The presence of {HEAD ~ various different microorganisms} in {TAIL ~ a single culture} is generally referred to as a mixed culture 
in
The presence of { HEAD ~ various different microorganisms } in { TAIL ~ a single culture } is generally referred to as a mixed culture
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH