Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FLAGELLATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,225 records · Page 68Linked to original sources
PubMed2002

Can phosphorus limitation inhibit dissolved organic carbon consumption in aquatic microbial food webs? A study of three food web structures in microcosms.

Microcosms with three different food web structures and phosphorus (P) limited growth medium were used to study the interactions between P and organic carbon (C) fractions in pelagic food webs. The cultures were run with low dilution to allow the biological processes to determine the outcome. A double isotope technique was used to follow the C and P compartments. In all systems the primary production was P limited. The measured P:C ratios and the observed accumulation of degradable dissolved organic carbon (DOC) indicated that the growth of heterotrophic bacteria was also P limited. The presence of neither algal grazers nor flagellates feeding on bacteria altered the limitation pattern. A net loss of P from the bacterial fraction was observed after the bloom. Different strategies for nutrient aquisition and growth are proposed as mechanisms enabling simultaneous P limitation of algae and bacteria, and a concomitant accumulation of degradable DOC. The ability of the algae to grow with low P:C ratio keeps the regeneration of P through grazers low enough to cause sustained P limitation of both algae and bacteria. The grazers were important producers of DOC when present. This implies that the usual assumption of carbon limited bacterial growth may lead to wrong conclusions regarding the dynamics of plankton communities and the DOC pool.

Animals↗
PubMed2005

Phage bacteriolysis, protistan bacterivory potential, and bacterial production in a freshwater reservoir: coupling with temperature.

Phage abundance and infection of bacterioplankton were studied from March to November 2003 in the Sep Reservoir (Massif Central, France), together with temperature, chlorophyll, bacteria (abundance and production), and heterotrophic nanoflagellates (abundance and potential bacterivory). Virus abundance (VA) ranged from 0.6 to 13 x 10(10) viruses l(-1), exceeding bacterial abundance (BA) approximately sixfold on average. In terms of carbon, viruses corresponded to up to 25% of bacterial biomass. A multiple regression model indicated that BA was the best predictor for VA (R(2) = 0.75). The frequency of infected bacteria (estimated from the percentage of visibly infected cells) varied from 1% to 32% and was best explained by a combination of temperature (R(2) = 0.20) and bacterial production (R(2) = 0.25). Viruses and flagellates contributed about equally to bacterial mortality. Both factors destroyed 55% of bacterial production, with a shift from phage bacteriolysis in early spring to protistan bacterivory in late summer. The vertical differences in most of the biological variables were not significant, contrasting with the seasonal differences (i.e., spring vs. summer-autumn). All biological variables under study were indeed significantly coupled to temperature. We regarded this to be the consequence of the enhanced discharge of the reservoir in 2003 (compared to previous years). This substantially weakened the stability and the thermal inertia of the water column, thereby establishing temperature as a stronger forcing factor in setting the conditions for optimal metabolic activity of microbial communities.

Bacteria↗
PubMed2004

Effects of small-scale turbulence on bacteria: a matter of size.

We examined the influence of small-scale turbulence and its associated shear on bacterioplankton abundance and cell size. We incubated natural microbial assemblages and bacteria-only fractions and subjected them to treatments with turbulence and additions of mineral nutrients and/or organic carbon. Bacterial abundance was not affected directly by turbulence in bacteria-only incubations. In natural microbial assemblage incubations, bacterial concentrations were higher under turbulence than in still-water controls when nutrients were added. In general, in the turbulence treatments bacteria increased significantly in size, mainly due to elongation of cells. The addition of inorganic nutrients had a negative effect on bacterial size, but a significantly positive effect on abundance independently of other factors such as turbulence and the presence of predators. Flagellate grazing did not trigger an increase in bacterial size as a grazing resistance response in unmixed containers. With the addition of organic carbon, bacteria elongated and partly settled to the bottom of the containers, in both the turbulent and still treatment, but bacterial abundance did not further increase. Furthermore, bacteria aggregated in the turbulence treatments after the second day of incubation even in the absence of other components of the microbial community. We found that turbulence and the associated shear increase bacterial size and change bacterial morphology, at least under certain nutrient conditions. This might be due to a physiological response (enhanced growth rate and/or unbalanced growth) or due to the selection of opportunistic strains when organic carbon is in excess compared to mineral nutrients. We suggest that shear associated with turbulent flow enhances the DOM flux to bacteria directly as well as indirectly through enhanced grazing activity and photosynthetic release. The formation of bacterial aggregates and filaments under turbulence might give selective advantage to bacteria in terms of nutrient uptake and grazing resistance.

Bacteria↗
PubMed2004

Annual patterns in bacterioplankton community variability in a humic lake.

Bacterioplankton community composition (BCC) was monitored in a shallow humic lake in northern Wisconsin, USA, over 3 years using automated ribosomal intergenic spacer analysis (ARISA). Comparison of ARISA profiles of bacterial communities over time indicated that BCC was highly variable on a seasonal and annual scale. Nonmetric multidimensional scaling (MDS) analysis indicated little similarity in BCC from year to year. Nevertheless, annual patterns in bacterioplankton community diversity were observed. Trends in bacterioplankton community diversity were correlated to annual patterns in community succession observed for phytoplankton and zooplankton populations, consistent with the notion that food web interactions affect bacterioplankton community structure in this humic lake. Bacterioplankton communities experience a dramatic drop in richness and abundance each year in early summer, concurrent with an increase in the abundance of both mixotrophic and heterotrophic flagellates. A second drop in richness, but not abundance, is observed each year in late summer, coinciding with an intense bloom of the nonphagotrophic dinoflagellate Peridinium limbatum. A relationship between bacterial community composition, size, and abundance and the population dynamics of Daphnia was also observed. The noted synchrony between these major population and species shifts suggests that linkages across trophic levels play a role in determining the annual time course of events for the microbial and metazoan components of the plankton.

Bacterial Physiological Phenomena↗
PubMed2006

Feeding characteristics of an amoeba (Lobosea: Naegleria) grazing upon cyanobacteria: food selection, ingestion and digestion progress.

Bacterivory by heterotrophic nanoflagellates and ciliates has been widely studied in aquatic environments, but data on the grazing of amoebae, are still scarce. From the water samples of Dianchi Lake (Kunming, Yunnan Province, China), we isolated an amoeba, designated as Naegleria sp. strain W2, which had potent grazing effects on some kind of cyanobacteria. The food selection mechanism and the digestion process of the amoeba were investigated in batch experiments. Predation experiments showed that filamentous cyanobacteria (e.g., Anabaena, Cylindrospermum, Gloeotrichia, and Phormidium) were readily consumed, with clearance rates ranging from 0.332 to 0.513 nL amoeba(-1) h(-1). The tight threads (Oscilltoria) and aggregates (Aphanizomenon) could not be ingested; however, their sonicated fragments were observed inside food vacuoles, suggesting that their morphologies prevent them from being ingested. Live video microscopy noted that unicellular Chroococcaceae (e.g., Synechococcus, Aphanocapsa, and Microcystis) were excreted after ingestion, indicating that food selection takes place inside food vacuoles. To determine whether the tastes or the toxins prevented them from being digested, heat-killed cells were retested for predation. Digestion rates and ingestion rates of the amoebae for filamentous cyanobacteria were estimated from food vacuole content volume. Through a "cold-chase" method, we found that the food vacuole contents declined exponentially in diluted amoebae cells, and digestion rates were relatively constant, averaging about 1.5% food vacuole content min(-1) at 28 degrees Celsius. Ingestion strongly depended on the satiation status of the amoebae, starved amoebae fed at higher rates compared with satiated amoebae. Our results suggest that the food selection and food processing mechanisms of the amoeba are similar to those of interception feeding flagellates; however, filamentous cyanobacteria cannot obtain a refuge under the grazing pressure of phagotrophic amoebae, which may widen our knowledge on the grazing of protists.

Amoeba↗
PubMed2000

Bacterioplankton Production in Humic Lake Örträsket in Relation to Input of Bacterial Cells and Input of Allochthonous Organic Carbon.

In order to compare riverine bacteria input with lake water bacterial production and grazing loss with output loss, a bacterial cell budget was constructed for humic Lake Örträsket in northern Sweden. The riverine input of bacterial cells in 1997 represented 29% of the number of bacterial cells produced within the layer of the lake affected by inlet water. A large share of the in situ lake bacterial production was consumed by grazers, mainly flagellates, which stresses the importance of bacteria as energy mobilizers for the pelagic food web in the lake. The bacterial production in Lake Örträsket, which is almost entirely dependent on humic material as an energy source, was clearly stimulated by high flow episodes which brought high amounts of little degraded material into the lake. During base flow condition the bacterial production in the inlet rivers was high, which led to an input of more degraded material to the lake. This material did not stimulate the lake bacterial production. Internal factors that determined the utilization of the allochthonous DOC in the lake were the retention time and the exposure to light and high temperatures. Thus, the potential for in situ production of bacteria in Lake Örträsket was to a large extent a function of how precipitation and runoff conditions affected terrestrial losses and river transport of humic material.

Journal Article↗
PubMed2001

Effects of Additions of DOC on Pelagic Biota in a Clearwater System: Results from a Whole Lake Experiment in Northern Sweden.

An oligotrophic clearwater lake, initially characterized by a pronounced dominance of autotrophic phytoplankton and mostly by one species, the green alga Botryococcus, was subject to additions of dissolved organic carbon in the form of white sugar (sucrose) during two consecutive years. The hypothesis tested was that it is organic carbon per se, and not other possible effects of humic substances, that determines the differences in structure of the planktonic ecosystem between humic and clearwater lakes. The additions of DOC resulted in a significant increase in bacterial biomass and a decrease in the biomass of autotrophic phytoplankton. The biomass of mixotrophic and heterotrophic flagellates instead increased significantly, whereas no effects were found to propagate to higher trophic levels. As a result of the changes among biota, total planktonic biomass also decreased to a level typical of nearby humic lakes. We suggest that it is the carbon component of humic material and its utilization by bacterioplankton that determines the structure and function of the pelagic food web in humic lakes.

Journal Article↗
PubMed2000

Molecular and functional characterization of a fish inducible-type nitric oxide synthase.

Using an oligonucleotide primer based on a partial goldfish inducible nitric oxide synthase (iNOS) sequence, a complete carp iNOS cDNA was isolated from an activated carp phagocyte cDNA library. Nucleotide and predicted amino acid sequence analysis indicate that carp iNOS encodes a 1,127-amino acid protein with 57% sequence identity to human iNOS. Like mammalian NOSs, carp iNOS protein contains putative binding sites for heme, tetrahydrobiopterin, calmodulin, flavine mononucleotide, flavine adenine dinucleotide, and NADPH. Phylogenetic analysis, using neighbor joining, showed that the carp iNOS protein clustered together with the other vertebrate iNOS proteins. Inducibility of carp iNOS was confirmed by reverse transcription-polymerase chain reaction after stimulation of carp phagocytes with lipopolysaccharide or the protozoan blood flagellate Trypanoplasma borreli. These stimulators produced high amounts of nitric oxide that were toxic for T. borreli in vitro. The nuclear transcription factor NF-kappaB was shown to play a role in the induction of iNOS transcription.

Amino Acid Sequence↗
PubMed2005

Characterization of a novel beta-agarase from marine Alteromonas sp. SY37-12 and its degrading products.

The phenotypic and agarolytic features of an unidentified marine bacteria isolated from the southern ocean of China was studied. The strain was gram-negative, aerobic, and polarly flagellated. It was identified as the genus Alteromonas according to its morphological and physiological characterization. In solid agar, the isolate produced a diffusible agarase that caused agar softening around the colonies. An extracellular agarase was purified by the procedure of ammonium sulfate precipitation, gel filtration on Sephacryl S-100HR, and ion-exchange chromatography on diethylaminoethyl-Sepharose. The purified protein exhibited a single band on SDS-PAGE with a molecular mass of 39.5 kDa. The enzyme hydrolyzed the beta-1,4-glycosidic linkages of agar, yielding neoagarotetraose and neoagarohexaose as the main products. The optimum reaction temperature of the agarase was 35 degrees C, with a narrow range from 30 to 45 degrees C. The enzyme activity reached the maximum at pH 7.0 and in the presence of 2% NaCl. Molecular mass and degrading products showed that the agarase from Alteromonas sp. SY 37-12 was much different from those previously reported.

Alteromonas↗
PubMed2026

Pseudaquabacterium prasiolae sp. nov., Isolated from the Freshwater Green Alga Prasiola japonica, and Rubrivivax soli sp. nov., Isolated from Soil, with Reclassification of Aquabacterium humicola as Pseudaquabacterium humicola comb. nov.

Two Gram-stain-negative, catalase- and oxidase-positive, strictly aerobic, non-flagellated rod-shaped bacteria, designated OR-4T and RP6-9T, were isolated from the freshwater green alga Prasiola japonica and soil in Republic of Korea, respectively. Strain OR-4T exhibited gliding motility, whereas strain RP6-9T lacked gliding motility. Strain OR-4T grew at 10-30 °C, pH 6.0-9.0, and 0-1.5% (w/v) NaCl, while strain RP6-9T grew at 20-35 °C, pH 6.0-9.0, and 0-1.0% (w/v) NaCl. Both strains contained ubiquinone-8 as the sole respiratory quinone and phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol as major polar lipids; strain OR-4T additionally possessed an unidentified phospholipid and an unidentified polar lipid. The predominant fatty acids of OR-4T were C12:0, C16:0, summed feature 3 (C16:1ω6c and/or C16:1ω7c), and summed feature 8 (C18:1ω7c and/or C18:1ω6c), whereas RP6-9T contained C12:0, C16:0, and summed feature 3 as major components. The genomic DNA G + C content of both strains was 71.0 mol%. Whole-genome-based phylogenomic analyses placed OR-4T and RP6-9T within the genera Pseudaquabacterium and Rubrivivax, respectively, forming distinct lineages. Comparative analyses of average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity further supported their assignment to these genera while confirming their separation from previously described species. Based on combined phenotypic, chemotaxonomic, and genomic evidence, strains OR-4T and RP6-9T represent novel species, for which the names Pseudaquabacterium prasiolae sp. nov. (type strain OR-4T =KACC 22752T =NBRC 116024T) and Rubrivivax soli sp. nov. (type strain RP6-9T =KACC 24055T =DSM 119932T) are proposed. Phylogenomic analyses also support the reclassification of Aquabacterium humicola as Pseudaquabacterium humicola comb. nov. (type strain RJY3T =KCTC 92105T =NBRC 115831T).

Phylogeny↗
PubMed2001

Developmentally regulated protein expression mediated by dimethylsulfoxide in Herpetomonas samuelpessoai.

We have analyzed the total cell extract, cell surface, and secretory protein profiles related to cellular differentiation triggered by dimethylsulfoxide in the insect trypanosomatid Herpetomonas samuelpessoai. The flagellates were cultivated in chemically defined conditions in the absence or in the presence of 4% DMSO, and the resolved protein bands were detected by SDS-PAGE gels and avidin-Western blotting. The cell-associated proteins showed a complex pattern of around 40 silver-staining bands ranging from 15 to 150 kDa. There were generally minor quantitative differences in the protein profile between the non-treated and the DMSO-treated cells. The cell-surface protein profile revealed by the incubation of live parasites with biotin showed a decrease in the expression of the 120 kDa biotinylated polypeptide observed in the DMSO-treated cells when compared with untreated ones. However, control samples of both systems showed an endogenous biotinylated polypeptide of 63 kDa which also presented gelatinolytic activity. The trypanosomatids released at least 10 polypeptides to the culture medium. A low molecular mass exopolypeptide (35 kDa) was found exclusively in untreated cells, whereas a high-molecular-mass exopolypetide (250 kDa) was preferentially found in DMSO-treated cells.

Animals↗
PubMed2000

Construction of a promoter-rescue plasmid for Butyrivibrio fibrisolvens and its use in characterization of a flagellin promoter.

The Butyrivibrio fibrisolvens/Escherichia coli shuttle vector pBHerm has been modified to produce a plasmid (pBHE) that can be used for the identification and characterization of promoters in B. fibrisolvens. pBHE allows the insertion of a test promoter immediately upstream of a promoterless erythromycin resistance gene (ermAM). The efficacy of the pBHE plasmid in isolating and characterizing promoters was tested by inserting the flagellin gene (flaA) promoter from B. fibrisolvens OR77. Transcription of the ermAM gene from the flaA promoter was significantly higher than that observed when the ermAM gene was under the control of its own promoter. The flagelling gene of OR77 appears to be transcribed from two different promoters that produce transcripts initiating approximately 130 bp apart. Two mutant flaA promoter constructs, containing mutations in the -10 and -35 regions of either of the two putative promoter regions, showed drastic alterations in both the origin and amounts of the two transcripts produced. Mutations in either promoter affected transcription from both promoters, indicating that both regions contribute to gene expression.

DNA, Bacterial↗
PubMed2001

Immunolocalization of tubulin isoforms and post-translational modifications in the protists Tritrichomonas foetus and Trichomonas vaginalis.

In the present report we show the distribution of multiple tubulin isoforms in Trichomonas vaginalis and Tritrichomonas foetus, flagellated parasitic protists of the urogenital tracts of human and cattle, respectively, using immunofluorescence and immunoelectron microscopy. We used several monoclonal and polyclonal anti-tubulin antibodies from different sources and recognizing variant tubulin isoforms. Our results demonstrate that: (1) there is a heterogeneous distribution of the different tubulin isoforms in the main microtubular cell structures, such as axostyle, flagella, basal bodies, and mitotic spindle, (2) the axostyle-pelta junction is a structure with high affinity for glutamylated tubulin antibodies in T. foetus, (3) the spindle labeling is positive to anti-glutamylated tubulin and anti-alpha-tubulin (TAT1 and purchased from Amersham) antibodies in T. vaginalis but it is negative in T. foetus, (4) the nuclear matrix and the cytosol presented positive reaction using glutamylated and TAT1 (anti-alpha-tubulin) antibodies only in T. vaginalis, and (5) the Golgi complex exhibited staining using the glutamylated tubulin antibody. The present data corroborate with the idea of the existence of a heterogeneous population of microtubules in these protists and of a subset of intracytoplasmic microtubules. Microtubule diversity may reflect distinct tubulins, diverse microtubule-associated proteins, or a combination of both.

Animals↗
PubMed2002

Integration of photo- and chemosensory signaling pathways in Chlamydomonas.

The behavior of Chlamydomonas reinhardtii Dangeard is regulated by both light and chemical stimuli. Generation of a transmembrane photoreceptor current is the earliest so far resolved event in phototaxis of green flagellates. Tryptone rapidly inhibits the photoreceptor current in gametes of C. reinhardtii and induces their accumulation. The time-course, concentration dependence and induction during gametogenesis of these two processes coincide. On the other hand, tryptone causes a weak stimulation of the photoreceptor current in the absence of any behavioral responses in vegetative cells. This shows that the tryptone-induced inhibition of the photoreceptor current in C. reinhardtii is due to activation of a gamete-specific chemosensory system, and that integration of the photo- and chemosensory signals already occurs at the initial steps of the signaling pathways.

Animals↗
PubMed2001

Chlorophyta exclusively use the 1-deoxyxylulose 5-phosphate/2-C-methylerythritol 4-phosphate pathway for the biosynthesis of isoprenoids.

The biosynthesis of the C5 building block of isoprenoids, isopentenyl diphosphate (IPP), proceeds in higher plants via two basically different pathways; in the cytosolic compartment sterols are formed via mevalonate (MVA), whereas in the plastids the isoprenoids are formed via the 1-deoxyxylulose 5-phosphate/2-C-methylerythritol 4-phosphate pathway (DOXP/MEP pathway). In the present investigation, we found for the Charophyceae, being close relatives to land plants, and in the original green flagellate Mesostignma virilde the same IPP biosynthesis pattern as in higher plants: sterols are formed via MVA, and the phytol-moiety of chlorophylls via the DOXP/MEP pathway. In contrast, representatives of four classes of the Chlorophyta (Chlorophyceae, Ulvophyceae, Trebouxiophyceae, Prasinophyceae) did not incorporate MVA into sterols or phytol. Instead, they incorporated [1-2H1]-1-deoxy-D-xylulose into phytol and sterols. The results indicate that the entire Chlorophyta lineage, which is well separated from the land plant/Charophyceae lineage, is devoid of the acetate/ MVA pathway and uses the DOXP/MEP pathway not only for plastidic, but also for cytosolic isoprenoid formation.

Carbon Radioisotopes↗
PubMed2002

The development of Blastocrithidia triatomae (Trypanosomatidae) in the reduviid bug Triatoma infestans (Insecta): influence of feeding.

The population density and composition of an established infection of Blastocrithidia triatomae in the intestinal tract of fifth instars of Triatoma infestans were compared in unfed bugs, at 4 h and up to 15 days after feeding, and also in feces and urine deposited in the first 4 h after feeding. In unfed bugs, about 1-2 million B. triatomae colonized the small intestine and rectum, mainly epimastigotes (85% and 80%, respectively). During excretion, the percentage of cysts increased within the first two drops (from 15% to 35%) and then decreased slowly, indicating a washing-out of these unattached stages. The initial reduction in the B. triatomae population lasted up to 6 days after feeding. By 15 days after feeding, the populations had strongly increased in the small intestine and rectum, to 22 million and 2 million flagellates, respectively, as had cysts, comprising some 50% of the total population in the rectum.

Animals↗
PubMed2003

Electron microscopic study of Tetratrichomonas didelphidis and its interaction with a prokaryotic cell.

Tetratrichomonas didelphidis is a flagellate protozoan found in the intestine of the opossum. The parasite lives in a hostile and stressed environment, where it interacts with microorganisms and can survive under extreme conditions for growth, involving strict anaerobiosis or equilibration with air and abundance or absence of nutrients. The in vitro cultivation of this protozoan depends upon Escherichia coli as a growth-promoting partner. In this study, we used scanning and transmission electron microscopy to observe the phagocytosis of bacteria by the protozoan, confirming the strong association between both cells and the growth dependence of T. didelphidis upon E. coli. After adherence to the protozoan surface, the bacteria induced the appearance of crater-like depressions and the ingested bacteria were intracellularly degraded.

Animals↗
PubMed2004

A trypanosome of Atlantic cod, Gadus morhua L., transmitted by the marine leech Calliobdella nodulifera (Malm, 1863) (Piscicolidae).

The fish leech, Calliobdella nodulifera, transmitted a trypanosome while feeding on laboratory-reared cod ( Gadus morhua). The flagellate body length increased from 43 microm 17 days post-infection (d.p.i.) to 57 microm 113 d.p.i. Characteristic features are cell striation, a nearly central nucleus and a short (3.5 microm) distance from the kinetoplast to the posterior end (PK). Following growth, the trypanosomes became increasingly slender, with fewer striae and a shorter flagellum, while the PK was unaffected. The trypanosomes differ morphologically from Trypanosoma murmanensis transmitted by the leech Johanssonia arctica.

Animals↗