Figure 5.

Stable isotope probing of bacterial communities utilizing ¹³C-labeled substrates. Buoyant density of extracted RNA in gradient fractions 3–15 following isopycnic density gradient centrifugation (A). Error bars are standard deviations of the mean (n = 4). DGGE profiles of bacterial communities present in density gradient fractions 3–15 from vegetated soils at time 0 and 24 h after the addition of ¹³C glucose (B). Density gradient fractions 3–5 were shown to contain ¹³C labeled RNA, as indicated by a general community shift into these fractions after labeled glucose addition. DGGE profiles of bacterial communities present in “heavy” density gradient fraction four from vegetated and bare soils, before and 24 h after the addition of ¹³C-labeled glucose (Glu), glycine (Gly), and phenol (Phe); M denotes marker lanes (C).