RESUMEN
A small irregular coccoid methanogenic bacterium (PAT) was isolated from the hindgut of the cockroach Periplaneta americana. Fluorescence microscopy and transmission electron microscopy of the hindgut of P. americana suggest that the organism occurs abundantly in the microbiota attached to the hindgut wall. The strain produces methane by the reduction of methanol and methylated amines with molecular hydrogen. Acetate, coenzyme M, yeast extract, tryptic soy broth and vitamins are required for growth. The cells lack a rigid cell wall and lyse immediately in buffers of low ionic strength. Maximum rate of growth (specific growth rate, 0.22 h(-1)) occurs in a rich medium at 39 degrees C, at a pH range of 7.2-7.7 and at a salt concentration below 100 mM NaCl. Sequence analysis of the small-subunit rDNA indicates that strain PAT is related to the family Methanosarcinaceae but does not belong to any previously described genus. Therefore, it is proposed that strain PAT be classified in a new genus, related to the Methanosarcinaceae, as Methanomicrococcus blatticola (type strain PAT = DSM 13328T).
Asunto(s)
Metano/metabolismo , Metanol/metabolismo , Methanosarcinales/clasificación , Metilaminas/metabolismo , Periplaneta/microbiología , Animales , ADN de Archaea/análisis , ADN de Archaea/genética , ADN Ribosómico/análisis , ADN Ribosómico/genética , Sistema Digestivo/microbiología , Methanosarcinales/genética , Methanosarcinales/fisiología , Datos de Secuencia Molecular , Oxidación-Reducción , ARN Ribosómico/genética , Análisis de Secuencia de ADNRESUMEN
A rabbit antiserum was raised against the photoactive yellow protein (PYP) from Ectothiorhodospira halophila and purified by adsorption experiments to obtain a highly specific polyclonal antiserum. This antiserum was used to obtain the following results. (i) In E. halophila, PYP can be isolated from the fraction of soluble proteins. In the intact cell, however, PYP appeared to be associated with (intra)cytoplasmic membranes, as was concluded from analysis of immunogold-labelled thin sections of the organism. (ii) The regulation of expression of PYP was studied by using dot blot assays, Western blotting (immunoblotting), and rocket immunoelectrophoresis. Under all conditions investigated (light color, salt concentration, and growth phase), PYP was expressed constitutively in E. halophila. However, when Rhodospirillum salexigens was grown aerobically, the expression of PYP was suppressed. (iii) A large number of prokaryotic microorganisms contained a single protein, with an apparent size of approximately 15 kDa, that cross-reacted with the antiserum. Among the positively reacting organisms were both phototrophic and chemotrophic, as well as motile and nonmotile, organisms. After separation of cellular proteins into a membrane fraction and soluble proteins, it was established that organisms adapted to growth at higher salt concentrations tended to have the cross-reacting protein in the soluble fraction. In the cases of R. salexigens and Chromatium salexigens, we have shown that the cross-reacting protein involved is strongly homologous to PYP from E. halophila.
Asunto(s)
Bacterias/química , Proteínas Bacterianas/aislamiento & purificación , Fotorreceptores Microbianos , Secuencia de Aminoácidos , Anticuerpos Antibacterianos , Bacterias/inmunología , Bacterias/metabolismo , Proteínas Bacterianas/biosíntesis , Proteínas Bacterianas/clasificación , Proteínas Bacterianas/inmunología , Compartimento Celular , Reacciones Cruzadas , Regulación Bacteriana de la Expresión Génica , Inmunohistoquímica , Microscopía Inmunoelectrónica , Datos de Secuencia Molecular , Homología de Secuencia de AminoácidoRESUMEN
The motile, alkalophilic, and extremely halophilic purple sulfur bacterium Ectothiorhodospira halophila is positively photophobotactic. This response results in the accumulation of bacteria in light spots (E. Hustede, M. Liebergesell, and H. G. Schlegel, Photochem. Photobiol. 50:809-815, 1989; D. E. McRee, J. A. Tainer, T. E. Meyer, J. Van Beeumen, M. A. Cusanovich, and E. D. Getzoff, Proc. Natl. Acad. Sci. USA 86:6533-6537, 1989; also, this work). In this study, we demonstrated that E. halophila is also negatively phototactic. Video analysis of free-swimming bacteria and the formation of cell distribution patterns as a result of light-color boundaries in an anaerobic suspension of cells revealed the existence of a repellent response toward intense (but nondamaging) blue light. In the presence of saturating background photosynthetic light, an increase in the intensity of blue light induced directional switches, whereas a decrease in intense blue light gave rise to suppression of these reversals. To our knowledge, this is the first report of a true repellent response to light in a free-swimming eubacterium, since the blue light response in Escherichia coli and Salmonella typhimurium (B. L. Taylor and D. E. Koshland, Jr., J. Bacteriol. 123:557-569, 1975), which requires an extremely high light intensity, is unlikely to be a sensory process. The wavelength dependence of this negative photoresponse was determined with narrow band pass interference filters. It showed similarity to the absorption spectrum of the photoactive yellow protein from E. halophila.