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Figure 2. Adherence of B. bifidum PRL2010, B. longum PRL2022, and B. breve PRL2012 to HT29-MTX cells monolayers and growth assay of B. bifidum PRL2010 in the presence of different concentrations of melatonin. (A) Displays the light microscopic images of HT29-MTX monolayers as observed with Giemsa staining of bifidobacterial species grown in the absence (1, 3, 5) or in the presence of melatonin (2, 4, 6), respectively. The bifidobacterial species shown in each image are: (1, 2) B. bifidum PRL2010, B. breve PRL2022 (3, 4), and B. longum PRL2012 (5, 6); (B) Depicts the percentage increase in adhesion capacity of B. bifidum PRL2010, B. longum PRL2022, and B. breve PRL2022 when in the presence of melatonin, compared to their adhesion in the absence of the hormone; (C) Represents the growth assay of B. bifidum PRL2010 in the presence of different amounts of melatonin. Each pillar shows the bacterial growth at the 19 selected melatonin concentrations from 8 µM to 58.59 pM or under control conditions (CTRL, growth of the bifidobacteria without the hormone). The OD_600nm values were expressed as the average of three independent replicates. No statistical significances were exhibited between the conditions, P-value > 0.