scholarly journals Co-occurring activity of two autotrophic pathways in symbionts of hydrothermal vent tubeworm Riftia pachyptila

2021 ◽  
Author(s):  
Juliana M. Leonard ◽  
Jessica Mitchell ◽  
Roxanne A. Beinart ◽  
Jennifer A. Delaney ◽  
Jon G. Sanders ◽  
...  
Keyword(s):  
High Pressure ◽  
Hydrothermal Vent ◽  
Dissolved Inorganic Carbon ◽  
Tricarboxylic Acid Cycle ◽  
Riftia Pachyptila ◽  
Acid Cycle ◽  
Citrate Lyase ◽  
Sulfur Oxidizing ◽  
Reductive Tricarboxylic Acid Cycle

Genome and proteome data predict the presence of both the reductive citric acid cycle (rCAC; also called the reductive tricarboxylic acid cycle) and Calvin-Benson-Bassham cycle (CBB) in “ Candidatus Endoriftia persephonae”, the autotrophic sulfur-oxidizing bacterial endosymbiont from 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 the CBB. R. pachyptila were incubated under in situ conditions in high-pressure aquaria under low (28-40 μmol hr −1 ) or high (180 - 276 μmol hr −1 ) rates of sulfide supply. Symbiont-bearing trophosome samples excised from R. pachyptila maintained under either condition were capable of similar rates of CO 2 fixation. Activities of rCAC enzyme ATP-dependent citrate lyase and CBB enzyme RubisCO did not differ between the two conditions, though 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 pools were variable, 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 CBB cycles exclusively. These observations are consistent with co-occurring activities of rCAC and CBB cycles 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 were maintained and monitored in high-pressure aquaria prior to measuring their 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 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.

scholarly journals Evidence for Autotrophic CO2 Fixation via the Reductive Tricarboxylic Acid Cycle by Members of the ε Subdivision of Proteobacteria

2005 ◽  
Vol 187 (9) ◽  
pp. 3020-3027 ◽  
Author(s):  
Michael Hügler ◽  
Carl O. Wirsen ◽  
Georg Fuchs ◽  
Craig D. Taylor ◽  
Stefan M. Sievert
Keyword(s):  
Carbon Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Calvin Cycle ◽  
Tricarboxylic Acid ◽  
Rrna Gene ◽  
Atp Citrate Lyase ◽  
Acid Cycle ◽  
Key Enzymes ◽  
Citrate Lyase ◽  
Reductive Tricarboxylic Acid Cycle

ABSTRACT Based on 16S rRNA gene surveys, bacteria of the ε subdivision of proteobacteria have been identified to be important members of microbial communities in a variety of environments, and quite a few have been demonstrated to grow autotrophically. However, no information exists on what pathway of autotrophic carbon fixation these bacteria might use. In this study, Thiomicrospira denitrificans and Candidatus Arcobacter sulfidicus, two chemolithoautotrophic sulfur oxidizers of the ε subdivision of proteobacteria, were examined for activities of the key enzymes of the known autotrophic CO2 fixation pathways. Both organisms contained activities of the key enzymes of the reductive tricarboxylic acid cycle, ATP citrate lyase, 2-oxoglutarate:ferredoxin oxidoreductase, and pyruvate:ferredoxin oxidoreductase. Furthermore, no activities of key enzymes of other CO2 fixation pathways, such as the Calvin cycle, the reductive acetyl coenzyme A pathway, and the 3-hydroxypropionate cycle, could be detected. In addition to the key enzymes, the activities of the other enzymes involved in the reductive tricarboxylic acid cycle could be measured. Sections of the genes encoding the α- and β-subunits of ATP citrate lyase could be amplified from both organisms. These findings represent the first direct evidence for the operation of the reductive tricarboxylic acid cycle for autotrophic CO2 fixation in ε-proteobacteria. Since ε-proteobacteria closely related to these two organisms are important in many habitats, such as hydrothermal vents, oxic-sulfidic interfaces, or oilfields, these results suggest that autotrophic CO2 fixation via the reductive tricarboxylic acid cycle might be more important than previously considered.

scholarly journals ELECTRON MICROSCOPE HISTOCHEMICAL EVIDENCE FOR A PARTIAL OR TOTAL BLOCK OF THE TRICARBOXYLIC ACID CYCLE IN THE MITOCHONDRIA OF PRESYNAPTIC AXON TERMINALS

1971 ◽  
Vol 51 (1) ◽  
pp. 216-222 ◽  
Author(s):  
Ferenc Hajós ◽  
Sándor Kerpel-Fronius
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Energy Coupling ◽  
Tricarboxylic Acid ◽  
Synaptic Function ◽  
Coupling Mechanism ◽  
Succinate Oxidation ◽  
Acid Cycle ◽  
Axon Terminals ◽  
Massive Accumulation

Respiration-linked, massive accumulation of Sr2+ is used to reveal the coupled oxidation of pyruvate, α-oxoglutarate, succinate, and malate by in situ mitochondria. All of these substrates were actively oxidized in the dendritic and perikaryal mitochondria, but no α-oxoglutarate or succinate utilization could be demonstrated in the mitochondria of the presynaptic axon terminals. A block at an early step of α-oxoglutarate and succinate oxidation is proposed to account for the negative histochemical results, since the positive reaction with pyruvate and malate proves that these mitochondria possess an intact respiratory chain and energy-coupling mechanism essential for Sr2+ accumulation. This indicates that the mitochondria in the axon terminals would be able to generate energy for synaptic function with at least some of the respiratory substrates. With regard to the block in the tricarboxylic acid cycle, the oxaloacetate necessary for citrate formation is suggested to be provided by fixation of CO2 into some of the pyruvate.

scholarly journals Bacterial symbiont subpopulations have different roles in a deep-sea symbiosis

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Tjorven Hinzke ◽  
Manuel Kleiner ◽  
Mareike Meister ◽  
Rabea Schlüter ◽  
Christian Hentschker ◽  
...  
Keyword(s):  
Deep Sea ◽  
Hydrothermal Vent ◽  
Carbon Fixation ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Bacterial Symbiont ◽  
Riftia Pachyptila ◽  
Physiological Diversity ◽  
Host Interaction ◽  
Sulfur Oxidizing

The hydrothermal vent tubeworm Riftia pachyptila hosts a single 16S rRNA phylotype of intracellular sulfur-oxidizing symbionts, which vary considerably in cell morphology and exhibit a remarkable degree of physiological diversity and redundancy, even in the same host. To elucidate whether multiple metabolic routes are employed in the same cells or rather in distinct symbiont subpopulations, we enriched symbionts according to cell size by density gradient centrifugation. Metaproteomic analysis, microscopy, and flow cytometry strongly suggest that Riftia symbiont cells of different sizes represent metabolically dissimilar stages of a physiological differentiation process: While small symbionts actively divide and may establish cellular symbiont-host interaction, large symbionts apparently do not divide, but still replicate DNA, leading to DNA endoreduplication. Moreover, in large symbionts, carbon fixation and biomass production seem to be metabolic priorities. We propose that this division of labor between smaller and larger symbionts benefits the productivity of the symbiosis as a whole.

scholarly journals Activity and androgenic control of enzymes associated with the tricarboxylic acid cycle, lipid oxidation and mitochondrial shuttles in the epididymis and epididymal spermatozoa of the rat

1978 ◽  
Vol 174 (3) ◽  
pp. 741-752 ◽  
Author(s):  
D E Brooks
Keyword(s):  
Lipid Oxidation ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Active Member ◽  
Carnitine Acetyltransferase ◽  
Atp Citrate Lyase ◽  
Acid Cycle ◽  
Citrate Lyase ◽  
Epididymal Spermatozoa ◽  
Glycerol 3 Phosphate Dehydrogenase

1. Enzyme activities (units/g wet wt.) were determined in the caput and cauda epididymidis and in epididymal spermatozoa of the rat. 2. The activity of most enzymes in the cauda was between 50 and 100% of that in the caput, except that ATP citrate lyase was barely detectable in the cauda. 3. Spermatozoa, unlike epididymal tissue, contained sorbitol dehydrogenase but lacked ATP citrate lyase. NADP+-malate dehydrogenase, mitochondrial glycerol 3-phosphate dehydrogenase, succinate dehydrogenase, carnitine acetyltransferase and citrate synthase were 5 to 400 times as active in spermatozoa as in epididymal tissue. 4. 2-Oxoglutarate dehydrogenase was the least active member of the tricarboxylic acid cycle in all tissues and most closely matched the measured flux through the cycle. 5. The concentrations of hydroxyacyl-CoA dehydrogenase and carnitine palmitoyltransferase were equivalent to the more active enzymes of the tricarboxylic acid cycle, indicating the capacity for extensive lipid oxidation, and the presence of 3-hydroxybutyrate dehydrogenase suggests that these tissues can also oxidize ketone bodies. 6. Transfer of reducing equivalents from cytoplasm to mitochondrion is unlikely to occur by means of the glycerol phosphate cycle because mitochondrial glycerol 3-phosphate dehydrogenase is relatively inactive in epididymal tissue, whereas the cytoplasmic enzyme has little activity in spermatozoa, but transfer may be accomplished by the malate-aspartate shuttle. 7. Transfer of acetyl units from mitochondrion to cytoplasm could be effected by the pyruvate-malate cycle in the caput of androgen-maintained rats, but not in the other tissues because of the low activity of ATP citrate lyase. Acetyl unit transfer could take place via acetylcarnitine, mediated by carnitine acetyltransferase. 8. Castration resulted in a decrease in the concentration of nearly all enzymes, although subsequent administration of testosterone restored concentrations to values similar to those in animals maintained by endogenous androgen. The extent to which enzyme concentration was changed by an alteration in androgen status was highly variable, but was most marked in the case of pyruvate carboxylase.

scholarly journals A Soluble NADH-Dependent Fumarate Reductase in the Reductive Tricarboxylic Acid Cycle of Hydrogenobacter thermophilus TK-6

2008 ◽  
Vol 190 (21) ◽  
pp. 7170-7177 ◽  
Author(s):  
Akane Miura ◽  
Masafumi Kameya ◽  
Hiroyuki Arai ◽  
Masaharu Ishii ◽  
Yasuo Igarashi
Keyword(s):  
Soluble Fraction ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Fumarate Reductase ◽  
High Sequence Identity ◽  
Catalytic Subunits ◽  
Acid Cycle ◽  
Genes Encoding ◽  
Hydrogenobacter Thermophilus ◽  
Reductive Tricarboxylic Acid Cycle

ABSTRACT Fumarate reductase (FRD) is an enzyme that reduces fumarate to succinate. In many organisms, it is bound to the membrane and uses electron donors such as quinol. In this study, an FRD from a thermophilic chemolithoautotrophic bacterium, Hydrogenobacter thermophilus TK-6, was purified and characterized. FRD activity using NADH as an electron donor was not detected in the membrane fraction but was found in the soluble fraction. The purified enzyme was demonstrated to be a novel type of FRD, consisting of five subunits. One subunit showed high sequence identity to the catalytic subunits of known FRDs. Although the genes of typical FRDs are assembled in a cluster, the five genes encoding the H. thermophilus FRD were distant from each other in the genome. Furthermore, phylogenetic analysis showed that the H. thermophilus FRD was located in a distinct position from those of known soluble FRDs. This is the first report of a soluble NADH-dependent FRD in Bacteria and of the purification of a FRD that operates in the reductive tricarboxylic acid cycle.

Sign in / Sign up

Export Citation Format

Share Document