SummaryThe suppressor mutation, named sfhC21, that allows Escherichia coli ftsH null mutant cells to survive was found to be an allele of fabZ encoding R-3-hydroxyacyl-ACP dehydrase, involved in a key step of fatty acid biosynthesis, and appears to upregulate the dehydrase. The ftsH1(Ts) mutation increased the amount of lipopolysaccharide at 42ЊC. This was accompanied by a dramatic increase in the amount of UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase [the lpxC (envA) gene product] involved in the committed step of lipid A biosynthesis. Pulse-chase experiments and in vitro assays with purified components showed that FtsH, the AAA-type membrane-bound metalloprotease, degrades the deacetylase. Genetic evidence also indicated that the FtsH protease activity for the deacetylase might be affected when acyl-ACP pools were altered. The biosynthesis of phospholipids and the lipid A moiety of lipopolysaccharide, both of which derive their fatty acyl chains from the same R-3-hydroxyacyl-ACP pool, is regulated by FtsH.

FtsH protein in Escherichia coli is an essential protein of 70.7 kDa (644 amino acid residues) with a putative ATP-binding sequence. Western blots (immunoblots) of proteins from fractionated cell extracts and immunoelectron microscopy of the FtsH-overproducing strain showed exclusive localization of the FtsH protein in the cytoplasmic membrane. Most of the FtsH-specific labeling with gold particles was observed in the cytoplasmic membrane and the adjacent cytoplasm; much less was observed in the outer membrane and in the bulk cytoplasm. Genetic analysis by TnphoA insertions intoftsH revealed that the 25-to 95-amino-acid region, which is flanked by two hydrophobic stretches, protrudes into the periplasmic space. From these results, we concluded that FtsH protein is an integral cytoplasmic membrane protein spanning the membrane twice and that it has a large cytoplasmic carboxy-terminal part with a putative ATP-binding domain. The average number of FtsH molecules per cell was estimated to be approximately 400.

Regulation of intracellular pH is critically important for many cellular functions. The quantification of proton extrusion in different types of cells and physiological conditions is pivotal to fully elucidate the mechanisms of pH homeostasis. Here we show the use of gold nanoparticles (AuNP) to create a high spatial resolution sensor for measuring extracellular pH in proximity of the cell membrane. We test the sensor on HepG2 liver cancer cells and MKN28 gastric cancer cells before and after inhibition of Na+/H+ exchanger. The gold surface conjugation strategy is conceived with a twofold purpose: i) to anchor the AuNP to the membrane proteins and ii) to quantify the local pH from AuNP using surface enhanced Raman spectroscopy (SERS). The nanometer size of the cell membrane anchored sensor and the use of SERS enable us to visualize highly localized variation of pH induced by H+ extrusion, which is particularly upregulated in cancer cells.

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The morphology and host-specificity of the histophagous apostome ciliate Vampyrophrya pelagica infecting pelagic copepods in the Seto Inland Sea, Japan, were intensively investigated. Four stages were reconfirmed in the life cycle of the ciliate. A mature cell within the phoront bears cilia ready for quick excystation, and unique lamellar structures in the cytoplasm appear to be precursors of food vacuole membranes. These lamellar structures completely disappear in the fully grown trophont. The phoronts were attached to the ventral surface of the copepod prosome or legs, but were almost totally absent on the urosome. The number of phoronts per copepod was up to 43 for the adult female of Paracalanus parvus s.l. Phoront attachment was found irrespective of developmental stage and sex of P. parvus s.l., although the early copepodid stages were less frequently infected than the later stages, and the adult female was more intensively infected than the adult male. There was a marked seasonal change in prevalence and host-specificity of the phoronts. From middle summer to early winter, P. parvus s.l., Acartia pacifica, Tortanus forcipatus, Euterpina acutifrons, and Corycaeus affinis were frequently infected, while Oithona spp. and Microsetella norvegica were rarely infected, whereas from late winter to early summer, phoronts were detected only on the large-sized calanoids, Calanus sinicus and Euchaeta plana. This may be explained by a combination of longevity and molting of copepods, turnover time of the apostome life cycle which depends on water temperature, and seasonal changes in the abundance and food selectivity of predatory chaetognaths. Considering the high prevalence of apostome ciliates on not only copepods but also other crustaceans in the world oceans, the ecological influence of these ciliates on marine ecosystems should be re-evaluated. KEY WORDS: Apostome ciliate· Vampyrophrya pelagica · Copepod · Parasite · Host · Histophagy · Trophodynamics Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 282: [129][130][131][132][133][134][135][136][137][138][139][140][141][142] 2004 are epibionts which live exclusively on the copepod body surface (Steuer 1932, Sewell 1951, Hiromi et al. 1985, Nagasawa 1986, Fernandez-Leborans & TatoPorto 2000.Apostome ciliates are known to infect a wide variety of marine and freshwater crustaceans including shallow-and deep-water copepods (Chatton & Lwoff, 1935, Sewell 1951, Kudo 1966, Lindley 1978, Grimes & Bradbury 1992, Ohtsuka et al. 2003. The complex, unique life cycle of the apostome ciliate Vampyrophrya pelagica (Chatton and Lwoff) on coastal copepods was elucidated by Grimes & Bradbury (1992). According to them, 4 functionally different stages are recognized in this apostome: phoront (resting stage), trophont (feeding stage), tomont (division stage), and tomite (infective stage). Excystation of the trophont is triggered either by injury to the host (single-host cycle) or by predation by invertebrate predators such as...

BackgroundEuglenophytes are a group of photosynthetic flagellates possessing a plastid derived from a green algal endosymbiont, which was incorporated into an ancestral host cell via secondary endosymbiosis. However, the impact of endosymbiosis on the euglenophyte nuclear genome is not fully understood due to its complex nature as a 'hybrid' of a non-photosynthetic host cell and a secondary endosymbiont.ResultsWe analyzed an EST dataset of the model euglenophyte Euglena gracilis using a gene mining program designed to detect laterally transferred genes. We found E. gracilis genes showing affinity not only with green algae, from which the secondary plastid in euglenophytes evolved, but also red algae and/or secondary algae containing red algal-derived plastids. Phylogenetic analyses of these 'red lineage' genes suggest that E. gracilis acquired at least 14 genes via eukaryote-to-eukaryote lateral gene transfer from algal sources other than the green algal endosymbiont that gave rise to its current plastid. We constructed an EST library of the aplastidic euglenid Peranema trichophorum, which is a eukaryovorous relative of euglenophytes, and also identified 'red lineage' genes in its genome.ConclusionsOur data show genome mosaicism in E. gracilis and P. trichophorum. One possible explanation for the presence of these genes in these organisms is that some or all of them were independently acquired by lateral gene transfer and contributed to the successful integration and functioning of the green algal endosymbiont as a secondary plastid. Alternative hypotheses include the presence of a phagocytosed alga as the single source of those genes, or a cryptic tertiary endosymbiont harboring secondary plastid of red algal origin, which the eukaryovorous ancestor of euglenophytes had acquired prior to the secondary endosymbiosis of a green alga.

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A colorless euglenoid flagellate Peranema trichophorum shows unique unidirectional gliding cell locomotion on the substratum at velocities up to 30 micro m/s by an as yet unexplained mechanism. In this study, we found that (1) treatment with NiCl(2) inhibited flagellar beating without any effect on gliding movement; (2) water currents applied to a gliding cell from opposite sides caused detachment of the cell body from the substratum. With only the anterior flagellum adhering to the substratum, gliding movement continued along the direction of the anterior flagellum; (3) gentle pipetting induced flagellar severance into various lengths. In these cells, gliding velocity was proportional to the flagellar length; and (4) Polystyrene beads were translocated along the surface of the anterior flagellum. All of these results indicate that a cell surface motility system is present on the anterior flagellum, which is responsible for cell gliding in P. trichophorum.