GROWTH PATTERNS AND MOTILITY OF SPIROGYRA SP. AND CLOSTERIUM ACEROSUM1,2

Spirogyra and Closterium exhibit active motility. This motility is associated with the secretion of pectic mucilage from the cells. The gliding of these cells is not directed toward light but photosynthesis is the energy source for it. The secretion of mucilage causes older Closterium cultures to become thick gelatinous clusters. Spirogyra filaments when undisturbed grow to form thick multistranded rings. This growth pattern might result from the tendency of the filaments to rotate on their long axis.     

ACTIVE GLIDING MOTILITY IN AN ARAPHID MARINE DIATOM,ARDISSONEA (FORMERLY SYNEDRA) CRYSTALLINA1

Active gliding movement over long distances was observed and filmed in the marine pennate diatom Ardissonea (Synedra) crystallina (Agardh) Kütz. Typical speeds measured ca. 1–2 μm-s^?1. Motion wax often smooth and steady; however, discontinuous jerky motions and rolling movements were common. Motion, was associated with secretion of twin or, less commonly, single straight trails of mucilage from one end of the cell. In a few instances, reversal in direction was related to cessation of mucilage secretion at one end and commencement at the other. Temporary cessation of movement due to an obstruction was accompanied by a build-up of mucilage at one end of the cell. Mucilage was apparently secreted at two specific sites at each end of the cell and was stained by alcian blue. Persistent trails were visible under scanning electron microscopy (SEM). SEM confirmed that cells had no raphes or labiate processes. The apparent site of secretion was a deep groove formed at the junction of the valve and valvocopula (first girdle band) at each end of the cell. Transmission electron microscopy confirmed the presence of mucilage vesicles in the cytoplasm, but these were not in any manner obviously related to secretion nor was any morphological structure associated with secretion. Cells often become epiphytic through secretion of a terminal stipe. Both stipe secretion and movement may involve the same structural differentiation of the frustule. These results demonstrate a previously unrecorded type of diatom motility. The mechanism, involves mucilage secretion and appears similar to that seen, for example, in some other algae such as the desmids (green algae).     

Photokinesis and Photophobic Responses in the Gliding Flagellate, Euglena mutabilis

A pronounced photokinesis (as indicated by increases in bothpercentage of motile cells and average speed of movement) aswell as step-up and step-down photophobic responses at light/darkboundaries in the gliding flagellate Euglena mutabilis was studiedusing time-lapse video-microscopy. The spectral sensitivitiesof all the observed lightdependent motor responses were similarto each other and showed an activity throughout the whole visiblespectrum with maximum peaks at about 410, 450, 470, 530, 580and 650 nm and a pronounced minimum at about 600 nm. Thus, thephotoreceptor pigments markedly differ from the closely relatedswimming flagellate Euglena gracilis in which a flavin typeblue light receptor is supposed to be responsible for the stimulusperception. Light microscopic studies of mucilage distributionand regeneration suggested that the gliding movements are effectedby parallel gliding of adjacent pellicular strips while themucilage produced on the cell surface and transported to therear end seems to be responsible for adhesion of the cell onthe substrate. (Received November 21, 1985; Accepted January 30, 1986)     

Some features of secretory systems in plants

Synopsis Recent work on secretion in plants is reviewed, with emphasis on the anatomy and physiology of root cap cells in higher plants, the stalked glands ofDrosera capensis, and the secretory mechanism ofDionaea muscipula. Cells of the root cap of higher plants switch from a geo-perceptive role to one of mucilage secretion at maturation. Features of this process, the role of the Golgi and the pathway for mucilage distribution are reviewed. In contrast, the stalked glands of the leaves ofDrosera capensis are much longer lived and have a complex anatomy. The mechanisms for mucilage secretion, protein absorption and the role of the cell membranes in the internal secretion of the protein are described, using data from X-ray microscopv. The secretion of fluid and protein byDionaea is stimulated by various nitrogen-containing compounds. Uric acid, often excreted by captured insects, is particularly effective in this respect.     

A MOLECULAR MOTOR FOR GLIDING MOTILITY IN CYANOBACTERIA

Motile microorganisms either swim, by using flagella or glide over surfaces by mechanisms that are poorly understood. In cyanobacteria, gliding motility appears as a relatively slow and smooth surface-associated translocation in the direction of the long axis of the filaments at rates up to a few micrometers a second. Many filamentous species translocate in a highly coordinated manner. Translational movements are usually accompanied by revolutions around the long axis of the filament. While moving, the cyanobacteria secrete slime which is left behind as a twisted and collapsed thin tube. The observation of the slime secretion process shows that the mucilage is formed as fine bands that emerge in close proximity to the cells cross walls. Ultrastructural studies have revealed that the cyanobacteria possess at their cross walls complex, pore-like organelles, which might be involved in slime secretion. As each cell possess two different sets of pores pointing in opposite direction, the coordinated activity of these structures could explain how the filament can reverse the direction of locomotion. Furthermore, ultrastructural studies have shown that rotating cyanobacteria possess cell surfaces formed by parallel, helically arranged surface fibrils. As the arrangement of these fibrils corresponds with the path of the filaments during locomotion, it might be imaginable that these fibrils serve as screw thread guiding the rotation of the filaments, with the necessary thrust for locomotion being derived from the secretion of slime using the pores at the cross walls.     

CELLULAR MOVEMENT IN THE CENTRIC DIATOM ODONTELLA SINENIS1

Cultured, actively growing cells of Odentella sinensis secrete mucilage, forming gelatinous masses; the mucilage can be visualised with Alcian Blue. When examined live with the light microscope, many cells exhibited continuous small shuffing and rocking movements that could last for long periods (30-40 min); the cells, however, were not translocated and remained relatively fixed in position with respect to their neighbours. Ultrastructural examination of these cells showed prominent aggregations of mucilage vesicles, derived from the Golgi bodies, at the base of the labiate processes, each of which is close to an elevation bearing an ocellus. In Ditylum brightwellii, similar aggreations of these vesides were also located at teh labiate processes; this diatom, too, secretes mucilage but does not have ocelli. We conclude that the movements observed in O. sinenisis are an indirect result of active muilage secretion through the labiate process. It has been suggested that the raphe may have evolved from the labiate process; our conclusion, therefore, has phylogenetic implications, suggesting a functional as well as a morphological relationship between the two valve structures.     

MUCILAGE PROCESSING AND SECRETION IN THE GREEN ALGA CLOSTERIUM. I. CYTOLOGY AND BIOCHEMISTRY1

Placoderm desmids (Conjugates, Chlorophyta) such as Closterium exhibit a gliding locomotory behavior. This results from the forceful extrusion of an acidic polysaccharide from one pole of the cell causing the cell to glide in the opposite direction. A biochemical and cytological analysis of gliding behavior was performed. The mucilage is a high molecular weight polysaccharide rich in glucuronic acid and fucose. Under normal growth conditions, 3 μg of mucilage is produced per cell in 30 days. Mucilage production increased 3–4 fold in cells challenged with low phosphate or nitrate conditions. A polyclonal antibody was raised against the mucilage and used in immunofluorescence studies. These results show that upon contact with another object Closterium aligns itself parallel to that object by a “jack-knife” motion. Subsequently, large amounts of mucilage are released to form elongate tubes enmeshing the cell with that object. In post-cytokinetic phases of the cell cycle, mucilage is extruded only through the pole of the developing semi-cell. Chlorotetracyclene-labeling of mucilage-secreting cells shows a correlation between calcium-rich loci on the cell surface and sites of mucilage release.     

Mutations in Flavobacterium johnsoniae sprE result in defects in gliding motility and protein secretion

Cells of the gliding bacterium Flavobacterium johnsoniae move rapidly over surfaces. Transposon mutagenesis was used to identify sprE, which is involved in gliding. Mutations in sprE resulted in the formation of nonspreading colonies on agar. sprE mutant cells in wet mounts were almost completely deficient in attachment to and movement on glass, but a small percentage of cells exhibited slight movements, indicating that the motility machinery was not completely disrupted. SprE is a predicted lipoprotein with a tetratricopeptide repeat domain. SprE is similar in sequence to Porphyromonas gingivalis PorW, which is required for secretion of gingipain protease virulence factors. Disruption of F. johnsoniae sprE resulted in decreased extracellular chitinase activity and decreased secretion of the cell surface motility protein SprB. Reduced secretion of cell surface components of the gliding machinery, such as SprB, may account for the defects in gliding. Orthologs of sprE are found in many gliding and nongliding members of the phylum Bacteroidetes, suggesting that similar protein secretion systems are common among members of this large and diverse group of bacteria.     

Zur Lateralpr?sentation des Mikado-Fasans (Syrmaticus mikado) in Gefangenschaft

Summary Although lateral display takes place during courtship too, this display is rather a part of the aggressive behaviour ofSyrmaticus mikado. It occurs more or less during the whole year and in both sexes.     

Flagella-dependent gliding motility inChlamydomonas

Summary Flagella are generally recognized as organelles of motility responsible for the ability ofChlamydomonas to swim through its environment. However, the same flagella are also responsible for an alternative form of whole cell locomotion, termed gliding. Use of paralyzed flagella mutants demonstrates that gliding is independent of axonemal bend propagation. Gliding motility results from an interaction of the flagellar surface with a solid substrate. Gliding is characterized by bidirectional movements at 1.6±0.3 m/second and occurs when the cell is in a characteristic gliding configuration, where the two flagella are oriented at 180° to one another. A variety of observations suggest that the leading flagellum is responsible for the force transduction resulting in cell locomotion, although both flagella have the capacity to function as the active flagellum. The characteristics of gliding motility have been compared with theChlamydomonas flagellar surface motility phenomenon defined as surface translocation of polystyrene microspheres.     

GLIDING MOTILITY IN THE BLUE-GREEN ALGA OSCILLATORIA PRINCEPS1

Gliding is an active movement displayed by a microorganism in contact with a solid substrate where there is no evidence of a motility organelle or of a conformational change in the organism. Gliding may be accompanied by rotations, reversals, flectional activity, and mucilage sheath production, as well as linear translation. Previous explanations of the mechanism responsible did not consider all these aspects of behavior. The gliding behavior and ultrastructure of the blue-green alga Oscillatoria princeps Vaucher were examined. O. princeps has a maximum observed gliding rate of 11.1 μm/sec. The trichomes can glide in either longitudinal direction following rapid and occasionally frequent reversals. Right-handed trichome rotation was always observed, which means that any surface point on these trichomes traces a 60-deg right-handed helix. A mucilage sheath envelopes the moving trichomes. The rate of gliding was reduced by viscous substrates, extreme pH, lysozyme, DNP, and cyanide, while sustained darkness had no inhibitory effect. Ultrastructurally, the cell wall is composed of an L-1 layer which is 10 nm thick and often ill-defined. The L-2 layer which is outside this is 200 nm thick and participates in septum formation. The L-3 layer is outside the L-2 and is continuous over the trichome surface. The L-4 “membrane” lies outside the L-3 layer. Grazing surface sections and freeze-etch replicas show a parallel and tight array of 6–9 nm wide continuous fibrils in the cell wall on the surface of the distinctive L-2 layer. Isolated wall fragments were tightly coiled inside out with the fibrils on the inside. The angle of orientation for the fibrils was to the right in a helix with a pitch of 60 deg. O. animalis, a blue-green alga with a movement tracing a left-handed helix, showed a similar array of fibrils oriented in a left-handed helix with a pitch of 60 deg. It is proposed that gliding is produced by unidirectional waves of bending in the fibrils which, act against the sheath or substrate, tints displacing the trichome.     

Type IV pili and cell motility

Type IV pili (Tfp) mediate the movement of bacteria over surfaces without the use of flagella. These movements are known as social gliding in Myxococcus xanthus and twitching in organisms such as Pseudomonas aeruginosa and Neisseria gonorrhoeae. Tfp are localized polarly. Type IV pilins have a signature N-terminal domain, which forms a coiled-coil with other monomer units to polymerize a pilus fibre. At least 10 more proteins at the base of the fibre are conserved; they are related to the type II secretion system. Movements produced by Tfp range from short, jerky displacements to lengthy, smooth ones. Tfp also participate in cell–cell interactions, pathogenesis, biofilm formation, natural DNA uptake, auto-aggregation of cells and development. What is the means by which Tfp bring about the movement of cells?     

ANALYSIS OF MUCILAGE SECRETION AND EXCRETION IN MICRASTERIAS (CHLOROPHYTA) BY MEANS OF IMMUNOELECTRON MICROSCOPY AND DIGITAL TIME LAPSE VIDEO MICROSCOPY1

Two different, independent, and alternative modes of mucilage excretion were found in the unicellular green alga Micrasterias denticulata Bréb. under constant culture conditions. The cells were capable of either excreting mucilage over all their cell surface or they extruded mucilage from one of their polar ends, which enabled directed movement such as photoorientation or escape from unfavorable environmental conditions. By means of a polyclonal antibody raised against Micrasterias mucilage, the secretory pathway of Golgi derived mucilage vesicles from their origin to their discharge was analyzed by means of conventional and energy filtering TEM. Depending on the stage of the cell cycle, mucilage vesicles were subjected to maturation processes. This may occur either after they have been pinched off from the dictyosomes (e.g. during cell growth) or when still connected to trans‐Golgi cisternae, as in the case of interphase cells. Only fully grown mature vesicles contained mucilage in its final composition as indicated by antibody labeling. After fusion of mucilage vesicles with vacuoles, no immunolabeling was found in vacuoles, indicating that the vesicle content was digested. Mucilage vesicles fused with the plasma membrane in areas of cell wall pores but were also able to excrete mucilage at any site directly through the respective cell wall layer. This result disproves earlier assumptions that the pore apparatus in desmids are the only mucilage excreting areas at the cell surface. Both mechanisms, excretion through the pores and through the cell wall, lead to formation of mucilage envelopes covering the entire cell surface.     

Development,structure, and occurrence of secretory trichomes ofPharbitis

Summary Secretory trichomes develop from epidermal cells on the leaf primordia and stem ofPharbitis nil. Following an initial growth phase, trichomes begin active secretion of a protein-carbohydrate mucilage. This mucilage covers the shoot apex and developing leaves ofPharbitis.The secretory cells possess cellular organelles in forms usually associated with actively secreting cells: many mitochondria, an elaborate network of rough endoplasmic reticulum (RER), many free ribosomes, and numerous dictyosomes. The role of the dictyosomes is twofold: 1. dictyosome vesicles bud coated vesicles which transport materials from the cell and, 2. dictyosome vesicles coalesce, forming large storage vesicles. The storage vesicles are surrounded by, and often in contact with, poculiform RER. The RER forms an interconnected network throughout the cytoplasm, extending from the nuclear envelope to the plasmalemma. Distended profiles of RER are frequently in direct contact with the plasmalemma. Thus, inPharbitis secretory trichomes, it is the coated vesicles and RER which are active in secretion export. These findings imply a secretory pathway which deviates from the usual pattern in glandular cells.Predoctoral fellow of National Science Foundation during part of the investigation.     

The hmp chemotaxis cluster regulates gliding in the filamentous cyanobacterium Nostoc punctiforme

Many bacteria are capable of movement over surfaces without flagella or pili; they glide. Nostoc punctiforme is a cyanobacterium that differentiates specialized gliding filaments called hormogonia, but the mechanism underlying their movement is currently unknown. Risser et al. characterize the h ormogonia m otility and p olysaccharide (hmp) locus that encodes proteins homologous to well‐studied chemotaxis systems. All but one of the genes in the locus were required for gliding motility and each protein localized as a ring near the cell junction. One protein, the CheA homologue HmpE, was capable of autophosphorylation and phosphotransfer to the CheY homologue HmpB. This study reveals the hmp locus as an important regulator of gliding and highlights N. punctiforme as a model for understanding gliding motility in a complex multicellular bacterium.     

A phylogenetic analysis of the purple photosynthetic bacteria

It is proposed that gliding motility in bacteria is based on rotary assemblies located in the cell envelope and that these assemblies may be analogous to basal regions of bacterial flagella. This proposal rests on the following evidence: (i) Structures resembling flagellar basal regions have been demonstrated in cells ofCytophaga johnsonae andFlexibacter columnaris, and such structures are absent from one nonmotile mutant ofF. columnaris. (ii) The effects of inhibitors of energy metabolism on gliding motility are identical with their effects on prokaryotic fiagellar motility. (iii) The active movement of latex spheres along surfaces of gliding bacteria appears to depend on mechanisms responsible for motility and can be explained by the presence of rotary surface assemblies.     

MOVEMENT MODALITIES AND RESPONSES TO ENVIRONMENTAL CHANGES OF THE MUDFLAT DIATOM CYLINDROTHECA CLOSTERIUM (BACILLARIOPHYCEAE)1

Cylindrotheca closterium (Ehrenberg) Reiman et Lewin is a raphid diatom widely distributed in mudflat assemblages. Video microscopy showed various movement modalities defined as smooth and corkscrew gliding, pirouette, pivot, rock and roll, rollover, and simultaneous pirouette and gliding. Z‐axis projection analysis of images revealed a unique gliding motif with corkscrew motions, which may have important ecological implications for C. closterium movement in muds. The general response to salinity alteration was a decrease in gliding movements with a concomitant increase in other modalities listed above. Short‐term responses to salinity change include dramatic alteration in modalities in hypo‐saline conditions and cessation of motility in extreme hyper‐saline environments. Modality changes were rapid and occurred within 5 s in response to hyper‐saline conditions. Hypo‐ or hyper‐saline conditions resulted in decreased gliding speed in standard media. Five‐ and 15‐day acclimation to salinity changes resulted in a progressive reduction in gliding movement, increased non‐gliding modalities and increased cell aggregation. Aggregation in hypo‐saline conditions was accompanied by a large increase in the polymer extracted by hot bicarbonate‐ and ethylenediamine tetraaceticacid‐ fractions of extracellular polymeric substance (EPS), the polymers of which have been implicated in cell attachment/motility phenomena. The monosaccharide profiles of these fractions were altered in response to hypo‐saline conditions. In general, monosaccharide profiles showed increased diversity upon cessation of motility and aggregation of cultures. The movement responses of C. closterium in response to environmental changes, accompanied by modifications in EPS, may form part of an adaptive strategy to survive in mudflats and could be useful as bioindicators of environmental changes.     

Participation of myosin in gliding motility and host cell invasion by Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular parasite that actively invades mammalian cells using a unique form of gliding motility that critically depends on actin filaments in the parasite. To determine if parasite motility is driven by a myosin motor, we examined the distribution of myosin and tested the effects of specific inhibitors on gliding and host cell invasion. A single 90 kDa isoform of myosin was detected in parasite lysates using an antisera that recognizes a highly conserved myosin peptide. Myosin was localized in T. gondii beneath the plasma membrane in a circumferential pattern that overlapped with the distribution of actin. The myosin ATPase inhibitor, butanedione monoxime (BDM), reversibly inhibited gliding motility across serum-coated slides. The myosin light-chain kinase inhibitor, KT5926, also blocked parasite motility and greatly reduced host cell attachment; however, these effects were primarily caused by its ability to block the secretion of microneme proteins, which are involved in cell attachment. In contrast, while BDM partially reduced cell attachment, it prevented invasion even under conditions in which microneme secretion was not affected, indicating a potential role for myosin in cell entry. Collectively, these results indicate that myosin(s) probably participate(s) in powering gliding motility, a process that is essential for cell invasion by T. gondii .     

The development of the mucilage gland of two Japanese species ofAlaria

The genusAlaria possesses a structure known as the mucilage gland which appears mainly on the frond. This is also true ofUndaria. The mucilage gland ofUndaria usually originates from some of the epidermal cells. However, observations of plants ofAlaria at various stages indicate that glands originate not only in the surface layer. There are still other glands which are initiated by some cortical cells situated directly beneath the epidermis. In both, a refractive substance is gradually accumulated as these cells enlarge. The mucilage glands starting in the surface (the primary mucilage glands) resemble those ofUndaria in their development, whereas those in the cortex (the secondary mucilage glands) are quite analogous to the secretory cells ofLaminaria, etc., which secrete mucilage into a mucilage canal in the first stage. Thus,Alaria seems to constitute a link betweenUndaria andLaminaria, etc.     

Investigations of decayed sandstone colonised by a species ofTrentepohlia

The occurrence of a sub-aerial microbial community dominated by a species ofTrentepohlia, a red-orange pigmented filamentous green alga, growing on a 13th century sandstone building in the Scottish borders appears to be associated with unusual stone decay. Decay, in the form of extensive surface spalling and grain dissagregation over large areas of external stonework, are coincident with the distribution of the algal community on the north facade of the building. Comparison of S.E.M. images taken of fresh intact stone and spalled stone from decayed zones suggests that the mechanisms of decay may, in part, be a physical process which results in quartz crystals becoming separated. The investigations carried out revealed little evidence of chemical processes which may be involved in the decay. Large filaments ofTrentepohlia are clearly visible growing vertically between separate grains of stone and the amount of highly absorbent mucilage present makes the friable dry spall become soft and gelatinous on wetting. It is possible that the observed decay may have been created through the mechanical action of wet-dry cycling of mucilage and expansive stress from the growth of algal filaments.