Negative Numbers in 32 bit Floating Point IEEE Numbers
Contrary to two's complement representation of negative integers, the negative numbers in IEEE floating-point are represented with only a sign bit change, as shown in there.
For example, $0\cdot01111100\cdot01000000000000000000000$ is the representation of $0.15625$, and $1\cdot01111100\cdot01000000000000000000000$ is the representation of $-0.15625$.
In particular, there are two representations of zero (the positive one and the negative one).