I need to compare the human gut microbes with human to identify functional genome similarity. Is there any online tool for comparing the genome between different species?
Do you mixing two similar but different things, i.e., functional genomics and comparative genomics.
If you want to compare genomes, it will be comparative genomics which would require genome (nucleotide) data.
For functional analysis and comparison, several other datasets would be required depending on the experimental design.
For comparative genomics too, you cannot use whole microbiome to compare against human genome. Such comparison itself is illogical. Why would one need to compare genome of a microbe to that of human.
There are several tools which can be used for the comparative analysis, but that can be discussed once the basics has been understood.
Most widely used tools for comparative genomic is ACT i. e. Artemis comparison tool and the BRIG i. e. BLAST ring image generator.
However this is another good tool.. https://academic.oup.com/bioinformatics/article/35/24/5303/5539862 (geneCO), you can access the paper via this link and check the tool.