scholarly journals Aestipascuomyces dupliciliberans gen. nov, sp. nov., the First Cultured Representative of the Uncultured SK4 Clade from Aoudad Sheep and Alpaca

2020 ◽  
Vol 8 (11) ◽  
pp. 1734
Author(s):  
Marcus Stabel ◽  
Radwa A. Hanafy ◽  
Tabea Schweitzer ◽  
Meike Greif ◽  
Habibu Aliyu ◽  
...  
Keyword(s):  
Phylogenetic Trees ◽  
Sequence Similarity ◽  
Domestic Sheep ◽  
Rrna Gene ◽  
High Sequence Identity ◽  
High Sequence Similarity ◽  
Sequence Identity ◽  
Zoospore Release ◽  
Wide Range ◽  
Summer Pasture

We report on the isolation of the previously-uncultured Neocallimastigomycota SK4 lineage, by two independent research groups, from a wild aoudad sheep rumen sample (Texas, USA) and an alpaca fecal sample (Baden-Württemberg, Germany). Isolates from both locations showed near-identical morphological and microscopic features, forming medium-sized (2–5 mm) white filamentous colonies with a white center of sporangia, on agar roll tubes and a heavy biofilm in liquid media. Microscopic analysis revealed monocentric thalli, and spherical polyflagellated zoospores with 7–20 flagella. Zoospore release occurred through an apical pore as well as by sporangial wall rupturing, a duality that is unique amongst described anaerobic gut fungal strains. Isolates were capable of growing on a wide range of mono-, oligo-, and polysaccharide substrates as the sole carbon source. Phylogenetic assessment based on the D1–D2 28S large rRNA gene subunit (D1–D2 LSU) and internal transcribed spacer-1 (ITS-1) regions demonstrated high sequence identity (minimum identity of 99.07% and 96.96%, respectively) between all isolates; but low sequence identity (92.4% and 86.7%, respectively) to their closest cultured relatives. D1–D2 LSU phylogenetic trees grouped the isolates as a new monophyletic clade within the Orpinomyces–Neocallimastix–Pecoramyces–Feramyces–Ghazallamyces supragenus group. D1–D2 LSU and ITS-1 sequences recovered from the obtained isolates were either identical or displayed extremely high sequence similarity to sequences recovered from the same aoudad sheep sample on which isolation was conducted, as well as several sequences recovered from domestic sheep and few other herbivores. Interestingly, members of the SK4 clade seem to be encountered preferably in animals grazing on summer pasture. We hence propose accommodating these novel isolates in a new genus, Aestipascuomyces (derived from the Latin word for “summer pasture”), and a new species, A. dupliciliberans. The type strain is Aestipascuomycesdupliciliberans strain R4.

scholarly journals Aestipascuomyces dupliciliberatus gen. nov, sp. nov., the First Cultured Representative of the Uncultured SK4 Clade from Aoudad Sheep and Alpaca

2020 ◽  
Author(s):  
Marcus Stabel ◽  
Radwa Hanafy ◽  
Tabea Schweitzer ◽  
Meike Greif ◽  
Habibu Aliyu ◽  
...  
Keyword(s):  
Phylogenetic Trees ◽  
Sequence Similarity ◽  
Microscopic Analysis ◽  
Domestic Sheep ◽  
High Sequence Identity ◽  
High Sequence Similarity ◽  
Sequence Identity ◽  
Zoospore Release ◽  
Wide Range ◽  
Summer Pasture

We report on the isolation of the previously uncultured Neocallimastigomycota SK4 lineage by two independent research groups from a wild aoudad sheep rumen sample (Texas, USA) and an alpaca fecal sample (Baden-Württemberg, Germany). Isolates from both locations showed near identical morphological and microscopic features, forming medium-sized white filamentous colonies with a white center of sporangia on agar roll tubes and a heavy biofilm in liquid media. Microscopic analysis revealed monocentric thalli, and spherical polyflagellated zoospores with 7–20 flagella. Zoospore release occurred through an apical pore as well as by sporangial wall rupturing, a duality that is unique amongst described AGF strains. Isolates were capable of growing on a wide range of mono-, oligo-, and polysaccharides substrates. Phylogenetic assessment based on the D1-D2 large rRNA subunit (D1-D2 LSU) and internal transcribed spacer-1 (ITS-1) regions demonstrated high sequence identity (minimum identity of 99.07% and 96.96%, respectively) between all isolates; but low sequence identity (92.4% and 86.7%, respectively) to their closest cultured relatives. D1-D2 LSU phylogenetic trees grouped the isolates as a new monophyletic clade within the Orpinomyces-Neocallimastix-Pecoramyces-Feramyces-Ghazallamyces supragenus group. D1-D2 LSU and ITS-1 sequences from the obtained isolates were either identical, or displayed extremely high sequence similarity to sequences recovered from the same Aoudad sheep sample on which isolation was conducted, as well as several sequences recovered from domestic sheep and few other herbivores. Interestingly, members of the SK4 clade seem to be encountered in animals grazing on summer pasture. We hence propose accommodating these novel isolates in a new genus, Aestipascuomyces (derived from the Latin word for “summer pasture”), and a new species, A. dupliciliberatus. The type strain is Aestipascuomyces dupliciliberatus strain R4.

scholarly journals Basfia succiniciproducens gen. nov., sp. nov., a new member of the family Pasteurellaceae isolated from bovine rumen

2010 ◽  
Vol 60 (1) ◽  
pp. 44-50 ◽  
Author(s):  
Peter Kuhnert ◽  
Edzard Scholten ◽  
Stefan Haefner ◽  
Désirée Mayor ◽  
Joachim Frey
Keyword(s):  
16S Rrna ◽  
Phylogenetic Trees ◽  
Sequence Similarity ◽  
Selective Medium ◽  
Phenotypic Characterization ◽  
Rrna Gene ◽  
New Taxon ◽  
High Sequence Similarity ◽  
Bovine Rumen ◽  
The Family

Gram-negative, coccoid, non-motile bacteria that are catalase-, urease- and indole-negative, facultatively anaerobic and oxidase-positive were isolated from the bovine rumen using an improved selective medium for members of the Pasteurellaceae. All strains produced significant amounts of succinic acid under anaerobic conditions with glucose as substrate. Phenotypic characterization and multilocus sequence analysis (MLSA) using 16S rRNA, rpoB, infB and recN genes were performed on seven independent isolates. All four genes showed high sequence similarity to their counterparts in the genome sequence of the patent strain MBEL55E, but less than 95 % 16S rRNA gene sequence similarity to any other species of the Pasteurellaceae. Genetically these strains form a very homogeneous group in individual as well as combined phylogenetic trees, clearly separated from other genera of the family from which they can also be separated based on phenotypic markers. Genome relatedness as deduced from the recN gene showed high interspecies similarities, but again low similarity to any of the established genera of the family. No toxicity towards bovine, human or fish cells was observed and no RTX toxin genes were detected in members of the new taxon. Based on phylogenetic clustering in the MLSA analysis, the low genetic similarity to other genera and the phenotypic distinction, we suggest to classify these bovine rumen isolates as Basfia succiniciproducens gen. nov., sp. nov. The type strain is JF4016T (=DSM 22022T =CCUG 57335T).

scholarly journals Amphritea ceti sp. nov., isolated from faeces of Beluga whale (Delphinapterus leucas)

2014 ◽  
Vol 64 (Pt_12) ◽  
pp. 4068-4072 ◽  
Author(s):  
Young-Ok Kim ◽  
Sooyeon Park ◽  
Doo Nam Kim ◽  
Bo-Hye Nam ◽  
Sung-Min Won ◽  
...  
Keyword(s):  
Phylogenetic Trees ◽  
Sequence Similarity ◽  
Beluga Whale ◽  
Delphinapterus Leucas ◽  
Rrna Gene ◽  
Phenotypic Properties ◽  
Content Type ◽  
Link Type ◽  
Beluga Whale Delphinapterus Leucas ◽  
Type Strains

A Gram-stain-negative, aerobic, non-spore-forming, non-flagellated and rod-shaped or ovoid bacterial strain, designated RA1T, was isolated from faeces collected from Beluga whale (Delphinapterus leucas) in Yeosu aquarium, South Korea. Strain RA1T grew optimally at 25 °C, at pH 7.0–8.0 and in the presence of 2.0 % (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences revealed that strain RA1T joins the cluster comprising the type strains of three species of the genus Amphritea , with which it exhibited 95.8–96.0 % sequence similarity. Sequence similarities to the type strains of other recognized species were less than 94.3 %. Strain RA1T contained Q-8 as the predominant ubiquinone and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C18 : 1ω7c and C16 : 0 as the major fatty acids. The major polar lipids of strain RA1T were phosphatidylethanolamine, phosphatidylglycerol, two unidentified lipids and one unidentified aminolipid. The DNA G+C content of strain RA1T was 47.4 mol%. The differential phenotypic properties, together with the phylogenetic distinctiveness, revealed that strain RA1T is separated from other species of the genus Amphritea . On the basis of the data presented, strain RA1T is considered to represent a novel species of the genus Amphritea , for which the name Amphritea ceti sp. nov. is proposed. The type strain is RA1T ( = KCTC 42154T = NBRC 110551T).

scholarly journals Pseudoseohaeicola caenipelagi gen. nov., sp. nov., isolated from a tidal flat

2015 ◽  
Vol 65 (Pt_6) ◽  
pp. 1819-1824 ◽  
Author(s):  
Sooyeon Park ◽  
Ji-Min Park ◽  
Chul-Hyung Kang ◽  
Song-Gun Kim ◽  
Jung-Hoon Yoon
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Tidal Flat ◽  
Type Strain ◽  
Type Species ◽  
Phylogenetic Trees ◽  
Sequence Similarity ◽  
Rrna Gene ◽  
Content Type ◽  
Link Type

A Gram-stain-negative, non-motile, aerobic and pleomorphic bacterium, designated BS-W13T, was isolated from a tidal flat on the South Sea, South Korea, and its taxonomic position was investigated using a polyphasic approach. Strain BS-W13T grew optimally at 25 °C, at pH 7.0–8.0 and in the presence of 1.0–2.0 % (w/v) NaCl. Neighbour-joining and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences showed that strain BS-W13T clustered with the type strain of Seohaeicola saemankumensis , showing the highest sequence similarity (95.96 %) to this strain. Strain BS-W13T exhibited 16S rRNA gene sequence similarity values of 95.95, 95.91, 95.72 and 95.68 % to the type strains of Sulfitobacter donghicola , Sulfitobacter porphyrae , Sulfitobacter mediterraneus and Roseobacter litoralis , respectively. Strain BS-W13T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The polar lipid profile of strain BS-W13T, containing phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminolipid and one unidentified lipid as major components, was distinguishable from those of some phylogenetically related taxa. The DNA G+C content of strain BS-W13T was 58.1 mol%. The phylogenetic data and differential chemotaxonomic and other phenotypic properties revealed that strain BS-W13T constitutes a novel genus and species within family Rhodobacteraceae of the class Alphaproteobacteria , for which the name Pseudoseohaeicola caenipelagi gen. nov., sp. nov. is proposed. The type strain is BS-W13T ( = KCTC 42349T = CECT 8724T).

scholarly journals Belliella aquatica sp. nov., isolated from a saline lake

2015 ◽  
Vol 65 (Pt_5) ◽  
pp. 1622-1627 ◽  
Author(s):  
Zhi-Ping Zhong ◽  
Ying Liu ◽  
Ting-Ting Hou ◽  
Yu-Guang Zhou ◽  
Hong-Can Liu ◽  
...  
Keyword(s):  
Type Species ◽  
Phylogenetic Trees ◽  
Saline Lake ◽  
Qaidam Basin ◽  
Sequence Similarity ◽  
Rrna Gene ◽  
Respiratory Quinone ◽  
Content Type ◽  
Link Type ◽  
Gram Staining

A Gram-staining-negative bacterium, strain TS-T86T, was isolated from Lake Tuosu, a saline lake (salinity 5.4 %, w/w) in Qaidam basin, China. Its taxonomic position was determined by using a polyphasic approach. Strain TS-T86T was strictly heterotrophic, aerobic and catalase- and oxidase-positive. Cells were non-spore-forming, non-motile rods, 0.4–0.6 µm wide and 1.2–2.3 µm long. Growth was observed in the presence of 0–9.0 % (w/v) NaCl (optimum, 2.0 %), at 4–35 °C (optimum, 25 °C) and at pH 7.0–10.5 (optimum, pH 8.5–9.0). Strain TS-T86T contained MK-7 as the predominant respiratory quinone. The major fatty acids (>10 %) were iso-C15 : 1 G, iso-C15 : 0, iso-C17 : 1ω9c, iso-C17 : 0 3-OH and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The polar lipids consisted of phosphatidylethanolamine, an unknown phospholipid, six unidentified aminolipids and two uncharacterized lipids. The DNA G+C content was 35 mol% (T m). Phylogenetic trees based on 16S rRNA gene sequences showed that strain TS-T86T was associated with the genus Belliella , and showed the highest sequence similarity to Belliella baltica BA134T (98.5 %) and then to Belliella kenyensis No.164T (95.7 %) and Belliella pelovolcani CC-SAL-25T (95.3 %). DNA–DNA relatedness of strain TS-T86T to Belliella baltica DSM 15883T was 32±3 %. It is concluded that strain TS-T86T represents a novel species of the genus Belliella , for which the name Belliella aquatica sp. nov. is proposed. The type strain is TS-T86T ( = CGMCC 1.12479T = JCM 19468T).

scholarly journals Novosphingobium gossypii sp. nov., isolated from Gossypium hirsutum

2015 ◽  
Vol 65 (Pt_9) ◽  
pp. 2831-2837 ◽  
Author(s):  
Peter Kämpfer ◽  
Karin Martin ◽  
John A. McInroy ◽  
Stefanie P. Glaeser
Keyword(s):  
Gossypium Hirsutum ◽  
Gene Sequence ◽  
Sequence Similarity ◽  
Rrna Gene ◽  
High Sequence Similarity ◽  
Polar Lipid Profile ◽  
Gene Sequence Analysis ◽  
Bacterium Strain ◽  
Type Strains ◽  
Sequence Similarities

A Gram-stain-negative, rod-shaped, non-spore-forming bacterium (strain JM-1396T) producing a yellow pigment, was isolated from the healthy internal stem tissue of post-harvest cotton (Gossypium hirsutum, cultivar ‘DES-119’) grown at the Plant Breeding Unit at the E. V. Smith Research Center in Tallassee (Macon county), AL, USA. 16S rRNA gene sequence analysis of strain JM-1396T showed high sequence similarity values to the type strains of Novosphingobium mathurense, Novosphingobium panipatense (both 98.6 %) and Novosphingobium barchaimii (98.5 %); sequence similarities to all other type strains of species of the genus Novosphingobium were below 98.3 %. DNA–DNA pairing experiments of the DNA of strain JM-1396T and N. mathurense SM117T, N. panipatense SM16T and N. barchaimii DSM 25411T showed low relatedness values of 8 % (reciprocal 7 %), 24 % (reciprocal 26 %) and 19 % (reciprocal 25 %), respectively. Ubiquinone Q-10 was detected as the dominant quinone; the fatty acids C18 : 1ω7c (71.0 %) and the typical 2-hydroxy fatty acid, C14 : 0 2-OH (11.7 %), were detected as typical components. The polar lipid profile contained the diagnostic lipids diphosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid and phosphatidylcholine. The polyamine pattern contained the major compound spermidine and only minor amounts of other polyamines. All these data revealed that strain JM-1396T represents a novel species of the genus Novosphingobium. For this reason we propose the name Novosphingobium gossypii sp. nov. with the type strain JM-1396T ( = LMG 28605T = CCM 8569T = CIP 110884T).

scholarly journals Aurantimicrobium minutum gen. nov., sp. nov., a novel ultramicrobacterium of the family Microbacteriaceae, isolated from river water

2015 ◽  
Vol 65 (Pt_11) ◽  
pp. 4072-4079 ◽  
Author(s):  
Ryosuke Nakai ◽  
Tomoya Baba ◽  
Hironori Niki ◽  
Miyuki Nishijima ◽  
Takeshi Naganuma
Keyword(s):  
River Water ◽  
Sequence Similarity ◽  
Rrna Gene ◽  
Phenotypic Characteristics ◽  
High Sequence Similarity ◽  
The Family ◽  
Western Japan ◽  
Unidentified Species ◽  
Diamino Acid ◽  
Ph Range

A Gram-stain-positive, aerobic, non-motile, curved (selenoid), rod-shaped actinobacterium, designated KNCT, was isolated from the 0.2 μm-filtrate of river water in western Japan. Cells of strain KNCT were ultramicrosized (0.04–0.05 μm3). The strain grew at 15–37 °C, with no observable growth at 10 °C or 40 °C. The pH range for growth was 7–9, with weaker growth at pH 10. Growth was impeded by the presence of NaCl at concentrations greater than 1 %. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain KNCT showed relatively high sequence similarity (97.2 %) to Alpinimonas psychrophila Cr8-25T in the family Microbacteriaceae. However, strain KNCT formed an independent cluster with cultured, but as-yet-unidentified, species and environmental clones on the phylogenetic tree. The major cellular fatty acids were anteiso-C15 : 0 (41.0 %), iso-C16 : 0 (21.8 %), C16 : 0 (18.0 %) and anteiso-C17 : 0 (12.9 %), and the major menaquinones were MK-11 (71.3 %) and MK-12 (13.6 %). The major polar lipids were phosphatidylglycerol and two unknown glycolipids. The cell-wall muramic acid acyl type was acetyl. The peptidoglycan was B-type, and contained 3-hydroxyglutamic acid, glutamic acid, aspartic acid, glycine, alanine and lysine, with the latter being the diagnostic diamino acid. The G+C content of the genome was unusually low for actinobacteria (52.1 mol%), compared with other genera in the family Microbacteriaceae. Based on the phenotypic characteristics and phylogenetic evidence, strain KNCT represents a novel species of a new genus within the family Microbacteriaceae, for which the name Aurantimicrobium minutum gen. nov., sp. nov. is proposed. The type strain of the type species is KNCT ( = NBRC 105389T = NCIMB 14875T).

Usitatibacter rugosus gen. nov., sp. nov. and Usitatibacter palustris sp. nov., novel members of Usitatibacteraceae fam. nov. within the order Nitrosomonadales isolated from soil

2021 ◽  
Author(s):  
Selma Vieira ◽  
Katharina J. Huber ◽  
Meina Neumann-Schaal ◽  
Alicia Geppert ◽  
Manja Luckner ◽  
...  
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Type Strain ◽  
Type Species ◽  
Sequence Similarity ◽  
Rrna Gene ◽  
The Novel ◽  
Content Type ◽  
Link Type ◽  
Wide Range

Members of the metabolically diverse order Nitrosomonadales inhabit a wide range of environments. Two strains affiliated with this order were isolated from soils in Germany and characterized by a polyphasic approach. Cells of strains 0125_3T and Swamp67T are Gram-negative rods, non-motile, non-spore-forming, non-capsulated and divide by binary fission. They tested catalase-negative, but positive for cytochrome c-oxidase. Both strains form small white colonies on agar plates and grow aerobically and chemoorganotrophically on SSE/HD 1 : 10 medium, preferably utilizing organic acids and proteinaceous substrates. Strains 0125_3T and Swamp67T are mesophilic and grow optimally without NaCl addition at slightly alkaline conditions. Major fatty acids are C16 : 1  ω7c, C16 : 0 and C14 : 0. The major polar lipids are diphosphatidylglycerol, phosphatidylethanolamine and phosphatidyglycerol. The predominant respiratory quinone is Q-8. The G+C content for 0125_3T and Swamp67T was 67 and 66.1 %, respectively. The 16S rRNA gene analysis indicated that the closest relatives (<91 % sequence similarity) of strain 0125_3T were Nitrosospira multiformis ATCC 25196T, Methyloversatilis universalis FAM5T and Denitratisoma oestradiolicum AcBE2-1T, while Nitrosospira multiformis ATCC 25196T, Nitrosospira tenuis Nv1T and Nitrosospira lacus APG3T were closest to strain Swamp67T. The two novel strains shared 97.4 % 16S rRNA gene sequence similarity with one another and show low average nucleotide identity of their genomes (83.8 %). Based on the phenotypic, chemotaxonomic, genomic and phylogenetic analysis, we propose the two novel species Usitatibacter rugosus sp. nov (type strain 0125_3T=DSM 104443T=LMG 29998T=CECT 9241T) and Usitatibacter palustris sp. nov. (type strain Swamp67T=DSM 104440T=LMG 29997T=CECT 9242T) of the novel genus Usitatibacter gen. nov., within the novel family Usitatibacteraceae fam. nov.

scholarly journals Limited Microcystin, Anatoxin and Cylindrospermopsin Production by Cyanobacteria from Microbial Mats in Cold Deserts

Toxins ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 244 ◽  
Author(s):  
Nataliia Khomutovska ◽  
Małgorzata Sandzewicz ◽  
Łukasz Łach ◽  
Małgorzata Suska-Malawska ◽  
Monika Chmielewska ◽  
...  
Keyword(s):  
Microbial Mats ◽  
Sequence Similarity ◽  
Extreme Environment ◽  
Toxin Production ◽  
High Mountain ◽  
Rrna Gene ◽  
High Sequence Similarity ◽  
Small Water ◽  
Two Samples ◽  
Liquid Chromatography Tandem Mass

Toxic metabolites are produced by many cyanobacterial species. There are limited data on toxigenic benthic, mat-forming cyanobacteria, and information on toxic cyanobacteria from Central Asia is even more scarce. In the present study, we examined cyanobacterial diversity and community structure, the presence of genes involved in toxin production and the occurrence of cyanotoxins in cyanobacterial mats from small water bodies in a cold high-mountain desert of Eastern Pamir. Diversity was explored using amplicon-based sequencing targeting the V3-V4 region of the 16S rRNA gene, toxin potential using PCR-based methods (mcy, nda, ana, sxt), and toxins by enzyme-linked immunosorbent assays (ELISAs) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Molecular identification of cyanobacteria showed a high similarity of abundant taxa to Nostoc PCC-73102, Nostoc PCC-7524, Nodularia PCC-935 and Leptolyngbya CYN68. The PCRs revealed the presence of mcyE and/or ndaF genes in 11 samples and mcyD in six. The partial sequences of the mcyE gene showed high sequence similarity to Nostoc, Planktothrix and uncultured cyanobacteria. LC-MS/MS analysis identified six microcystin congeners in two samples and unknown peptides in one. These results suggest that, in this extreme environment, cyanobacteria do not commonly produce microcystins, anatoxins and cylindrospermopsins, despite the high diversity and widespread occurrence of potentially toxic taxa.

scholarly journals NADPH-dependent extracellular superoxide production is vital to photophysiology in the marine diatom Thalassiosira oceanica

2019 ◽  
Vol 116 (33) ◽  
pp. 16448-16453 ◽  
Author(s):  
Julia M. Diaz ◽  
Sydney Plummer ◽  
Colleen M. Hansel ◽  
Peter F. Andeer ◽  
Mak A. Saito ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Cell Types ◽  
Redox Balance ◽  
Superoxide Production ◽  
Marine Phytoplankton ◽  
Marine Diatom ◽  
High Sequence Similarity ◽  
Whole Cells ◽  
Wide Range ◽  
Diphenylene Iodonium

Reactive oxygen species (ROS) like superoxide drive rapid transformations of carbon and metals in aquatic systems and play dynamic roles in biological health, signaling, and defense across a diversity of cell types. In phytoplankton, however, the ecophysiological role(s) of extracellular superoxide production has remained elusive. Here, the mechanism and function of extracellular superoxide production by the marine diatom Thalassiosira oceanica are described. Extracellular superoxide production in T. oceanica exudates was coupled to the oxidation of NADPH. A putative NADPH-oxidizing flavoenzyme with predicted transmembrane domains and high sequence similarity to glutathione reductase (GR) was implicated in this process. GR was also linked to extracellular superoxide production by whole cells via quenching by the flavoenzyme inhibitor diphenylene iodonium (DPI) and oxidized glutathione, the preferred electron acceptor of GR. Extracellular superoxide production followed a typical photosynthesis-irradiance curve and increased by 30% above the saturation irradiance of photosynthesis, while DPI significantly impaired the efficiency of photosystem II under a wide range of light levels. Together, these results suggest that extracellular superoxide production is a byproduct of a transplasma membrane electron transport system that serves to balance the cellular redox state through the recycling of photosynthetic NADPH. This photoprotective function may be widespread, consistent with the presence of putative homologs to T. oceanica GR in other representative marine phytoplankton and ocean metagenomes. Given predicted climate-driven shifts in global surface ocean light regimes and phytoplankton community-level photoacclimation, these results provide implications for future ocean redox balance, ecological functioning, and coupled biogeochemical transformations of carbon and metals.

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