ABSTRACT Deep sequencing has revolutionized our understanding of the bacterial RNA world and has facilitated the identification of 280 small RNAs (sRNAs) in Salmonella . Despite the suspicions that sRNAs may play important roles in Salmonella pathogenesis, the functions of most sRNAs remain unknown. To advance our understanding of RNA biology in Salmonella virulence, we searched for sRNAs required for bacterial invasion into nonphagocytic cells. After screening 75 sRNAs, we discovered that the ablation of InvS caused a significant decrease of Salmonella invasion into epithelial cells. A proteomic analysis showed that InvS modulated the levels of several type III secreted Salmonella proteins. The level of PrgH, a type III secretion apparatus protein, was significantly lower in the absence of InvS, consistent with the known roles of PrgH in effector secretion and bacterial invasion. We discovered that InvS modulates fimZ expression and hence flagellar gene expression and motility. We propose that InvS coordinates the increase of PrgH and decrease in FimZ that promote efficient Salmonella invasion into nonphagocytic cells. IMPORTANCE Salmonellosis continues to be the most common foodborne infection reported by the CDC in the United States. Central to Salmonella pathogenesis is the ability to invade nonphagocytic cells and to replicate inside host cells. Invasion genes are known to be regulated by protein transcriptional networks, but little is known about the role played by small RNAs (sRNAs) in this process. We have identified a novel sRNA, InvS, that is involved in Salmonella invasion. Our result will likely provide an opportunity to better understand the fundamental question of how Salmonella regulates invasion gene expression and may inform strategies for therapeutic intervention.
Abstract The intracellular K + level in bacteria is strictly controlled by K + uptake and efflux systems. Among these, KdpFABC is a high-affinity K + transporter system that is generally activated by the KdpDE two-component system in response to K + limitation stress. However, the regulatory mechanism remains obscure in bacteria lacking the kdpDE genes. Here we report that the transcription of a kdpFABC operon is distinctively regulated by a cyclic diadenylate monophosphate (c-di-AMP) riboswitch located at the 5′-untranslated region of kdp transcript, and binding of c-di-AMP to the riboswitch promotes its intrinsic termination that blocks the kdpFABC transcription. Further, the intracellular c-di-AMP concentration was found to decrease under the K + limitation stress, leading to transcriptional read-through over the terminator to allow kdpFABC expression. This regulatory element is found predominantly in the Bacillus cereus group and correlate well with the K + and c-di-AMP homeostasis that affects a variety of crucial cellular functions.
Intracellular pH critically affects various biological processes, and an appropriate cytoplasmic pH is essential for ensuring bacterial growth. Glucose is the preferred carbon source for most heterotrophs; however, excess glucose often causes the accumulation of acidic metabolites, lowering the intracellular pH and inhibiting bacterial growth.
ABSTRACT Cyclic dimeric adenosine 3′,5′-monophosphate (c-di-AMP) is an emerging second messenger in bacteria and archaea that is synthesized from two molecules of ATP by diadenylate cyclases and degraded to pApA or two AMP molecules by c-di-AMP-specific phosphodiesterases. Through binding to specific protein- and riboswitch-type receptors, c-di-AMP regulates a wide variety of prokaryotic physiological functions, including maintaining the osmotic pressure, balancing central metabolism, monitoring DNA damage and controlling biofilm formation and sporulation. It mediates bacterial adaptation to a variety of environmental parameters and can also induce an immune response in host animal cells. In this review, we discuss the phylogenetic distribution of c-di-AMP-related enzymes and receptors and provide some insights into the various aspects of c-di-AMP signaling pathways based on more than a decade of research. We emphasize the key role of c-di-AMP in maintaining bacterial osmotic balance, especially in Gram-positive bacteria. In addition, we discuss the future direction and trends of c-di-AMP regulatory network, such as the likely existence of potential c-di-AMP transporter(s), the possibility of crosstalk between c-di-AMP signaling with other regulatory systems, and the effects of c-di-AMP compartmentalization. This review aims to cover the broad spectrum of research on the regulatory functions of c-di-AMP and c-di-AMP signaling pathways.
Objective To investigate the alteration of the level of senesence-associated β-galactosidase(SA-β-Gal) in the replicative senescence of normal human diploid fibroblasts(HDF). Methods Specimens were taken for cell culture, the aging process was displayed by growth curve of cell line and β-galactosidase histochemical staining. Results The expression of SA-β-Gal tended to be more apparent in old cells(60% postitive cells)than in young cells(4% positive cells). Conclusion The present result might provide experimental data for establishing fibroblast senescent aging model in vitro.
The development of oil cells in stem, leaf, flower and seed of Magnolia denudata was studied with the methods of paraffine section and semithin section. The results indicate that oil cells initiate in the same pattern from all the organs examined. Oil cell initials are easily identified from the tissue arounded by their densely cytoplasm, bigger and apparent nucleus and low vacuolization. With the gradual vacuolization of the oil cell, a large vacuole is formed. After the oil cell reaches its fully maturity, the cytoplasm and the nucleus are disintegrated. So the whole volume of the oil cell is filled by the large vacuole, which becomes oil sac finially.In some oil cells,the cupule can be observed, but the occurance of lysis cavaties from oil cells raported by other authors is not found. In addition,the development steps of oil cells are not consistent with those of the structure of organs and they are distributed. Plate 1, Ref 10
Takes the case of Protel 99se and Protel DXP, This paper studies the different operational approach and process of global edit function. The circuit designer will do hundreds of the same operations one by one .The operations are very bald.The global edit function mentioned in this paper, which will greatly enhance work rate and reduce product development cycle. The method has solve the problem, it could amend the attribute of the same groupware.
Objective To investigate the alteration of the ultrastructure of fibroblasts isolated from human skin. Methods Fibroblasts from human normal skin were taken for successive cell culture. The aging processs was displayed by phase reverse microscope and ultrastructure observed by transmission electron microscope. Results Cells below 45 passages proliferated rapidly, those from 45 to 60 passages grew slowly gradually and those beyond 61 passages showed significant senescence. No significant change in ultrastructure was observed in cells below 40 passages, but great alteration was found beyond 41 passages. Conclusion Fibroblasts before 40 passages are suitable for seeds cells for skin tissue engineering.
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