Satellite remote sensing data can be used to model marine microbial metabolite turnover

Sampling ecosystems, even at a local scale, at the temporal and spatial resolution necessary to capture natural variability in microbial communities are prohibitively expensive. We extrapolated marine surface microbial community structure and metabolic potential from 72 16S rRNA amplicon and 8 metagenomic observations using remotely sensed environmental parameters to create a system-scale model of marine microbial metabolism for 5904 grid cells (49 km2) in the Western English Chanel, across 3 years of weekly averages. Thirteen environmental variables predicted the relative abundance of 24 bacterial Orders and 1715 unique enzyme-encoding genes that encode turnover of 2893 metabolites. The genes’ predicted relative abundance was highly correlated (Pearson Correlation 0.72, P-value <10−6) with their observed relative abundance in sequenced metagenomes. Predictions of the relative turnover (synthesis or consumption) of CO2 were significantly correlated with observed surface CO2 fugacity. The spatial and temporal variation in the predicted relative abundances of genes coding for cyanase, carbon monoxide and malate dehydrogenase were investigated along with the predicted inter-annual variation in relative consumption or production of ~3000 metabolites forming six significant temporal clusters. These spatiotemporal distributions could possibly be explained by the co-occurrence of anaerobic and aerobic metabolisms associated with localized plankton blooms or sediment resuspension, which facilitate the presence of anaerobic micro-niches. This predictive model provides a general framework for focusing future sampling and experimental design to relate biogeochemical turnover to microbial ecology

Microbial diversity in waters, sediments and microbial mats evaluated using fatty acid-based methods

The review summarises recent advances towards a greater comprehensive assessment of microbial diversity in aquatic environments using the fatty acid methyl esters and phospholipid fatty acids approaches. These methods are commonly used in microbial ecology because they do not require the culturing of micro-organisms, are quantitative and reproducible and provide valuable information regarding the structure of entire microbial communities. Because some fatty acids are associated with taxonomic and functional groups of micro-organisms, they allow particular groups of micro-organisms to be distinguished. The integration of fatty acid-based methods with stable isotopes, RNA and DNA analyses enhances our knowledge of the role of micro-organisms in global nutrient cycles, functional activity and phylogenetic lineages within microbial communities. Additionally, the analysis of fatty acid profiles enables the shifts in the microbial diversity in pristine and contaminated environments to be monitored. The main objective of this review is to present the use of lipid-based approaches for the characterisation of microbial communities in water columns, sediments and biomats

Microbial sources of intact polar diacylglycerolipids in the Western North Atlantic Ocean

► Microibal sources of intact polar diacylglycerolipids were identified. ► Photoautotrophs are sole source of sulfoquinovosyldiacylglycerol. ► Eukaryotic phytoplankton are likely source of a betaine lipid. ► Heterotrophic bacteria are sole source of phosphatidylglycerol.Intact polar membrane lipids are essential components of microbial membranes and recent work has uncovered a diversity of them occurring in the ocean. While it has long been understood that lipid composition varies across microbial groups, the microbial origins of the intact polar lipids in the surface ocean remain to be fully explained. This study focused on identifying the microbial sources of intact polar diacylglycerolipids (IP-DAGs) in the surface waters of the western North Atlantic Ocean. We used three approaches to define these microbial sources: (i) 13C tracing to identify photoautotrophic and heterotrophic production of the major classes of IP-DAGs, (ii) cell sorting flow cytometry of Prochlorococcus, Synechococcus and heterotrophic bacteria to determine IP-DAG composition and (iii) regrowth incubations targeting IP-DAG production by heterotrophic bacteria. Stable isotope tracing indicated that sulfoquinovosyldiacylglycerol (SQDG) and diacylglyceryl-trimethyl-homoserine (DGTS) were produced predominantly by photoautotrophs, while phosphatidylglycerol (PG) production was dominated by heterotrophic bacteria. Of the cells sorted with flow cytometry, Prochlorococcus and Synechococcus were found to have abundant glycolipids, while heterotrophic bacteria were dominated by phospholipids. The regrowth incubations showed that the growth of heterotrophic bacteria correlated with an increase in the concentration of PG, phosphatidylethanolamine (PE) and monoglycosyldiacylglycerol (MGDG). The finding of MGDG in heterotrophic bacteria differs from previous work, which had asserted that the membranes of heterotrophic bacteria in this environment were composed entirely of phospholipids. Overall, our findings indicate that phytoplankton are the primary source of SQDG and DGTS, while heterotrophic bacteria are the dominant source of PG, making these three compounds promising biomarkers for the study of microbes in the surface ocean

Harmful cyanobacterial aerosolization dynamics in the airshed of a eutrophic estuary

In addition to obvious negative effects on water quality in eutrophic aquatic ecosystems, recent work suggests that cyanobacterial harmful algal blooms (CHABs) also impact air quality via emissions carrying cyanobacterial cells and cyanotoxins. However, the environmental controls on CHAB-derived aerosol and its potential public health impacts remain largely unknown. Accordingly, the aims of this study were to 1) investigate the occurrence of microcystins (MC) and putatively toxic cyanobacterial communities in particulate matter ≤ 2.5 μm in diameter (PM2.5), 2) elucidate environmental conditions promoting their aerosolization, and 3) identify associations between CHABs and PM2.5 concentrations in the airshed of the Chowan River-Albemarle Sound, an oligohaline, eutrophic estuary in eastern North Carolina, USA. In summer 2020, during peak CHAB season, continuous PM2.5 samples and interval water samples were collected at two distinctive sites for targeted analyses of cyanobacterial community composition and MC concentration. Supporting air and water quality measurements were made in parallel to contextualize findings and permit statistical analyses of environmental factors driving changes in CHAB-derived aerosol. MC concentrations were low throughout the study, but a CHAB dominated by Dolichospermum occurred from late June to early August. Several aquatic CHAB genera recovered from Chowan River surface water were identified in PM2.5 during multiple time points, including Anabaena, Aphanizomenon, Dolichospermum, Microcystis, and Pseudanabaena. Cyanobacterial enrichment in PM2.5 was indistinctive between subspecies, but at one site during the early bloom, we observed the simultaneous enrichment of several cyanobacterial genera in PM2.5. In association with the CHAB, the median PM2.5 mass concentration increased to 8.97 μg m−3 (IQR = 5.15), significantly above the non-bloom background of 5.35 μg m−3 (IQR = 3.70) (W = 1835, p < 0.001). Results underscore the need for highly resolved temporal measurements to conclusively investigate the role that CHABs play in regional air quality and respiratory health risk.[Display omitted]•No microcystins were quantified in the airshed of the Chowan River in 2020.•Several toxigenic, bloom forming cyanobacteria were identified in PM2.5.•Aquatic cyanobacteria influence the abundance of airborne cyanobacteria.•Dolichospermum, Microcystis, and Aphanizomenon were aerosolized concurrently.•CHAB activity was linked to elevated PM2.5 mass concentrations