FIG. 1.

Microbial community composition of the autotrophic nitrifying biofilm as quantitatively determined by FISH. The α-Proteobacteria is the bacterial group that hybridized with probe ALF968, excluding the genus Nitrobacter that hybridized with probe NIT3. The β-Proteobacteria is the bacterial group that hybridized with probe BET42a, excluding the ammonia-oxidizing bacteria that hybridized with probe Nso190. The number of cells that hybridized with a given probe in each microscopic field was expressed as a percentage of the total surface area of bacteria that hybridized with mixed probes EUB338, EUB338 II, and EUB338 III. The values are the means ± standard errors of duplicate samples.