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Lopez-Siles M Khan TM Duncan SH Harmsen HJ Garcia-Gil LJ Flint HJ 《Applied and environmental microbiology》2012,78(2):420-428
Faecalibacterium prausnitzii is one of the most abundant commensal bacteria in the healthy human large intestine, but information on genetic diversity and substrate utilization is limited. Here, we examine the phylogeny, phenotypic characteristics, and influence of gut environmental factors on growth of F. prausnitzii strains isolated from healthy subjects. Phylogenetic analysis based on the 16S rRNA sequences indicated that the cultured strains were representative of F. prausnitzii sequences detected by direct analysis of fecal DNA and separated the available isolates into two phylogroups. Most F. prausnitzii strains tested grew well under anaerobic conditions on apple pectin. Furthermore, F. prausnitzii strains competed successfully in coculture with two other abundant pectin-utilizing species, Bacteroides thetaiotaomicron and Eubacterium eligens, with apple pectin as substrate, suggesting that this species makes a contribution to pectin fermentation in the colon. Many F. prausnitzii isolates were able to utilize uronic acids for growth, an ability previously thought to be confined to Bacteroides spp. among human colonic anaerobes. Most strains grew on N-acetylglucosamine, demonstrating an ability to utilize host-derived substrates. All strains tested were bile sensitive, showing at least 80% growth inhibition in the presence of 0.5 μg/ml bile salts, while inhibition at mildly acidic pH was strain dependent. These attributes help to explain the abundance of F. prausnitzii in the colonic community but also suggest factors in the gut environment that may limit its distribution. 相似文献
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M Tanweer Khan Sylvia H Duncan Alfons J M Stams Jan Maarten van Dijl Harry J Flint Hermie J M Harmsen 《The ISME journal》2012,6(8):1578-1585
Faecalibacterium prausnitzii is one of the most abundant bacteria in the human gut ecosystem and it is an important supplier of butyrate to the colonic epithelium. Low numbers of faecalibacteria have been associated with inflammatory bowel disease. Despite being extremely oxygen sensitive, F. prausnitzii is found adherent to the gut mucosa where oxygen diffuses from epithelial cells. This paradox is now explained on the basis of gas tube experiments, flavin-dependent reduction of 5,5′-dithiobis-2-nitrobenzoate and microbial fuel cell experiments. The results show that F. prausnitzii employs an extracellular electron shuttle of flavins and thiols to transfer electrons to oxygen. Both compounds are present in the healthy human gut. Our observations may have important implications for the treatment of patients with Crohn''s disease, for example, with flavin- or antioxidant rich diets, and they provide a novel key insight in host–microbe interactions at the gut barrier. 相似文献
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ZxAKT1 is essential for K+ uptake and K+/Na+ homeostasis in the succulent xerophyte Zygophyllum xanthoxylum
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Qing Ma Jing Hu Xiang‐Rui Zhou Hui‐Jun Yuan Tanweer Kumar Sheng Luan Suo‐Min Wang 《The Plant journal : for cell and molecular biology》2017,90(1):48-60
The inward‐rectifying K+ channel AKT1 constitutes an important pathway for K+ acquisition in plant roots. In glycophytes, excessive accumulation of Na+ is accompanied by K+ deficiency under salt stress. However, in the succulent xerophyte Zygophyllum xanthoxylum, which exhibits excellent adaptability to adverse environments, K+ concentration remains at a relatively constant level despite increased levels of Na+ under salinity and drought conditions. In this study, the contribution of ZxAKT1 to maintaining K+ and Na+ homeostasis in Z. xanthoxylum was investigated. Expression of ZxAKT1 rescued the K+‐uptake‐defective phenotype of yeast strain CY162, suppressed the salt‐sensitive phenotype of yeast strain G19, and complemented the low‐K+‐sensitive phenotype of Arabidopsis akt1 mutant, indicating that ZxAKT1 functions as an inward‐rectifying K+ channel. ZxAKT1 was predominantly expressed in roots, and was induced under high concentrations of either KCl or NaCl. By using RNA interference technique, we found that ZxAKT1‐silenced plants exhibited stunted growth compared to wild‐type Z. xanthoxylum. Further experiments showed that ZxAKT1‐silenced plants exhibited a significant decline in net uptake of K+ and Na+, resulting in decreased concentrations of K+ and Na+, as compared to wild‐type Z. xanthoxylum grown under 50 mm NaCl. Compared with wild‐type, the expression levels of genes encoding several transporters/channels related to K+/Na+ homeostasis, including ZxSKOR, ZxNHX, ZxSOS1 and ZxHKT1;1, were reduced in various tissues of a ZxAKT1‐silenced line. These findings suggest that ZxAKT1 not only plays a crucial role in K+ uptake but also functions in modulating Na+ uptake and transport systems in Z. xanthoxylum, thereby affecting its normal growth. 相似文献
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Phosphatase Activity Toward Abnormally Phosphorylated τ: Decrease in Alzheimer Disease Brain 总被引:1,自引:0,他引:1
Cheng-Xin Gong Sadia Shaikh Jian-Zhi Wang Tanweer Zaidi Inge Grundke-Iqbal Khalid Iqbal 《Journal of neurochemistry》1995,65(2):732-738
Abstract: Microtubule-associated protein τ is abnormally hyperphosphorylated and aggregated in affected neurons of Alzheimer disease brain. This hyperphosphorylated τ can be dephosphorylated at some of the abnormal phosphorylated sites by purified protein phosphatase-1, 2A, and 2B in vitro. In the present study, we have developed an assay to measure protein phosphatase activity toward τ-1 sites (Ser199 /Ser202 ) using the hyperphosphorylated τ isolated from Alzheimer disease brain as substrate. Using this assay, we have identified that in normal brain, protein phosphatase-2A and 2B and, to a lesser extent, 1 are involved in the dephosphorylation of τ. The K m values of dephosphorylation of the hyperphosphorylated τ by protein phosphatase-2A and 2B are similar. The τ phosphatase activity is decreased by ∼30% in brain of Alzheimer disease patients compared with those of age-matched controls. These findings suggest that a defect of protein phosphatase could be the cause of the abnormal hyperphosphorylation of τ in Alzheimer disease. 相似文献
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Cristina Landeta Laura McPartland Ngoc Q. Tran Brian M. Meehan Yifan Zhang Zaidi Tanweer Shoko Wakabayashi Jeremy Rock Taehyun Kim Deepak Balasubramanian Rebecca Audette Melody Toosky Jessica Pinkham Eric J. Rubin Stephen Lory Gerald Pier Dana Boyd Jon Beckwith 《Molecular microbiology》2019,111(4):918-937
In bacteria, disulfide bonds confer stability on many proteins exported to the cell envelope or beyond, including bacterial virulence factors. Thus, proteins involved in disulfide bond formation represent good targets for the development of inhibitors that can act as antibiotics or anti‐virulence agents, resulting in the simultaneous inactivation of several types of virulence factors. Here, we present evidence that the disulfide bond forming enzymes, DsbB and VKOR, are required for Pseudomonas aeruginosa pathogenicity and Mycobacterium tuberculosis survival respectively. We also report the results of a HTS of 216,767 compounds tested against P. aeruginosa DsbB1 and M. tuberculosis VKOR using Escherichia coli cells. Since both P. aeruginosa DsbB1 and M. tuberculosis VKOR complement an E. coli dsbB knockout, we screened simultaneously for inhibitors of each complemented E. coli strain expressing a disulfide‐bond sensitive β ‐galactosidase reported previously. The properties of several inhibitors obtained from these screens suggest they are a starting point for chemical modifications with potential for future antibacterial development. 相似文献
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Kamaluddin Rishi Muni Singh Malik Zainul Abdin Mather Ali Khan Tanweer Alam Salim Khan Lal Chand Prasad Arun Kumar Joshi 《Journal of Plant Biology》2007,50(4):504-507
To understand the genetic control of grain filling duration (GFD), i.e., the number of days from anthesis to physiological
maturity, we studied the F1, F2, BC1 and BC2 generations of six spring wheat crosses from nine varieties/genotypes. Generation mean analysis for gene effects indicated
that one or more types of epistasis were significant in all crosses. In each pairing, the F1 and F2 means were either intermediate or closer to the mean of the parent having the longer GFD. Our narrow-sense heritability estimate
was reasonably high, at 47.67 (based on diallel analysis). This demonstrated that progress could be made from the selection
in these crosses for either long or short GFD. The two early varieties that had identical maturity durations differed in their
GFD values, indicating that maturity dates are not good criteria when choosing parents for modifying GFD. To utilize favorable
additive × additive effects during this selection, we suggest that a single seed descent (SSD) or bulk popula-tion approach
be adopted. In comparison, dominance effects would prove quite useful in hybrid wheat breeding programs. 相似文献
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Mihaela Gadjeva Jill Nagashima Tanweer Zaidi Robert A. Mitchell Gerald B. Pier 《PLoS pathogens》2010,6(3)
Pseudomonas aeruginosa causes severe sight-threatening corneal infections, with the inflammatory response to the pathogen being the major factor resulting in damage to the cornea that leads to loss of visual acuity. We found that mice deficient for macrophage migration inhibitory factor (MIF), a key regulator of inflammation, had significantly reduced consequences from acute P. aeruginosa keratitis. This improvement in the outcome was manifested as improved bacterial clearance, decreased neutrophil infiltration, and decreased inflammatory responses when P. aeruginosa-infected MIF knock out (KO) mice were compared to infected wild-type mice. Recombinant MIF applied to infected corneas restored the susceptibility of MIF deficient mice to P. aeruginosa-induced disease, demonstrating that MIF is necessary and sufficient to cause significant pathology at this immune privileged site. A MIF inhibitor administered during P. aeruginosa-induced infection ameliorated the disease-associated pathology. MIF regulated epithelial cell responses to infection by enhancing synthesis of proinflammatory mediators in response to P. aeruginosa infection and by promoting bacterial invasion of corneal epithelial cells, a correlate of virulence in the keratitis model. Our results uncover a host factor that elevates inflammation and propagates bacterial cellular invasion, and further suggest that inhibition of MIF during infection may have a beneficial therapeutic effect. 相似文献