Seasonal patterns in microbial carbon and iron transporter expression in the Southern Ocean
Debeljak, P.; Bayer, B.; Sun, Y.; Herndl, G.J.; Obernosterer, I. (2023). Seasonal patterns in microbial carbon and iron transporter expression in the Southern Ocean. Microbiome 11(1): 187. https://dx.doi.org/10.1186/s40168-023-01600-3
In: Microbiome. BIOMED CENTRAL LTD: London. e-ISSN 2049-2618, more
Background: Heterotrophic microbes in the Southern Ocean are challenged by the double constraint of low con?centrations of organic carbon (C) and iron (Fe). These essential elements are tightly coupled in cellular processes; however, the prokaryotic requirements of C and Fe under varying environmental settings remain poorly studied. Here, we used a combination of metatranscriptomics and metaproteomics to identify prokaryotic membrane transport?ers for organic substrates and Fe in naturally iron-fertilized and high-nutrient, low-chlorophyll waters of the Southern Ocean during spring and late summer.Results Pronounced diferences in membrane transporter profles between seasons were observed at both sites, both at the transcript and protein level. When specifc compound classes were considered, the two approaches revealed diferent patterns. At the transcript level, seasonal patterns were only observed for subsets of genes belong?ing to each transporter category. At the protein level, membrane transporters of organic compounds were relatively more abundant in spring as compared to summer, while the opposite pattern was observed for Fe transporters. These observations suggest an enhanced requirement for organic C in early spring and for Fe in late summer. Mapping transcripts and proteins to 50 metagenomic-assembled genomes revealed distinct taxon-specifc seasonal diferences pointing to potentially opportunistic clades, such as Pseudomonadales and Nitrincolaceae, and groups with a more restricted repertoire of expressed transporters, such as Alphaproteobacteria and Flavobacteriaceae.Conclusion The combined investigations of C and Fe membrane transporters suggest seasonal changes in the microbial requirements of these elements under diferent productivity regimes. The taxon-specifc acquisition strategies of diferent forms of C and Fe illustrate how diverse microbes could shape transcript and protein expres?sion profles at the community level at diferent seasons. Our results on the C- and Fe-related metabolic capabili?ties of microbial taxa provide new insights into their potential role in the cycling of C and Fe under varying nutrient regimes in the Southern Ocean.
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