, 2010). To date, Fe(II)-dependent or -enhanced growth has been shown only for a handful of freshwater isolates including species from the genera Gallionella and Sideroxydans (Hallbeck & Pederson, 1991; Emerson & Moyer, 1997; Weiss et al., 2007). Since the known FeOB are phylogenetically and physiologically diverse and the functional genes unique to Fe(II) oxidation are unknown, the use of nonculture-based, molecular methods to study FeOB ecology and distribution can be problematic. It therefore remains critical to further our knowledge of FeOB using enrichment and isolation techniques. The genus Dechlorospirillum has been primarily described in the literature
as a perchlorate and nitrate reducer (Coates, 1999; Bender et al., 2004; Bardiya & Bae, 2008), and Fe(II)-oxidation-dependent growth of this genus has not been demonstrated previously. The objective Selleck Tanespimycin of our studies was to determine whether a Dechlorospirillum sp. isolated from an Fe(II)-oxidizing, microbial mat is involved in and benefits from microaerophilic Fe(II) oxidation in gradient cultures. The inoculum consisted of sediment and microbial mat samples collected in June 2007 from a
portion of Jackson Creek (Bloomington, IN) fed by an iron-rich groundwater spring. In addition to irregular mats several centimeter thick on the creek bed, the creek also contained orange, bulbous, and filamentous formations of up to 20 cm diameter. Apoptosis inhibitor Under microscopic examination, we found that these formations primarily consist of both iron (oxy)hydroxide precipitates and mostly empty, Leptothrix-like sheaths. In addition to the sheaths, large numbers of other bacteria were observed including occasional spiral stalks characteristic of Gallionella. The pH of the site water was 6.6 on the day
of inoculum collection and typically ranges from 5.8 to 6.8. During the period that samples were obtained, the spring water typically contained 0.36–1.8 mM Fe2+, 0.02–0.18 mM NO3−, and approximately 2 mg L−1 dissolved organic carbon. Samples of the flocculent mat and sediment were collected in sterile bottles, returned to the laboratory, and used to inoculate gradient-culture bottles on the day of collection. Opposing-gradient-culture Protein kinase N1 systems, inoculation procedures, and enrichment transfers were similar to those described elsewhere (Emerson & Moyer, 1997; Sobolev & Roden, 2001). Initially, we used 250- or 40-mL screw-cap bottles containing a lower layer of 50 mM FeCl2, stabilized by 2% Difco noble agar (Becton, Dickinson and Company, MD) and buffered at pH 7 by 20 mM 1,4-piperazinediethanesulfonic acid (PIPES). The upper layer consisted of 0.5% noble agar, 30 mM NaHCO3, 10 mM NH4Cl, 1 mM KH2PO4, 5 mL L−1 vitamin solution (Strąpoćet al., 2008), and 2.5 mL L−1 trace mineral solution (Strąpoćet al., 2008).