Summary
Aquatic environments contain large communities of microorganisms whose synergistic interactions mediate the cycling of major and trace nutrients, including vitamins. B‐vitamins are essential ...coenzymes that many organisms cannot synthesize. Thus, their exchange among de novo synthesizers and auxotrophs is expected to play an important role in the microbial consortia and explain some of the temporal and spatial changes observed in diversity. In this study, we analyzed metatranscriptomes of a natural marine microbial community, diel sampled quarterly over one year to try to identify the potential major B‐vitamin synthesizers and consumers. Transcriptomic data showed that the best‐represented taxa dominated the expression of synthesis genes for some B‐vitamins but lacked transcripts for others. For instance, Rhodobacterales dominated the expression of vitamin‐B12 synthesis, but not of vitamin‐B7, whose synthesis transcripts were mainly represented by Flavobacteria. In contrast, bacterial groups that constituted less than 4% of the community (e.g., Verrucomicrobia) accounted for most of the vitamin‐B1 synthesis transcripts. Furthermore, ambient vitamin‐B1 concentrations were higher in samples collected during the day, and were positively correlated with chlorophyll‐a concentrations. Our analysis supports the hypothesis that the mosaic of metabolic interdependencies through B‐vitamin synthesis and exchange are key processes that contribute to shaping microbial communities in nature.
The role of B vitamins in marine biogeochemistry Sañudo-Wilhelmy, Sergio A; Gómez-Consarnau, Laura; Suffridge, Christopher ...
Annual review of marine science,
01/2014, Letnik:
6
Journal Article
Recenzirano
Odprti dostop
The soluble B vitamins (B1, B7, and B12) have long been recognized as playing a central metabolic role in marine phytoplankton and bacteria; however, the importance of these organic external ...metabolites in marine ecology has been largely disregarded, as most research has focused on inorganic nutrients and trace metals. Using recently available genomic data combined with culture-based surveys of vitamin auxotrophy (i.e., vitamin requirements), we show that this auxotrophy is widespread in the marine environment and occurs in both autotrophs and heterotrophs residing in oligotrophic and eutrophic environments. Our analysis shows that vitamins originate from the activities of some bacteria and algae and that taxonomic changes observed in marine phytoplankton communities could be the result of their specific vitamin requirements and/or vitamin availability. Dissolved vitamin concentration measurements show that large areas of the world ocean are devoid of B vitamins, suggesting that vitamin limitation could be important for the efficiency of carbon and nitrogen fixation in those regions.
The flavins (including flavin mononucleotide (FMN) and riboflavin (RF)) are a class of organic compounds synthesized by organisms to assist in critical redox reactions. While known to be secreted ...extracellularly by some species in laboratory-based cultures, flavin concentrations are largely unreported in the natural environment. Here, we present pore water and water column profiles of extracellular flavins (FMN and RF) and two degradation products (lumiflavin and lumichrome) from a coastal marine basin in the Southern California Bight alongside ancillary geochemical and 16S rRNA microbial community data. Flavins were detectable at picomolar concentrations in the water column (93–300 pM FMN, 14–40 pM RF) and low nanomolar concentrations in pore waters (250–2070 pM FMN, 11–210 pM RF). Elevated pore water flavin concentrations displayed an increasing trend with sediment depth and were significantly correlated with the total dissolved Fe (negative) and Mn (positive) concentrations. Network analysis revealed a positive relationship between flavins and the relative abundance of Dehalococcoidia and the MSBL9 clade of Planctomycetes, indicating possible secretion by members of these lineages. These results suggest that flavins are a common component of the so-called shared extracellular metabolite pool, especially in anoxic marine sediments where they exist at physiologically relevant concentrations for metal oxide reduction.
B vitamins are some of the most commonly required biochemical cofactors in living systems. Therefore, cellular metabolism of marine vitamin-requiring (auxotrophic) phytoplankton and bacteria would ...likely be significantly compromised if B vitamins (thiamin B ₁, riboflavin B ₂, pyridoxine B ₆, biotin B ₇, and cobalamin B ₁₂) were unavailable. However, the factors controlling the synthesis, ambient concentrations, and uptake of these key organic compounds in the marine environment are still not well understood. Here, we report vertical distributions of five B vitamins (and the amino acid methionine) measured simultaneously along a latitudinal gradient through the contrasting oceanographic regimes of the southern California-Baja California coast in the Northeast Pacific margin. Although vitamin concentrations ranged from below the detection limits of our technique to 30 pM for B ₂ and B ₁₂ and to ∼500 pM for B ₁, B ₆, and B ₇, each vitamin showed a different geographical and depth distribution. Vitamin concentrations were independent of each other and of inorganic nutrient levels, enriched primarily in the upper mesopelagic zone (depth of 100–300 m), and associated with water mass origin. Moreover, vitamin levels were below our detection limits (ranging from ≤0.18 pM for B ₁₂ to ≤0.81 pM for B ₁) in extensive areas (100s of kilometers) of the coastal ocean, and thus may exert important constraints on the taxonomic composition of phytoplankton communities, and potentially also on rates of primary production and carbon sequestration.
Most phytoplankton, including harmful algal bloom (HAB)-forming species, have an absolute requirement for vitamin B
12
(cobalamin). However, the cycling of vitamin B
12
in the ocean is still poorly ...understood. For example, in the Ariake Sea, where local fisheries have been affected by HABs, the impact of vitamin B
12
on phytoplankton dynamics has never been evaluated. This study reports the surface distribution of cyanocobalamin (CN-B
12
, a type of vitamin B
12
) in the Ariake Sea and its adjacent areas. The field measurements were complemented with an additional onboard CN-B
12
incubation experiment to elucidate the importance of the coenzyme on the growth of natural phytoplankton communities. Dissolved CN-B
12
behaved dynamically and was often depleted in surface waters. Dominant phytoplankton in the Ariake Sea changed seasonally; all these taxa include vitamin B
12
auxotrophs. The distribution of CN-B
12
was controlled by dynamic production and consumption by natural phytoplankton and bacterial communities. We attempted to measure the concentration of particulate CN-B
12
; it was undetectable suggesting that CN-B
12
form of vitamin B
12
is not dominant inside the cell. No clear relationship existed between CN-B
12
and any oceanographic parameters, suggesting that river discharge is unlikely a major source of CN-B
12
in this area. Bottle incubation experiments showed that CN-B
12
and nitrate additions promoted the growth of diatom
Chaetoceros
spp., implying that some phytoplankton groups are co-limited by them. These preliminary results suggest that vitamin B
12
may affect the composition of the phytoplankton community in the Ariake Sea.
The Enzymology of Ocean Global Change Hutchins, David A; Sañudo-Wilhelmy, Sergio A
Annual review of marine science,
01/2022, Letnik:
14, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A small subset of marine microbial enzymes and surface transporters have a disproportionately important influence on the cycling of carbon and nutrients in the global ocean. As a result, they largely ...determine marine biological productivity and have been the focus of considerable research attention from microbial oceanographers. Like all biological catalysts, the activity of these keystone biomolecules is subject to control by temperature and pH, leaving the crucial ecosystem functions they support potentially vulnerable to anthropogenic environmental change. We summarize and discuss both consensus and conflicting evidence on the effects of sea surface warming and ocean acidification for five of these critical enzymes carbonic anhydrase, ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO), nitrogenase, nitrate reductase, and ammonia monooxygenase and one important transporter (proteorhodopsin). Finally, we forecast how the responses of these few but essential biocatalysts to ongoing global change processes may ultimately help to shape the microbial communities and biogeochemical cycles of the future greenhouse ocean.
All known phototrophic metabolisms on Earth rely on one of three categories of energy-converting pigments: chlorophyll-
(rarely -
), bacteriochlorophyll-
(rarely -
), and retinal, which is the ...chromophore in rhodopsins. While the significance of chlorophylls in solar energy capture has been studied for decades, the contribution of retinal-based phototrophy to this process remains largely unexplored. We report the first vertical distributions of the three energy-converting pigments measured along a contrasting nutrient gradient through the Mediterranean Sea and the Atlantic Ocean. The highest rhodopsin concentrations were observed above the deep chlorophyll-
maxima, and their geographical distribution tended to be inversely related to that of chlorophyll-
. We further show that proton-pumping proteorhodopsins potentially absorb as much light energy as chlorophyll-
-based phototrophy and that this energy is sufficient to sustain bacterial basal metabolism. This suggests that proteorhodopsins are a major energy-transducing mechanism to harvest solar energy in the surface ocean.
Microbial rhodopsins are simple light‐harvesting complexes that, unlike chlorophyll photosystems, have no iron requirements for their synthesis and phototrophic functions. Here, we report the ...environmental concentrations of rhodopsin along the Subtropical Frontal Zone off New Zealand, where Subtropical waters encounter the iron‐limited Subantarctic High Nutrient Low Chlorophyll (HNLC) region. Rhodopsin concentrations were highest in HNLC waters where chlorophyll‐a concentrations were lowest. Furthermore, while the ratio of rhodopsin to chlorophyll‐a photosystems was on average 20 along the transect, this ratio increased to over 60 in HNLC waters. We further show that microbial rhodopsins are abundant in both picoplankton (0.2–3 μm) and in the larger (>3 μm) size fractions of the microbial community containing eukaryotic plankton and/or particle‐attached prokaryotes. These findings suggest that rhodopsin phototrophy could be critical for microbial plankton to adapt to resource‐limiting environments where photosynthesis and possibly cellular respiration are impaired.
Understanding biogeochemical cycling of trace metals in the ocean requires information about variability in metal concentrations and distribution over short, e.g., diel, time scales. Such variability ...and the factors that influence it are poorly characterized. To address this shortcoming, we measured trace metal concentrations in the total dissolved, colloidal, and soluble fractions every 3–4 h for several consecutive days and nights in surface waters from a coastal station. Our results show that both the concentration and the size partitioning of some biologically essential (Fe, Cu, Co, and Cd) and anthropogenic (Pb) metals are subjected to diel variations that may be related to both inorganic and biological processes (e.g., photolysis of high-molecular-weight dissolved organic matter, photoinduced reduction/oxidation of metal(hydrous)oxides, uptake by growing phytoplankton, degradation of organic matter, lysis, and grazing). The largest fluctuations were observed in the soluble and colloidal pools. Soluble Fe varied during the day-night cycle by a factor of 40, and the contribution of colloidal Pb to the total dissolved fraction increased from 6 ± 3% during the day to as much as 70–80% during the night. Our results suggest that changes occurring over time scales of hours need to be considered when collecting and interpreting trace metal data from the surface ocean.
We present the first comprehensive investigation of the concentrations, fluxes and sources of aerosol trace elements over the Gulf of Aqaba. We found that the mean atmospheric concentrations of ...crustally derived elements such as Al, Fe and Mn (1081, 683, and 16.7 ng m−3) are about 2–3 times higher than those reported for the neighboring Mediterranean area. This is indicative of the dominance of the mineral dust component in aerosols over the Gulf. Anthropogenic impact was lower in comparison to the more heavily populated areas of the Mediterranean. During the majority of time (69%) the air masses over the Gulf originated from Europe or Mediterranean Sea areas delivering anthropogenic components such as Cu, Cd, Ni, Zn, and P. Airflows derived from North Africa in contrast contained the highest concentrations of Al, Fe, and Sr but generally lower Cu, Cd, Ni, Zn, and P. Relatively high Pb, Ni, and V were found in the local and Arabian airflows suggesting a greater influence of local emission of fuel burning. We used the data and the measured trace metal seawater concentrations to calculate residence times of dissolved trace elements in the upper 50 m surface water of the Gulf (with respect to atmospheric input) and found that the residence times for most elements are in the range of 5–37 years while Cd and V residence times are longer.
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