Changes in Activity and Community Composition Shape Bacterial Responses to Size-Fractionated Marine DOM

Abstract

To study the response of bacteria to different size-fractions of naturally occurring dissolved organic matter (DOM), a natural prokaryotic community from North Atlantic mesopelagic waters (1000 m depth) was isolated and grown in (i) 0.1-μm filtered seawater (CONTROL), (ii) the low-molecular-weight (<1 kDa) DOM fraction (L-DOM), and (iii) the recombination of high- (>1 kDa) and low-molecular-weight DOM fractions (H + L-DOM), to test the potential effect of ultrafiltration on breaking the DOM size continuum. Prokaryotic abundance and leucine incorporation were consistently higher in the H + L-DOM niche than in the L-DOM and CONTROL treatments, suggesting a different interaction with each DOM fraction and the disruption of the structural DOM continuum by ultrafiltration, respectively. Rhodobacterales (Alphaproteobacteria) and Flavobacteriales (Bacteroidetes) were particularly enriched in L-DOM and closely related to the colored DOM (CDOM) fraction, indicating the tight link between these groups and changes in DOM aromaticity. Conversely, some other taxa that were rare or undetectable in the original bacterial community were enriched in the H + L-DOM treatment (e.g., Alteromonadales belonging to Gammaproteobacteria), highlighting the role of the rare biosphere as a seed bank of diversity against ecosystem disturbance. The relationship between the fluorescence of protein-like CDOM and community composition of populations in the H + L-DOM treatment suggested their preference for labile DOM. Conversely, the communities growing on the L-DOM niche were coupled to humic-like CDOM, which may indicate their ability to degrade more reworked DOM and/or the generation of refractory substrates (as by-products of the respiration processes). Most importantly, L- and/or H + L-DOM treatments stimulated the growth of unique bacterial amplicon sequence variants (ASVs), suggesting the potential of environmental selection (i.e., changes in DOM composition and availability), particularly in the light of climate change scenarios. Taken together, our results suggest that different size-fractions of DOM induced niche-specialization and differentiation of mesopelagic bacterial communities.

Microbiota of the Rearing Water ofPenaeus stylirostrisLarvae Influenced by Lagoon Seawater and Specific Key Microbial Lineages of Larval Stage and Survival

“…6B ). These 3 families could be involved in the carbon, nitrogen, and phosphorus biogeochemical cycles by removing or transforming various substrates such as sugars, chitin, and organic acid ( 33 – 35 , 38 , 39 ) during the early stage of rearing. However, the Pearson correlation showed that only the Marinobacteraceae were a biomarker related to the “Nauplii Good” condition ( Fig.…”

Empirical leucine-to-carbon conversion factors in north-eastern Atlantic waters (50–2000 m) shaped by bacterial community composition and optical signature of DOM

“…Overall, we did not find a correlation between eCFs and ASV richness (SChao 1 ) or the Shannon diversity index. However, those indices may not reflect whether specific microbial taxa are relevant in the degradation of marine DOM 13 . Nevertheless, our study displayed shifts in eCF values which might be partially related to several specific groups.…”

“…Depth-dependent biogeographical patterns of CFs, and in turn PHP, are likely dependent on both the availability of substrates for prokaryotic activity as well as on the capability of certain microorganisms to use those resources depending on their nature and quality 13 . Therefore, the composition of the DOM pool may have a role in shaping bacterial community structure and vice versa 14 , 15 , and these factors likely influence PHP, as well.…”

Distribution and microbial degradation of dissolved organic carbon in the northern South China Sea

“…Based on these studies, the molecular size and chemical composition of DOC, which are likely linked to its variable radiocarbon age (via D 14 C), appeared to be the primary controls on its bioavailability and degradation in the ocean (Walker et al, 2011;Walker et al, 2016;Shen and Benner, 2020). In addition to quantifying the removal of oceanic DOC, these experiments were also used as platforms to assess the transformation of DOC composition as well as the concomitant shifts in microbial community structures (Carlson et al, 2004;Liu et al, 2020;Varela et al, 2020). While these bioassay experiments focused on the microbial degradation of DOC and provided potential linkages between DOC utilization and microbial lineages, the variation in the D 14 C-DOC values (or radiocarbon ages) during DOC degradation is still enigmatic and only supposed, lacking direct evidence of simultaneous carbon isotope measurements of DOC (both d 13 C-DOC and D 14 C-DOC).…”