Taxonomic and functional diversity of aquatic heterotrophs is sustained by dissolved organic matter chemodiversity

Abstract

Dissolved organic matter (DOM) is ubiquitous in aquatic ecosystems and fundamental for planetary processes and ecosystem functioning. While the link between microbial community composition and heterotrophic utilization of DOM has been recognized, the full diversity of organic compounds, their bioavailability, degradability and specific influences on the diversity and function of heterotrophs are still not clear. Here we experimentally investigate heterotrophic bacteria in thirty-three freshwater model communities. We identified 34 different heterotrophs growing in ambient lake DOM with taxonomic affiliations matching abundant freshwater bacterioplankton. We further describe 25 different heterotrophs growing in the phycosphere of M. Aeruginosa and 6 heterotrophs growing on the DOM produced by M. Aeruginosa with taxonomic affiliation in accord to phycosphere heterotrophs. In our experiment we observed that heterotrophs that live in the phycosphere remove more dissolved organic carbon than abundant freshwater heterotrophs. Moreover, phycosphere heterotrophs have bigger genomes than abundant lake bacteria. Altogether of the 4224 chemical features that were resolved by LC-MS, only 1229 were seen in all three treatments. None of the common/shared compounds were removed across all the model communities, suggesting contrasting niches of the studied taxa. Altogether our study highlights how each model community, with its unique taxonomic assemblages and organotroph functioning is upkept by the chemodiversity of DOM.

Progress and challenges in exploring aquatic microbial communities using non-targeted metabolomics

“…For example, heterotrophic bacteria that grow in the physcosphere of freshwater cyanobacteria Microcystis aeruginosa and on its DOM drew down more dissolved organic carbon than nonphycosphere-inhabiting-heterotrophs, particularly removing more lipids, organic acids and organoheterocyclic molecules [58]. The phycosphere-heterotrophs also had larger genome sizes, reflecting the wider resource pool of DOM available in the phycosphere to maintain larger genomes [59].…”

Evaluation of Data-Dependent MS/MS Acquisition Parameters for Non-Targeted Metabolomics and Molecular Networking of Environmental Samples: Focus on the Q Exactive Platform

“…Spectral libraries provide the highest confidence level for high-throughput metabolite annotation. − Multiple workflows and open-source software solutions exist for feature detection, network propagation, spectral matching, and in silico annotation as well as repository scale analysis of MS/MS spectra, ,− which have been used in numerous lab-culture, mesocosm, and environmental studies. − While non-targeted metabolomics aims to annotate and provide relative quantification of all metabolites present in a sample, most of the MS/MS spectra remain unidentified …”

Evaluation of Data Dependent MS/MS Acquisition Parameters for Non-targeted Metabolomics and Molecular Networking of Environmental Samples - Focus on the Q Exactive Platform

“…Spectral libraries provide the highest confidence level for high-throughput metabolite annotation [9][10][11][12][13][14][15] . Multiple workflows and open-source software solutions exist for feature detection, network propagation, spectral matching and in silico annotation as well as repository scale analysis of MS/MS spectra 13,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] , which have been used in numerous lab-culture, mesocosm, and environmental studies [35][36][37][38][39][40][41][42] . While non-targeted metabolomics aims to annotate and provide relative quantification of all metabolites present in a sample, most of the MS/MS spectra remain unidentified 43 .…”