Bacterial interactions during sequential degradation of cyanobacterial necromass in a sulfidic arctic marine sediment

Abstract

SummarySeafloor microorganisms impact global carbon cycling by mineralizing vast quantities of organic matter (OM) from pelagic primary production, which is predicted to increase in the Arctic because of diminishing sea ice cover. We studied microbial interspecies‐carbon‐flow during anaerobic OM degradation in arctic marine sediment using stable isotope probing. We supplemented sediment incubations with 13C‐labeled cyanobacterial necromass (spirulina), mimicking fresh OM input, or acetate, an important OM degradation intermediate and monitored sulfate reduction rates and concentrations of volatile fatty acids (VFAs) during substrate degradation. Sequential 16S rRNA gene and transcript amplicon sequencing and fluorescence in situ hybridization combined with Raman microspectroscopy revealed that only few bacterial species were the main degraders of 13C‐spirulina necromass. Psychrilyobacter, Psychromonas, Marinifilum, Colwellia, Marinilabiaceae and Clostridiales species were likely involved in the primary hydrolysis and fermentation of spirulina. VFAs, mainly acetate, produced from spirulina degradation were mineralized by sulfate‐reducing bacteria and an Arcobacter species. Cellular activity of Desulfobacteraceae and Desulfobulbaceae species during acetoclastic sulfate reduction was largely decoupled from relative 16S rRNA gene abundance shifts. Our findings provide new insights into the identities and physiological constraints that determine the population dynamics of key microorganisms during complex OM degradation in arctic marine sediments.© 2018 Society for Applied Microbiology and John Wiley & Sons Ltd

Uncultured Gammaproteobacteria and Desulfobacteraceae Account for Major Acetate Assimilation in a Coastal Marine Sediment

“…Our approach, however, indicated that the Desulfobulbaceae displayed even higher assimilation rates than the Desulfobacteraceae both in whole core and in slurry experiments. Among the Desulfobacteraceae the Sva0081-MBG assimilated acetate in higher rates than the average Desulfobacteraceae population (Figure 3), while in arctic sediment, this group was reported to assimilate only small amounts of acetate into biomass (Müller et al, 2018). Interestingly, the Sva0081-MBG is consistently found in high cell abundances in Wadden Sea sediments (up to 8% of total cell counts, Ovanesov, 2012) and has been frequently detected in various types of marine sediments worldwide (Wang et al, 2013; Liu et al, 2014; Zheng et al, 2014; Dyksma et al, 2017; Probandt et al, 2017; Müller et al, 2018).…”

Effects of organic matter and low oxygen on the mycobenthos in a coastal lagoon

“…7B), suggests that they were also important degraders of the added lignocellulose extract under anoxic conditions. The role of sulfate reducing bacteria (SRB) in organic matter remineralization marine sediments is well known (Jørgensen, 1982), and proceeds often through the utilization of low molecular weight volatile fatty acids (Muller et al, 2018). Thus, the increased growth of SRB in the samples that received lignocellulose is likely due to their utilization of low molecular weight volatiles produced during the degradation of the lignocellulose by the greater microbial community.…”

Anaerobic bacterial degradation of protein and lipid macromolecules in subarctic marine sediment

“…The microbial degradation of organic macromolecules in anoxic marine sediments is a complex inter-species process involving "primary degraders" that break down larger macromolecules into oligomers and monomers for fermentation to alcohols, lactate, and/or short-chain volatile fatty acids (VFAs), which are then mineralized to CH 4 , CO 2 and/or H 2 [21]. "Terminal oxidizers" of fermentation products prevalent in marine sediments, such as sulfatereducing microorganisms (SRM), have been relatively well studied [22][23][24][25][26][27]. On the other hand, the key microbial players responsible for the primary hydrolysis of different types of organic matter and macromolecules are poorly understood.…”