Abundant iron and sulfur oxidizers in the stratified sediment of a eutrophic freshwater reservoir with annual cyanobacterial blooms

Abstract

The microbial community in eutrophic freshwater sediment was investigated from a 67-cm-deep sediment core collected from the Daechung Reservoir in South Korea, where cyanobacterial blooms have occurred annually for the past 30 years. The majority of core sediments were characterized by dark-grayish, fine-grained mud with abundant gas-escaped and thinly laminated layers. Intervals of summer and winter seasons were represented by periodic peaks of geochemical profiles of parameters such as grain size and relative carbon mass ratios to various nutrients such as nitrogen, sulfur, and phosphorus. In bacteria, Proteobacteria (66.6%) was the most prevalent phylum, followed by Chloroflexi (8.9%), Bacteroidetes (5.1%), and Spirochaetes (2.6%). Archaea were also abundant, representing approximately half of the total prokaryotes in the sediments. Notably, three Bacteria (Sulfuricurvum, Sideroxydans, and Gallionella) and one Archaea (Thermoplasmata) accounted for 43.4% and 38.4% of the total bacteria and archaea, respectively, implying that iron and sulfur oxidizing microorganisms dominate in this eutrophic freshwater sediment. These results indicate that 1) eutrophic freshwater lakes in monsoon climates undergo a stratified sedimentary process with seasonal and annual variations in geochemical and microbial profiles, and 2) the microbial oxidative metabolism of iron and sulfur is notably active in sediments from a eutrophic lake.

Soil Bacterial and Archaeal Communities and Their Potential to Perform N-Cycling Processes in Soils of Boreal Forests Growing on Well-Drained Peat

“…The only archaeal phylotype found in both coniferous forest networks belonged to the acidophilic class Thermoplasmata (phylum Euryarchaeota ). Members of the class Thermoplasmata have previously been found in soils of boreal acidic forests ( Kemnitz et al, 2007 ) and cold-temperate forests ( Isoda et al, 2017 ), and are related to iron and sulfur cycling ( Jin et al, 2016 ) and methanogenesis ( Iino et al, 2013 ).…”

Genomic and Metabolic Insights into Denitrification, Sulfur Oxidation, and Multidrug Efflux Pump Mechanisms in the Bacterium Rhodoferax sediminis sp. nov.

“…Strain CHu59-6-5 T was recovered from a 67 cm-long sediment core (36 • 22'30" N, 127 • 33'58" E) collected at a water depth of 17 m from the Daechung Reservoir using a modified gravity corer (Wildco, FL, USA) ( Figure 1). The Daechung Reservoir is located in the central region of South Korea, which is a large branch-type lake, and the reservoir has a 72 m-high dam with a gross storage capacity of 1490 Mm 3 , where cyanobacterial blooms occur every year because of eutrophication and global warming [12][13][14][15]. Approximately one gram of sediment sample was applied to the serial dilution method in a 0.85% saline solution.…”

“…Cell growth was investigated in different bacteriological media: R2A agar, tryptic soy agar (TSA; Difco, NJ, USA), Luria-Bertani (LB; Difco, NJ, USA) and nutrient agar (NA; Difco, NJ, USA). The growth temperature range was checked at 4,8,15,20,30,37 and 42 • C. The pH range for growth was determined by measuring the OD values of R2A broth cultures after 3 days. Then, pH was adjusted to 5-10 at intervals of 1 pH unit with appropriate biological buffers [18,19].…”

Genomic insights into a novel species Rhodoferax aquaticus sp. nov., isolated from freshwater

“…Strain Gr-4 T was recovered from a freshwater sample of Daechung Reservoir (36° 28′ 40″ N, 127° 28′ 53″ E), where cyanobacterial blooms occur every year because of eutrophication and global warming [9, 10]. The surface water samples were directly spread onto modified 1/10 Reasoner's 2A (R2A) medium [11] and incubated at 25 °C under heterotrophic conditions.…”