PubMed · 4787597
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L Ashby. Prospect for pollution.. https://pubmed.ncbi.nlm.nih.gov/4787597/
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Diverse microorganisms couple the oxidation of carbon monoxide gas (CO) to the reduction of protons, producing hydrogen gas (H2) using nickel-containing CO dehydrogenase/energy-converting hydrogenase (Ni-CODH/ECH). Although this process yields one of the lowest free-energy gains in biology, its physiological role at environmentally relevant CO levels remains unresolved. Here, we show that Ni-CODH/ECH functions as a survival-oriented energy conservation system that enables heterotrophic facultative anaerobes to survive electron acceptor limitation, rather than primarily supporting growth or CO detoxification. Analysis of 387 genomes of Anoxybacillaceae species revealed that Ni-CODH/ECH had a patchy distribution and, with one exception, was mutually exclusive with the oxygen-tolerant molybdenum-containing CODH, suggesting ecological specialization. Culture experiments using three isolates (Parageobacillus sp. G301, P. thermoglucosidasius NBRC 107763, and Thermolongibacillus altinsuensis B1-1) demonstrated that CO-dependent proton respiration is activated during stationary phase when exogenous electron acceptors are limiting, maintaining cell density under 25% CO, whereas no effect was observed in a Ni-CODH knockout (ΔcooCSF) strain. RNA-seq analysis of Parageobacillus sp. G301 under twelve conditions revealed that Ni-CODH/ECH genes are highly expressed (top 0.2%-1.9% of all genes) under electron acceptor-free conditions, independent of CO presence, under the predicted control of the redox-dependent transcriptional repressor Rex. ΔcooCSF cultures accumulated more CO than the wild-type (WT), suggesting trace CO scavenging by the WT. Together, our results redefine Ni-CODH/ECH as a redox-regulated auxiliary energy-conservation strategy that supports survival and maintenance in anaerobic energy-limited environments using two ubiquitous substrates. This work extends the carboxydovore paradigm of trace gas-based survival from aerobic to spatiotemporally variable anaerobic environments.
We present here the synthesis, characterization, and flash photolysis study of [(F(8)TPP)Fe(II)(CO)(THF)] (1) [F(8)TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2-)]. Complex 1 crystallizes from THF/heptane solvent system as a tris-THF solvate, [(F(8)TPP)Fe(II)(CO)(THF)].3THF (1.3THF), with ferrous ion in the porphyrin plane (C(61)H(52)F(8)FeN(4)O(5); a = 11.7908(2) A, b = 20.4453(2) A, c = 39.9423(3), alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees; orthorhombic, P2(1)2(1)2(1), Z = 8; Fe-N(4)(av) = 2.00 A; N-Fe-N (all) = 90.0 degrees ). This complex (as 1.THF) has also been characterized by (1)H NMR [six-coordinate, low-spin heme; CD(3)CN, RT, delta 8.82 (s, pyrrole-H, 8H), 7.89 (s, para-phenyl-H, 8H), 7.46 (s, meta-phenyl-H, 4H), 3.58 (s, THF, 8H), 1.73 (s, THF, 8H)], (2)H NMR (pyrrole-deuterated analogue) [(F(8)TPP-d(8))Fe(II)(CO)(THF)] [THF, RT, delta 8.78 ppm (s, pyrrole-D)], (13)C NMR (on (13)CO-enriched adduct) [THF-d(8), RT, delta 206.5 ppm; CD(2)Cl(2), RT, delta 206.1 ppm], UV-vis [THF, RT, lambda(max), 411 (Soret), 525 nm], and IR [293 K, solution, nu(CO) 1979 cm(-)(1) (THF), 1976 cm(-)(1) (acetone), 1982 cm(-)(1) (CH(3)CN)] spectroscopies. In order to more fully understand the intricacies of solvent-ligand binding (as compared to CO rebinding to the photolyzed heme), we have also synthesized the bis-THF adduct [(F(8)TPP)Fe(II)(THF)(2)]. Complex 2 also crystallizes from THF/heptane solvent system as a bis-THF solvate, [(F(8)TPP)Fe(II)(THF)(2)].2THF (2.2THF), with ferrous iron in the porphyrin plane (C(60)H(52)F(8)FeN(4)O(4); a = 21.3216(3) A, b = 12.1191(2) A, c = 21.0125(2) A, alpha = 90 degrees, beta = 105.3658(5) degrees, gamma = 90 degrees; monoclinic, C2/c, Z = 4; Fe-N(4)(av) = 2.07 A; N-Fe-N (all) = 90.0 degrees ). Further characterization of 2 includes UV-vis [THF, lambda(max), 421 (Soret), 542 nm] and (1)H NMR [six-coordinate, high spin heme; THF-d(8), RT, delta 56.7 (s, pyrrole-H, 8H), 8.38 (s, para-phenyl-H, 8H), 7.15 (s, meta-phenyl-H, 4H)] spectroscopies. Flash photolysis studies employing 1 were able to resolve the CO rebinding kinetics in both THF and cyclohexane solvents. In CO saturated THF [[CO] approximately 5 mM] and at [1] congruent with 5 microM, the conversion of [(F(8)TPP)Fe(II)(THF)(2)] (produced after photolytic displacement of CO) to [(F(8)TPP)Fe(II)(CO)(THF)] was monoexponential, with k(obs) = 1.6 (+/-0.2) x 10(4) s(-)(1). Reduction in [CO] by vigorous Ar purging gave k(obs) congruent with 10(3) s(-)(1) in cyclohexane. The study presented in this report lays the foundation for applying fast-time scale studies based on CO flash photolysis to the more complicated heterobimetallic heme/Cu systems.
Cocaine and nicotine have a number of similar behavioral and neurobiological effects. This study compared the acute effects of cocaine and cigarette smoking on luteinizing hormone (LH), testosterone (T), and prolactin. Twenty-four men who met American Psychiatric Association Diagnostic and Statistical Manual criteria for cocaine abuse or nicotine dependence were given intravenous cocaine (0.4 mg/kg) or placebo-cocaine, or smoked a low or high nicotine cigarette under controlled conditions. Placebo-cocaine or low nicotine cigarette smoking did not change LH, T, or prolactin. Peak plasma levels of 254 +/- 18 ng cocaine/ml and 22.6 +/- 3.4 ng nicotine/ml were measured at 8 and 14 min, respectively. LH increased significantly after both i.v. cocaine and high nicotine cigarette smoking (P < 0.01). These LH increases were significantly correlated with increases in cocaine and nicotine plasma levels (P < 0.001-0.003), and high nicotine cigarette smoking stimulated significantly greater increases in LH release than i.v. cocaine (P < 0.05). Testosterone levels did not change significantly after either cocaine or after high nicotine cigarette smoking. After i.v. cocaine, prolactin decreased significantly and remained below baseline levels throughout the sampling period (P < 0.05-0.01). After high nicotine cigarette smoking, prolactin increased to hyperpro-lactinemic levels within 6 min and remained significantly above baseline levels for 42 min (P < 0.05-0.03). The rapid increases in LH and reports of subjective "high" after both i.v. cocaine and high nicotine cigarette smoking illustrate the similarities between these drugs and suggest a possible contribution of LH to their abuse-related effects.