Box plots showing the abundance of six taxa in relation to the total amount of bacteria in samples from patients with chronic (n = 21) or necrotizing gingivitis (n = 21). Data are shown for the phylum Bacteroidetes, the families Bacteroidaceae and Prevotellaceae, the genus Prevotella and the species P. gingivalis, P. endodontalis und T. forsythia. Note that y-axis scales are different for each taxon. 16S rRNA probes used to detect the different taxa are described in Supplementary Table S1. p-values were calculated with the Bonferroni-corrected Mann–Whitney test; p < 0.0001 (****), p < 0.01 (**). CG, chronic gingivitis; NG, necrotizing gingivitis. CFB935; BAC303; PRV392; L–P GIN 1006–2; Pend740; Tfor127 are probes with different targets (see Table 1).