Answer:
900 nanometer (nm)
Step-by-step explanation:
Given that,
Length of a bacterial cell = 0.9 micrometer (µm)
There is a direct relationship between the nanometer and the micrometer scale,
It is that 1 micrometer (μm) = 1000 nanometer (nm)
Therefore, 0.9 μm = 900 nm
Thus, the length of the given bacterial cell is 900 nanometer (nm).