Brownish spots on the OP50 Lawn

Whenever i chunk to newly seeded plates i see a very dull brownish spots around the chunk…are these contaminations or are these just OP50 aggregates???

Probably contamination on the plate from which the chunk originated.

I sometimes saw those spots too. They’re definitely contamination,while I don’t find the source.

Yeah, some contaminating bugs grow slowly enough that you don’t see the contamination interspersed amongst the OP50 on plates that are only 3-4 days old. But you will see the telltale spots around a chunk. Most contaminants, of course, grow more aggressively.