| Lifestyle |
All wild-type strains
upon initial isolation are dependent on intraperiplasmic
growth in susceptible prey; the reason for the dependence
is unknown. Growth of isolates in the absence of prey has
been achieved in some cases with media supplemented with
high concentrations of bacterial cell extracts.
Only predacious bdellovibrios have been
obtained on initial isolation from nature, but mutants
capable of axenic growth (growth in the absence of prey
cells, "prey-independent" strains) have been
derived from the predacious strains. Some strains are
facultative, i.e. capable of growth in the presence or
absence of prey cells.
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| Pathogenicity |
Predator This genus consists of a group of remarkable
bacteria which are predacious upon other Gram-negative
bacteria.. Bdellovibrios exhibit amorphologically and
physiologically biphasic life cycle, alternating between
a non-growing predatory phase and an intracellular
reproductive phase . The highly motile Bdellovibrio
appears to locate its prey by means of chance collision;
it forceably strikes and attaches to the generally much
larger prey cell, then rapidly penetrates into the prey's
periplasmic space. The prey cell containing the invading
bdellovibrio usually rounds up and swells into a
spherical form (bdelloplast). The Bdellovibrio kills the
prey cell very early in the attack; indeed, the prey cell
loses essentially all metabolic potential, including
energy generation, biosynthesis, and the activity of
degradative enzymes. The prey cell, soon after attack, is
functionally a substrate for bdellovibrio development.
The developing Bdellovibrio elongates into a snake form
at the expense of the prey's protoplast. The
spiral-shaped nonmotile cell then fragments into motile,
unit-sized predacious vibrios which leave the prey (now a
"ghost" cell) to begin the cycle anew.
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