Phylogenomics of the archaeal flagellum: rare horizontal gene transfer in a unique motility structure

Background  

As bacteria, motile archaeal species swim by means of rotating flagellum structures driven by a proton gradient force. Interestingly, experimental data have shown that the archaeal flagellum is non-homologous to the bacterial flagellum either in terms of overall structure, components and assembly. The growing number of complete archaeal genomes now permits to investigate the evolution of this unique motility system.     

Identification of Archaea-specific chemotaxis proteins which interact with the flagellar apparatus

Background  

Archaea share with bacteria the ability to bias their movement towards more favorable locations, a process known as taxis. Two molecular systems drive this process: the motility apparatus and the chemotaxis signal transduction system. The first consists of the flagellum, the flagellar motor, and its switch, which allows cells to reverse the rotation of flagella. The second targets the flagellar motor switch in order to modulate the switching frequency in response to external stimuli. While the signal transduction system is conserved throughout archaea and bacteria, the archaeal flagellar apparatus is different from the bacterial one. The proteins constituting the flagellar motor and its switch in archaea have not yet been identified, and the connection between the bacterial-like chemotaxis signal transduction system and the archaeal motility apparatus is unknown.     

Gene trap mutation of murine Outer dense fiber protein-2 gene can result in sperm tail abnormalities in mice with high percentage chimaerism

Background  

Outer dense fiber protein 2, Odf2, is a major component of the outer dense fibers, ODF, in the flagellum of spermatozoa. ODF are associated with microtubule doublets that form the axoneme. We recently demonstrated that tyrosine phosphorylation of Odf2 is important for sperm motility. In the course of a study of Odf2 using Odf2 mouse knockout lines we observed that males of a high percentage chimaerism, made using XL169 embryonic stem cells, were infertile, whereas mice of low-medium percentage chimaerism were fertile.     

Statistical characterization of the GxxxG glycine repeats in the flagellar biosynthesis protein FliH and its Type III secretion homologue YscL

Background  

FliH is a protein involved in the export of components of the bacterial flagellum and we herein describe the presence of glycine-rich repeats in FliH of the form AxxxG(xxxG) _m xxxA, where the value of m varies considerably in FliH proteins from different bacteria. While GxxxG and AxxxA patterns have previously been described, the long glycine repeat segments in FliH proteins have yet to be characterized. The Type III secretion system homologue to FliH (YscL, AscL, PscL, etc.) also contains a similar GxxxG repeat, and hence the presence of the repeat is evolutionarily conserved in these proteins, suggesting an important structural role or biological function.     

Spatiotemporal association of DNAJB13 with the annulus during mouse sperm flagellum development

Background  

The sperm annulus is a septin-based fibrous ring structure connecting the midpiece and the principal piece of the mammalian sperm flagellum. Although ultrastructural abnormalities and functional importance of the annulus have been addressed in Sept4-null mutant mice and a subset of human patients with asthenospermia syndrome, little is known about how the structure is assembled and positioned to the midpiece-principal piece junction during mammalian sperm flagellum development.     

Novel sex cells and evidence for sex pheromones in diatoms

Background

Diatoms belong to the stramenopiles, one of the largest groups of eukaryotes, which are primarily characterized by a presence of an anterior flagellum with tubular mastigonemes and usually a second, smooth flagellum. Based on cell wall morphology, diatoms have historically been divided into centrics and pennates, of which only the former have flagella and only on the sperm. Molecular phylogenies show the pennates to have evolved from among the centrics. However, the timing of flagellum loss – whether before the evolution of the pennate lineage or after – is unknown, because sexual reproduction has been so little studied in the ‘araphid’ basal pennate lineages, to which Pseudostaurosira belongs.

Methods/Principal Finding

Sexual reproduction of an araphid pennate, Pseudostaurosira trainorii, was studied with light microscopy (including time lapse observations and immunofluorescence staining observed under confocal scanning laser microscopy) and SEM. We show that the species produces motile male gametes. Motility is mostly associated with the extrusion and retrieval of microtubule-based ‘threads’, which are structures hitherto unknown in stramenopiles, their number varying from one to three per cell. We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male gametes after an initial ‘random walk’.

Conclusions/Significance

The threads superficially resemble flagella, in that both are produced by male gametes and contain microtubules. However, one striking difference is that threads cannot beat or undulate and have no motility of their own, and they do not bear mastigonemes. Threads are sticky and catch and draw objects, including eggs. The motility conferred by the threads is probably crucial for sexual reproduction of P. trainorii, because this diatom is non-motile in its vegetative stage but obligately outbreeding. Our pheromone experiments are the first studies in which gametogenesis has been induced in diatoms by cell-free exudates, opening new possibilities for molecular ‘dissection’ of sexualization.     

Bacterial and archaeal flagella as prokaryotic motility organelles

The properties and molecular organization of flagella—the bacterial and archaeal motility organelles—are reviewed. The organization of these functional motility elements of prokaryotic organisms belonging to different kingdoms is compared. A mechanism for both in vivo and in vitro assembly of bacterial flagellum filaments (BFFs) is discussed, and similarity is supposed between flagellin and actin with regard to their polymeric forms (BFF and F-actin). Our own data on intracellular fixation of the Halobacterium salinarium flagellum are presented. Comparative characteristics of intracellular fixation of bacterial and archaeal flagella are also described.Translated from Biokhimiya, Vol. 69, No. 11, 2004, pp. 1477–1488.Original Russian Text Copyright © 2004 by Metlina.     

Kinetics of metal toxicity in plant roots and its effects on root morphology

Aims

We evaluated the efficacy of biochar application for suppressing bacterial wilt of tomato and identified the potential underlying mechanisms involved in the disease control.

Methods

We measured the impact of two different sized biochar (53–120 μm and 380–830 μm) on bacterial wilt incidence in a greenhouse experiment. The efficiency of different sized biochar for the adsorption of tomato root exudates and the pathogen was further examined in vitro. We also quantified the effects of biochar and tomato root exudates on two pathogen virulence factors, chemotaxis, swarming motility and examined the effect of biochar on pathogen root colonization.

Results

Fine biochar application (3%; w:w) significantly decreased the bacterial wilt incidence by 19.9%. Biochar with different particle size had similar adsorption capacity for root exudates, while fine biochar was efficient (91%) in pathogen adsorption. Root exudates and fine biochar increased the chemotaxis ability of pathogen, while fine biochar reduced pathogen swarming motility and rhizosphere colonization.

Conclusions

Application of fine biochar can significantly decreased bacterial wilt incidence. This was mechanistically explained by biochar ability to 1) adsorb pathogen directly and indirectly via adsorption of root exudates (based on pathogen chemotaxis) and to 2) directly suppress pathogen swarming motility and subsequent root colonization.

     

Inorganic polyphosphate occurs in the cell wall of <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> and accumulates during cytokinesis

Background  

Inorganic polyphosphate (poly P), linear chains of phosphate residues linked by energy rich phosphoanhydride bonds, is found in every cell and organelle and is abundant in algae. Depending on its localization and concentration, poly P is involved in various biological functions. It serves, for example, as a phosphate store and buffer against alkali, is involved in energy metabolism and regulates the activity of enzymes. Bacteria defective in poly P synthesis are impaired in biofilm development, motility and pathogenicity. PolyP has also been found in fungal cell walls and bacterial envelopes, but has so far not been measured directly or stained specifically in the cell wall of any plant or alga.     

New structural and functional defects in polyphosphate deficient bacteria: A cellular and proteomic study

Background  

Inorganic polyphosphate (polyP), a polymer of tens or hundreds of phosphate residues linked by ATP-like bonds, is found in all organisms and performs a wide variety of functions. PolyP is synthesized in bacterial cells by the actions of polyphosphate kinases (PPK1 and PPK2) and degraded by exopolyphosphatase (PPX). Bacterial cells with polyP deficiencies due to knocking out the ppk1 gene are affected in many structural and important cellular functions such as motility, quorum sensing, biofilm formation and virulence among others. The cause of this pleiotropy is not entirely understood.     

Arp2/3 complex activity in filopodia of spreading cells

Background  

Cells use filopodia to explore their environment and to form new adhesion contacts for motility and spreading. The Arp2/3 complex has been implicated in lamellipodial actin assembly as a major nucleator of new actin filaments in branched networks. The interplay between filopodial and lamellipodial protrusions is an area of much interest as it is thought to be a key determinant of how cells make motility choices.     

How Bacteriophage χ Attacks Motile Bacteria

Bacteriophage chi attaches to the filament of a bacterial flagellum by means of a tail fiber, but the ultimate receptor site for the phage is located at the base of the bacterial flagellum. Here, the phage injects its deoxyribonucleic acid into the bacterium, leaving the empty phage attached at the base. It is suggested that chi slides along the filament of the flagellum to the base, owing to the movement of the flagellum. The role of motility would thus be to provide for rapid adsorption of the phage by guiding the phage to the adsorption sites at the bases of the flagella. Bacteria whose motility has been strongly inhibited by cold or anaerobic conditions still adsorb chi at the filaments and bases of flagella if a high multiplicity is used. This indicates that direct collisions with the bases may also be possible. Bacteria must be flagellated in order for chi to attach, but only a short flagellum, perhaps only the flagellar base, is necessary.     

Interactions between flagellar and type III secretion proteins in <Emphasis Type="Italic">Chlamydia pneumoniae</Emphasis>

Background  

Flagellar secretion systems are utilized by a wide variety of bacteria to construct the flagellum, a conserved apparatus that allows for migration towards non-hostile, nutrient rich environments. Chlamydia pneumoniae is an obligate, intracellular pathogen whose genome contains at least three orthologs of flagellar proteins, namely FliI, FlhA and FliF, but the role of these proteins remains unknown.     

Automated characterization of cell shape changes during amoeboid motility by skeletonization

Background  

The ability of a cell to change shape is crucial for the proper function of many cellular processes, including cell migration. One type of cell migration, referred to as amoeboid motility, involves alternating cycles of morphological expansion and retraction. Traditionally, this process has been characterized by a number of parameters providing global information about shape changes, which are insufficient to distinguish phenotypes based on local pseudopodial activities that typify amoeboid motility.     

Prenatal household size and composition are associated with infant fecal bacterial diversity in Cebu,Philippines

Objectives

The gut microbiome (GM) connects physical and social environments to infant health. Since the infant GM affects immune system development, there is interest in understanding how infants acquire microbes from mothers and other household members.

Materials and Methods

As a part of the Cebu Longitudinal Health and Nutrition Survey (CLHNS), we paired fecal samples (proxy for the GM) collected from infants living in Metro Cebu, Philippines at 2 weeks (N = 39) and 6 months (N = 36) with maternal interviews about prenatal household composition. We hypothesized that relationships between prenatal household size and composition and infant GM bacterial diversity (as measured in fecal samples) would vary by infant age, as well as by household member age and sex. We also hypothesized that infant GM bacterial abundances would differ by prenatal household size and composition.

Results

Data from 16 S rRNA bacterial gene sequencing show that prenatal household size was the most precise estimator of infant GM bacterial diversity, and that the direction of the association between this variable and infant GM bacterial diversity changed between the two time points. The abundances of bacterial families in the infant GM varied by prenatal household variables.

Conclusions

Results highlight the contributions of various household sources to the bacterial diversity of the infant GM, and suggest that prenatal household size is a useful measure for estimating infant GM bacterial diversity in this cohort. Future research should measure the effect of specific sources of household bacterial exposures, including social interactions with caregivers, on the infant GM.

     

Relationship between semen characteristics and body size in Barbus barbus L. (Teleostei: Cyprinidae) and effects of ions and osmolality on sperm motility

The objectives of the present study were to determine the relationships among length and weight of males, sperm volume, spermatozoa concentration, total number of spermatozoa, ionic contents and osmolality of seminal plasma in Barbus barbus. The effect of osmolality on sperm motility parameters after activation in NaCl, KCl, or sucrose solutions was also examined. There were significant correlations between spermatozoa concentration – length (R = + 0.7) and – weight (R = + 0.8) of males. No significant correlations were observed between the total number of spermatozoa, sperm volume, and length and weight of males. Seminal plasma osmolality was higher when the total number of spermatozoa (R = + 0.6) and sperm volume (R = + 0.6) were higher. Sperm motility and velocity was positively correlated with osmolality (R = + 0.5). The correlation between sperm motility and K⁺ was negative (R = 0.5), but positively correlated with Ca²⁺ (R = 0.8), Na⁺ (R = 0.8), and Cl⁻ (R = 0.8). There was a rapid decrease (P < 0.05) in sperm motility parameters after sperm activation. Just after sperm activation, beating waves propagated along the full length of flagella. At latter stages post sperm activation, the waves appeared only in proximal part of the flagellum. The highest spermatozoa velocity and percentage of motility were observed at 215–235 mOsmol kg^− 1 in NaCl, KCl or sucrose. The tip of the flagellum became curled into a loop shape which shortened the flagellum after activation of sperm in distilled water. B. barbus sperm is very similar to that of other cyprinids in terms of ionic contents and osmolality of the seminal plasma, mechanism of sperm activation and behavior and motility of sperm during swimming period.     

Involvement of SPI-2-encoded SpiC in flagellum synthesis in Salmonella enterica serovar Typhimurium

Background  

SpiC encoded within Salmonella pathogeniCity island 2 on the Salmonella enterica serovar Typhimurium chromosome is required for survival within macrophages and systemic infection in mice. Additionally, SpiC contributes to Salmonella-induced activation of the signal transduction pathways in macrophages by affecting the expression of FliC, a component of flagella filaments. Here, we show the contribution of SpiC in flagellum synthesis.     

Certain Strongylocentrotus purpuratus sperm mitochondrial proteins co-purify with low density detergent-insoluble membranes and are PKA or PKC-substrates possibly involved in sperm motility regulation

Background

Sea urchin sperm motility is regulated by Speract, a sperm-activating peptide (SAP) secreted from the outer egg coat. Upon binding to its receptor in the sperm flagellum, Speract induces a series of ionic and metabolic changes in Strongylocentrotus purpuratus spermatozoa that regulate their motility. Among these events, protein phosphorylation is one of the most relevant and evidence indicates that some proteins of the Speract signaling cascade localize in low density detergent-insoluble membranes (LD-DIM).

Methods

LD-DIM-derived proteins from immotile, motile or Speract-stimulated S. purpuratus sperm were resolved in 2-D gels and the PKA and PKC substrates detected with specific antibodies were identified by LC–MS/MS.

Results

Differential PKA and PKC substrate phosphorylation levels among the LD-DIM isolated from sperm in different motility conditions were found and identified by mass spectrometry as: ATP synthase, creatine kinase, NADH dehydrogenase (ubiquinone) flavoprotein 2, succinyl-CoA ligase and the voltage-dependent anion channel 2 (VDAC2), which are mitochondrial proteins, as well as, the cAMP-dependent protein kinase type II regulatory (PKA RII) subunit, Tubulin β chain and Actin Cy I changed their phosphorylation state.

Conclusions

Some mitochondrial proteins regulated by PKA or PKC may influence sea urchin sperm motility.

General significance

The fact that a high percentage (66%) of the PKA or PKC substrates identified in LD-DIM are mitochondrial proteins suggests that the phosphorylation of these proteins modulates sea urchin sperm motility via Speract stimulation by providing sufficient energy to sperm physiology. Those mitochondrial proteins are indeed PKA- or PKC-substrates in the sea urchin spermatozoa.