Bacterial community structure and novel species of magnetotactic bacteria in sediments from a seamount in the Mariana volcanic arc

Abstract

Seamounts are undersea mountains rising abruptly from the sea floor and interacting dynamically with underwater currents. They represent unique biological habitats with various microbial community structures. Certain seamount bacteria form conspicuous extracellular iron oxide structures, including encrusted stalks, flattened bifurcating tubes, and filamentous sheaths. To extend our knowledge of seamount ecosystems, we performed an integrated study on population structure and the occurrence of magnetotactic bacteria (MTB) that synthesize intracellular iron oxide nanocrystals in sediments of a seamount in the Mariana volcanic arc. We found Proteobacteria dominant at 13 of 14 stations, but ranked second in abundance to members of the phylum Firmicutes at the deep-water station located on a steep slope facing the Mariana-Yap Trench. Live MTB dwell in biogenic sediments from all 14 stations ranging in depth from 238 to 2,023 m. Some magnetotactic cocci possess the most complex flagellar apparatus yet reported; 19 flagella are arranged in a 3:4:5:4:3 array within a flagellar bundle. Phylogenetic analysis of 16S rRNA gene sequences identified 16 novel species of MTB specific to this seamount. Together the results obtained indicate that geographic properties of the seamount stations are important in shaping the bacterial community structure and the MTB composition.

Single‐cell determination of iron content in magnetotactic bacteria: implications for the iron biogeochemical cycle

“…Analyses of AMB-1 cells cultivated with no iron added to the growth medium showed similar values to the 10 μM condition (see Supporting Information Table S5), showing that 0.5 × 10 −6 ng per cell is an appropriate conservative estimate of bacterial iron content. The dissolved iron concentration in the ocean is also low, but MTB observed in marine environments show chains of magnetite containing 10-20 crystals as in AMB-1 (Liu et al, 2017). M MTB can thus be estimated for MTB populations in freshwater (2.5 × 10 3 ≤ M MTB ≤ 2.5 × 10 5 kg), oceans (2 × 10 3 ≤ M MTB ≤ 2 × 10 5 kg) and estuaries (6 × 10 1 ≤ M MTB ≤ 3 × 10 4 kg).…”

Characterization and Quantification of Magnetofossils Within Abyssal Manganese Nodules From the Western Pacific Ocean and Implications for Nodule Formation

“…To further investigate ancient microbial activity in incipient nodules, we sought to quantify microbial abundances during nodule formation. MTB cells generally contain a single magnetosome chain (Dong et al, 2016;Liu et al, 2017), but some species can also produce multiple intracellular chains (Lin et al, 2009;Pan et al, 2005). Based on reports of MTB cells and magnetofossil chains from Pacific Ocean sediments (Dong et al, 2016;Liu et al, 2017;Oda et al, 2018;Yamazaki & Shimono, 2013;Yuan et al, 2020), we assume that MTB cells contain a single chain with 20 ± 5 magnetosomes.…”

“…MTB cells generally contain a single magnetosome chain (Dong et al, 2016;Liu et al, 2017), but some species can also produce multiple intracellular chains (Lin et al, 2009;Pan et al, 2005). Based on reports of MTB cells and magnetofossil chains from Pacific Ocean sediments (Dong et al, 2016;Liu et al, 2017;Oda et al, 2018;Yamazaki & Shimono, 2013;Yuan et al, 2020), we assume that MTB cells contain a single chain with 20 ± 5 magnetosomes. Low MTB concentrations (0.04-0.7%) in modern microbial communities have been measured in seafloor environments based on identified MTB gene sequences in Genbank (Dong et al, 2016;Liu et al, 2017).…”

“…Based on reports of MTB cells and magnetofossil chains from Pacific Ocean sediments (Dong et al, 2016;Liu et al, 2017;Oda et al, 2018;Yamazaki & Shimono, 2013;Yuan et al, 2020), we assume that MTB cells contain a single chain with 20 ± 5 magnetosomes. Low MTB concentrations (0.04-0.7%) in modern microbial communities have been measured in seafloor environments based on identified MTB gene sequences in Genbank (Dong et al, 2016;Liu et al, 2017). A 1% content was assumed here because not all genes will be identified in such sequencing.…”

“…MTB and MOB are two of the most common bacteria in seafloor microbial communities (Dong et al, 2016;Jiang et al, 2019;Liao et al, 2011;Liu et al, 2017;Wang et al, 2010). Both of their fossils are preserved within nodules.…”