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Pore-forming protein (porin) was isolated from N,N-dimethyl-dodecylaminoxid (LDAO)-extracted outer membranes of Synechococcus PCC 6301 and purified by ion exchange chromatography on DEAE-Sephacel column. The apparent molecular mass on SDS-PAGE was determined to be about 52000. The native porin was reconstituted into black lipid bilayer membranes and showed a single-channel conductance of 5.5 nS in 1 M KCl. The porin was found to be N-terminally blocked. The C-terminal amino acid sequence was identified as Phe-Thr-Phe. Amino acid analysis suggested that the porin protein consists of about 420 amino acid residues, yielding a polarity of 43.6% and a molecular mass of 45000 in contrast to the mobility on SDS-PAGE. [ABSTRACT FROM AUTHOR]

A purified sheath fraction and an outer membrane fraction were obtained from the cyanobacterium Fischerella sp. PCC 7414. The sheath had a fine structure with osmiophilic fibers running in parallel to the cell surface in two distinct layers. The sheath fraction contained mainly neutral sugars (Glc, Man, Gal, Xyl, Fuc, 2- O-methylhexose), GlcN, uronic acids, and minor components such as amino acids, sulfate, phosphate, and fatty acids. The protein moiety was removable from the sheath fraction by treatment with boiling sodium dodecyl sulfate. The presence of three different 3-hydroxy fatty acids (3-OH-14:0, 3-OH-16:0, 3-OH-18:0) in addition to GlcN indicated the presence of lipopolysaccharide in the outer membrane. One major (M 50,000) and two minor (M 54,000 and 65,000) proteins were detected as constituents of the outer membrane. [ABSTRACT FROM AUTHOR]

The outer membrane of Prochlorothrix hollandica is covered with a network of fine fibrils on its surface and separated from the cytoplasmic membrane by an electrondense peptidoglycan layer (8 to 20 nm thick). The thylakoid membranes are arranged in stacked and unstacked regions which present four characteristic fracture faces with different numbers and sizes of intramembrane particles. Cell inclusions such as polyhedral bodies (carboxysomes), ribosomes, and polyphosphate granules were found in Prochlorothrix hollandica. Another type of cell inclusions was identified by its characteristic shape (a cylindre with conical caps) and a regular striation as gas vesicles. It is concluded that the organism is in its morphological structure similar to the cyanobacteria. [ABSTRACT FROM AUTHOR]

A ninhydrin-positive, phosphorus-negative lipid from Paracoccus denitrificans ATCC 13543 has been isolated and purified by mild alkaline methanolysis followed by silicic acid column chromatography and preparative thin-layer chromatography. The lipid was identified as an ornithine-containing lipid. The major ester-linked fatty acid was cis vaccenic acid. Major amide-linked fatty acids were 3-OH-20:1 and 3-OH-18:0. Ornithine-containing lipid was a major lipid component of P. denitrificans. Phospholipids made up about 57% and ornithine-containing lipid about 14% of the weight of the total lipid of the organism. The ratios of lipid ornithine: lipid phosphorus were 0.23, 0.65 and 0.58 in cytoplasmic membrane, outer membrane, and an NaCl extract, which is thought to represent chiefly outer membrane, respectively. Thus ornithine-containing lipid appears to be present in larger amounts in outer membrane than cytoplasmic membrane. No substantial variations in lipid ornithine levels were noted in stationary phase versus exposnential phase organisms, organisms grown in complex medium versus organisms grown in minimal medium with and without amino acid supplements, or in organisms grown in low phosphate-containing medium. [ABSTRACT FROM AUTHOR]

Logarithmically growing cells of Escherichia coli were fixed with glutaraldehyde and incubated with antimaltose-binding protein F coupled to horseradish peroxidase (molecular weight of the complex 80,000). The position of this complex within the cell envelope was determined by reacting with diaminobenzidine-HO, staining with osmium tetroxide and processing for thin section electron microscopy. The following observations were made: (i) induction of the maltose-binding protein resulted in swelling and staining of the outer membrane; (ii) the swelling and staining was more prominent in short cells, less prominent or absent in long cells; (iii) rare examples exhibited granular staining in the space between the plasma membrane and the peptidoglycan layer. These stainings were observable mainly in pole caps; (iv) a mutant lacking the receptor for phage λ showed altered staining pattern. Treatment of glutaraldehyde-fixed cells with EDTA-lysozyme prevented the specific labelling of the maltose-binding protein. [ABSTRACT FROM AUTHOR]

Radioactive mono-N-acetyl-C-polymyxin B or natural polymyxin B are within 60 s absorbed by isolated inner (cytoplasmic) and outer membranes from Salmonella typhimurium G30. The sigmoidal binding isotherms indicate saturation of inner and outer membranes with approximately 30 and 60 nmoles polymyxin B bound per mg membrane, respectively. Based on the known content of these membranes in lipopolysaccharide, phosphatidylglycerol, cardiolipin and phosphatidylethanolamine, a calculation of the theoretical binding capacities yields almost identical values if lipopolysaccharide, phosphatidylglycerol and cardiolipin are assumed to function as the actual binding sites for the antibiotic in the isolated membranes. The excellent agreement between theoretical evaluation and experimental determination of polymyxin B-binding capacities leaves little doubt that the named anionic compounds are the chemoreceptors for the cationic antibiotic. This is further substantiated by very similar binding and killing kinetics of polymyxin B. [ABSTRACT FROM AUTHOR]

Mercury resistance shown by a strain of Enterobacter aerogenes was found to be determined by a plasmid. The resistance appeared to be not due to enzymatic volatilization of mercury, but due to the alteration in cellular permeability to mercury. Comparison of the outer membrane proteins was made between the resistant cells and the sensitive counterparts obtained by the treatment with mitomycin C, showing that two proteins with molecular weight of 46,000 and 44,000 had disappeared from the outer membrane along with the plasmid by the curing. These results suggest that the two membrane proteins mediating the cellular permeability to mercury compound may be responsible for the mercury resistance of the strain. [ABSTRACT FROM AUTHOR]