Flagellar Sensilla of Sphecodes Bees (Hymenoptera, Halictidae)

The antenna of Sphecodes bees were investigated as regards the type and distribution of the sensilla. Eleven species originating from Sweden were used. Totally 325 specimens were studied. The distribution of sensilla placodea and sensilla trichodea on the antennal segments were studied in the light stereomicroscope. One to three antennae per species were also examined by SEM. The following types of sensilla were found: s. placodea; pit organs; s. campaniformia; s. basiconica; s. trichodea A, B and CD; and setae. The distribution of sensilla, especially s. placodea and s. trichodea A, was found to be species-specific in the male sex and their diagnostic value in taxonomy is stressed. In the female sex no specific characteristics were found, although two groups could be distinguished.     

The DHC1b (DHC2) Isoform of Cytoplasmic Dynein Is Required for Flagellar Assembly

Dyneins are microtubule-based molecular motors involved in many different types of cell movement. Most dynein heavy chains (DHCs) clearly group into cytoplasmic or axonemal isoforms. However, DHC1b has been enigmatic. To learn more about this isoform, we isolated Chlamydomonas cDNA clones encoding a portion of DHC1b, and used these clones to identify a Chlamydomonas cell line with a deletion mutation in DHC1b. The mutant grows normally and appears to have a normal Golgi apparatus, but has very short flagella. The deletion also results in a massive redistribution of raft subunits from a peri-basal body pool (Cole, D.G., D.R. Diener, A.L. Himelblau, P.L. Beech, J.C. Fuster, and J.L. Rosenbaum. 1998. J. Cell Biol. 141:993–1008) to the flagella. Rafts are particles that normally move up and down the flagella in a process known as intraflagellar transport (IFT) (Kozminski, K.G., K.A. Johnson, P. Forscher, and J.L. Rosenbaum. 1993. Proc. Natl. Acad. Sci. USA. 90:5519–5523), which is essential for assembly and maintenance of flagella. The redistribution of raft subunits apparently occurs due to a defect in the retrograde component of IFT, suggesting that DHC1b is the motor for retrograde IFT. Consistent with this, Western blots indicate that DHC1b is present in the flagellum, predominantly in the detergent- and ATP-soluble fractions. These results indicate that DHC1b is a cytoplasmic dynein essential for flagellar assembly, probably because it is the motor for retrograde IFT.     

Flagellar apparatus ultrastructure inMesostigma viride (Prasinophyceae)

The ultrastructure of the flagellar apparatus ofMesostigma viride Lauterborn (Prasinophyceae) has been studied in detail with particular reference to absolute configurations, numbering of basal bodies, basal body triplets and flagellar roots. The two basal bodies are interconnected by three connecting fibers (one distal fiber = synistosome, and two proximal fibers). The flagellar apparatus shows 180° rotational symmetry; four microtubular flagellar roots and two system II fibers are present. The microtubular roots represent a 4-6-4-6-system. The left roots (1s, 2s) consist of 4 microtubules, each with the usual 3 over 1 root tubule pattern. Each right root (1d, 2d) is proximally associated with a small, but typical multi-layered structure (MLS). The latter displays several layers corresponding to the S₁ (the spline microtubules: 5–7), and presumably the S₂—S₄ (the lamellate layers) of the MLS of theCharophyceae. At its proximal origin (near the basal bodies) each right root originates with only two microtubules, the other spline microtubules being added more distally. The structural and positional information obtained in this study strongly suggest that one of the right roots (1d) ofMesostigma is homologous to the MLS-root of theCharophyceae and sperm cells of archegoniate land plants. Thus the typical cruciate flagellar root system of the green algae and the unilateral flagellar root system of theCharophyceae and archegoniates share a common ancestry. Some functional and phylogenetic aspects of MLS-roots are discussed.Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.     

Studies on the Nervous Regulation of the Heart Beat in Decapod Crustacea

The effect of electrical stimulation of cardioaccelerator and cardioinhibitor nerves on the mechanically recorded heart beat of crayfish was studied. Similar experiments were performed with the lobster, Homarus americanus. Quantitative relationships between uni- and bilateral accelerator and/or inhibitor nerve stimulation and the resulting change in frequency and amplitude of the heart beat were established. With increasing frequency of stimulation the accelerator nerves show a relative decrease in their action, while that of the inhibitor nerves increases. It appears that left and right regulator nerves have synaptic contacts at the same areas of the postsynaptic cells within the heart ganglion. Similar results are obtained whether all impulses arrive over one, or over the other, or over both accelerator (or inhibitor) nerves; the resulting acceleration or inhibition depends strictly on the number of accelerator, or inhibitor impulses arriving at the ganglion. The ganglion cells can adapt to the inhibitor action. This is shown to be a postsynaptic phenomenon. Adaptation to accelerator stimulation is virtually absent. Characteristic after-effects of the accelerator and inhibitor action were observed and quantitatively evaluated. The interpretation of the results is based on the assumption of chemical transmitter substances. It is concluded that the accelerating transmitter decays slowly while the inhibitory transmitter is inactivated relatively rapidly.     

Switching of Bacterial Flagellar Motors Is Triggered by Mutant FliG

Binding of the chemotaxis response regulator CheY-P promotes switching between rotational states in flagellar motors of the bacterium Escherichia coli. Here, we induced switching in the absence of CheY-P by introducing copies of a mutant FliG locked in the clockwise (CW) conformation (FliG^CW). The composition of the mixed FliG ring was estimated via fluorescence imaging, and the probability of CW rotation (CW_bias) was determined from the rotation of tethered cells. The results were interpreted in the framework of a 1D Ising model. The data could be fit by assuming that mutant subunits are more stable in the CW conformation than in the counterclockwise conformation. We found that CW_bias varies depending on the spatial arrangement of the assembled subunits in the FliG ring. This offers a possible explanation for a previous observation of hysteresis in the switch function in analogous mixed FliM motors—in motors containing identical fractions of mutant FliM^CW in otherwise wild-type motors, the CW_bias differed depending on whether mutant subunits were expressed in strains with native motors or native subunits were expressed in strains with mutant motors.     

Flagellar regeneration and associated scale deposition inPyramimonas gelidicola (Prasinophyceae,Chlorophyta)

Summary During regeneration of mechanically amputated flagella, flagellar scales and the subtending membrane accumulate in a villiform scale reservoir in which the scales interact to form patterns on the villi reminiscent of the arrangement they later assume on the flagellum. The reservoir membrane is continuous with the plasmalemma, and the scales, attached directly and indirectly to the membrane, leave the reservoir and migrate toward the developing flagella where they assemble into highly ordered layers. It is proposed that scale-scale interactions induce a process of auto-assembly initiating the complex arrangement of scale tiers on the flagellum and cell body.     

FlgM Is Secreted by the Flagellar Export Apparatus in Bacillus subtilis

The bacterial flagellum is assembled from over 20 structural components, and flagellar gene regulation is morphogenetically coupled to the assembly state by control of the anti-sigma factor FlgM. In the Gram-negative bacterium Salmonella enterica, FlgM inhibits late-class flagellar gene expression until the hook-basal body structural intermediate is completed and FlgM is inhibited by secretion from the cytoplasm. Here we demonstrate that FlgM is also secreted in the Gram-positive bacterium Bacillus subtilis and is degraded extracellularly by the proteases Epr and WprA. We further demonstrate that, like in S. enterica, the structural genes required for the flagellar hook-basal body are required for robust activation of σ^D-dependent gene expression and efficient secretion of FlgM. Finally, we determine that FlgM secretion is strongly enhanced by, but does not strictly require, hook-basal body completion and instead demands a minimal subset of flagellar proteins that includes the FliF/FliG basal body proteins, the flagellar type III export apparatus components FliO, FliP, FliQ, FliR, FlhA, and FlhB, and the substrate specificity switch regulator FliK.     

Flagellar sensillum patterns in Nyssoninae and Philanthinae wasps (Hymenoptera, Sphecidae)

Morphology and distributional patterns of antenna1 sensilla were compared between four species in three genera of Sphecidae. Sensilla placodea have plates that are raised to resemble low domes in Argogorytes mystaceus and A. fargei or low pegs in Bembix rostrata and Cerceris rybyensis . Sensilla basiconica occur in both sexes of Bembix and Cerceris , but, similarly to Apidae ( s. laf .), only in females of Argogorytes . The antennae of the two species of Argogorytes differ primarily in being larger in A. mysfaceus , thus permitting space for more sensilla. In Bembix rostrata , the male antennae are adapted to function as 'gripping' organs.     

Flagellar membrane proteins of Tetraselmis striata butcher (Chlorophyta)

Highly purified flagella of the green alga Tetraselmis striata (Chlorophyta) were extracted by Triton X-114 phase partitioning. SDS-PAGE analysis revealed that most proteins were present in the aqueous phase, only two prominent flagellar membrane proteins (fmp) of apparent molecular weight 145 and 57 kDa (fmp145 and fmp57) were enriched in the detergent phase. Fmp145 was purified by gel permeation chromatography. Glycosidase treatment in combination with lectin blot analysis showed that fmp145 is a glycoprotein containing 3-5 N-glycans of the high mannose and/or hybrid type. A polyclonal antibody (anti-fmp136) was raised against the deglycosylated form of fmp145 and used to localize fmp145 by immunofluorescence and immunoelectron microscopy. Immunogold labeling showed fmp145 to be present between the scale layers and the flagellar membrane. During flagellar regeneration fmp145 is incorporated evenly and rapidly into the newly developing flagella. Anti-fmp136 specifically cross-reacted with flagella of only a subgroup of Tetraselmis strains characterized by a specific flagellar hair type (type II according to Marin et al. 1993) and thus could be a useful immunomarker for the identification of Tetraselmis strains by fluorescence microscopy.     

Isolation of the Flagellar Swelling and Identification of Retinal in the Phototactic Flagellate, Ochromonas danica (Chrysophyceae)

Ochromonas danica, a freshwater, planktonic chrysophyte, is capable of sensing the light conditions of its environment. This biflagellate alga has a swelling near the base of the short flagellum and a chloroplastidic stigma in close association with it. A procedure is described for the isolation of this three dimensional flagellar swelling, the presumed photoreceptor. In contrast to an earlier method developed for the isolation of the paraflagellar swelling from Euglena gracilis, the protocol reported here for Ochromonas results in higher yields that should facilitate future biochemical investigations and could open avenues of investigation for the isolation and purification of the presumptive receptor protein. To verify the hypothesis that a rhodopsin-like protein might be present in this alga, we applied a standard extraction procedure successfully used in the identification of retinal. We here report the purification and identification of all-trans retinal in Ochromonas cells by column chromatography, HPLC and GC-MS. Since retinal is the chromophore of rhodopsin-like proteins, this finding may suggest that in these unicellular algae, too, a rhodopsin-like protein could be the photoreceptor pigment.     

The Ovary of Tubifex tubifex (Clitellata,Naididae, Tubificinae) Is Composed of One,Huge Germ-Line Cyst that Is Enriched with Cytoskeletal Components

Recent studies on the ovary organization and oogenesis in Tubificinae have revealed that their ovaries are small polarized structures that are composed of germ cells in subsequent stages of oogenesis that are associated with somatic cells. In syncytial cysts, as a rule, each germ cell is connected to the central cytoplasmic mass, the cytophore, via only one stable intercellular bridge (ring canal). In this paper we present detailed data about the composition of germ-line cysts in Tubifex tubifex with special emphasis on the occurrence and distribution of the cytoskeletal elements. Using fixed material and live cell imaging techniques, we found that the entire ovary of T. tubifex is composed of only one, huge multicellular germ-line cyst, which may contain up to 2,600 cells. Its architecture is broadly similar to the cysts that are found in other clitellate annelids, i.e. a common, anuclear cytoplasmic mass in the center of the cyst and germ cells that are connected to it via intercellular bridges. The cytophore in the T. tubifex cyst extends along the long axis of the ovary in the form of elongated and branched cytoplasmic strands. Rhodamine-coupled phalloidin staining revealed that the prominent strands of actin filaments occur inside the cytophore. Similar to the cytophore, F-actin strands are branched and they are especially well developed in the middle and outermost parts of the ovary. Microfilaments are also present in the ring canals that connect the germ cells with the cytophore in the narrow end of the ovary. Using TubulinTracker, we found that the microtubules form a prominent network of loosely and evenly distributed tubules inside the cytophore as well as in every germ cell. The well-developed cytoskeletal elements in T. tubifex ovary seem to ensure the integrity of such a huge germ-line cyst of complex (germ cells - ring canals - cytophore) organization. A comparison between the cysts that are described here and other well-known female germ-line cysts is also made.     

Flagellar Axonemes with 10 Microtubular Doublets in Spermatozoa from Gall-midges (Diptera,Cecidomyiidae)

Abstract The spermatozoa of some gall-midges (Cecidomyiidae, Lestremiinae), belonging to the tribe Micromyini, were seen to have an axoneme that consists of 10, instead of nine, microtubular doublets surrounding a central cylinder. In some related species within the same tribe the axoneme was found to contain a similar cylinder but to have nine doublets, as in typical flagella, or to have nine doublets and no central structure. These three types of axonemes can be given the shorthand designations “10+cyl”,“9+cyl”, and “9+0”. The tribe Lestremiini is characterized by a giant axoneme having 150 doublets in two rows reversely oriented. Other characteristics of examined spermatozoa are the electron density of the B-tubules of the axoneme, a feature shared by all members of the subfamily Lestremiinae, and the presence of a prominent cytoplasmic droplet containing numerous, regularly spaced microtubules, which is shared by all Micromyidi. These axonemal models are discussed from a phylogenetic point of view.     

Rhesus Monkeys (Macaca mulatta) Detect Rhythmic Groups in Music,but Not the Beat

It was recently shown that rhythmic entrainment, long considered a human-specific mechanism, can be demonstrated in a selected group of bird species, and, somewhat surprisingly, not in more closely related species such as nonhuman primates. This observation supports the vocal learning hypothesis that suggests rhythmic entrainment to be a by-product of the vocal learning mechanisms that are shared by several bird and mammal species, including humans, but that are only weakly developed, or missing entirely, in nonhuman primates. To test this hypothesis we measured auditory event-related potentials (ERPs) in two rhesus monkeys (Macaca mulatta), probing a well-documented component in humans, the mismatch negativity (MMN) to study rhythmic expectation. We demonstrate for the first time in rhesus monkeys that, in response to infrequent deviants in pitch that were presented in a continuous sound stream using an oddball paradigm, a comparable ERP component can be detected with negative deflections in early latencies (Experiment 1). Subsequently we tested whether rhesus monkeys can detect gaps (omissions at random positions in the sound stream; Experiment 2) and, using more complex stimuli, also the beat (omissions at the first position of a musical unit, i.e. the ‘downbeat’; Experiment 3). In contrast to what has been shown in human adults and newborns (using identical stimuli and experimental paradigm), the results suggest that rhesus monkeys are not able to detect the beat in music. These findings are in support of the hypothesis that beat induction (the cognitive mechanism that supports the perception of a regular pulse from a varying rhythm) is species-specific and absent in nonhuman primates. In addition, the findings support the auditory timing dissociation hypothesis, with rhesus monkeys being sensitive to rhythmic grouping (detecting the start of a rhythmic group), but not to the induced beat (detecting a regularity from a varying rhythm).     

Flagellar Morphology of Vibrio parahaemolyticus (Fujino et al) Sakazaki,Iwanami and Fukumi 19631

The flagellar morphology of 88 Vibrio parahaemolyticus strains, including a strain descended from Fujino's original strain EB101 (= ATCC17802 = KM1339) was studied. EB101 and 83 other strains (95%) showed mixed polar and peritrichous type of flagellation when grown on modified MOF (MMOF) agar after 16-hr incubation at 20 C. Cultures containing numerous peritrichous cells showed wiggly movements in moist preparations and rapidly spreading growth in semisolid agar plates. Peritrichous flagella were easily removed mechanically from the soma. The mean wavelengths of polar and peritrichous flagella were 2.53 μm (normal type) and 1.72 μm (atypical curly type) respectively. Peritrichous cells on solid media appeared after incubation for 2.5 hr at 37 C and 7 hr at 20 C. Overnight incubation at 37 C and acidity of the medium due to fermentation of carbohydrate markedly ruined peritrichous flagella. Electron micrograph of cells grown on MMOF agar revealed a sheathed polar flagellum and unsheathed peritrichous flagella. A hook structure was demonstrated at the proximal end of the latter. Polar monotrichous cultures in MMOF broth sometimes contained some cells having several or many peritrichous flagella of atypical curly type. Seven strains of Vibrio cholerae were exclusively polar monotrichous on solid and in liquid media. The flagellation of V. parahaemolyticus is concluded as being a mixed polar-peritrichous type. This fact would indicate that V. parahaemolyticus should be excluded from the genus Vibrio, since the genus Vibrio was defined as polar monotrichous.     

The GTPase Activity of FlhF Is Dispensable for Flagellar Localization,but Not Motility,in Pseudomonas aeruginosa

The opportunistic human pathogen Pseudomonas aeruginosa uses two surface organelles, flagella and pili, for motility and adhesion in biotic and abiotic environments. Polar flagellar placement and number are influenced by FlhF, which is a signal recognition particle (SRP)-type GTPase. The FlhF proteins of Bacillus subtilis and Campylobacter jejuni were recently shown to have GTPase activity. However, the phenotypes associated with flhF deletion and/or mutation differ between these organisms and P. aeruginosa, making it difficult to generalize a role for FlhF in pseudomonads. In this study, we confirmed that FlhF of P. aeruginosa binds and hydrolyzes GTP. We mutated FlhF residues that we predicted would alter nucleotide binding and hydrolysis and determined the effects of these mutations on FlhF enzymatic activity, protein dimerization, and bacterial motility. Both hydrolytically active and inactive FlhF point mutants restored polar flagellar assembly, as seen for wild-type FlhF. However, differential effects on flagellar function were observed in single-cell assays of swimming motility and flagellar rotation. These findings indicate that FlhF function is influenced by its nucleotide binding and hydrolytic activities and demonstrate that FlhF affects P. aeruginosa flagellar function as well as assembly.