FIG 4.

Nitrite affinities of NOB. K_m values of members of the genera Nitrospira (circles), Nitrotoga (diamond), and Nitrobacter (squares) are shown (pure cultures, filled symbols; enrichment cultures, half-filled symbols). Cultures were derived from activated sludge (green), freshwater (blue), and soil (orange). Phylogenetic affiliations, including Nitrospira lineages I and II, are displayed at the top (unkn., unknown). The values shown were obtained from this study (indicated by a superscript letter a) and references 16, 20, 45, 46, 49, and 71 (indicated by superscript numbers).