RILs (recombinant inbred lines) of the cross Kefeng-1 (Resistance, R)?×?NN1138-2 (Susceptible, S) were used to examine the inheritance of SC5-resistance. The F1 was resistant and the F2 and RILs segregated in a 3R:1S and 1R:1S ratio, respectively, indicating a single dominant gene conferring the Kefeng-1 resistance. Subsequently, the genomic region conferring the resistance was found in “Bin 352–Bin353 with 500 kb” on Chromosome 2 using the phenotyping data of the 427 RILs and a high-density genetic map with 4703 bin markers. In the 500 kb genomic region, 38 putative genes are contained. The association analysis between the SNPs in a putative gene and the resistance phenotype for the 427 RILs prioritized 11 candidate genes using Chi-square criterion. The expression levels of these genes were tested by qRT-PCR. On infection with SC5, 7 out of the 11 genes had differential expression in Kefeng-1 and NN1138-2. Furthermore, integrating SNP-phenotype association analysis with qRT-PCR expression profiling analysis, Glyma02g13495 was found the most possible candidate gene for SC5-resistance. This finding can facilitate the breeding for SC5-resistance through marker-assisted selection and provide a platform to gain a better understanding of SMV-resistance gene system in soybean. 相似文献
74.
Inter-organellar communication and interactions are necessary and accepted consequences of the segregation of biochemical functions into subcellular organelles. Recently, Heidi McBride and her collaborators found a novel link between mitochondria and peroxisomes in their discovery of mitochondria-derived vesicles (MDVs), which appear to fuse with a fraction of pre-existing peroxisomes in mammalian cells. We discuss the potential role of this vesicle population in the context of pathways for the exchange of metabolites and/or macromolecules between these compartments. 相似文献
75.
Subramanian Vedhanarayanan Karthikeyan Subbu Perumal Krithika Arun Shetty Perumal Yogeeswari Dharmarajan Sriram 《Bioorganic & medicinal chemistry letters》2009,19(11):3006-3009
A series of novel 2-aryl-3,4-dihydro-2H-thieno[3,2-b]indoles has been synthesised regioselectively in good yields from the reaction of 5-aryldihydro-3(2H)-thiophenones and arylhydrazine hydrochloride. This reaction is found to be assisted by microwaves. The thieno[3,2-b]indoles were evaluated for their in vitro activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant M. tuberculosis (MDR-TB). Among 22 compounds screened, [2-(2,4-dichlorophenyl)-7-fluoro-3,4-dihydro-2H-thieno[3,2-b]indole] (6t) was found to the most active compound with MIC of 0.4 μg/mL against MTB and MDR-TB. 相似文献
76.
Taras Y. Nazarko Jean-Claude Farré Suresh Subramani 《Molecular biology of the cell》2009,20(17):3828-3839
Autophagy is a major pathway of intracellular degradation mediated by formation of autophagosomes. Recently, autophagy was implicated in the degradation of intracellular bacteria, whose size often exceeds the capacity of normal autophagosomes. However, the adaptations of the autophagic machinery for sequestration of large cargos were unknown. Here we developed a yeast model system to study the effect of cargo size on the requirement of autophagy-related (Atg) proteins. We controlled the size of peroxisomes before their turnover by pexophagy, the selective autophagy of peroxisomes, and found that peroxisome size determines the requirement of Atg11 and Atg26. Small peroxisomes can be degraded without these proteins. However, Atg26 becomes essential for degradation of medium peroxisomes. Additionally, the pexophagy-specific phagophore assembly site, organized by the dual interaction of Atg30 with functionally active Atg11 and Atg17, becomes essential for degradation of large peroxisomes. In contrast, Atg28 is partially required for all autophagy-related pathways independent of cargo size, suggesting it is a component of the core autophagic machinery. As a rule, the larger the cargo, the more cargo-specific Atg proteins become essential for its sequestration. 相似文献
77.
Subramani Ramesh Mahalingam Rajesh Narayanasamy Mathivanan 《Bioprocess and biosystems engineering》2009,32(6):791-800
Totally 191 different marine actinomycetes were isolated from 256 different marine samples collected from the Bay of Bengal
and its associated Pulicat lake and Pichavaram mangrove, India. Among them, 157 produced caseinase, 113 produced gelatinase
and 108 produced both the protease enzymes. An isolate coded as MML1614 was selected for further study as it exhibited high
proteolytic activity. The MML1614 was identified as Streptomyces fungicidicus based on polyphasic taxonomical approach including 16S rRNA sequence analysis. The culture conditions were standardized for
the growth and protease production in S. fungicidicus MML1614. The protease was isolated from a 6-day-old culture filtrate of S. fungicidicus MML1614 and partially purified up to 4.5-fold. The protease was optimally active at pH 9 and 40 °C and it was stable up to
pH 11 and 60 °C. PMSF and NaCl inhibited the enzyme activity up to 22 and 11%, respectively. The partially purified protease
removed the blood stain more effectively when combined with different detergents than the detergents alone. 相似文献
78.
Palanisamy Jayakumar Esaki Muthu Shankar Murugesan Karthikeyan 《Bioscience Hypotheses》2009,2(5):282-285
Immune reconstitution inflammatory syndrome (IRIS) is an inflammatory manifestation that occurs subsequent to initiation of highly active antiretroviral therapy in terminal (HAART) HIV infection, mainly due to the restoration of robust immune responses directed against latent microbial antigens. IRIS is believed to be multifactorial and less studied. Herein, we postulate that hypothalamo-pituitary-adrenal (HPA) dysregulation, a well-documented manifestation in HIV/AIDS, could possibly disturb the balance between pro-inflammatory and anti-inflammatory cytokines leading to clinical IRIS. Drugs, opportunistic infections, stress and numerous intrinsic and extrinsic factors have been described to be the possible causes of IRIS in HIV illness. 相似文献
79.
80.
Krishnamoorthy Venkateskumar Subramani Parasuraman Raju Gunasunderi Krishnan Sureshkumar M. Muralidhar Nayak Syed Adnan Ali Shah Khassen Khoo Heng Wei Kai 《AAPS PharmSciTech》2017,18(6):2085-2094
The dissolution and subsequent oral bioavailability of acyclovir (ACY) is limited by its poor aqueous solubility. An attempt has been made in this work to provide mechanistic insights into the solubility enhancement and dissolution of ACY by using the water-soluble carrier polyethylene glycol 6000 (PEG6000). Solid dispersions with varying ratios of the drug (ACY) and carrier (PEG6000) were prepared and evaluated by phase solubility, in vitro release studies, kinetic analysis, in situ perfusion, and in vitro permeation studies. Solid state characterization was done by powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) analysis, and surface morphology was assessed by polarizing microscopic image analysis, scanning electron microscopy, atomic force microscopy, and nuclear magnetic resonance analysis. Thermodynamic parameters indicated the solubilization effect of the carrier. The aqueous solubility and dissolution of ACY was found to be higher in all samples. The findings of XRD, DSC, FTIR and NMR analysis confirmed the formation of solid solution, crystallinity reduction, and the absence of interaction between the drug and carrier. SEM and AFM analysis reports ratified the particle size reduction and change in the surface morphology in samples. The permeation coefficient and amount of ACY diffused were higher in samples in comparison to pure ACY. Stability was found to be higher in dispersions. The results suggest that the study findings provided clear mechanical insights into the solubility and dissolution enhancement of ACY in PEG6000, and such findings could lay the platform for resolving the poor aqueous solubility issues in formulation development. 相似文献