Ultrastructure and chemical composition of the sheath of Leptothrix discophora SP-6 (original) (raw)
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Applied and Environmental Microbiology, 1992
Leptothrix discophora SP-6 was isolated from the outflow reservoir of an artificial iron seep. Its sheathforming phenotype was maintained by slow growth in a mineral salts-vitamin-pyruvate medium under minimal aeration at 20 to 25°C. A sheathless variant, SP-6(sl), was isolated from smooth colonies that appeared on spread plates after rapid growth of SP-6 in well-aerated cultures. SP-6 and SP-6(sl) are closely related but not identical to the previously studied sheathless strain SS-1 (ATCC 43182). Increasing Mn 2+ concentrations in the growth medium of SP-6 increased the phase density of the sheath, indicating increased Mn oxide deposition in the sheath. Electron microscopy of cultures grown without added Mn 2+ revealed that the sheath consisted of a well-defined inner layer, 30 to 100 nm thick, and a diffuse outer capsular layer of variable thickness. Mn oxides were identified in the sheath by their characteristic ultrastructure, electron density, and X-ray-dispersive energy spectr...
Formation of artificial sheaths of Leptothrix sp . under laboratory conditions
2015
Correspondance: Ralitsa Angelova Department of General and Industrial Microbiology, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria. Tel: +359 896 858 712 e-mail: raly_angelova@abv.bg; ABSTRACT The object of this research are the neutrophilic sheath forming iron bacteria from genus Leptothrix isolated from natural stream located in Vitosha Mountain. These bacteria facilitate the iron mineralization and formation the insoluble ferric oxides/(oxy)hydroxides after Fe 2+ -oxidation at neutral pH. The aim of this investigation is establishing the conditions for the formation of tubular structures (sheaths) typical for these bacteria. For this goal cultivation on an elective growth medium and the characterization of the structures formed by optical microscopy and SEM, SEM/EDX, TEM and XRD were performed. The formation of the sheaths was observed at 20 о С using a flask-shaking technique. It started after 7 days of the cultivation. Light micrograph images and SEM unveiled that the...
RoleofDisulfide BondsinMaintaining theStructural Integrity oftheSheath ofLeptothrix discophora SP6
1993
caused more rapid degradation ofthesheath thancyanide or sulfite. Treatment ofthesheath with1N NaOH resulted inrapid breakdown, while treatment with1N HCIresulted inslowbut significant hydrolysis. Transmission electron microscopy showedthatthe6.5-nm fibrils previously showntobe an integral structural element ofthesheath fabric (D.EmersonandW.C.Ghiorse, J.Bacteriol. 175:7808-7818, 1993) were progressively dissociated intorandommasses duringDTT-induced degradation. Quantitation of disulfide bondswithDTT showedthatthesheaths contained approximately 2.2,umol ofdisulfides per mg of sheathprotein. Reaction with5,5'-dithio-bis-(2-nitrobenzoic acid)showedthatsheaths alsocontained approximately 0.8,umoloffreesulfhydryls per mg ofprotein. A sulfhydryl-specific fluorescent probe (fluorescein 5-maleimide) showedthatthefreesulfhydryls insheathed cell filaments were evenly distributed throughout thesheath. Sodiumdodecyl sulfate-polyacrylamide gelelectrophoresis autoradiography of ('4C)i...
Influence of Manganese on Growth of a Sheathless Strain of Leptothrix discophora
Applied and Environmental Microbiology, 1985
Mn 2+ exerted various effects on the growth of Leptothrix discophora strain SS-1 in batch cultures depending on the concentration added to the medium. Concentrations of 0.55 to 5.5 μM Mn 2+ , comparable to those in the environment from which strain SS-1 was isolated, decreased cell yield and prolonged stationary-phase survival, but did not affect growth rate. Elevated concentrations of 55 to 910 μM Mn 2+ also decreased cell yield and prolonged survival, but growth rate was decreased as well. The addition of 1,820 μM Mn 2+ caused a decline in cell numbers followed by an exponential rise after 80 h of incubation, indicating the development of a population of cells resistant to Mn 2+ toxicity. When 360 μM Mn 2+ or less was added to growth flasks, Mn 2+ was oxidized to manganese oxide (MnO x , where x is ∼2), which appeared as brown particles in the medium. Quantification of Mn oxidation during growth of cultures to which 55 μM Mn 2+ was added showed that nearly all of the Mn 2+ was oxi...
Enzymatic iron oxidation by Leptothrix discophora: identification of an iron-oxidizing protein
Applied and Environmental Microbiology, 1992
An iron-oxidizing factor was identified in the spent culture medium of the iron- and manganese-oxidizing bacterial strain Leptothrix discophora SS-1. It appeared to be a protein, with an apparent molecular weight of approximately 150,000. Its activity could be demonstrated after fractionation of the spent medium by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A spontaneous mutant of L. discophora SS-1 was isolated which excreted neither manganese- nor iron-oxidizing activity, whereas excretion of other proteins seemed to be unaffected. Although the excretion of both metal-oxidizing factors was probably linked, the difference in other properties suggests that manganese and iron oxidation represent two different pathways. With a dot-blot assay, it was established that different bacterial species have different metal-oxidizing capacities. Whereas L. discophora oxidized both iron and manganese, Sphaerotilus natans oxidized only iron and two Pseudomonas spp. oxidized only m...
The EMBO journal, 1983
Proteins can be extracted from the slime sheath of Dictyostelium discoideum slugs by denaturing agents. A subset of these proteins is also released by cellulase digestion of the sheath, implying that protein-protein and protein-cellulose interactions are involved in sheath protein retention. It seems probable that the cellulose-associated sheath proteins are also associated with the cellulose of mature stalk cells. Monoclonal antibodies directed against sheath demonstrate extensive sharing of antigenic determinants between sheath proteins and a limited degree of antigenic sharing between sheath and slug cell proteins. All of the proteins recognised by these monoclonal antibodies are developmentally regulated. These results are discussed in terms of the structure of the sheath and its possible role(s) in D. discoideum development.
Carbon and Steel Surfaces Modified by Leptothrix discophora SP-6: Characterization and Implications
Environmental Science & Technology, 2007
Leptothrix discophora SP-6, a type of manganese(Mn)oxidizing bacteria, has been known to accumulate Mn oxides from the aqueous environment and thus play a key role in microbiologically influenced corrosion by increasing the electrochemical potential of steel and other metals. Similarly, this bacterium was found to modify the surface of glassy carbon in aqueous solution and increase its potential (i.e., ennoblement). In the latter case, biomineralized Mn oxides can be used as cathodic reactants for a new generation of microbial fuel cells featuring a biocathode. In this preliminary study, factors affecting the biofilm formation and biomineralization processes were examined. The inflow of air into the culture medium was found essential to sustain the ennoblement of substrate electrodes. The OCP and FESEM/EDS data indicated that a smoother initial substrate surface generally led to better ennoblement. Polarizing the carbon electrode at +500 mV SCE for 15 min was found to facilitate the ennoblement on carbon electrodes, and so did coating it with a poly(L-lysine) layer. Independent of substrate material, initial surface roughness, and pretreatment, there were three parameters in the EIS equivalent circuit that correlated well with the OCP indicating the level of ennoblement by L. discophora SP-6, i.e., electrolyte resistance, double-layer capacitance, and low-frequencies capacitance. These fascinating findings merit further investigation as they may shed light on the fundamental bacteria/substrate interactions and help advance the knowledge base needed for the engineering applications.
Characterization of extracellular polymers of Phaeocystis globosa and P. antarctica
Marine Ecology Progress Series, 2003
Extracellular polymers of Phaeocystis globosa and P. antarctica were characterized by elemental analysis, X-ray photoelectron spectroscopy (XPS), and matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) analysis. The 2 species were grown in axenic and bacterized cultures to examine the effect of bacterial degradation on the composition of the extracellular polymers. The C:N ratios for extracellular polymers from P. globosa and P. antarctica grown under these conditions were lower (< 9) than in previous reports (>12). P. antarctica polymer C:N was significantly lower than that of P. globosa. Contrary to expectations, the polymer C:N from bacterized cultures was slightly lower than from axenic cultures. XPS analysis indicated that the polymers are carbohydrate-rich, and MALDI-TOF-MS analysis showed that the nitrogen was not proteinaceous, but probably originated from low molecular weight compounds such as amino sugars. The low C:N ratios suggest that extracellular polymers may directly provide a substrate for bacteria and heterotrophic protists without the need for other sources of nitrogen.