Algal polysaccharides are an important component of the flux of carbon rich organic matter from the surface ocean into its depth. Most marine polysaccharides are synthesized at the surface by microalgae whose annual production is on par with all plants on land even though they only account for about 1-2% of the marine biomass. This competitive production is caused by intense growth and short lifespans; microalgae live fast and die young (weeks) compared to terrestrial plants (years). They pursue a boom and bust life style with rapid growth and abrupt population crashes whereby algal blooms can appear and disappear within weeks or even days. During growth and upon death microalgae secrete copious amounts of polysaccharides. These are known to spontaneously aggregate into particles, which can more rapidly sink through the water column and inject carbon into deeper waters (the biological pump). Bacteria colonize particles and use enzymes to recycle polysaccharides leading to intense bacterial growth and particle dissolution. This way the interplay between particle formation and its dissolution may regulate the biological pump and dictate how much carbon is stored in the oceans. Despite the relevance of this process the structures of algal polysaccharides and their recycling by marine microbes remain a mystery. To shed light on this black box of the marine carbon cycle we study the functional evolution of the bacterial enzymatic machines and how they process algal polysaccharides in the ocean.
Unfried, F., Becker, S., Robb, C. S., Hehemann, J.-H., Markert, S., Heiden, S. E., … Schweder, T. 2018. Adaptive mechanisms that provide competitive advantages to marine bacteroidetes during microalgal blooms. The ISME Journal.https://doi.org/10.1038/s41396-018-0243-5
Reisky, L., Büchsenschütz, H. C., Engel, J., Song, T., Schweder, T., Hehemann, J.-H.*, & Bornscheuer, U. T.* (2018). Oxidative demethylation of algal carbohydrates by cytochrome P450 monooxygenases. Nature Chemical Biology.https://doi.org/10.1038/s41589-018-0005-8
Becker, S., Scheffel, A., Polz, M. F., & Hehemann, J.-H.* (2017). Accurate quantification of laminarin in marine organic matter with enzymes from marine microbes. Applied and Environmental Microbiology.https://doi.org/10.1128/AEM.03389-16
Hehemann, J.-H., Arevalo, P., Datta, M. S., Yu, X., Corzett, C. H., Henschel, A., … Polz, M. F. (2016). Adaptive radiation by waves of gene transfer leads to fine-scale resource partitioning in marine microbes. Nature Communications, 7, 12860.https://doi.org/10.1038/ncomms12860
Yawata, Y., Cordero, O. X., Menolascina, F., Hehemann, J.-H., Polz, M. F., & Stocker, R. (2014). Competition-dispersal tradeoff ecologically differentiates recently speciated marine bacterioplankton populations. Proceedings of the National Academy of Sciences of the United States of America, 111(15), 5622–5627.https://doi.org/10.1073/pnas.1318943111
Hehemann, J.-H., Kelly, A. G., Pudlo, N. A., Martens, E. C., & Boraston, A. B. (2012). Bacteria of the human gut microbiome catabolize red seaweed glycans with carbohydrate-active enzyme updates from extrinsic microbes. Proceedings of the National Academy of Sciences of the United States of America, 109(48), 19786–19791.https://doi.org/10.1073/pnas.1211002109
Hehemann, J.-H., Correc, G., Barbeyron, T., Helbert, W., Czjzek, M., & Michel, G. (2010). Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota. Nature, 464(7290), 908–12.https://doi.org/10.1038/nature08937