Unusual marine unicellular symbiosis with the nitrogen-fixing cyanobacterium UCYN-A

Zehr, Jonathan P.; Shilova, Irina N.; Farnelid, Hanna; Muñoz-Marín, María del Carmen; Turk‐Kubo, Kendra A.

doi:10.1038/nmicrobiol.2016.214

Cited by 78 publications

(74 citation statements)

References 92 publications

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“…Journal of Geophysical Research: Oceans 10.1002/2017JC013047 Perez et al, 2016). Additionally, the symbiont has the ability to carry out ATP synthesis from sunlight through PSI driven cyclic electron flow (Bandyopadhyay et al, 2010(Bandyopadhyay et al, , 2011Martinez-Perez et al, 2016;Zehr et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

On the Relationship Between Hydrogen Saturation in the Tropical Atlantic Ocean and Nitrogen Fixation by the Symbiotic Diazotroph UCYN‐A

et al. 2018

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Dissolved hydrogen measurements were made at high resolution in surface waters along a tropical north Atlantic transect between Guadeloupe and Cape Verde in 2015 (Meteor 116). Parallel water samples acquired to assess the relative abundance of the nifH gene from several types of diazotrophs, indicated that Trichodesmium and UCYN‐A were dominant in this region. We show that a high degree of correlation exists between the hydrogen saturations and UCYN‐A nifH abundance, and a weak correlation with Trichodesmium. The findings suggest that nitrogen fixation by UCYN‐A is a major contributor to hydrogen supersaturations in this region of the ocean. The ratio of hydrogen released to nitrogen fixed has not been determined for this symbiont, but the indications are that it may be high in comparison with the small number of diazotrophs for which the ratio has been measured in laboratory cultures. We speculate that this would be consistent with the diazotroph being an exosymbiont on its haptophyte host. Our high resolution measurements of hydrogen concentrations are capable of illustrating the time and space scales of inferred activity of diazotrophs in near real‐time in a way that cannot be achieved by biological sampling and rate measurements requiring incubations with 15N2. Direct measurement of high resolution spatial variability would be relatively challenging through collection and analysis of biological samples by qPCR, and extremely challenging by 15N‐uptake techniques, neither of which methods yields real‐time data. Nonetheless, determination of fixation rates still firmly depends on the established procedure of incubations in the presence of 15N2.

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Section: Discussionmentioning

confidence: 99%

On the Relationship Between Hydrogen Saturation in the Tropical Atlantic Ocean and Nitrogen Fixation by the Symbiotic Diazotroph UCYN‐A

et al. 2018

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“…Cyanobacteria are a phylogenetically coherent group of bacteria characterized by their ability to perform oxygenic photosynthesis (Stanier and Cohen‐Bazire, ; Giovannoni et al ., ). Nonetheless, some cyanobacterial non‐photosynthetic mutants have evolved as obligate endosymbionts (Zehr et al ., ). Although non‐photosynthetic bacteria such as Melainabacteria and Sericytochromatia have been included into the phylum ‘cyanobacteria’ (Soo et al ., ), in our opinion they constitute different groups of organisms (see also Pakrasi and Zehr, ).…”

Section: Introductionmentioning

confidence: 97%

Genetic responses to carbon and nitrogen availability in Anabaena

Herrero

Flores

2018

Environmental Microbiology

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Heterocyst-forming cyanobacteria are filamentous organisms that perform oxygenic photosynthesis and CO fixation in vegetative cells and nitrogen fixation in heterocysts, which are formed under deprivation of combined nitrogen. These organisms can acclimate to use different sources of nitrogen and respond to different levels of CO . Following work mainly done with the best studied heterocyst-forming cyanobacterium, Anabaena, here we summarize the mechanisms of assimilation of ammonium, nitrate, urea and N , the latter involving heterocyst differentiation, and describe aspects of CO assimilation that involves a carbon concentration mechanism. These processes are subjected to regulation establishing a hierarchy in the assimilation of nitrogen sources -with preference for the most reduced nitrogen forms- and a dependence on sufficient carbon. This regulation largely takes place at the level of gene expression and is exerted by a variety of transcription factors, including global and pathway-specific transcriptional regulators. NtcA is a CRP-family protein that adjusts global gene expression in response to the C-to-N balance in the cells, and PacR is a LysR-family transcriptional regulator (LTTR) that extensively acclimates the cells to oxygenic phototrophy. A cyanobacterial-specific transcription factor, HetR, is involved in heterocyst differentiation, and other LTTR factors are specifically involved in nitrate and CO assimilation.

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“…In fact, there are only two bona fide primary endosymbioses known that gave rise to widespread organelles over the long history of eukaryotes; the event from which all plastids originated, as explained above, and a prior event that led to the evolution of mitochondria. Other more taxonomically limited cases of organelle origin are associated with the photosynthetic amoeba lineage Paulinella (see below), the nonphotosynthetic organelle of the trypanosomatids (Kostygov et al, 2016;Morales et al, 2016) and nitrogen-fixing spheroid bodies in the rhopalodiacean diatoms (Nakayama et al, 2014;Zehr et al, 2016). The rarity of primary endosymbiosis has fascinated scientists for many years and is usually attributed to the extensive innovations required for organelle establishment.…”

Section: Complex Biotic Interactions Explain Plastid Originmentioning

confidence: 99%

Biotic interactions as drivers of algal origin and evolution

et al. 2017

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Contents 670 I. 671 II. 671 III. 676 IV. 678 678 References 678 SUMMARY: Biotic interactions underlie life's diversity and are the lynchpin to understanding its complexity and resilience within an ecological niche. Algal biologists have embraced this paradigm, and studies building on the explosive growth in omics and cell biology methods have facilitated the in-depth analysis of nonmodel organisms and communities from a variety of ecosystems. In turn, these advances have enabled a major revision of our understanding of the origin and evolution of photosynthesis in eukaryotes, bacterial-algal interactions, control of massive algal blooms in the ocean, and the maintenance and degradation of coral reefs. Here, we review some of the most exciting developments in the field of algal biotic interactions and identify challenges for scientists in the coming years. We foresee the development of an algal knowledgebase that integrates ecosystem-wide omics data and the development of molecular tools/resources to perform functional analyses of individuals in isolation and in populations. These assets will allow us to move beyond mechanistic studies of a single species towards understanding the interactions amongst algae and other organisms in both the laboratory and the field.

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Unusual marine unicellular symbiosis with the nitrogen-fixing cyanobacterium UCYN-A

Cited by 78 publications

References 92 publications

On the Relationship Between Hydrogen Saturation in the Tropical Atlantic Ocean and Nitrogen Fixation by the Symbiotic Diazotroph UCYN‐A

On the Relationship Between Hydrogen Saturation in the Tropical Atlantic Ocean and Nitrogen Fixation by the Symbiotic Diazotroph UCYN‐A

Genetic responses to carbon and nitrogen availability in Anabaena

Biotic interactions as drivers of algal origin and evolution

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