Mazal Varon

Properties of marine bdellovibrios

Marine bdellovibrio isolates from the Israeli littoral of the Mediterranean Sea were screened and characterized in terms of host range, temperature and salinity ranges, cation requirement, mutation frequency, and G + C% mole content. Ten types of isolates were distinguished on the basis of these parameters.

Elongation and cell division in Bdellovibrio bacteriovorus.

Elongation and division of Bdellovibrio bacteriovorus were studied in axenic synchronous cultures. The cells elongate unidirectionally from one end attaining a length of several “unit cells”, and then divide into the corresponding number of cells. The length of the filament and, consequently, the progeny number, vary within the range of two to several dozen cells, according to the conditions used. A protein and a low molecular weight component are required for normal division.

Inhibition of the Predatory Activity of Bdellovibrio by Various Environmental Pollutants

The predatory activity of bdellovibrios is affected by various environmental pollutants such as detergents, heavy metals, and pesticides. This was shown in a two-membered system ofBdellovibrio andPhotobacterium, in which the effect of the predator on the bioluminescence of the prey indicated the activity of the former. The high sensitivity of the bdellovibrios toward certain chemicals (e.g., CdCl2) indicates the possibility of using the system for biological monitoring of those chemicals.

Early effects of Bdellovibrio infection on the syntheses of protein and RNA of host bacteria

Abstract Bdellovibrio bacteriovorus 109 inhibited the induced synthesis of β-galactosidase of host E. coli bacteria. RNA synthesis of the host was inhibited 3 min after infection; this was followed by the inhibition of protein synthesis 5–6 min later. The halt in RNA synthesis also occurred in host-parasite mixtures where penetration of the parasite was blocked by streptomycin.

Interaction of Bdellovibrio with Its Prey in Mixed Microbial Populations

The interaction ofBdellovibrio with its prey can be affected by the presence of other microorganisms regardless of whether they serve as a prey for the bdellovibrios. This was shown in a system in which the fate of one prey could be followed in mixed bacterial populations thanks to a specific trait, bioluminescence. The attacking bdellovibrio causes decay of bioluminescence, and the rate of light decay of the population indicates the rate at which the luminous bacteria are attacked. Using this system it was found that different bacteria affected the predatorprey interaction in different ways: some “competed” with the original prey for the predator; others enhanced the activity of the predator toward the original prey, and others inhibited it. The significance of these findings in relation to the distribution and activity ofBdellovibrio in the natural ecosystem is discussed.

The maintenance ofBdellovibrio at low prey density

A mathematical model for the interaction ofBdellovibrio and its prey predicted that a relatively high prey density (7×105 cells ml−1) would be required for the establishment of an equilibrium in a mixed population [8]. The present report shows thatBdellovibrio can be maintained in a continuous culture when the prey cell density is much lower (2–5×104 cells ml−1), and closer to that of naturally occurring bacterial populations in sea waters.

THE BDELLOPHAGE THREE-MEMBERED PARASITIC SYSTEM

AbstractThe Bdellovibrio bacteriophage three-membered system consists of a bacteriophage (bdellophage) whose host is a small bacterium (Bdellovibrio) which grows parasitically in the periplasmic space of another bacterium. This review describes how bdellophages were discovered and the special features of their hyperparasitic system. Before going on with the story of the bdellophage, a short description of its host – the Bdellovibrio – seems necessary (a detailed description will be found in the several reviews which have appeared lately).1-3

Effect of polyamines on the intraperiplasmic growth of Bdellovibrio at low cell densities

Bdellovibrios which have penetrated into the periplasmic space of their potential prey, are incapable of completing their growth cycle in a suspension of low cell density. The addition of polyamines to such suspension allows normal growth of the bdellovibrios.