Microbial Communities of Ferromanganese Sedimentary Layers and Nodules of Lake Baikal (Bolshoy Ushkany Island)

Abstract

Ferromanganese (Fe-Mn) sedimentary layers and nodules occur at different depths within sediments at deep basins and ridges of Lake Baikal. We studied Fe-Mn nodules and host sediments recovered at the slope of Bolshoy Ushkany Island. Layer-by-layer 230Th/U dating analysis determined the initial age of the Fe-Mn nodule formation scattered in the sediments as 96 ± 5–131 ± 8 Ka. The distribution profiles of the main ions in the pore waters of the studied sediment are similar to those observed in the deep-sea areas of Lake Baikal, while the chemical composition of Fe-Mn nodules indicates their diagenetic formation with hydrothermal influence. Among the bacteria in microbial communities of sediments, members of organoheterotrophic Gammaproteobacteria, Chloroflexi, Actinobacteriota, Acidobacteriota, among them Archaea—chemolithoautotrophic ammonia-oxidizing archaea Nitrososphaeria, dominated. About 13% of the bacterial 16S rRNA gene sequences in Fe-Mn layers belonged to Methylomirabilota representatives which use nitrite ions as electron acceptors for the anaerobic oxidation of methane (AOM). Nitrospirota comprised up to 9% of the layers of Bolshoy Ushkany Island. In bacterial communities of Fe-Mn nodule, a large percentage of sequences were attributed to Alphaproteobacteria, Actinobacteriota and Firmicutes, as well as a variety of OTUs with a small number of sequences characteristic of hydrothermal ecosystems. The contribution of representatives of Methylomirabilota and Nitrospirota in communities of Fe-Mn nodule was minor. Our data support the hypothesis that chemolithoautotrophs associated with ammonium-oxidizing archaea and nitrite-oxidizing bacteria can potentially play an important role as primary producers of Fe-Mn substrates in freshwater Lake Baikal.

Microbial Communities in Ferromanganese Sediments from the Northern Basin of Lake Baikal (Russia)

“…According to the authors, the dissolution of the buried Fe-Mn oxide layer is ultimately controlled by AOM using SO 4 2− and/or Fe(III) as electron acceptors in deeper sediments, with the formation of an upper dynamic Fe-Mn oxide layer due to the O 2 diffusion from the water column in the sediments [ 9 , 11 ]. The hypothesis of the diagenetic formation of Fe-Mn layers resulting from the biogenic activity in the freshwater sediments of Lake Baikal corresponds to the studies by Dubinina [ 44 ], Granina [ 8 ], and Zakharova et al [ 45 ], as well as to our previous results of the study of communities in the sediments with Fe-Mn layers near Bolshoy Ushkany Island [ 22 ]. To develop this hypothesis, we investigated the diversity and structure of microbial communities in the sediments of the northern basin of Lake Baikal, where Granina [ 8 ] and Och et al [ 9 ] indicated a different type of diagenetic redistribution of Fe and Mn.…”

“…Noteworthy is that members of Methylomirabiota , as well as the species Nitrospira , the most identical to the bacteria from the seeps enriched in Fe, were found in the microbial communities from the sediments enriched in iron of lakes Superior [ 4 ] and Constance [ 6 ]. The archaeal diversity in this sedimentary zone of Lake Baikal differed less significantly; as in other basins, chemolithotrophic ammonia-oxidizing archaea, Nitrososphaeria , dominated [ 22 , 84 ]. Among the members of this class in the sediments from Lake Baikal, we detected archaea of the orders Nitrosopumilales and Nitrososphaerales , known participants in aerobic ammonia oxidation [ 85 ].…”

“…Iron and manganese cycles are also known to be closely related to the carbon and nitrogen cycles [ 106 ]. In the communities of the investigated sediments from the northern basin of Lake Baikal, like in other areas of the lake [ 22 , 84 ], a high percentage were organotrophic Actinobacteriota , genomes of which also contained genes for assimilatory sulfate reduction and Fe(II) oxidation (cbb3 and bc1cytochrome oxidase). According to [ 107 ], members of this phylum can carry out chemolithotrophic Fe(II) oxidation.…”

“…Another type was detected in the northern basin, where massive interlayers enriched in iron and manganese are rather formed in the upper oxidized sedimentary layer, near the redox boundary. The role of hydrothermal processes in the diagenesis of Fe-Mn layers and crusts near the Ushkany Islands has so far remained unknown [ 22 ].…”

Novel Insights on the Bacterial and Archaeal Diversity of the Panarea Shallow-Water Hydrothermal Vent Field

“…Anaerolineaceae and Calditrichaceae have been reported as key bacterial taxa of shallow-water hydrothermal vents, involved not only in organic carbon remineralization but also in nitrogen cycling [15,42,43], and include moderate thermophilic chemoheterotrophs, which grow by fermentation of peptides or carbohydrates compounds and have been described as anaerobic digesters in several organic-rich habitats [44][45][46]. Analogously, bacteria within the orders Ardenticantales and Woesearchaeales (ammonium-oxidizing archaea) are known as key components of the microbial assemblages at hydrothermal vents, also participating in C, N, and especially Fe cycling [47][48][49]. In this regard, the reported presence of particularly high Fe concentration in the Panarea sediments [50] can explain the local proliferation of bacteria whose metabolic functions are strictly dependent Such taxonomic features largely differ from those previously reported in other Panarea or Vulcano Island hot vents, in which sulphur-oxidizing bacteria belonging to Campylobacterota (previously, Epsilonproteobacteria), such as Sulfurimonas, Arcobacter and Sulfurovum spp.…”