Differential incorporation of one-carbon substrates among microbial populations identified by stable isotope probing from the estuary to South China Sea

Abstract

Methanol (MOH) and monomethylamine (MMA) are two typical one-carbon (C1) compounds found in natural environments. They play an important role in marine and atmospheric chemistry, cloud formation, and global climate. The main biological sink of MOH and MMA is rapid consumption by marine microbes. Here, field-based time-series incubations with supplemental 13C-labelled MOH and MMA and isotope ratio analyses were performed. A substantial difference in the MOH and MMA incorporation rates and bacterial taxa were observed between the South China Sea (SCS) and the Pearl River estuary. C1 substrates were assimilated more quickly in the estuary than the SCS shelf where MOH and MMA had similar bio-availability. However, microbial responses to MMA may be faster than to MOH in the coastal and basin surface water of the SCS despite similar active bacterial populations. Three ecological types of bacteria, in terms of response to supplemented MOH and MMA, were identified: rapid incorporation (I, dominant C1-incorporating group), slow incorporation (II, minor C1-incorporating group), and no incorporation (III, C1-non-incorporating group). Members of the families Methylophilaceae (β-Proteobacteria) and Piscirickettsiaceae (γ-Proteobacteria) belonged to type I and actively incorporated substrates in the estuary and SCS, respectively. Diverse MOH and MMA-incorporating type II bacteria were identified by stable isotope probing in the SCS, and could play a more important role in the transformation of C1 compounds in marine environments than hitherto assumed.

Aerobic bacterial methane synthesis

“…Several studies speak to the general importance of GB and MeA beyond simply their ubiquity and abundance in marine environments. Potential fates include assimilation as a carbon source, oxidized for energy, or used as a nitrogen source (19,22,25,(66)(67)(68). These examples represent metabolisms that would compete with a MeA → CH 4 pathway, but it is still reasonable to consider its potential for CH 4 synthesis.…”

Communal metabolism by Methylococcaceae and Methylophilaceae is driving rapid aerobic methane oxidation in sediments of a shallow seep near Elba, Italy

“…Methylophilaceae related to Methylotenera/Methylophilus spp., in contrast, are only rarely observed at marine methane seeps (Ruff et al, 2013;Paul et al, 2017). With the notable exception of the OM43 clade (Giovannoni et al, 2008), members of the Methylophilaceae family are typically not abundant in marine environments and seem to prefer environments with lower salinity such as estuaries or freshwater (Kalyuzhnaya et al, 2006;Kalyuzhnaya et al, 2012;Deng et al, 2018). Intriguingly, in sediments of Lake Washington (WA), a well-studied freshwater lake featuring high methane fluxes, cooperations between Methylococcaceae and Methylophilaceae have been observed as well (Kalyuzhnaya et al, 2008;Beck et al, 2013).…”

The Global Budget of Atmospheric Methanol: New Constraints on Secondary, Oceanic, and Terrestrial Sources

“…This source is offset by microbial uptake rates of up to 150 nM day −1 (Dixon et al., 2011b), giving methanol turnover times of <1 day. Methanol‐consuming microbes have recently been observed and characterized in a wide variety of ocean environments (Arrieta et al., 2016; Deng et al., 2018; Dinasquet et al., 2018; Dixon et al., 2011a; Dixon & Nightingale, 2012; Dixon et al., 2013; Ramachandran & Walsh, 2015; Sargeant et al., 2016), including some obligate methylotrophs (Giovannoni et al., 2008), suggesting a critical role for methanol in the ocean microbiome. These various pathways of methanol production and destruction can be highly variable in both time and space.…”