Insights into the Structure and Metabolic Function of Microbes That Shape Pelagic Iron-Rich Aggregates (“Iron Snow”)

Abstract

dMicrobial ferrous iron [Fe(II)] oxidation leads to the formation of iron-rich macroscopic aggregates ("iron snow") at the redoxcline in a stratified lignite mine lake in east-central Germany. We aimed to identify the abundant Fe-oxidizing and Fe-reducing microorganisms likely to be involved in the formation and transformation of iron snow present in the redoxcline in two basins of the lake that differ in their pH values. Nucleic acid-and lipid-stained microbial cells of various morphologies detected by confocal laser scanning microscopy were homogeneously distributed in all iron snow samples. The dominant iron mineral appeared to be schwertmannite, with shorter needles in the northern than in the central basin samples. Total bacterial 16S rRNA gene copies ranged from 5.0 ؋ 10 8 copies g (dry weight) ؊1 in the acidic central lake basin (pH 3.3) to 4.0 ؋ 10 10 copies g (dry weight) ؊1 in the less acidic (pH 5.9) northern basin. Total RNA-based quantitative PCR assigned up to 61% of metabolically active microbial communities to Fe-oxidizing-and Fe-reducing-related bacteria, indicating that iron metabolism was an important metabolic strategy. Molecular identification of abundant groups suggested that iron snow surfaces were formed by chemoautotrophic iron oxidizers, such as Acidimicrobium, Ferrovum, Acidithiobacillus, Thiobacillus, and Chlorobium, in the redoxcline and were rapidly colonized by heterotrophic iron reducers, such as Acidiphilium, Albidiferax-like, and Geobacter-like groups. Metaproteomics yielded 283 different proteins from northern basin iron snow samples, and protein identification provided a glimpse into some of their in situ metabolic processes, such as primary production (CO 2 fixation), respiration, motility, and survival strategies.

Bacterial Community Structures in Freshwater Polar Environments of Svalbard

“…Filamentous sulfur bacteria of the genus Beggiatoa appear to play an important ecological role in the Arctic archipelago of Svalbard (31). Moreover, microbial ferrous oxidation was recently found to contribute to macroscopic aggregate formation in aquatic ecosystems (37). Dissimilatory sulfate reduction appears to be restricted because only a single OTU related to an Albidiferax sp.…”

Characterization of biofilm and corrosion of cast iron pipes in drinking water distribution system with UV/Cl2 disinfection

“…At stage II, the dominant genera NRB were 64.1%, and among them, Dechloromonas (Weber et al, 2006a) and Hyphomicrobium were 45.23% and 1.3% inducing redox of iron, and 17.5% NRB produced siderophores. While IRB, including Rhodobacter (Dobbin et al, 1996), Ferribacterium (Cummings et al, 1999), Acidobacterium and Albidiferax (Lu et al, 2013), decreased to 3.6%, and IOB such as Sediminibacterium and Pedomicrobium were 0.5%, the rhizobia were 2.6%. In the AR with Cl 2 alone, at stage I, the relative abundance of the same rhizobia was 7.7%, including Bradyrhizobium, Rhizobium and Mesorhizobium, while the relative abundance of NRB was 12.8%, including 6.5% NRB inducing redox of iron, such as Hyphomicrobium (3.5%) and Herbaspirillum (3%) (Geissler et al, 2011), and 6.3% NRB producing siderophores, such as Sphingomonas, Acinetobacter and Azospirillum.…”

Identification of Mn(II)-Oxidizing Bacteria from a Low-pH Contaminated Former Uranium Mine

“…Purified genomic DNA (10 ng) was used as the template in the Maxima SYBR green qPCR master mix (Fermentas, Germany). Plasmids CB54 (accession number HE604015) and NR27 (accession number HE604080) were used as standards (45). Thermocycling was performed with the following temperature program: 10 min at 95°C and 50 cycles of 30 s at 95°C, 45 s at 57°C, 60 s at 72°C, and 10 s at 78°C.…”