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Biomedical subjects

M Kessel

Publications and source records attributed to M Kessel.

At least 145 records · Page 8Linked to original sources
PubMed1977

Assembly site of cyanophage LPP-2-SPI in Plectonema boryanum.

Electron microscope studies of infection by the temperature cyanophage SPI show two possible assembly sites within the host Plectonema boryanum: the nucleoplasm and a phage-created space, the "virogenic stroma". Induced prophages appear to develop preferentially in the nucleoplasm.

Cell Nucleus↗
PubMed1975

The ultrastructure and development of the colonial sheath of Microcystis marginata.

The colonial sheath of Microcystis marginata has a definite structure as seen by light and electron microscopy, consisting of a relatively smooth inner surface and densely packed, long fibrils on the outer surface. The sheath initially forms around the single cell and expands by continual deposition of sheath material to accomodate the synchronously dividing cells of the colony.

Microcystis↗
PubMed1974

Growth cycle of predacious Bdellovibrios in a host-free extract system and some properties of the host extract.

Host-free growth and reproduction of a host-dependent strain of Bdellovibrio bacteriovorus incubated with an extract from host cells were studied. The morphological changes occurring in the cells were correlated with deoxyribonucleic acid (DNA) synthesis as measured by labeled nucleotide or orthophosphate incorporation. The host-free developmental cycle of Bdellovibrio is similar to that of the two-membered system; the early loss of flagella, the elongation into filaments, and multiple fission into flagellated progeny are typical for both host-free and intraperiplasmic development of bdellovibrios. Filament length and time of division appear to depend on the concentration of the host extract. Host extract was found to be heat stable and DNase stable, and Pronase sensitive and RNase sensitive. Addition of ribonucleic acid to the extract medium at various times during the Bdellovibrio growth cycle demonstrated that host extract is required continuously during the cycle for growth. The observations reported give a unified picture of Bdellovibrio development and allow for the suggestion that wild-type bdellovibrios depend upon the presence of some host factor for induction of DNA synthesis, whereas depletion of host factor triggers division. The ecological implications of such host dependence are discussed.

Bacteria↗
PubMed1973

Development of bdellophage VL-1 in parasitic and saprophytic bdellovibrios.

Ultrastructure was correlated with growth kinetics of bdellophage VL-1 infecting host-dependent ("parasitic") Bdellovibrio bacteriovorus 109J in its Escherichia coli B host (the three-membered system), as well as in the host-independent ("saprophytic") derivative of the Bdellovibrio. Electron microscope observations showed the arrested growth of the phage-infected bdellovibrios, polar localization of the phage progeny, and stages in their release. Present evidence indicates that bdellophage DNA is derived from both the Bdellovibrio and its host cell.

Bacteria↗