Which one of the following is wrong statement?

1. Anabaena and Nostoc are capable of fixing nitrogen in free living state also.
2. Root nodule forming nitrogen fixers live as aerobes under free-living conditions.
3. Phosphorus is a constituent of cell membranes, certain nucleic acids and cell proteins.
4. Nitrosomonas and Nitrobacter are chemoautotrophs.

Phosphorus is a constituent of nucleic acids of both DNA and RNA but absent in cell membranes and cell proteins.