PubMed Health⌕ Search

Biomedical subjects

J Gumpert

Publications and source records attributed to J Gumpert.

At least 19 recordsLinked to original sources
PubMed1990

Periodically curved bilayer structures observed in hyphal cells or stable L-form cells of a Streptomyces strain, and in liposomes formed by the extracted lipids.

Periodically curved bilayer structures showing a tetragonal pattern were revealed by freeze-fracture electron microscopy in hyphal cells, stable L-form cells, and liposomes prepared from extracted lipids of Streptomyces hygroscopicus NG 33-354. The pattern is formed by alternating convex and concave curvatures of the bilayer. It has been found with different repeat distances (multiples of about 15 nm) and with a different degree of expression (from just visible to very pronounced). An interpretation as infinite periodic minimal surface (IPMS) structures is more probable than an inducement of the pattern by underlying small vesicles. The occurrence of nonbilayer textures and the similarity of the tetragonal pattern with a 'bilayer sector' from a cubic phase structure (Anderson, S. et al. (1988) Chem. Rev. 88, 221-242) support such an interpretation.

Cell Membrane↗
PubMed1989

Novel shuttle vectors for improved streptokinase expression in streptococci and bacterial L-forms.

Novel shuttle vectors of small size and increased copy number capable of replication in Escherichia coli, L-forms of Proteus mirabilis, and streptococci were constructed from a streptococcal erythromycin-resistant plasmid and an Escherichia coli phasmid. The streptokinase gene, skc, was inserted into one of them, and skc expression was studied in Streptococcus sanguis, Streptococcus lactis, and in an L-form strain (LVI) of Proteus mirabilis. The new streptokinase shuttle plasmid, pMLS10 (7.3 kb), specified higher Skc yields in all hosts when compared to pSM752 constructed previously. In particular Proteus mirabilis LVI(pMLS10) proved to be the most productive host, exhibiting complete secretion of the active protein at yields as high as 24000 unit per ml.

Electrophoresis, Polyacrylamide Gel↗
PubMed1989

Heterologous signal peptide processing in fusion interferon synthesis by engineered L-forms of Proteus mirabilis.

A recombinant DNA Proteus mirabilis L-form expression system, LVI (pJS127), was used to synthesize human fusion interferon alpha 1 (f-IFN-alpha 1). In the expression plasmid used, the complete coding sequence of IFN-alpha 1 was linked to the streptococcal speA promoter and the 5' end of the speA structural gene including its signal sequence coding region. LVI (pJS127) was capable of complete secretion into the culture medium of biologically active f-IFN-alpha 1 whose identity was confirmed by immunological and chemical evidence. In particular, bacterial L-forms were for the first time shown to be capable of correct signal peptide processing, as determined by N-terminal sequencing of the secreted f-IFN.

Amino Acids↗
PubMed1989

Complete secretion of activable bovine prochymosin by genetically engineered L forms of Proteus mirabilis.

To circumvent problems encountered in the synthesis of active chymosin in a number of bacteria and fungi, a recombinant DNA L-form expression system that directed the complete secretion of fully activable prochymosin into the extracellular culture medium was developed. The expression plasmid constructions involved the in-frame fusion of prochymosin cDNA minus codons 1 to 4 to streptococcal pyrogenic exotoxin type A gene (speA') sequences, including the speA promoter, ribosomal binding site, and signal sequence and five codons of mature SpeA. Secretion of fusion prochymosin enzymatically and immunologically indistinguishable from bovine prochymosin was achieved after transformation of two stable protoplast type L-form strains derived from Proteus mirabilis. The secreted proenzyme was converted by autocatalytic processing to chymosin showing milk-clotting activity. In controlled laboratory fermentation processes, a maximum specific rate of activable prochymosin synthesis of 0.57 x 10(-3)/h was determined from the time courses of biomass dry weight and product formation. Yields as high as 40 +/- 10 micrograms/ml were obtained in the cell-free culture fluid of strain L99 carrying a naturally altered expression plasmid of increased segregational stability. The expression-secretion system described may be generally useful for production of recombinant mammalian proteins synthesized intracellularly as aberrantly folded insoluble aggregates.

Animals↗
PubMed1989

[Lipopolysaccharide-containing cytoplasmic membranes as immunostimulants of peritoneal macrophages].

It was established that cytoplasmic membranes from the stable L-forms of E. coli WF+ induced a 4-5 fold increase of the number of peritoneal exudative cells in mice after single i.p. inoculation. The animals treated with membranes reacted with 4-5 fold higher number of these cells after an i.p. infection by parent form cells or L-form cells, as compared with the reaction of infected, nontreated by membranes mice. The macrophage bactericidal activity was 6-10 fold increased. Using electron microscopy, it was established that the phagosomes containing membranes and their remnants were localized in the peripheral part of the cytoplasm or near the nucleus, without neighbouring lysosomes during the 24-hour interaction. Single cases of phagolysosome fusion were observed.

Adjuvants, Immunologic↗
PubMed1987

Electron microscopic and biophysical studies of liposome membrane structures to characterize similar features of the membranes of Streptomyces hygroscopicus.

To characterize the novel non-planar plasma membrane structure of bacteria (wafer structure), liposome membranes from the bacterial lipid mixture and individual lipid fractions were prepared and investigated by freeze-fracture electron microscopy, microcalorimetry and 31P-NMR spectroscopy. The phospholipid content of the membranes is essential for the formation of the non-planar membrane structure and there is no indication that the formation of the structure is connected with temperature-induced lipid phase transition processes. An exaggerated form of the wafer structure (raspberry structure) is also visible and additionally, in both cases, many small spherical vesicles are observed. We suggest that both membrane features of the liposomal and bacterial membranes are induced by these vesicles, forming a hexagonal or cubic organization of vesicles on the cytoplasmic surface of the biological membrane, and in between the multilamellae in the artificial membranes.

Calorimetry↗
PubMed1986

Phage adsorption and productive lysis in stable protoplast type L-forms of Bacillus subtilis and Streptomyces hygroscopicus.

Transferable productive lysis in stable protoplast type L-form cells of Bacillus subtilis was produced by 6 phages out of 14 strains virulent for the parent B. subtilis 170 and 1997. Most of these phages lytic for L-forms show the phi 29 morphology characteristic for the smallest B. subtilis phages containing double-stranded DNA. Among 31 actinophages, 23 of which were virulent for Streptomyces hygroscopicus, only SLE 109 and phi c 31 gave productive infection of the stable protoplast type L-form of S. hygroscopicus NG 33--354. Electron microscopic investigation and treatment by DNAse demonstrated that infection of L-form cells is an adsorption-injection process, and that it is not caused by transfection of free phage DNA or endocytotic uptake of phage particles. Because in both stable L-forms cell wall biosynthesis is blocked irreversibly the results allow the conclusion that specific receptors must be localized in the cytoplasmic membrane for those phages producing transferable lysis in protoplast type L-forms. Localization of receptors for certain phages in the cytoplasmic membrane seems to occur in many Gram-positive bacteria, but not in Gram-negative bacteria.

Adsorption↗
PubMed1986

Structures of liposome membranes as models for similar features of cytoplasmic membranes of bacteria.

To characterize a special kind of membrane structure, visible in the cytoplasmic membranes of a Streptomyces hygroscopicus strain, liposome membranes were prepared from their extracted lipid mixture and from their lipid fractions (phospholipids, glycolipids, neutral lipids) and investigated by freeze-fracture electron microscopy. Liposome membranes made of the extracted lipid mixture reveal this special membrane structure, named wafer structure, from its regular pattern of bulges (30-40 nm in diameter). That is the proof that this membrane feature is a lipid structure. Liposome membranes prepared from the lipid fractions show the wafer structure if they are made of the phospholipid fraction only or in combination of this fraction with one or both of the other lipid fractions, indicating that wafer structure formation is primarily connected with the phospholipid content of the membranes. The glycolipid- and neutral lipid fractions amplify this phospholipid structure only. Additional to the wafer structure a raspberry structure with bulges of 55-65 nm in diameter is visible in some case. Obviously both structures are related.

Cell Membrane↗
PubMed1985

Occurrence of squalene and dehydrosqualene in streptomycetes.

Squalene, dehydrosqualene and related hydrocarbons were found to constitute an essential part of the neutral lipid fraction extracted from mycelia and membranes of S. hygroscopicus, S. griseus and S. noursei. In comparison with the fraction of the triglycerides, these terpenoid compounds failed to incorporate (U-14C)-acetic acid throughout pulse labelling experiments. This suggested that the pertinent precursors were formed via alternative routes, for instance by catabolising branched-chain amino acids.

Acetates↗
PubMed1983

Ultrastructural characterization of core structures and paracrystalline inclusion bodies in L-form cells of streptomycetes.

Protoplast type L-form cells of Streptomyces hygroscopicus and S. griseus contain different types of inclusion bodies. Cytoplasmic cores and paracrystalline structures are peculiar inclusions which could not be observed in normal parent bacteria. The cytoplasmic cores are 1-4 micron long and 0.05-0.25 micron broad straight and stiff non-tubular structures consisting of homogeneous mode-rate electron opaque material. Paracrystalline inclusions have side-lengths between 0.2 and 0.5 micron and show a characteristic pattern of 15-20 nm thick straight dark lines and electron lucent intervening spaces of 20-30 nm. Both cytoplasmic cores and paracrystalline inclusions are apparently proteins. Their occurrence in L-form cells indicates an altered synthesis of one or several proteins in these cell types.

Cell Nucleus↗
PubMed1982

Fatty acid composition of lipids of Escherichia coli W 1655 F+ and its stable protoplast type L-form.

The comparative fatty acid analysis of extractable and non-extractable lipids of Escherichia coli W 1655 F+ and its stable protoplast type L-form shows quantitative as well as qualitative differences. From 10 different fatty acids obtained 16:0, 17:0 and 18:0 are present at about the same quantities in the lipid fractions of the bacterial and L-form. The absence of larger amounts of 12:0, 14:0, and 14:beta OH fatty acids in non-extractable L-form lipids reflects the loss of the cell wall in L-form cells. 16:1 fatty acid was found in L-form lipids only. This qualitative difference and the 2-3 times higher content of 18:1 in L-form lipids and the 7 times lower content of cyc 19:0 in extractable lipids of the L-form may be interpreted as alterations characteristic for the changed composition of the cytoplasmic membrane in L-form cells.

Chromatography, Gas↗
PubMed1982

Growth characteristics and ultrastructure of protoplast type L-forms from streptomycetes.

L-form colonies from S. hygroscopicus, S. griseus and S. levoris were isolated after incubation of lysozyme protoplasts on an osmotically stabilized complex agar medium. Unstable and stable L-forms grow on solid and in liquid media. L-form colonies are 5-10 times smaller than normal colonies and show a typical morphology for each species. In ultrathin sections L-form cells are characterized by nucleoid areas with typical core-like structures, by a ribosome-rich cytoplasm with different inclusion bodies, and by a cytoplasmic membrane. Because there are no cell wall structures L-forms of the three Streptomyces species belong to the protoplast type. Analysis of cell size and cell shape shows a variation in diameter and a cell propagation by regular and irregular division- and budding-like processes. Many L-form cells contain more than two chromosomes. The results are discussed with regard to the cellular organisation of streptomycetes and the nature of the stable L-form.

Cell Membrane↗