diameter were transferred into SRB medium and checked
for purity microscopically. Furthermore, the purity of the
isolate was checked at 55 and 70 uC. SRB medium supplemented
with 2 g Difco yeast extract l21, 2 g tryptone l21
and 10 mM glucose with air in the headspace was used
to check for aerobic contaminants. The latter medium
prepared anaerobically with N2 (100 %; 200 kPa) or H2
(100 %; 100 kPa) as the gas phase was used to detect
anaerobic contaminants. The presence of possible autotrophic
contaminants was checked in SRB medium where
sulfate was omitted but where 2 g Difco yeast extract l21
and 2 mM acetate were added. Stock cultures of strain
CIR29812T were stored in SRB medium at 4 uC. However,
frequent transfers (twice per month) with 10% (v/v) of
inoculum in freshly prepared culture medium were found
optimal to ensure re-growth. Alternatively, the isolate was
stored in liquid nitrogen in the same medium containing
5% (w/v) DMSO.
Cells of strain CIR29812T were small rods, approximately
0?8–1 mm in length and 0?4–0?5 mm in width, with a single
polar flagellum (Fig. 1a, b). Cells occurred singly, in pairs
or in chains of three cells, and elongated during the
stationary phase of growth. Occasionally, visible creamy
aggregates that corresponded to large clumps of cells
could be observed in the liquid medium. No spores were
produced.
Unless otherwise stated, growth experiments were performed
in duplicate in SRB medium supplemented with