Many of the first prokaryotes to be cultured in a scientific lab were human or animal pathogens. why would these species be more readily cultured than non-pathogenic prokaryotes?
pathogenic prokaryotes are hardier than non-pathogenic prokaryotes.
non-pathogenic prokaryotes require more supplements in their growth media.
most of the necessary culture conditions could be inferred for pathogenic prokaryotes.
pathogenic bacteria can grow as free bacteria, but non-pathogenic bacteria only grow as parts of large colonies.