@article{CookLiCaietal.2019, author = {Cook, Katherine V. and Li, Chuang and Cai, Haiyuan and Krumholz, Lee R. and Hambright, K. David and Paerl, Hans W. and Steffen, Morgan M. and Wilson, Alan E. and Burford, Michele A. and Grossart, Hans-Peter and Hamilton, David P. and Jiang, Helong and Sukenik, Assaf and Latour, Delphine and Meyer, Elisabeth I. and Padisak, Judit and Qin, Boqiang and Zamor, Richard M. and Zhu, Guangwei}, title = {The global Microcystis interactome}, series = {Limnology and oceanography}, volume = {65}, journal = {Limnology and oceanography}, publisher = {Wiley}, address = {Hoboken}, issn = {0024-3590}, doi = {10.1002/lno.11361}, pages = {S194 -- S207}, year = {2019}, abstract = {Bacteria play key roles in the function and diversity of aquatic systems, but aside from study of specific bloom systems, little is known about the diversity or biogeography of bacteria associated with harmful cyanobacterial blooms (cyanoHABs). CyanoHAB species are known to shape bacterial community composition and to rely on functions provided by the associated bacteria, leading to the hypothesized cyanoHAB interactome, a coevolved community of synergistic and interacting bacteria species, each necessary for the success of the others. Here, we surveyed the microbiome associated with Microcystis aeruginosa during blooms in 12 lakes spanning four continents as an initial test of the hypothesized Microcystis interactome. We predicted that microbiome composition and functional potential would be similar across blooms globally. Our results, as revealed by 16S rRNA sequence similarity, indicate that M. aeruginosa is cosmopolitan in lakes across a 280 degrees longitudinal and 90 degrees latitudinal gradient. The microbiome communities were represented by a wide range of operational taxonomic units and relative abundances. Highly abundant taxa were more related and shared across most sites and did not vary with geographic distance, thus, like Microcystis, revealing no evidence for dispersal limitation. High phylogenetic relatedness, both within and across lakes, indicates that microbiome bacteria with similar functional potential were associated with all blooms. While Microcystis and the microbiome bacteria shared many genes, whole-community metagenomic analysis revealed a suite of biochemical pathways that could be considered complementary. Our results demonstrate a high degree of similarity across global Microcystis blooms, thereby providing initial support for the hypothesized Microcystis interactome.}, language = {en} } @article{RevereyGanzertLischeidetal.2018, author = {Reverey, Florian and Ganzert, Lars and Lischeid, Gunnar and Ulrich, Andreas and Premke, Katrin and Grossart, Hans-Peter}, title = {Dry-wet cycles of kettle hole sediments leave a microbial and biogeochemical legacy}, series = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, volume = {627}, journal = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0048-9697}, doi = {10.1016/j.scitotenv.2018.01.220}, pages = {985 -- 996}, year = {2018}, abstract = {Understanding interrelations between an environment's hydrological past and its current biogeochemistry is necessary for the assessment of biogeochemical and microbial responses to changing hydrological conditions. The question how previous dry-wet events determine the contemporary microbial and biogeochemical state is addressed in this study. Therefore, sediments exposed to the atmosphere of areas with a different hydrological past within one kettle hole, i.e. (1) the predominantly inundated pond center, (2) the pond margin frequently desiccated for longer periods and (3) an intermediate zone, were incubated with the same rewetting treatment. Physicochemical and textural characteristics were related to structural microbial parameters regarding carbon and nitrogen turnover, i.e. abundance of bacteria and fungi, denitrifiers (targeted by the nirK und nirS functional genes) and nitrate ammonifiers (targeted by the nrfA functional gene). Our study reveals that, in combination with varying sediment texture, the hydrological history creates distinct microbial habitats with defined boundary conditions within the kettle hole, mainly driven by redox conditions, pH and organic matter (OM) composition. OM mineralization, as indicated by CO2-outgassing, was most efficient in exposed sediments with a less stable hydrological past. The potential for nitrogen retention via nitrate ammonification was highest in the hydrologically rather stable pond center, counteracting nitrogen loss due to denitrification. Therefore, the degree of hydrological stability is an important factor leaving a microbial and biogeochemical legacy, which determines carbon and nitrogen losses from small lentic freshwater systems in the long term run.}, language = {en} } @article{GrossartMassanaMcMahonetal.2019, author = {Grossart, Hans-Peter and Massana, Ramon and McMahon, Katherine D. and Walsh, David A.}, title = {Linking metagenomics to aquatic microbial ecology and biogeochemical cycles}, series = {Limnology and oceanography}, volume = {65}, journal = {Limnology and oceanography}, publisher = {Wiley}, address = {Hoboken}, issn = {0024-3590}, doi = {10.1002/lno.11382}, pages = {S2 -- S20}, year = {2019}, abstract = {Microbial communities are essential components of aquatic ecosystems through their contribution to food web dynamics and biogeochemical processes. Aquatic microbial diversity is immense and a general challenge is to understand how metabolism and interactions of single organisms shape microbial community dynamics and ecosystem-scale biogeochemical transformations. Metagenomic approaches have developed rapidly, and proven to be powerful in linking microbial community dynamics to biogeochemical processes. In this review, we provide an overview of metagenomic approaches, followed by a discussion on some recent insights they have provided, including those in this special issue. These include the discovery of new taxa and metabolisms in aquatic microbiomes, insights into community assembly and functional ecology as well as evolutionary processes shaping microbial genomes and microbiomes, and the influence of human activities on aquatic microbiomes. Given that metagenomics can now be considered a mature technology where data generation and descriptive analyses are relatively routine and informative, we then discuss metagenomic-enabled research avenues to further link microbial dynamics to biogeochemical processes. These include the integration of metagenomics into well-designed ecological experiments, the use of metagenomics to inform and validate metabolic and biogeochemical models, and the pressing need for ecologically relevant model organisms and simple microbial systems to better interpret the taxonomic and functional information integrated in metagenomes. These research avenues will contribute to a more mechanistic and predictive understanding of links between microbial dynamics and biogeochemical cycles. Owing to rapid climate change and human impacts on aquatic ecosystems, the urgency of such an understanding has never been greater.}, language = {en} } @article{MannaZoccaratoBanchietal.2022, author = {Manna, Vincenzo and Zoccarato, Luca and Banchi, Elisa and Arnosti, Carol and Grossart, Hans-Peter and Celussi, Mauro}, title = {Linking lifestyle and foraging strategies of marine bacteria}, series = {Environmental microbiology reports}, volume = {14}, journal = {Environmental microbiology reports}, number = {4}, publisher = {Wiley}, address = {Hoboken}, issn = {1758-2229}, doi = {10.1111/1758-2229.13059}, pages = {549 -- 558}, year = {2022}, abstract = {Microbe-mediated enzymatic hydrolysis of organic matter entails the production of hydrolysate, the recovery of which may be more or less efficient. The selfish uptake mechanism, recently discovered, allows microbes to hydrolyze polysaccharides and take up large oligomers, which are then degraded in the periplasmic space. By minimizing the hydrolysate loss, selfish behaviour may be profitable for free-living cells dwelling in a patchy substrate landscape. However, selfish uptake seems to be tailored to algal-derived polysaccharides, abundant in organic particles, suggesting that particle-attached microbes may use this strategy. We tracked selfish polysaccharides uptake in surface microbial communities of the northeastern Mediterranean Sea, linking the occurrence of this processing mode with microbial lifestyle. Additionally, we set up fluorescently labelled polysaccharides incubations supplying phytodetritus to investigate a 'pioneer' scenario for particle-attached microbes. Under both conditions, selfish behaviour was almost exclusively carried out by particle-attached microbes, suggesting that this mechanism may represent an advantage in the race for particle exploitation. Our findings shed light on the selfish potential of particle-attached microbes, suggesting multifaceted foraging strategies exerted by particle colonizers.}, language = {en} } @article{PerkinsSantosRoseetal.2022, author = {Perkins, Anita K. and Santos, Isaac R. and Rose, Andrew L. and Schulz, Kai G. and Grossart, Hans-Peter and Eyre, Bradley D. and Kelaher, Brendan P. and Oakes, Joanne M.}, title = {Production of dissolved carbon and alkalinity during macroalgal wrack degradation on beaches}, series = {Biogeochemistry}, volume = {160}, journal = {Biogeochemistry}, number = {2}, publisher = {Springer}, address = {Dordrecht}, issn = {0168-2563}, doi = {10.1007/s10533-022-00946-4}, pages = {159 -- 175}, year = {2022}, abstract = {Marine macroalgae are a key primary producer in coastal ecosystems, but are often overlooked in blue carbon inventories. Large quantities of macroalgal detritus deposit on beaches, but the fate of wrack carbon (C) is little understood. If most of the wrack carbon is respired back to CO2, there would be no net carbon sequestration. However, if most of the wrack carbon is converted to bicarbonate (alkalinity) or refractory DOC, wrack deposition would represent net carbon sequestration if at least part of the metabolic products (e.g., reduced Fe and S) are permanently removed (i.e., long-term burial) and the DOC is not remineralised. To investigate the release of macroalgal C via porewater and its potential to contribute to C sequestration (blue carbon), we monitored the degradation of Ecklonia radiata in flow-through mesocosms simulating tidal flushing on sandy beaches. Over 60 days, 81\% of added E. radiata organic matter (OM) decomposed. Per 1 mol of detritus C, the degradation produced 0.48 +/- 0.34 mol C of dissolved organic carbon (DOC) (59\%) and 0.25 +/- 0.07 mol C of dissolved inorganic carbon (DIC) (31\%) in porewater, and a small amount of CO2 (0.3 +/- 0.0 mol C; ca. 3\%) which was emitted to the atmosphere. A significant amount of carbonate alkalinity was found in porewater, equating to 33\% (0.27 +/- 0.05 mol C) of the total degraded C. The degradation occurred in two phases. In the first phase (days 0-3), 27\% of the OM degraded, releasing highly reactive DOC. In the second phase (days 4-60), the labile DOC was converted to DIC. The mechanisms underlying E. radiata degradation were sulphate reduction and ammonification. It is likely that the carbonate alkalinity was primarily produced through sulphate reduction. The formation of carbonate alkalinity and semi-labile or refractory DOC from beach wrack has the potential to play an overlooked role in coastal carbon cycling and contribute to marine carbon sequestration.}, language = {en} } @article{MasigolKhodaparastMostowfizadehGhalamfarsaetal.2020, author = {Masigol, Hossein and Khodaparast, Seyed Akbar and Mostowfizadeh-Ghalamfarsa, Reza and Rojas-Jimenez, Keilor and Woodhouse, Jason Nicholas and Neubauer, Darshan and Grossart, Hans-Peter}, title = {Taxonomical and functional diversity of Saprolegniales in Anzali lagoon, Iran}, series = {Aquatic Ecology}, volume = {54}, journal = {Aquatic Ecology}, number = {1}, publisher = {Springer Science}, address = {Dordrecht}, issn = {1573-5125}, doi = {10.1007/s10452-019-09745-w}, pages = {323 -- 336}, year = {2020}, abstract = {Studies on the diversity, distribution and ecological role of Saprolegniales (Oomycota) in freshwater ecosystems are currently receiving attention due to a greater understanding of their role in carbon cycling in various aquatic ecosystems. In this study, we characterized several Saprolegniales species isolated from Anzali lagoon, Gilan province, Iran, using morphological and molecular methods. Four species of Saprolegnia were identified, including S. anisospora and S. diclina as first reports for Iran, as well as Achlya strains, which were closely related to A. bisexualis, A. debaryana and A. intricata. Evaluation of the ligno-, cellulo- and chitinolytic activities was performed using plate assay methods. Most of the Saprolegniales isolates were obtained in autumn, and nearly 50\% of the strains showed chitinolytic and cellulolytic activities. However, only a few Saprolegniales strains showed lignolytic activities. This study has important implications for better understanding the ecological niche of oomycetes, and to differentiate them from morphologically similar, but functionally different aquatic fungi in freshwater ecosystems.}, language = {en} } @article{HiltGrossartMcGinnisetal.2022, author = {Hilt, Sabine and Grossart, Hans-Peter and McGinnis, Daniel F. and Keppler, Frank}, title = {Potential role of submerged macrophytes for oxic methane production in aquatic ecosystems}, series = {Limnology and oceanography}, journal = {Limnology and oceanography}, publisher = {Wiley}, address = {Hoboken}, issn = {0024-3590}, doi = {10.1002/lno.12095}, pages = {13}, year = {2022}, abstract = {Methane (CH4) from aquatic ecosystems contributes to about half of total global CH4 emissions to the atmosphere. Until recently, aquatic biogenic CH4 production was exclusively attributed to methanogenic archaea living under anoxic or suboxic conditions in sediments, bottom waters, and wetlands. However, evidence for oxic CH4 production (OMP) in freshwater, brackish, and marine habitats is increasing. Possible sources were found to be driven by various planktonic organisms supporting different OMP mechanisms. Surprisingly, submerged macrophytes have been fully ignored in studies on OMP, yet they are key components of littoral zones of ponds, lakes, and coastal systems. High CH4 concentrations in these zones have been attributed to organic substrate production promoting classic methanogenesis in the absence of oxygen. Here, we review existing studies and argue that, similar to terrestrial plants and phytoplankton, macroalgae and submerged macrophytes may directly or indirectly contribute to CH4 formation in oxic waters. We propose several potential direct and indirect mechanisms: (1) direct production of CH4; (2) production of CH4 precursors and facilitation of their bacterial breakdown or chemical conversion; (3) facilitation of classic methanogenesis; and (4) facilitation of CH4 ebullition. As submerged macrophytes occur in many freshwater and marine habitats, they are important in global carbon budgets and can strongly vary in their abundance due to seasonal and boom-bust dynamics. Knowledge on their contribution to OMP is therefore essential to gain a better understanding of spatial and temporal dynamics of CH4 emissions and thus to substantially reduce current uncertainties when estimating global CH4 emissions from aquatic ecosystems.}, language = {en} } @article{BizicIonescuKarnataketal.2022, author = {Bizic, Mina and Ionescu, Danny and Karnatak, Rajat and Musseau, Camille L. and Onandia, Gabriela and Berger, Stella A. and Nejstgaard, Jens C. and Lischeid, Gunnar and Gessner, Mark O. and Wollrab, Sabine and Grossart, Hans-Peter}, title = {Land-use type temporarily affects active pond community structure but not gene expression patterns}, series = {Molecular ecology}, volume = {31}, journal = {Molecular ecology}, number = {6}, publisher = {Wiley}, address = {Hoboken}, issn = {0962-1083}, doi = {10.1111/mec.16348}, pages = {1716 -- 1734}, year = {2022}, abstract = {Changes in land use and agricultural intensification threaten biodiversity and ecosystem functioning of small water bodies. We studied 67 kettle holes (KH) in an agricultural landscape in northeastern Germany using landscape-scale metatranscriptomics to understand the responses of active bacterial, archaeal and eukaryotic communities to land-use type. These KH are proxies of the millions of small standing water bodies of glacial origin spread across the northern hemisphere. Like other landscapes in Europe, the study area has been used for intensive agriculture since the 1950s. In contrast to a parallel environmental DNA study that suggests the homogenization of biodiversity across KH, conceivably resulting from long-lasting intensive agriculture, land-use type affected the structure of the active KH communities during spring crop fertilization, but not a month later. This effect was more pronounced for eukaryotes than for bacteria. In contrast, gene expression patterns did not differ between months or across land-use types, suggesting a high degree of functional redundancy across the KH communities. Variability in gene expression was best explained by active bacterial and eukaryotic community structures, suggesting that these changes in functioning are primarily driven by interactions between organisms. Our results indicate that influences of the surrounding landscape result in temporary changes in the activity of different community members. Thus, even in KH where biodiversity has been homogenized, communities continue to respond to land management. This potential needs to be considered when developing sustainable management options for restoration purposes and for successful mitigation of further biodiversity loss in agricultural landscapes.}, language = {en} } @article{SchornSalmanCarvalhoLittmannetal.2019, author = {Schorn, Sina and Salman-Carvalho, Verena and Littmann, Sten and Ionescu, Danny and Grossart, Hans-Peter and Cypionka, Heribert}, title = {Cell architecture of the giant sulfur bacterium achromatium oxaliferum}, series = {FEMS Microbiology Ecology}, volume = {96}, journal = {FEMS Microbiology Ecology}, number = {2}, publisher = {Oxford University Press}, address = {Oxford}, issn = {1574-6941}, doi = {10.1093/femsec/fiz200}, pages = {1 -- 8}, year = {2019}, abstract = {Achromatium oxaliferum is a large sulfur bacterium easily recognized by large intracellular calcium carbonate bodies. Although these bodies often fill major parts of the cells' volume, their role and specific intracellular location are unclear. In this study, we used various microscopy and staining techniques to identify the cell compartment harboring the calcium carbonate bodies. We observed that Achromatium cells often lost their calcium carbonate bodies, either naturally or induced by treatments with diluted acids, ethanol, sodium bicarbonate and UV radiation which did not visibly affect the overall shape and motility of the cells (except for UV radiation). The water-soluble fluorescent dye fluorescein easily diffused into empty cavities remaining after calcium carbonate loss. Membranes (stained with Nile Red) formed a network stretching throughout the cell and surrounding empty or filled calcium carbonate cavities. The cytoplasm (stained with FITC and SYBR Green for nucleic acids) appeared highly condensed and showed spots of dissolved Ca2+ (stained with Fura-2). From our observations, we conclude that the calcium carbonate bodies are located in the periplasm, in extra-cytoplasmic pockets of the cytoplasmic membrane and are thus kept separate from the cell's cytoplasm. This periplasmic localization of the carbonate bodies might explain their dynamic formation and release upon environmental changes.}, language = {en} } @article{FaschingAkotoyeBižićetal.2020, author = {Fasching, Christina and Akotoye, Christian and Bižić, Mina and Fonvielle, Jeremy Andre and Ionescu, Danny and Mathavarajah, Sabateeshan and Zoccarato, Luca and Walsh, David A. and Grossart, Hans-Peter and Xenopoulos, Marguerite A.}, title = {Linking stream microbial community functional genes to dissolved organic matter and inorganic nutrients}, series = {Limnology and oceanography}, volume = {65}, journal = {Limnology and oceanography}, publisher = {Wiley}, address = {Hoboken}, issn = {0024-3590}, doi = {10.1002/lno.11356}, pages = {S71 -- S87}, year = {2020}, abstract = {There is now increasing evidence for the importance of microbial regulation of biogeochemical cycling in streams. Resource availability shapes microbial community structure, but less is known about how landscape-mediated availability of nutrients and carbon can control microbial functions in streams. Using comparative metagenomics, we examined the relationship between microbial functional genes and composition of dissolved organic matter (DOM), nutrients, and suspended microbial communities in 11 streams, divided into three groups based on the predominant land cover category (agriculture, forested, or wetland). Using weighted gene co-occurrence network analysis, we identified clusters of functions related to DOM composition, agricultural land use, and/or wetland and forest land cover. Wetland-dominated streams were characterized by functions related to nitrogen metabolism and processing of aromatic carbon compounds, with strong positive correlations with dissolved organic carbon concentration and DOM aromaticity. Forested streams were characterized by metabolic functions related to monomer uptake and carbohydrates, such as mannose and fructose metabolism. In agricultural streams, microbial functions were correlated with more labile, protein-like DOM, PO4, and NO3, likely reflecting functional adaptation to labile DOM and higher nutrient concentrations. Distinct changes in the functional composition and loss of functional diversity of microorganisms became evident when comparing natural to agricultural catchments. Although all streams showed signs of functional redundancy, loss of species richness per function in agricultural catchments suggests that microbial functions in natural catchments may be more resilient to disturbance. Our results provide new insight into microbial community functions involved in nutrient and carbon biogeochemical cycles and their dependence on specific environmental settings.}, language = {en} }