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Biomedical subjects

T Imaeda

Publications and source records attributed to T Imaeda.

At least 109 records · Page 6Linked to original sources
PubMed1978

Physiological factors involved in the transformation of Mycobacterium smegmatis.

Transfer of streptomycin resistance and changes from methionine and leucine auxotrophy to prototrophy were achieved in Mycobacterium smegmatis by transformation. Recipient cells were more resistant to mitomycin C and methyl methlanesulfonate treatments than were wild-type cells. A high level of calcium ions was essential for transformation, especially during DNA adsorption, whereas the presence of magnesium ions and the exposure of recipient cells to mild doses of UV light enhanced recombination frequencies. Transformants were not isolated when recipient cell-DNA mixtures were first treated with deoxyribonuclease. Recipient cells at various stages of growth showed similar transformabilities. Transformation was successful only when recipient cells were incubated on rich agar medium after mixture with DNA. Exposure of recipient cells to Pronase before treatment with donor DNA did not affect transformation, suggesting the absence of a protein competence factor. Throughout the present experiments, cotransformation frequencies were very low and unselected-marker segregation patterns were independent, indicating that the methionine, leucine, and streptomycin markers are not closely linked in M. smegmatis.

Calcium↗
PubMed1977

Ultrastructure of Nocardia-like variants of Mycobacterium smegmatis and chemical composition of the basal cell wall layer.

Mycobacterium smegmatis, its orange-red--pigmented (OR) variants, and back mutant strains were examined by electron microscopy using ultrathin sectioning, negative or positive staining, and freeze-fracture-etching methods. The parental and back mutant strains showed almost identical ultrastructures. Specifically, thick ramified fibers measuring about 15 nm in diameter were always visible in the positively stained cell wall, although they were not readily visualized with negative staining or freeze-fracture-etching. In contrast, the cell walls of OR variants contained fibrous networks measuring about 11 nm in diameter, which could be observed by positive and negative staining as well as freeze-fracture-etching. Although cytoplasmic structures appeared similar among the four strains examined, mesosomes were significantly more abundant in the OR variants. The basal layer of the cell wall obtained as a phenol residue consisted of a dense membranous matrix containing scattered fibrous structures in the parental and back mutant strains, and fibrous networks in the OR variants. Chemical analyses showed that the basal layers of all four strains contained the same neutral sugars, amino sugars, and amino acids, i.e., arabinose, galactose, muramic acid, glucosamine, alanine, glutamic acid, and diaminopimelic acid. The alpha-branched, beta-hydroxylated fatty acids contained in the basal layers differ among the four strains, however, with nocardomycolic acids being present in the OR variants and mycolic acids in the parental and back mutant strains. Our previous conclusion that OR variants of M. smegmatis have characteristics similar to those of nocardia is supported by the present study.

Amino Acids↗
PubMed1976

Isolation and characterization of nocardia-like variants of Mycobacterium smegmatis.

Orange-red-pigmented (OR) colonies were isolated from cream-yellow-pigmented Mycobacterium smegmatis after exposure to either mycobacteriophage MC4 or ultraviolet light; these variant strains were designated OR4 and ORuv, respectively. Early subculture of OR-colonies did not show any segregation of parental-type cells. However, colonies resembling the parental strains, possibly representing a back mutant (REV-OR4), were occasionally found during subculture of established OR-colonies or upon treatment with N-nitrose-N'-nitro-N-methylguanidine. The OR-variants were characterized by their lytic response to nocardiophage, but not to mycobacteriophages, presence of alpha-branched, beta-hydroxylated fatty acids of the Nocardia-type, and a guanine plus cytosine value of deoxyribonucleic acid (DNA) between 62 and 64 mol%. They were more resistant to the lethal action of both ultraviolet light and mitomycin C treatment than the parental and back mutant strains. Although the OR-variants in this study possess characteristics common to the genus Nocardia or some of the 'rhodochrous' mycobacteria, evidence is presented that they form a new class of mycobacterial variants.

Fatty Acids↗
PubMed1975

Ultrastructure of L-phase variants isolated from a culture of Mycobacterium phlei.

Relatively stable L-phase colonies were isolated from old cultures of a selected clone of Mycobacterium phlei. The colonies grew at 52 degrees C and were composed of rod-shaped, oval or spherical cells. Large amoeba-like cells were occasionally present. These were usually limited by a double-layered membrane and devoid of normal cell-wall components such as bacteriophage receptors. The large amoeba-like bodies sometimes showed both outer and inner double-layered membranes, especially in pseudopodium-like cellular extensions. An unusual feature of rod-shaped cells was retention of the original shape despite the loss of their cell walls. Two types of walled cells occurred during successive transfers of L colonies. One was the true revertant which had characteristics in common with the wild-type M. phlei, such as growth at 52 degrees C and ultrastructural organisation. The other, designated as the "atypical-cell-wall variant", was characterised by growth at 52 degrees C, thick cell walls, and disordered septation. Wild-type M. phlei, L variants, revertants and atypical-cell-wall variants released mycobacteriophage particles. These bacteriophages were almost identical in respect to morphology, host range, and neutralisation by antiserum. The results obtained suggest strongly that all types of cells examined were derived from M. phlei.

Cell Membrane↗
PubMed1974

Growth inhibitory activity of deoxyribonucleic acid-containing factor(s) isolated from lepromatous lesions.

Deoxyribonucleic acid-containing factor(s) isolated from Mycobacterium leprae suspensions obtained from lepromas of nine patients showed growth inhibitory activity against Micrococcus and both orange-red-pigmented and coccoid mutants of mycobacteria. No growth inhibition was observed for parent mycobacterial species, Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus epidermidis.

DNA, Viral↗
PubMed1971

Interaction of Pseudomonas bacteriophage 2 with the slime polysaccharide and lipopolysaccharide of Pseudomonas aeruginosa strain B1.

Purified slime polysaccharide B and lipopolysaccharide of Pseudomonas aeruginosa strain BI were shown to possess receptor-like properties in inactivating Pseudomonas phage 2, whereas lipoprotein and glycopeptide fractions were devoid of activity. On a weight basis, slime polysaccharide B was more effective than lipopolysaccharide in inactivating phage. The specificity of the reaction with slime polysaccharide B was indicated by the fact that slime polysaccharide A of P. aeruginosa strain EI failed to inactivate phage 2. Electron micrographs showed phage 2 in typical, tail-first position of attachment on intact cells of strain BI, slime polysaccharide B, and lipopolysaccharide. Tail fibers were discernible during phage attachment.

Adsorption↗