Respiratory Chain Supercomplexes in Mitochondria

Artificial construction of the biocoenosis of deep-sea ecosystem via seeping methane

Deep-sea ecosystems, such as cold seeps and hydrothermal vents, have high biomass, even though they are located in the benthic zone, where no sunlight is present to provide energy for organism proliferation. Based on the coexistence of the reduced gases and chemoautotrophic microbes, it is inferred that the energy from the reduced gases supports the biocoenosis of deep-sea ecosystems. However, there is no direct evidence to support this deduction. Here, we developed and placed a biocoenosis generator, a device that continuously seeped methane, on the 1000-m deep-sea floor of the South China Sea to artificially construct a deep-sea ecosystem biocoenosis. The results showed that microorganisms, including bacteria and archaea, appeared in the biocoenosis generator first, followed by jellyfish and Gammaridea arthropods, indicating that a biocoenosis had been successfully constructed in the deep sea. Anaerobic methane-oxidizing archaea, which shared characteristics with the archaea of natural deep-sea cold seeps, acted as the first electron acceptors of the emitted methane; then, the energy in the electrons was transferred to downstream symbiotic archaea and bacteria and finally to animals. Nitrate-reducing bacteria served as partners to complete anaerobic oxidation of methane process. Further analysis revealed that viruses coexisted with these organisms during the origin of the deep-sea biocoenosis. Therefore, our study mimics a natural deep-sea ecosystem and provides the direct evidence to show that the chemical energy of reduced organic molecules, such as methane, supports the biocoenosis of deep-sea ecosystems.

Molecular changes in mitochondrial respiratory activity and metabolic enzyme activity in muscle of four pig breeds with distinct metabolic types

Skeletal muscles are metabolically active and have market value in meat-producing farm animals. A better understanding of biological pathways affecting energy metabolism in skeletal muscle could advance the science of skeletal muscle. In this study, comparative pathway-focused gene expression profiling in conjunction with muscle fiber typing were analyzed in skeletal muscles from Duroc, Pietrain, and Duroc-Pietrain crossbred pigs. Each breed type displayed a distinct muscle fiber-type composition. Mitochondrial respiratory activity and glycolytic and oxidative enzyme activities were comparable among genotypes, except for significantly lower complex I activity in Pietrain pigs homozygous-positive for malignant hyperthermia syndrome. At the transcriptional level, lactate dehydrogenase B showed breed specificity, with significantly lower expression in Pietrain pigs homozygous-positive for malignant hyperthermia syndrome. A similar mRNA expression pattern was shown for several subunits of oxidative phosphorylation complexes, including complex I, complex II, complex IV, and ATP synthase. Significant correlations were observed between mRNA expression of genes in focused pathways and enzyme activities in a breed-dependent manner. Moreover, expression patterns of pathway-focused genes were well correlated with muscle fiber-type composition. These results stress the importance of regulation of transcriptional rate of genes related to oxidative and glycolytic pathways in the metabolic capacity of muscle fibers. Overall, the results further the breed-specific understanding of the molecular basis of metabolic enzyme activities, which directly impact meat quality.