Way back in 2010 we (Abedon and Thomas-Abedon) suggested that the growth of phage plaques within bacterial lawns could serve as mimics of bacteriophage interaction with bacterial biofiolms. In fact, we made a rather extensive argument with six Roman numeraled points: (i) constraint of bacterial movement, (ii) bacterial growth within lawns as microcolonies, (iii) inhibition of phage movement, (iv) plaque-like phage growth within actual biofilms, (v) possible temporary shielding of bacteria within lawn microcolonies from phage attack, and (vi) variation in bacterial physiologies again as found within microcolonies within lawns and as potentially equivalent to bacterial microcolonies within biofilms. We concluded that, “Given these similarities, phage plaques as a facile laboratory model therefore could enrich our understanding of phage-bacterial interrelations as they may occur during the phage therapy of biofilm-producing bacterial infections.”
Indeed, we noted as well that Gallet et al. (2009) described phage formation of plaques also as phage growth within a “biofilm-like environment”.
Here I provide a quote from an earlier publication which serves to further these arguments. From Gilbert and Brown (1995) [Mechanisms of the protection of bacterial biofilms from antibacterial agents, p. 118-130. In J. W. Costerton and H. Lappin-Scott (ed.), Microbial biofilms. Cambridge University Press, Cambridge, UK.], p. 119:
The most simple in vitro method of generating biofilms to study antimicrobial sensitivity is to inoculate the surface of an agar plate to produce a confluent growth. Such cultures, whilst not fully duplicating the in vivo situation, have been suggested to model the close proximity of individual cells to one another and the various gradients found in biofilms. In this respect, colonies grown on agar may bе representative of biofilms at solid-air interfaces.
Of course, one cannot claim that bacteria growing within soft agar overlays are perfect representations of naturally occurring biofilm structures. Nonetheless, as we’ve noted previously, e.g., Abedon and Yin (2009), plaque formation within them is a lot more complex than people otherwise may realize.