How can I find some pieces of the genome of a microorganism?
You can use already available tools to extract information from available database. For finding specific genes, use this. For protein, use this. There are lot more tools. Just explore NCBI, EMBL or DDBJ sites. All information is self explanatory. 
If you want specialized information for specific organism, you can use specialized database ( like Flybase for flies, SGD for common yeast, EnsemblBacteria for bacteria and archaea or HGMD for human mutations. Best way is to search in Google. You will get everything you want :D