Supplementary Figure 1. Nucleotide sequence of the 951 bp product obtained by PCR
of chromosomal DNA from the GEI--strain using primers p346f/p349r. The positions of
primers p346f and p349r are indicated. The 50 bp direct repeat sequence is indicated in
bold (nucleotides 408-457) and the 77 bp tRNA-Met gene is indicated in uppercase (nt
413-489). The portion of the sequence confirmed by sequencing is underlined.
Supplementary Figure 2. Southern blot of chromosomal DNA isolated from the wild
type, the GEI-- and the GEI+-strains. Lanes 1 and 8 is bacteriophage  DNA digested with
HindIII. Chromosomal DNAs of D. vulgaris strains were digested with EcoRI (lanes 2, 5,
9 and 12), SalI (lanes 3, 6, 11 and 13), and PstI (lanes 4, 7, 10 and 14). All indicated
lengths are in kilobases (kb). The blot was hybridized with the radioactively labeled 951
bp PCR product amplified from the GEI--strain with primers p346f and p349r.
Qualitative inspection indicates that the wild-type pattern more closely resembles that of
the GEI+- than that of the GEI--strain. The intensities of bands of 4066 and 2986 bp in the
SalI digest of the GEI+- strain and of 2087 bp in the SalI digest of the GEI--strain were
used for quantitation. These are marked (*).
Supplementary Figure 3. Nitrite removal by Nrf+-strains of D. vulgaris. Nitrite (2 mM)
was added () in mid-log phase (sulfide concentration of 8-10 mM, lactate concentration
of 20-25 mM) to cells growing in WP-LS. Time courses are shown for the concentration
of NO2- (, scale on the right), for the cell density (, OD600 , scale on the left) and for
the polysulfide concentration (, OD410, scale on the left). No significant polysulfide
formation is observed in these Nrf+-strains. The data shown are averages of duplicate
experiments.
(A)
(B)
Supplementary Figure 4. Motility of GEI+- and GEI--strains. (A) Swarming on
anaerobic soft agar plates. The fraction of the total surface occupied by the swarming
cells was recorded as a function of time as the average of duplicate experiments. (B)
Entry of strains in aerobic capillaries. Capillaries, containing medium C and a headspace
of air were sealed at the top, transferred to the anaerobic hood and inserted into a midlogphase culture of either the GEI+- or the GEI--strain. The number of colony-forming units
(CFUs) present in the capillaries was determined by dilution plating at the indicated
times. The data at time zero reflect the CFU/ml of the midlog-phase culture. The data are
averages of triplicate experiments.