As I installed Trinity RNA Seq tool, I want to do de novo sequencing to something.
Genome size is base pair (= bp) size, not gene number.
As to check the behavior of Trinity, small genome size (base pairs) is better.
I found this NCBI's page to check genome size for each organism by sorting the genome size.
- Genome List - Genome - NCBI: Size is the size of bp.
- Genome size - Wikipedia: In the graph "tree of life with genome sizes as outer bars", "genome size" is actually used as "gene number". That's confusing.
"Mycoplasma genitalium"  genome size is 0.58 Mbp = 580,000 bp. It's very small. And it is used for Craig Ventor's minimal cell  It looks good to dig the detail by Trinity.
By the way, I found Japanese article about the genome size for each organism with photos. This web site looks very good to know biology.