1.	Reproduction is rapid.
2.	Many progeny are produced.
3.	The haploid genome allows all mutations to be expressed directly.
4.	Asexual reproduction simplifies the isolation of genetically pure strains.
5.	Growth in the laboratory is easy and requires little space.
6.	Genomes are small.
7.	Techniques are available for isolating and manipulating their genes.
8.	They have medical importance.
9.	They can be genetically engineered to produce substances of commercial value.