Look at these papers, for example.
Nat Commun. 2013;4:2469. doi: 10.1038/ncomms3469.
Human gut microbiota community structures in urban and rural populations in Russia.
Rural and urban microbiota To be or not to be?
These authors compared Russian bacterial population with Europian, USA, etc.
Early childhood gut microbiome shapes immune defence (russian Karelia)