Malaria sporozoites leave behind trails of circumsporozoite protein during gliding motility

As Plasmodium sporozoites undergo gliding motility in vitro, they leave behind trails of circumsporozoite (CS) protein that correspond to their patterns of movement. This light microscopic observation was made using Plasmodium berghei sporozoites, a monoclonal antibody (MAb H4) directed against the immunodominant repetitive epitope of the CS protein of P. berghei, and an immunogold-silver staining (IGSS) technique. Sporozoites pretreated with agents that inhibit sporozoite motility and invasiveness did not produce trails. Sporozoites that glided on microscope slides coated with MAb H4 left behind considerably longer CS protein trails than those on uncoated slides, and the staining of these trails was more intense. The fact that the CS protein is an exoantigen continuously released as trails by motile sporozoites, together with our previous finding that anti-CS protein antibodies inhibit sporozoite motility, strongly suggests that the CS protein plays a role in gliding motility. The sensitive IGSS technique used in this study may be a useful tool in the study of the translocation of surface proteins during gliding of other apicomplexans, other protists, and bacteria.     

Malaria Sporozoites Leave Behind Trails of Circumsporozoite Protein During Gliding Motility1

As Plasmodium sporozoites undergo gliding motility in vitro, they leave behind trails of circumsporozoite (CS) protein that correspond to their patterns of movement. This light microscopic observation was made using Plasmodium berghei sporozoites, a monoclonal antibody (MAb H4) directed against the immunodominant repetitive epitope of the CS protein of P. berghei, and an immunogold-silver staining (IGSS) technique. Sporozoites pretreated with agents that inhibit sporozoite motility and invasiveaess did not produce trails. Sporozoites that glided on microscope slides coated with MAb H4 left behind considerably longer CS prolem trails than those on uncoated slides, and the staining of these trails was more intense. The fact that the CS protein is an exoantigen continuously released as trails by motile sporozoites, together with our previous finding that anti-CS protein antibodies inhibit sporozoite motility, strongly suggests that the CS protein plays a role in gliding motility. The sensitive IGSS technique used in this study may be a useful tool in the study of the translocation of surface proteins during gliding of other apicomplexans, other protists, and bacteria.     

Electron Microscopic Analysis of Circumsporozoite Protein Trail Formation by Gliding Malaria Sporozoites

Immunoelectron microscopic techniques were utilized to characterize the morphology of circumsporozoite protein-containing trails deposited on various substrates by gliding Plasmodium berghei and Plasmodium falciparum sporozoites. The basic components of the trails are beadlike particles, 25 to 90 nm in diameter, which are devoid of unit membrane and have an electronlucent center. Trails were captured on formvar-covered grids coated with anticircumsporozoite protein monoclonal antibodies and compared with trails produced on uncoated formvar; the results suggest that material containing circumsporozoite protein forms the matrix within which the particles are embedded. The trails exhibit morphological features similar to those displayed by circumsporozoite precipitation reactions; of note is the demonstration of sheaths of circumsporozoite protein-containing material that emanate from sporozoites prior to their gliding. The sheaths narrow into accumulations of electron-dense material, which eventually taper to form typical trails. The structural manifestation of sheaths and other morphological details of the formed trails enables us to correlate sporozoite behavior during trail formation with the motile actions of gliding sporozoites observed by light microscopy.     

Electron microscopic analysis of circumsporozoite protein trail formation by gliding malaria sporozoites.

Immunoelectron microscopic techniques were utilized to characterize the morphology of circumsporozoite protein-containing trails deposited on various substrates by gliding Plasmodium berghei and Plasmodium falciparum sporozoites. The basic components of the trails are beadlike particles, 25 to 90 nm in diameter, which are devoid of unit membrane and have an electron-lucent center. Trails were captured on formvar-covered grids coated with anticircumsporozoite protein monoclonal antibodies and compared with trails produced on uncoated formvar; the results suggest that material containing circumsporozoite protein forms the matrix within which the particles are embedded. The trails exhibit morphological features similar to those displayed by circumsporozoite precipitation reactions; of note is the demonstration of sheaths of circumsporozoite protein-containing material that emanate from sporozoites prior to their gliding. The sheaths narrow into accumulations of electron-dense material, which eventually taper to form typical trails. The structural manifestation of sheaths and other morphological details of the formed trails enables us to correlate sporozoite behavior during trail formation with the motile actions of gliding sporozoites observed by light microscopy.     

How myxobacteria glide

BACKGROUND: Many microorganisms, including myxobacteria, cyanobacteria, and flexibacteria, move by gliding. Although gliding always describes a slow surface-associated translocation in the direction of the cell's long axis, it can result from two very different propulsion mechanisms: social (S) motility and adventurous (A) motility. The force for S motility is generated by retraction of type 4 pili. A motility may be associated with the extrusion of slime, but evidence has been lacking, and how force might be generated has remained an enigma. Recently, nozzle-like structures were discovered in cyanobacteria from which slime emanated at the same rate at which the bacteria moved. This strongly implicates slime extrusion as a propulsion mechanism for gliding. RESULTS: Here we show that similar but smaller nozzle-like structures are found in Myxococcus xanthus and that they are clustered at both cell poles, where one might expect propulsive organelles. Furthermore, light and electron microscopical observations show that slime is secreted in ribbons from the ends of cells. To test whether the slime propulsion hypothesis is physically reasonable, we construct a mathematical model of the slime nozzle to see if it can generate a force sufficient to propel M. xanthus at the observed velocities. The model assumes that the hydration of slime, a cationic polyelectrolyte, is the force-generating mechanism. CONCLUSIONS: The discovery of nozzle-like organelles in various gliding bacteria suggests their role in prokaryotic gliding. Our calculations and our observations of slime trails demonstrate that slime extrusion from such nozzles can account for most of the observed properties of A motile gliding.     

Substratum requirements for bacterial gliding motility

Flexibacter FS-1 filaments are unable to glide on agarose gels or on charge-neutralized glass unless those substrata are supplemented with the charged, cold water-soluble fraction of agar, or a variety of polyanionic polysaccharides derived from plants, yeasts and bacteria. Two graft polymers of xanthan gum also promote gliding motility under these conditions, as do an extracellular product of the bacteria themselves. A number of other polymers and small molecular species are ineffective as supplements. These results are considered in the context of the soil habitat of this Flexibacter. Among a variety of other gliding bacteria tested, several strains of the order Cytophagales also were unable to glide on agarose.Abbreviations CWSF Cold water-soluble fraction of agar - PMC 5 mM K phosphate buffer (pH 7)+0.1 mM MgCl₂+0.5 mM CaCl₂     

Type IV pili-dependent gliding motility in the Gram-positive pathogen Clostridium perfringens and other Clostridia

Bacteria can swim in liquid media by flagellar rotation and can move on surfaces via gliding or twitching motility. One type of gliding motility involves the extension, attachment and retraction of type IV pili (TFP), which pull the bacterium towards the site of attachment. TFP-dependent gliding motility has been seen in many Gram-negative bacteria but not in Gram-positive bacteria. Recently, the genome sequences of three strains of Clostridium perfringens have been completed and we identified gene products involved in producing TFP in each strain. Here we show that C. perfringens produces TFP and moves with an unusual form of gliding motility involving groups of densely packed cells moving away from the edge of a colony in curvilinear flares. Mutations introduced into the pilT and pilC genes of C. perfringens abolished motility and surface localization of TFP. Genes encoding TFP are also found in the genomes of all nine Clostridium species sequenced thus far and we demonstrated that Clostridium beijerinckii can move via gliding motility. It has recently been proposed that the Clostridia are the oldest Eubacterial class and the ubiquity of TFP in this class suggests that a Clostridia-like ancestor possessed TFP, which evolved into the forms seen in many Gram-negative species.     

A Gliding Bacterium Strain Inhibits Adhesion and Motility of Another Gliding Bacterium Strain in a Marine Biofilm

Two species of gliding bacteria were isolated from a marine biofilm. They were described and identified as members of the genus Cytophaga. One of them (RB1057) produced an extracellular inhibitor of colony expansion of the other (RB1058). The inhibitor was characterized as a glycoprotein with an apparent molecular mass of 60 kDa. It inhibited RB1058 adhesion to and gliding on substrata. Motility and adhesion of several other aquatic gliding bacteria were not measurably affected by this agent.     

Strangers in the dark: behavioral and biochemical evidence for trail pheromones in Hawaiian tree snails

The importance of pheromones in insect and mammal social systems is well documented, but few studies have addressed the role of pheromones in land snail behavior. In this investigation, we used a series of behavioral trials and direct analysis in real time mass spectrometry (MS) to test the hypothesis that land snails use mucous trails in orientation and chemical communication. We worked with six endemic Hawaiian land snail species in four genera, three subfamilies, and two families. We tested conspecific trail following in five of these species, and trail following occurred at a statistically significant frequency for each of the species tested (n=181, p‐values ranged <0.0001–0.0494). Percentage of conspecific trials that showed trail following ranged 66.7–94.1%. None of the interspecific tests revealed evidence of trail following among species (n=105, with p‐values of 0.0577–0.5000). Juvenile achatinelline snails did not follow trails of conspecific juveniles (n=30, p=0.5722) or adults (n=30, p=0.4278), nor did adults follow juvenile trails (n=30, p=0.5722). Comparative MS analysis of adult and juvenile trails showed distinct chemical signatures in the two groups. Signals corresponding to medium‐ and long‐chain fatty acids and other unidentified small molecules were present in adult but not in juvenile trails. Considered together, these results support the hypotheses that trail following could serve an important social and reproductive function. This discovery provides evidence for the presence of an ephemeral tree snail pheromone, which could have important implications for the conservation of these increasingly rare and threatened species.     

Both CP15 and CP25 are left as trails behind gliding sporozoites of Cryptosporidium parvum (Apicomplexa)

Abstract Sporozoites of Cryptosporidium parvum were examined after gliding upon glass microscope slides using monoclonal antibodies to the 15 and 25 kDa surface molecules and immunogold-silver enhancement. Both antibodies bound to surface antigen deposited as trails behind parasites, suggesting that both surface molecules are involved in substrate attachment.     

Influence of snail mucus trails and first snail meal on the behavior of malacophagous sciomyzid larvae

There has been considerable focus on the natural enemies of snails, particularly those of medical and veterinary significance. Much attention has focussed on members of the Family Sciomyzidae (Diptera), the majority of which feed on a range of mollusc species. However, little is known about the influence of first snail meal on subsequent prey choices, an important consideration in biocontrol. We examined neonate larval responses of Ilione albiseta to fresh and aged snail mucus trails of three snail species. Median neonate response rates to aged mucus trails for all three snail species tested were significantly (P < 0.001) weaker than for fresh mucus trails indicating a strategy which enhances the likelihood of reaching prey snail species without expending energy following “cold” trails. More than 78% of first instar larvae, fed on one snail species (Radix peregra or Stagnicola palustris) and subsequently offered a choice of these two snail species for the second snail meal, selected the snail species of the first snail meal suggesting that the first snail meal influences subsequent prey selection. However, the impact of the first snail meal on larval trail-following behavior is less clear-cut. While there may be some preference for the mucus trail of the snail species on which neonate larvae have fed, this does not exclude the larvae from following the mucus trails of other snail species. The results are discussed in the context of the potential use of I. albiseta as a biocontrol agent of vectors of snail borne diseases.     

Immunofluorescent microscopical visualization of trails left by gliding Cryptosporidium parvum sporozoites

Cryptosporidium parvum sporozoites that exhibited gliding motility in vitro were examined by immunofluorescence with anticryptosporidial monoclonal antibodies (Mabs) for surface antigen deposition on poly-L-lysine-coated glass microscope slides. The Mabs that revealed trails are specific for an immunodominant 23-kDa antigen previously localized to the sporozoite surface.     

Phenotypic and genomic studies of "Cytophaga psychrophila" isolated from diseased rainbow trout (Oncorhynchus mykiss) in France

Five strains of gliding bacteria were isolated in France from farmed diseased rainbow trouts reared at low water temperature. The resemblance of these bacteria to the known fish pathogen "Cytophaga psychrophila" led to their comparative study with reference strain NCMB 1947 and with an American isolate. Morphological, physiological, and biochemical characteristics of the seven strains proved to be similar. Comparison of their DNA by the S1 nuclease DNA-DNA hybridization method showed that the seven strains formed a tight genomic species with DNA relatedness above 90%. This is the first identification of this fish pathogen in a European country. The main phenotypic characteristics differentiating this bacterium from other nonpathogenic gliding bacteria of fish origin include a poor gliding movement, yellow compact or weakly rhizoid colonies on solid media, and the presence of flexirubin-type pigments. The inability to metabolize any carbohydrates, the strong proteolytic activity, the absence of growth in more than 0.5% NaCl, and the tolerance to a maximum temperature of 25 degrees C are also useful characteristics of this group of bacteria.     

A mechanical model of wing and theoretical estimate of taper factor for three gliding birds

We tested a mechanical model of wing, which was constructed using the measurements of wingspan and wing area taken from three species of gliding birds. In this model, we estimated the taper factors of the wings for jackdaw (Corrus monedula), Harris’ hawk (Parabuteo unicinctas) and Lagger falcon (Falco jugger) as 1.8, 1.5 and 1.8, respectively. Likewise, by using the data linear regression and curve estimation method, as well as estimating the taper factors and the angle between the humerus and the body, we calculated the relationship between wingspan, wing area and the speed necessary to meet the aerodynamic requirements of sustained flight. In addition, we calculated the relationship between the speed, wing area and wingspan for a specific angle between the humerus and the body over the range of stall speed to maximum speed of gliding flight. We then compared the results for these three species of gliding birds. These comparisons suggest that the aerodynamic characteristics of Harris’ hawk wings are similar to those of the falcon but different from those of the jackdaw. This paper also presents two single equations to estimate the minimum angle between the humerus and the body as well as the minimum span ratio of a bird in gliding flight.     

Proteins antigenically related to methyl-accepting chemotaxis proteins of Escherichia coli detected in a wide range of bacterial species.

The four methyl-accepting chemotaxis proteins of Escherichia coli, often called transducers, are transmembrane receptor proteins that exhibit substantial identity among the sequences of their cytoplasmic domains. Thus, antiserum raised to one of these proteins recognizes the others and might be expected to recognize related proteins in other bacteria. We used antiserum raised to the transducer Trg in immunoblot experiments to probe a wide range of bacterial species for the presence of antigenically related proteins. Such proteins were detected in over 20 different species, representing 6 of the 11 eubacterial phyla defined by analysis of rRNA sequences as well as one archaebacterial group. Species containing proteins antigenically related to the transducers of E. coli included members of all four subdivisions of the phylum in which E. coli is placed, members of four of the six subdivisions of spirochetes, and two gliding bacteria. These observations provide substantial support for the notion that methyl-accepting taxis proteins are widely distributed among the diversity of bacterial species.     

Mycoplasmas: a distinct cytoskeleton for wall-less bacteria

The bacterial genus Mycoplasma includes a large number of highly genomically-reduced species which in nature are associated with hosts either commensally or pathogenically. Several Mycoplasma species, including Mycoplasma pneumoniae, feature a multifunctional polar structure, the terminal organelle. Essential for colonization of the host and for gliding motility, the terminal organelle is associated with an internal cytoskeleton crucial to its assembly and function. This cytoskeleton is structurally and compositionally novel as compared with the cytoskeletons of other organisms, including other bacteria, is also involved in the cell division process. In this review we discuss the cytoskeletal structures and protein components of the attachment organelle and how they might interact and contribute to its various functions.     

Radio‐tracking three Sugar Gliders using forested highway median strips at Bongil Bongil National Park,north‐east New South Wales

Major roads and highways disrupt ecological flows and create barriers or filters to the movement of many species of wildlife, including gliding mammals. Mitigating these impacts presents major challenges for road authorities. One approach has been the retention of forest vegetation in median strips to serve as ‘stepping stones’ for gliding mammals to cross road gaps otherwise beyond their glide capacity. A recently upgraded section of the Pacific Highway through tall open forest near Bonville in north‐east New South Wales retained forest within two 10‐ to 45‐m‐wide median strips separating each carriageway and a service road. We investigated whether Sugar Gliders (Petaurus breviceps) used these median strips to cross an 85 to 135 m‐wide road corridor. Three radio‐collared Sugar Gliders (one male and two females) moved between both highway medians and forest on either side of the road corridor during 32 days of radio‐tracking. Although the sample size is small, these results suggest that highway median strips, featuring mature vegetation with a major den tree, can provide ‘stepping stones’ for gliding mammals to cross a highway that would otherwise function as a movement barrier or filter. Longer‐term research with greater numbers of animals at this and other sites is required to determine whether such strips would be commonly used when den trees are absent and whether gliding via median strips may also increase road mortality of the species.     

Phylogenetic convergence and multiple shell shape optima for gliding scallops (Bivalvia: Pectinidae)

An important question in evolutionary biology is how often, and to what extent, do similar ecologies elicit distantly related taxa to evolve towards the same phenotype? In some scenarios, the repeated evolution of particular phenotypes may be expected, for instance when species are exposed to common selective forces that result from strong functional demands. In bivalved scallops (Pectinidae), some species exhibit a distinct swimming behaviour (gliding), which requires specific biomechanical attributes to generate lift and reduce drag during locomotive events. Further, a phylogenetic analysis revealed that gliding behaviour has independently evolved at least four times, which raises the question as to whether these independent lineages have also converged on a similar phenotype. Here, we test the hypothesis that gliding scallops display shell shape convergence using a combination of geometric morphometrics and phylogenetic comparative methods that evaluate patterns of multivariate trait evolution. Our findings reveal that the gliding species display less morphological disparity and significant evolutionary convergence in morphospace, relative to expectations under a neutral model of Brownian motion for evolutionary phenotypic change. Intriguingly, the phylomorphospace patterns indicate that gliding lineages follow similar evolutionary trajectories to not one, but two regions of morphological space, and subsequent analyses identified significant differences in their biomechanical parameters, suggesting that these two groups of scallops accomplish gliding in different ways. Thus, whereas there is a clear gliding morphotype that has evolved convergently across the phylogeny, functionally distinct morphological subforms are apparent, suggesting that there may be two optima for the gliding phenotype in the Pectinidae.     

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.     

Novel mechanisms power bacterial gliding motility

For many bacteria, motility is essential for survival, growth, virulence, biofilm formation and intra/interspecies interactions. Since natural environments differ, bacteria have evolved remarkable motility systems to adapt, including swimming in aqueous media, and swarming, twitching and gliding on solid and semi‐solid surfaces. Although tremendous advances have been achieved in understanding swimming and swarming motilities powered by flagella, and twitching motility powered by Type IV pili, little is known about gliding motility. Bacterial gliders are a heterogeneous group containing diverse bacteria that utilize surface motilities that do not depend on traditional flagella or pili, but are powered by mechanisms that are less well understood. Recently, advances in our understanding of the molecular machineries for several gliding bacteria revealed the roles of modified ion channels, secretion systems and unique machinery for surface movements. These novel mechanisms provide rich source materials for studying the function and evolution of complex microbial nanomachines. In this review, we summarize recent findings made on the gliding mechanisms of the myxobacteria, flavobacteria and mycoplasmas.