Flagellum

Summary

A flagellum (fləˈdʒɛləm; : flagella) (Latin for 'whip' or 'scourge') is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates. A microorganism may have from one to many flagella. A gram-negative bacterium Helicobacter pylori for example uses its multiple flagella to propel itself through the mucus lining to reach the stomach epithelium, where it may cause a gastric ulcer to develop. In some bacteria the flagellum can also function as a sensory organelle, being sensitive to wetness outside the cell. Across the three domains of Bacteria, Archaea, and Eukaryota the flagellum has a different structure, protein composition, and mechanism of propulsion but shares the same function of providing motility. The Latin word flagellum means "whip" to describe its lash-like swimming motion. The flagellum in archaea is called the archaellum to note its differ

Official source

https://en.wikipedia.org/wiki/Flagellum

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Mechanism of DegU-dependent activation of flagellar gene transcription in Listeria monocytogenes

Diane Baer

Flagellar motility is an important process for bacterial survival. It allows bacteria to move to aquire nutrients or to retreat from unfavorable environments. In the Gram-positive bacterium Listeria monocytogenes, flagellar motility is a temperature-dependent process, being restricted to temperatures below 37°C. This regulation is mediated by the activities of the DegU response regulator, the MogR transcriptional repressor and GmaR, the MogR antirepressor. Transcriptional regulation of the fliN-gmaR promoter is central to flagellar motility regulation as pfliN-gmaR is transcriptionally activated by DegU and is also MogR repressed. However, the mechanism by which DegU mediates transcriptional activation of the fliN-gmaR promoter is not well understood. In this study, we further investigated the mechanisms controlling transcription initiating at the fliN-gmaR promoter by performing two comprehensive transposon mutagenesis screens to identify any additional factors involved in the activation and repression of pfliN-gmaR. The mutagenesis screen performed at 30°C to identify factors involved in pfliN-gmaR transcriptional activation led to the identification of a novel factor. We demonstrated that Lmo0866, a protein from the DEAD-box protein family, is required for transcriptional activation of pfliN-gmaR and therefore flagellar motility. Moreover, we identified CodY as being involved in the repression of pfliN-gmaR at 37°C.

2010

The observation that the membranes of flagella are enriched in sterols and sphingolipids has led to the hypothesis that flagella might be enriched in raft-forming lipids. However, a detailed lipidomic analysis of flagellar membranes is not available. Novel protocols to detach and isolate intact flagella from Trypanosoma brucei procyclic forms in combination with reverse-phase liquid chromatography high-resolution tandem mass spectrometry allowed us to determine the phospholipid composition of flagellar membranes relative to whole cells. Our analyses revealed that phosphatidylethanolamine, phosphatidylserine, ceramide and the sphingolipids inositol phosphorylceramide and sphingomyelin are enriched in flagella relative to whole cells. In contrast, phosphatidylcholine and phosphatidylinositol are strongly depleted in flagella. Within individual glycerophospholipid classes, we observed a preference for ether-type over diacyl-type molecular species in membranes of flagella. Our study provides direct evidence for a preferential presence of raft-forming phospholipids in flagellar membranes of T. brucei.

Company Of Biologists Ltd2015

Mutations in the polyglutamylase geneTTLL5, expressed in photoreceptor cells and spermatozoa, are associated with cone-rod degeneration and reduced male fertility

Hereditary retinal degenerations encompass a group of genetic diseases characterized by extreme clinical variability. Following next-generation sequencing and autozygome-based screening of patients presenting with a peculiar, recessive form of cone-dominated retinopathy, we identified five homozygous variants [p.(Asp594fs), p.(Gln117*), p.(Met712fs), p.(Ile756Phe), and p.(Glu543Lys)] in the polyglutamylase-encoding gene TTLL5, in eight patients from six families. The two male patients carrying truncating TTLL5 variants also displayed a substantial reduction in sperm motility and infertility, whereas those carrying missense changes were fertile. Defects in this polyglutamylase in humans have recently been associated with cone photoreceptor dystrophy, while mouse models carrying truncating mutations in the same gene also display reduced fertility in male animals. We examined the expression levels of TTLL5 in various human tissues and determined that this gene has multiple viable isoforms, being highly expressed in testis and retina. In addition, antibodies against TTLL5 stained the basal body of photoreceptor cells in rat and the centrosome of the spermatozoon flagellum in humans, suggesting a common mechanism of action in these two cell types. Taken together, our data indicate that mutations in TTLL5 delineate a novel, allele-specific syndrome causing defects in two as yet pathogenically unrelated functions, reproduction and vision.

Oxford University Press2016