skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Cooccurring Activities of Two Autotrophic Pathways in Symbionts of the Hydrothermal Vent Tubeworm Riftia pachyptila
ABSTRACT Genome and proteome data predict the presence of both the reductive citric acid cycle (rCAC; also called the reductive tricarboxylic acid cycle) and the Calvin-Benson-Bassham cycle (CBB) in “ Candidatus Endoriftia persephonae,” the autotrophic sulfur-oxidizing bacterial endosymbiont from the giant hydrothermal vent tubeworm Riftia pachyptila . We tested whether these cycles were differentially induced by sulfide supply, since the synthesis of biosynthetic intermediates by the rCAC is less energetically expensive than that by the CBB. R. pachyptila was incubated under in situ conditions in high-pressure aquaria under low (28 to 40 μmol · h −1 ) or high (180 to 276 μmol · h −1 ) rates of sulfide supply. Symbiont-bearing trophosome samples excised from R. pachyptila maintained under the two conditions were capable of similar rates of CO 2 fixation. Activities of the rCAC enzyme ATP-dependent citrate lyase (ACL) and the CBB enzyme 1,3-bisphosphate carboxylase/oxygenase (RubisCO) did not differ between the two conditions, although transcript abundances for ATP-dependent citrate lyase were 4- to 5-fold higher under low-sulfide conditions. δ 13 C values of internal dissolved inorganic carbon (DIC) pools were varied and did not correlate with sulfide supply rate. In samples taken from freshly collected R. pachyptila , δ 13 C values of lipids fell between those collected for organisms using either the rCAC or the CBB exclusively. These observations are consistent with cooccurring activities of the rCAC and the CBB in this symbiosis. IMPORTANCE Previous to this study, the activities of the rCAC and CBB in R. pachyptila had largely been inferred from “omics” studies of R. pachyptila without direct assessment of in situ conditions prior to collection. In this study, R. pachyptila was maintained and monitored in high-pressure aquaria prior to measuring its CO 2 fixation parameters. Results suggest that ranges in sulfide concentrations similar to those experienced in situ do not exert a strong influence on the relative activities of the rCAC and the CBB. This observation highlights the importance of further study of this symbiosis and other organisms with multiple CO 2 -fixing pathways, which recent genomics and biochemical studies suggest are likely to be more prevalent than anticipated.  more » « less
Award ID(s):
1952676
PAR ID:
10300376
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Editor(s):
Atomi, Haruyuki
Date Published:
Journal Name:
Applied and Environmental Microbiology
Volume:
87
Issue:
17
ISSN:
0099-2240
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Applied and Environmental Microbiology)
    Bose, Arpita (Ed.)
    ABSTRACT Using dissolved inorganic carbon (DIC) as a major carbon source, as autotrophs do, is complicated by the bedeviling nature of this substance. Autotrophs using the Calvin-Benson-Bassham cycle (CBB) are known to make use of a toolkit comprised of DIC transporters and carbonic anhydrase enzymes (CA) to facilitate DIC fixation. This minireview provides a brief overview of the current understanding of how toolkit function facilitates DIC fixation inCyanobacteriaand someProteobacteriausing the CBB and continues with a survey of the DIC toolkit gene presence in organisms using different versions of the CBB and other autotrophic pathways (reductive citric acid cycle, Wood-Ljungdahl pathway, hydroxypropionate bicycle, hydroxypropionate-hydroxybutyrate cycle, and dicarboxylate-hydroxybutyrate cycle). The potential function of toolkit gene products in these organisms is discussed in terms of CO2and HCO3−supply from the environment and demand by the autotrophic pathway. The presence of DIC toolkit genes in autotrophic organisms beyond those using the CBB suggests the relevance of DIC metabolism to these organisms and provides a basis for better engineering of these organisms for industrial and agricultural purposes. 
    more » « less
  2. ; ; ; ; ; ; ; (, International Journal of Molecular Sciences)
    The starch metabolic network was investigated in relation to other metabolic processes by examining a mutant with altered single-gene expression of ATP citrate lyase (ACL), an enzyme responsible for generating cytosolic acetyl-CoA pool from citrate. Previous research has shown that transgenic antisense plants with reduced ACL activity accumulate abnormally enlarged starch granules. In this study, we explored the underlying molecular mechanisms linking cytosolic acetyl-CoA generation and starch metabolism under short-day photoperiods. We performed transcriptome and quantification of starch accumulation in the leaves of wild-type and antisense seedlings with reduced ACL activity. The antisense-ACLA mutant accumulated more starch than the wild type under short-day conditions. Zymogram analyses were conducted to compare the activities of starch-metabolizing enzymes with transcriptomic changes in the seedling. Differential expression between wild-type and antisense-ACLA plants was detected in genes implicated in starch and acetyl-CoA metabolism, and cell wall metabolism. These analyses revealed a strong correlation between the transcript levels of genes responsible for starch synthesis and degradation, reflecting coordinated regulation at the transcriptomic level. Furthermore, our data provide novel insights into the regulatory links between cytosolic acetyl-CoA metabolism and starch metabolic pathways. 
    more » « less
  3. ; ; ; ; ; ; ; (, The ISME Journal)
    null (Ed.)
    Abstract The microbial fixation of N 2 is the largest source of biologically available nitrogen (N) to the oceans. However, it is the most energetically expensive N-acquisition process and is believed inhibited when less energetically expensive forms, like dissolved inorganic N (DIN), are available. Curiously, the cosmopolitan N 2 -fixing UCYN-A/haptophyte symbiosis grows in DIN-replete waters, but the sensitivity of their N 2 fixation to DIN is unknown. We used stable isotope incubations, catalyzed reporter deposition fluorescence in-situ hybridization (CARD-FISH), and nanoscale secondary ion mass spectrometry (nanoSIMS), to investigate the N source used by the haptophyte host and sensitivity of UCYN-A N 2 fixation in DIN-replete waters. We demonstrate that under our experimental conditions, the haptophyte hosts of two UCYN-A sublineages do not assimilate nitrate (NO 3 − ) and meet little of their N demands via ammonium (NH 4 + ) uptake. Instead the UCYN-A/haptophyte symbiosis relies on UCYN-A N 2 fixation to supply large portions of the haptophyte’s N requirements, even under DIN-replete conditions. Furthermore, UCYN-A N 2 fixation rates, and haptophyte host carbon fixation rates, were at times stimulated by NO 3 − additions in N-limited waters suggesting a link between the activities of the bulk phytoplankton assemblage and the UCYN-A/haptophyte symbiosis. The results suggest N 2 fixation may be an evolutionarily viable strategy for diazotroph–eukaryote symbioses, even in N-rich coastal or high latitude waters. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; (, The ISME Journal)
    Abstract Investigations of the metabolic capabilities of anaerobic protists advances our understanding of the evolution of eukaryotic life on Earth and for uncovering analogous extraterrestrial complex microbial life. Certain species of foraminiferan protists live in environments analogous to early Earth conditions when eukaryotes evolved, including sulfidic, anoxic and hypoxic sediment porewaters. Foraminifera are known to form symbioses as well as to harbor organelles from other eukaryotes (chloroplasts), possibly bolstering the host’s independence from oxygen. The full extent of foraminiferal physiological capabilities is not fully understood. To date, evidence for foraminiferal anaerobiosis was gleaned from specimens first subjected to stresses associated with removal from in situ conditions. Here, we report comprehensive gene expression analysis of benthic foraminiferal populations preserved in situ on the euxinic (anoxic and sulfidic) bathyal seafloor, thus avoiding environmental alterations associated with sample recovery, including pressure reduction, sunlight exposure, warming, and oxygenation. Metatranscriptomics, metagenome-assembled genomes, and measurements of substrate uptake were used to study the kleptoplastidic foraminifer Nonionella stella inhabiting sulfur-oxidizing bacterial mats of the Santa Barbara Basin, off California. We show N. stella energy generation under dark euxinia is unusual because it orchestrates complex metabolic pathways for ATP production and carbon fixation through the Calvin cycle. These pathways include extended glycolysis, anaerobic fermentation, sulfide oxidation, and the presence of a membrane-bound inorganic pyrophosphatase, an enzyme that hydrolyzes inorganic pyrophosphate to actively pump protons across the mitochondrial membrane. 
    more » « less
  5. (, The FASEB journal)
    ATP citrate lyase (ACL) catalyzes the ATP-dependent conversion of citrate to the fatty acid precursor, acetyl-CoA. ACL presence in yeasts has been associated with their ability to accumulate lipids (i.e., oleaginous phenotype), but little is known about the regulation of this enzyme in oleaginous yeasts. In the model oleaginous yeast Yarrowia lipolytica, ACL is a heterodimer comprised of a catalytic and a regulatory subunit, encoded by the ACL1 and ACL2 genes, respectively. From the earlier studies, it was shown that the loss of ACL1 resulted in lower lipid levels and altered fatty acid profiles. However, the regulation of ACL expression and activity during lipogenesis has not been studied. To better understand the role, ACL plays during lipogenesis in Y.lipolytica, we generated antibodies against its two subunits (i.e., Acl1 and Acl2). We also constructed strains that lack Acl2 (i.e., acl2Δ) and strains that overexpress Acl1 and Acl2 either alone or in combination. Preliminary experiments showed that the overexpression of Acl1 increased the protein levels of Acl2. We are currently analyzing the effects of Acl2 overexpression and the time-dependent regulation of Acl1 and Acl2. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email