I'm lost.........

The G-C content of Micrococcus is 66-75% and of Stahylococcus, 30-40 moles %. Are these two genera closely related? Please explain.....

I don't think so:
See:
http://en.wikipedia.org/wiki/GC-content

To determine if two genera are closely related based on their G-C content, you can compare the percentages and moles of G-C content. In this case, the G-C content of Micrococcus is 66-75%, while Staphylococcus has a G-C content of 30-40 moles %.

By comparing these values, it is clear that the G-C content of Micrococcus is significantly higher than that of Staphylococcus. This suggests that the two genera are not closely related. Higher G-C content typically indicates a higher stability of DNA, while lower G-C content indicates a lower stability.

Additionally, G-C content is often used as a measure of genetic relatedness in phylogenetic studies. The more similar the G-C content is between two organisms, the more closely related they are considered to be.

In summary, based on the significant difference in G-C content between Micrococcus and Staphylococcus, it is unlikely that these two genera are closely related.