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1. Cell Aggregation and Aerobic Respiration Are Important for Zymomonas mobilis ZM4 Survival in an Aerobic Minimal Medium

   https://doi.org/10.1128/AEM.00193-19  

   Jones-Burrage, Sara E.; Kremer, Timothy A.; McKinlay, James B.; Müller, Volker (May 2019, Applied and Environmental Microbiology)

   ABSTRACT Zymomonas mobilis produces ethanol from glucose near the theoretical maximum yield, making it a potential alternative to the yeast Saccharomyces cerevisiae for industrial ethanol production. A potentially useful industrial feature is the ability to form multicellular aggregates called flocs, which can settle quickly and exhibit higher resistance to harmful chemicals than single cells. While spontaneous floc-forming Z. mobilis mutants have been described, little is known about the natural conditions that induce Z. mobilis floc formation or about the genetic factors involved. Here we found that wild-type Z. mobilis forms flocs in response to aerobic growth conditions but only in a minimal medium. We identified a cellulose synthase gene cluster and a single diguanylate cyclase that are essential for both floc formation and survival in a minimal aerobic medium. We also found that NADH dehydrogenase 2, a key component of the aerobic respiratory chain, is important for survival in a minimal aerobic medium, providing a physiological role for this enzyme, which has previously been found to be disadvantageous in a rich aerobic medium. Supplementation of the minimal medium with vitamins also promoted survival but did not inhibit floc formation. IMPORTANCE The bacterium Zymomonas mobilis is best known for its anaerobic fermentative lifestyle, in which it converts glucose into ethanol at a yield surpassing that of yeast. However, Z. mobilis also has an aerobic lifestyle, which has confounded researchers with its attributes of poor growth, accumulation of toxic acetic acid and acetaldehyde, and respiratory enzymes that are detrimental for aerobic growth. Here we show that a major Z. mobilis respiratory enzyme and the ability to form multicellular aggregates, called flocs, are important for survival, but only during aerobic growth in a medium containing a minimum set of nutrients required for growth. Supplements, such as vitamins or yeast extract, promote aerobic growth and, in some cases, inhibit floc formation. We propose that Z. mobilis likely requires aerobic respiration and floc formation in order to survive in natural environments that lack protective factors found in supplements such as yeast extract. 

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2. Aerobic Catalyzed Oxidative Cross-Coupling of N , N -Disubstituted Anilines and Aminonaphthalenes with Phenols and Naphthols

   https://doi.org/10.1021/acs.orglett.0c00046  

   Paniak, Thomas J.; Kozlowski, Marisa C. (March 2020, Organic Letters)
3. Association of EGLN1 gene with high aerobic capacity of Peruvian Quechua at high altitude

   https://doi.org/10.1073/pnas.1906171116  

   Brutsaert, Tom D.; Kiyamu, Melisa; Elias Revollendo, Gianpietro; Isherwood, Jenna L.; Lee, Frank S.; Rivera-Ch, Maria; Leon-Velarde, Fabiola; Ghosh, Sudipta; Bigham, Abigail W. (November 2019, Proceedings of the National Academy of Sciences)

   Highland native Andeans have resided at altitude for millennia. They display high aerobic capacity (VO 2 max) at altitude, which may be a reflection of genetic adaptation to hypoxia. Previous genomewide (GW) scans for natural selection have nominated Egl-9 homolog 1 gene ( EGLN1 ) as a candidate gene. The encoded protein, EGLN1/PHD2, is an O 2 sensor that controls levels of the Hypoxia Inducible Factor-α (HIF-α), which regulates the cellular response to hypoxia. From GW association and analysis of covariance performed on a total sample of 429 Peruvian Quechua and 94 US lowland referents, we identified 5 EGLN1 SNPs associated with higher VO 2 max (L⋅min −1 and mL⋅min −1 ⋅kg −1 ) in hypoxia (rs1769793, rs2064766, rs2437150, rs2491403, rs479200). For 4 of these SNPs, Quechua had the highest frequency of the advantageous (high VO 2 max) allele compared with 25 diverse lowland comparison populations from the 1000 Genomes Project. Genotype effects were substantial, with high versus low VO 2 max genotype categories differing by ∼11% (e.g., for rs1769793 SNP genotype TT = 34.2 mL⋅min −1 ⋅kg −1 vs. CC = 30.5 mL⋅min −1 ⋅kg −1 ). To guard against spurious association, we controlled for population stratification. Findings were replicated for EGLN1 SNP rs1769793 in an independent Andean sample collected in 2002. These findings contextualize previous reports of natural selection at EGLN1 in Andeans, and support the hypothesis that natural selection has increased the frequency of an EGLN1 causal variant that enhances O 2 delivery or use during exercise at altitude in Peruvian Quechua. 

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4. Captivity affects mitochondrial aerobic respiration and carotenoid metabolism in the house finch ( Haemorhous mexicanus )

   https://doi.org/10.1242/jeb.246980  

   Koch, Rebecca E.; Okegbe, Chidimma; Ramanathan, Chidambaram; Zhu, Xinyu; Hare, Ethan; Toomey, Matthew B.; Hill, Geoffrey E.; Zhang, Yufeng (April 2024, Journal of Experimental Biology)

   In many species of animals, red carotenoid-based coloration is produced by metabolizing yellow dietary pigments, and this red ornamentation can be an honest signal of individual quality. However, the physiological basis for associations between organism function and the metabolism of red ornamental carotenoids from yellow dietary carotenoids remains uncertain. A recent hypothesis posits that carotenoid metabolism depends on mitochondrial performance, with diminished red coloration resulting from altered mitochondrial aerobic respiration. To test for an association between mitochondrial respiration and red carotenoids, we held wild-caught, molting male house finches in either small bird cages or large flight cages to create environmental challenges during the period when red ornamental coloration is produced. We predicted that small cages would present a less favorable environment than large flight cages and that captivity itself would decrease both mitochondrial performance and the abundance of red carotenoids compared to free-living birds. We found that captive-held birds circulated fewer red carotenoids, showed increased mitochondrial respiratory rates, and had lower complex II respiratory control ratios—a metric associated with mitochondrial efficiency—compared to free-living birds, though we did not detect a difference in the effects of small cages versus large cages. Among captive individuals, the birds that circulated the highest concentrations of red carotenoids had the highest mitochondrial respiratory control ratio for complex II substrate. These data support the hypothesis that the metabolism of red carotenoid pigments is linked to mitochondrial aerobic respiration in the house finch, but the mechanisms for this association remain to be established. 

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5. WHAT more IS

   https://doi.org/10.1111/phpe.12121  

   Wellwood, Alexis (December 2018, Philosophical Perspectives)