Flagellar motion stops once Bdellovibrio has penetrated its prey, and the flagella is then shed. Host-independent Bdellovibrio appear amorphous, and larger than the predatory phase. Culture conditions B. bacteriovorus appears to be ubiquitous in nature and manmade habitats. They have been found in soil samples, rhizosphere of plant roots, rivers, oceans, sewage, intestines and feces of birds and mammals, and even in oyster shells and the gills of crabs. B. bacteriovorus are able to thrive in almost any habitat, the general requirements are that there needs to be oxygen and some other Gram-negative bacteria present in its environment. Its optimal temperature is between 28-30°C, making B. bacteriovorus a mesophile. Bdellovibrio is grown in the laboratory in its stationary HI (host-independent) phase at 29°C on yeast peptone broth agar. Host-dependent (predatory) cultures are grown with a population of E. coli S-17 at 29°C for 16 hrs. They may also be cultured using YPSC (yeast extract, peptone, sodium acetate, calcium chloride) overlays or prey lysates. Life cycle and parasitism Bdellovibrio cells can swim as fast as 160 µm/s, or over 100 times their body-length per second. It swims using a single sheathed polar flagellum with a characteristic dampened filament waveform. Bdellovibrio attacks other Gram-negative bacteria by attaching itself to the prey cell's outer membrane and peptidoglycan layer, after which it creates a small hole in the outer membrane. The Bdellovibrio cell then enters the host periplasmic space. It remains reversibly attached to it for a short "recognition" period. After the recognition period, it becomes irreversibly attached via the pole opposite the flagellum. Once inside the periplasm, the Bdellovibrio cell seals the membrane hole and converts the host cell to a spherical morphology, this is due to secretion of L,D transpeptidases which breaks the peptidoglycan apart, and therefore causes the cell to become amorphous. The two-cell complex formed is called a bdelloplast. The Bdellovibrio cell uses hydrolytic enzymes to break down the host cell molecules, which it uses to grow filamentously. When the host cell nutrients are exhausted, the filament septates to form progeny Bdellovibrios. The progeny become motile before they lyse the host cell and are released into the environment. The entire life cycle takes three to four hours, and produces an average of 3–6 progeny cells from a single E. coli, or up to 90 from larger prey such as filamentous E. coli. Targets of Bdellovibrio species, including Vibrio vulnificus, may