Ancestry and adaptive radiation of Bacteroidetes as assessed by comparative genomics

To date, the phylum Bacteroidetes comprises more than 1,500 described species with diverse ecological roles. However, there is little understanding of archetypal Bacteroidetes traits at a genomic level. In this study, a representative set of 89 Bacteroidetes genomes was compiled, and pairwise reciprocal best-match gene comparisons and gene syntenies were used to identify common traits that allowed Bacteroidetes evolution and adaptive radiation to be traced. The type IX secretion system (T9SS) was highly conserved among all studied Bacteroidetes. Class-level comparisons furthermore suggested that the ACIII-caa₃COX super-complex evolved in the ancestral aerobic bacteroidetal lineage, and was secondarily lost in extant anaerobic Bacteroidetes. Another Bacteroidetes-specific respiratory chain adaptation was the sodium-pumping Nqr complex I that replaced the ancestral proton-pumping complex I in marine species. T9SS plays a role in gliding motility and the acquisition of complex macro-molecular organic compounds, and the ACIII-caa₃COX super-complex allows effective control of electron flux during respiration. This combination likely provided ancestral Bacteroidetes with a decisive competitive advantage to effectively scavenge, uptake and degrade complex organic molecules, and therefore has played a pivotal role in the successful adaptive radiation of the phylum.     

Lipids of the marine bacterium Flexibacter polymorphus

This paper reports on the total fatty acid composition of a marine bacterium representative of the genus Flexibacter. Flexibacter polymorphus is unusual in containing a high proportion of the polunsaturated acid C20:53 whilst the level of branched fatty acids is low. These facts suggest that the membrane flexibility necessary for its gliding motility is a function of the polyunsaturated fatty acid composition. Biosynthetic precursors to the C20:5 acid are present which are characteristic of an oxygen-dependent pathway. The fatty acid composition of the structural lipids is influenced by changes in the culture medium. Na₂S inhibits production of the C20:5 acid at levels much lower than that at which it is known to inhibit growth. The intracellular granules observable in F. polymorphus do not contain elemental sulphur, in contrast to Beggiatoa sps., but instead probably contain lipids.     

Lack of relationship between gliding cyanobacteria and filamentous gliding heterotrophic eubacteria: comparison of 16S rRNA catalogues of Spirulina,Saprospira, Vitreoscilla,Leucothrix, and Herpetosiphon

Spirulina platensis and Spirulina maxima were characterized by 16S ribosomal RNA oligonucleotide cataloguing. Both species are highly related. They fall into the main group of the cyanobacteria, showing a remote relationship to Nostoc, Fischerella, Aphanocapsa, and also to Prochloron. Low similarity coefficients were found between the Spirulina species and certain organotrophic and sulfide oxidizing bacteria, viz. Saprospira grandis, Vitreoscilla stercoraria, Leucothrix mucor, Herpetosiphon aurantiacus, and Beggiatoa leptomitiformis, respectively. This result does not support the classical hypothesis that certain filamentous gliding bacteria are apochlorotic cyanobacteria.     

Triclosan: a widely used biocide and its link to antibiotics

Mycoplasmas are cell wall-less bacteria at the low extreme in genome size in the known prokaryote world, and the minimal nature of their genomes is clearly reflected in their metabolic and regulatory austerity. Despite this apparent simplicity, certain species such as Mycoplasma pneumoniae possess a complex terminal organelle that functions in cytadherence, gliding motility, and cell division. The attachment organelle is a membrane-bound extension of the cell and is characterized by an electron-dense core that is part of the mycoplasma cytoskeleton, defined here for working purposes as the protein fraction that remains after extraction with the detergent Triton X-100. This review focuses on the architecture and assembly of the terminal organelle of M. pneumoniae. Characterizing the downstream consequences of defects involving attachment organelle components has made it possible to begin to elucidate the probable sequence of certain events in the biogenesis of this structure.     

Dorsal-ventral differentiation in Simonsiella and other aspects of its morphology and ultrastructure

The morphology and ultrastructure of the aerobic, Gram-negative multicellular-filamentous bacteria of the genus Simonsiella were investigated by scanning and transmission electron microscopy. The flat, ribbon-shaped, multicellular filaments show dorsal-ventral differentiation with respect to their orientations to solid substrata. The dorsal surface, orientated away from the substrate, is convex and possesses an unstructured capsule. The ventral surface, on which the organisms adhere and glide, is concave and has an extracellular layer with fibrils extending at right angles from the cell wall. The cytoplasm in the ventral region contains a proliferation of intracytoplasmic membranes and few ribosomes in comparison to the cytoplasm in other parts of the cell. Centripetal cell wall formation is asymmetrical and commences preferentially in the ventral region. Quantitative differences in morphology and cytology exist among selected Simonsiella strains. Functional aspects of this dorsalventral differentiation are discussed with respect to the colonization and adherence of Simonsiella to mucosal squamous epithelial cells in its ecological habitat, the oral cavities of warm-blooded vertebrates.List of Abbreviations SEM scanning electron microscope - TEM transmission electron microscope     

Inhibition of Cytophaga U67 gliding motility by inhibitors of polypeptide synthesis

Gliding motility of Cytophaga U67 and several other cytophagas was inhibited by a growth-permissive concentration of chloramphenicol (50 g/ml). Several other inhibitors of polypeptide synthesis also demonstrated this effect. Short-term exposure to several of these inhibitors resulted in reversible inhibition of gliding by growing cells. In wet mounts chloramphenicol-grown cells demonstrated non-translocational tumbling. Electrophoretic patterns of polypeptides released by ethylenediaminetetraacetate treatment of control and chloramphenicol-grown cells were distinct. Gliding of a spontaneous mutant was resistant to chloramphenicol at 50 g/ml; its motility was inhibited at the growth-permissive concentration of 400 g/ml.     

Gliding motility of Peloploca spp., and their distribution in the sediment and water column of a eutrophic lake

Observations indicating gliding motility in the gas-vacuolate, filamentous organism Peloploca were made using microcapillary tubes. Tubes containing semi-solid agar, incubated in sediment cores gave good enrichments of Peloploca spp. The organisms, which had the form of helical bundles of filaments, were seen to corkscrew through the agar at up to 2–3 m s^-1.The vertical distribution of Peloploca spp. in the sediment and water column of a eutrophic lake was examined periodically during summer stratification. The organisms were confined to anoxic conditions in the sediment prior to stratification. With increasing anoxia in the hypolimnion, the population shifted upwards in the sediment, and towards the end of stratification, in the most reducing conditions, appeared in the lower hypolimnion. Anaerobically incubated sediment cores also showed the movement of the Peloploca population from sediment into the overlying water.It is suggested that the gliding motility and helical morphology of Peloploca bundles enable them to migrate through sediment in response to oxygen and Eh gradients, in addition to their use of gas vacuoles to adjust their position in the water column. The taxonomic implications of gliding motility in Peloploca spp. are discussed.     

Improvement of glidobactin A production byPolyangium brachysporum

Summary Glidobactins A, B and C are lipopeptide antitumor antibiotics produced by the gliding bacteriumPolyangium brachysporum sp. nov. No. K481-B101. The production of glidobactin A was examined in shake flasks and laboratory fermentors. Medium screening and optimization led to approximately five fold increases in glidobactin A titers in shake flasks and a ten fold increase in titers in 40-1 batch fermentations. Utilization of a stepped glucose feeding protocol resulted in glidobactin A titers of 1860 g/ml after 144 h of fermentation.     

Carotenoid glucosides and menaquinones from the gliding bacterium Herpetosiphon giganteus Hp a2

The gliding bacterium Herpetosiphon giganteus Hp a2 was shown to contain -carotene, one monoglucosyloxy and two new diglucosyloxy carotenoids with a x-O-acyl-diglucosyloxy carotenoid as main component. Flexirubin-like pigments could not be detected in this organism.As in the Myxobacterales and Cytophagales (Kleinig et al., 1974) menaquinones (MK-6 and MK-7) were found to be the only isoprenoid quinones present in Herpetosiphon.The chemosystematic implications of these findings are briefly discussed.     

Isosphaera pallida,gen. and comb. nov., a gliding,budding eubacterium from hot springs

An unusual filamentous, budding bacterium was isolated from several North American hot springs and named Isosphaera pallida. Filaments are composed of spherical cells 2.5–3.0 m in diameter, with cell growth and division occurring by formation of intercalary buds. These obligately aerobic, heterotrophic isolates closely resemble Isocystis pallida Woronichin, which has been previously described as a cyanobacterium, and later as a yeast, based on collected specimens.Isolates were salmon-colored due to the presence of carotenoids and contained gas vesicles. Growth occurred at temperatures up to 55° C in defined media using 0.025% glucose or lactate as carbon sources. Glucose concentrations of 0.05% or higher inhibited growth of the culture.Ultrathin sections observed by TEM revealed an unusual tri-laminar wall structure. Pit-like ultrastructural features were found in the cell wall. Growth of cultures was not inhibited by penicillin G, and the Gram reaction gave variable results.Cells formed motile, macroscopic aggregates (comets) when harvested from liquid cultures and plated on media containing Gelrite (Kelco Co.) as a solidifying agent. Aggregation and motility were observed in both the light and the dark. However, comets were strongly phototactic. Negative stains revealed numerous pili, but not flagella.We propose that this highly unusual prokaryote be placed in a new genus.