Exclusion zones form in co-cultures of A. graevenitziiand S. aureus.
Formation of exclusion zones appeared to exhibit species specificity
within the Streptococcus genus. To test whether this phenomenon
might also occur for different major Firmicutes genera we co-culturedA. graevenitzii with the GFP-expressing strain ofStaphylococcus aureus (SH1000-GFP ) that had previously
been shown to grow in our device. We observed formation of exclusion
zones around A. graevenitzii colonies in co-culture with S.
aureus (Fig. 3A,B), demonstrating that this effect is not specific to
streptococcal species. Exclusion zones did not form in co-cultures ofS. aureus and A. naeslundii , suggesting that this
phenomenon is not common to all actinomyces (Fig. 3C). Importantly, the
ability to use a GFP-labelled strain in our studies provided
considerable benefits with respect to automated image analysis.