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Biomedical subjects

M Shilo

Publications and source records attributed to M Shilo.

At least 37 records · Page 2Linked to original sources
PubMed1970

Early host damage in the infection cycle of Bdellovibrio bacteriovorus.

The effects of bdellovibrio infection on host permeability and respiration were investigated by measuring respiration rates and the rate of o-nitrophenyl-beta-d-galactopyranoside hydrolysis during the course of single infection cycles of Bdellovibrio bacteriovorus strain 109 growing on Escherichia coli ML 35 (lac i(-)z(+)y(-)). The data show that among the very early consequences of parasite attack on the host are an increase in permeability and a general disruption of respiratory activity of the host, and it is suggested that both phenomena stem from early damage to host membrane. The rapid onset of damage after inception of the cycle and the failure of streptomycin to prevent the damage indicate that complete penetration of the parasite into the host is not a requirement for the observed effects. The data also show that bdellovibrio does not use host energy-generating mechanisms for its growth and suggest that the parasites may have a search mechanism that permits them, to some degree, to distinguish between infected and uninfected hosts.

Bacteria↗
PubMed1970

Lysis of blue-green algae by myxobacter.

Enrichment from local fishponds led to the isolation of a bacterium capable of lysing many species of unicellular and filamentous blue-green algae, as well as certain bacteria. The isolate is an aflagellate, motile rod which moves in a gliding, flexuous manner; the organism is capable of digesting starch and agar, but not cellulose and gelatin. Its deoxyribonucleic acid base pair composition (per cent guanine plus cytosine approximately 70) shows a close resemblance to that of the fruiting myxobacteria. Algae in lawns on agar plates were lysed rapidly by the myxobacter, but only limited and slow lysis occurred in liquid media, and no lysis took place when liquid cultures were shaken. No diffusible lytic factors would be demonstrated. Continuous observation of the lytic process under a phase-contrast microscope suggested that a close contact between the polar tip of the myxobacter and the alga is necessary for lysis. The lytic action is limited to the vegetative cells of the algae, whereas heterocysts are not affected. The gas vacuoles of the algal host are the only remnant visible after completion of digestion by the myxobacter.

Bacteria↗
PubMed1969

Interaction of Bdellovibrio bacteriovorus and host bacteria. II. Intracellular growth and development of Bdellovibrio bacteriovorus in liquid cultures.

The intracellular life cycle of Bdellovibrio bacteriovorus 109 growing on Escherichia coli in a dilute nutrient medium exhibits a period of constant infective titer while the parasite grows and elongates inside the host cell. This period is terminated after 2 to 4 hr, and the number of the plaque-forming units in the culture rises rapidly to as much as six times the initial titer. The growth pattern of Bdellovibrio is similar with actively growing or resting host cells, or with host cells killed by ultraviolet irradiation or by heating at 70 C. The yield of B. bacteriovorus strain 109 in two-membered cultures with E. coli B depends on the host concentration and may reach 7.5 x 10(10) cells per ml. Penicillin, which has no effect on the attachment and penetration of Bdellovibrio, inhibits its multiplication.

Bacteria↗
PubMed1968

Effect of cyanophage infection on CO2 photoassimilation in Plectonema boryanum.

Cyanophage infection effects a rapid and complete cessation of CO(2) photoassimilation in Plectonema cells. From the amount of infected cells lysed, it was established that this phenomenon cannot be ascribed to lysis of the host cells either from within or from without. The possibility that the effect is due to nitrogen starvation, induced secondarily by cyanophage multiplication, was ruled out when it was found that nitrogen supplementation did not influence the inhibition. It is suggested that the arrest of CO(2) photoassimilation is an integral part of the cyanophage infection cycle in P. boryanum. This idea is supported by the nondependence of the cyanophage-induced inhibition on the input multiplicity, by the light requirement for the inhibition, and by the fact that infected Plectonema cells with inhibited CO(2) photo-assimilation support normal multiplication of the cyanophage. The pattern of light requirement for this viral inhibition further supports this suggestion.

Carbon Dioxide↗
PubMed1966

The cytotoxic principle of the phytoflagellate Prymnesium parvum.

The cytotoxic events leading to lysis induced in Ehrlich ascites tumor (E.A.) cells by Prymnesium parvum cell extracts were followed microscopically and measured quantitatively as changes in E.A. cell volume, uptake of trypan blue, and release of macromolecular constituents from the cells. Cell swelling was the most immediate response to P. parvum cytotoxin, while cell death and lysis were later events distinguished by a decline in cell volume, uptake of dye, and appearance of cellular macromolecules free in the incubation medium. The pH and temperature were shown to affect the outcome of the lytic sequence. At either low pH or temperature, cells swelled but did not lyse until the pH or temperature was raised. On the other hand, cells swollen at the higher pH or temperature could be protected from lysis by lowering either the pH or the temperature.

Animals↗