Caulobacter - stalked bacteria
Caulobacter cells with different stalk lengths.
The stalk of a Caulobacter cell is neither a flagellum nor a pilus. It is part of the cell and contains cytoplasm. Its length does not only depend on the cell age but increases with increasing phosphate limitation in the environment. Whether the stalk is involved in phosphate uptake is under debate, but it exposes the cell above the ground to better nutrient fluxes.
