Rhizobium meliloti MVII-1 and Rhizobium lupini H13-3, two strains with five to ten peritrichously inserted complex flagella, were studied with respect to motility and chemotaxis. Cells of both these strains move rapidly with speeds up to 40 pm s-I (R. meZiZoti) and 60 pm s-' ( R . Zupini) respectively. Increasing viscosity causes little reduction in their swimming velocities as compared with Salmonella typhimurium propelled by plain flagella. It is suggested that complex flagella possess a high 'flexural rigidity', which serves to maintain a helix conformation favourable for propulsive efficiency at increased viscosities. C hemotaxis in R . meliloti MVII-1 and R . lupini H13-3 was studied and the conditions required have been defined using the capillary tube assay. All 20 common L-amino acids and L-homoserine were shown to be attractive to R . meliloti MVII-1 with thresholds varying from lop6 M (proline) to M (aspartate). Leucine, proline and lysine elicited optimal responses. R hizobium lupini H13-3 was also attracted by L-amino acids except for leucine, which elicited no response. Aspartate was a significantly better attractant of R . Zupini H13-3 than of R . meliloti MVII-1, and glycine, isoleucine, homoserine, serine, threonine, cysteine, glutamine and glutamate were

Abstract. An angular plate-shaped weakly motile mesophilic methanogen was isolated from a swamp of drilling waste in Italy. Growth occurs on H 2 /C0 2 or on formate. Acetate is required in addition. The optimal doubling time is 7h at 40" C. The cell envelope is composed most likely of glycoprotein subunits in hexagonal arrangement. The GC-content of its DNA is 47.5 mol%. On the basis of DNA-RNA hybridization it was found to represent a new family, the Methanoplanaceae within the order Mcthanomicrobiales.Key words: Methanogens -Archaebacteria -Cell division -Glycoprotein -Acetate -Taxonomy Recently, a square-shaped flat bacterium was discovered in a saturated salt brine (Walsby 1980; Stoeckcnius 1981), which, however, cannot yet be cultivated in the laboratory. It was assumed (Walsby 1980) that the unusual shape may be explained by the absence of cell turgor in bacteria in a high ionic strength environment. From the composition of its envelope, Walsby (1980) speculates that this organism belongs to the archaebacteria.I lere, we report on the isolation and properties of another Hat archaebaclerium, which, however, grows at much lower ionic strength and which belongs to the methanogens. Materials and Methods StrainsMethanogenium marisnigri* DSM 1498, was obtained from the Deutsche Sammlung von Mikroorganismen, Göttingen. Cull arc ConditionsThe isolate M3 was cultivated by using the technique described by Halch and Wolfe (1976). If not mentioned otherwise, the isolate was grown in % *MCP medium, that is medium 3 of Halch el al. (1979), modified by the use of "Pepton aus Casein, tryptisch verdaut" (Merck) instead of Irypliease (HHl.) and by adjusting the pi I to (>.9 (11 2 S0 4 ).Twenty milliliter cultures were grown in stoppered pressurized UK) ml serum bottles (Hormioli. Italy) made of "type I IP-glass by incubation in water bath shakers (New Brunswick) at 140rpm and 37 "C..ihbrrvhitii'ns tilt*. I itiauiik* I losinc; SPS: Sodium dodccylsulfalc (Sodium lauryl sulfate) Methanogenium marisnigri, as a reference, was grown in the same medium. PlatingPolysilicate plates were prepared as described (Stettcr ct al. 1981) except that they were equilibrated with MG-medium containing penicillin, vancomycin, kanamycin (each 150 ug/ml) and tetracycline (100 ug/ml) to prevent eubacterial contaminations. Light MicroscopyThe cells were viewed and photographed with a Leitz Ortholuxll microscope, equipped with a vario-orlhomat camera system (Leitz). Fluorescence was observed in a Zeiss Standard fluorescence microscope with an excitation filler H436 and a selection filler LP 470. Electron MicroscopyFor thin sectioning, cell sediments were fixed in MG-medium not containing organic components with 20 g glutaraldehyde/l for 2h and post fixed with 10 g Os0 4 /l for 1 h. Durcupan (Fluka) epoxy resin was used for embedding and thin sections were contrasted with lead citrate (5 min), uranylacetate (5 min) and again with lead citrate (3 min). For shadowing, the cells were fixed on parlodion coated grids and shadowcasted (Edwards vacuum co...

The complex flagella of Rhizobium meliloti 2011 and MVII-1 were analyzed with regard to serology, fine structure, subunits, and amino acid composition. The serological identities of flagellar filaments of the two strains were demonstrated by double immunodiffusion with antiflagellin antiserum. The filaments had a diameter of 16 nm. Their morphology was dominated by the prominent undulations of an external three-start helix running at a 10-nm axial distance and at an angle of 320. Faint nearly axial striations indicated the presence of a tubular core of a different helical order. The complex filaments consisted of 40,000-dalton flagellin monomers. Typically, the amino acid composition was 3 to 4% higher in nonpolar residues and 5 to 7% lower in aspartic and glutamic acids (and their amides) than that of plain flagellar proteins. There were no immunochemical relationships among Pseudomonas rhodos, Rhizobium lupini, and R. meliloti complex flagella, suggesting that the latter represent a new class.

Effects of diazepam (Valium) on photosynthesis, chlorophyll/photosynthesis ratios, respiration, uptake of rubidium ions, and ultrastructure of Scenedesmus obliquus synchronized by a light-dark regimen of 14:10 hrs were determined. 80 and 160 muM diazepam, added to the nutrient medium at the start of the light-dark change (i.e., start of the cell cycle) gradually reduced rates of photosynthesis, below the initial rates from the beginning of the experiment. Contents of chlorophyll, however, remained nearly unaffected. Consequently, the diazepam-treated cells had a higher chlorophyll/photosynthesis ratio--also with regard to respiration in order to calculate the gross photosynthesis. The occurrence of photorespiration cannot be assumed. The net influx of rubidium was slightly reduced by 100 muM diazepam 0.5 and 2.0 hrs after the start of the cell cycle and was strongly inhibited after 5 to 14 hrs. 80 and 160 muM diazepam caused separation of thylakoids, formation of giant mitochondria and enlargement of vacuoles.