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1. Cyanobacteria from marine oxygen-deficient zones encode both form I and form II Rubiscos

   https://doi.org/10.1073/pnas.2418345121  

   Jaffe, Alexander L; Harrison, Kaitlin; Wang, Renée Z; Taylor-Kearney, Leah J; Jain, Navami; Prywes, Noam; Shih, Patrick M; Young, Jodi; Rocap, Gabrielle; Dekas, Anne E (November 2024, Proceedings of the National Academy of Sciences)

   Cyanobacteria are highly abundant in the marine photic zone and primary drivers of the conversion of inorganic carbon into biomass. To date, all studied cyanobacterial lineages encode carbon fixation machinery relying upon form I Rubiscos within a CO₂-concentrating carboxysome. Here, we report that the uncultivated anoxic marine zone (AMZ) IB lineage of Prochlorococcus from pelagic oxygen-deficient zones (ODZs) harbors both form I and form II Rubiscos, the latter of which are typically noncarboxysomal and possess biochemical properties tuned toward low-oxygen environments. We demonstrate that these cyanobacterial form II enzymes are functional in vitro and were likely acquired from proteobacteria. Metagenomic analysis reveals that AMZ IB are essentially restricted to ODZs in the Eastern Pacific, suggesting that form II acquisition may confer an advantage under low-O₂conditions. AMZ IB populations express both forms of Rubisco in situ, with the highest form II expression at depths where oxygen and light are low, possibly as a mechanism to increase the efficiency of photoautotrophy under energy limitation. Our findings expand the diversity of carbon fixation configurations in the microbial world and may have implications for carbon sequestration in natural and engineered systems. 

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2. Diverse Coordination Geometries Derived from Trisaminocyclohexane Ligands with Appended Outer‐Sphere Hydrogen Bond Donors

   https://doi.org/10.1002/ejic.202300434  

   Ekanayake, Danushka M.; Sheridan, Patrick E.; Lindeman, Sergey V.; Fiedler, Adam T. (November 2023, European Journal of Inorganic Chemistry)

   Abstract With the aim of constructing hydrogen‐bonding networks in synthetic complexes, two new ligands derived fromcis,cis‐1,3,5‐triaminocyclohexane (TACH) have been prepared that feature pendant pyrrole or indole rings as outer‐sphere H‐bond donors. The TACH framework offers a facial arrangement of threeN‐donors, thereby mimicking common coordination motifs in the active sites of nonheme Fe and Cu enzymes. X‐ray structural characterization of a series of Cu^I‐X complexes (X=F, Cl, Br, NCS) revealed that these neutral ligands (H₃L^R, R=pyrrole or indole) coordinate in the intended facialN₃manner, yielding four‐coordinate complexes with idealizedC₃symmetry. The N−H units of the outer‐sphere heterocycles form a hydrogen‐bonding cavity around the axial (pseudo)halide ligand, as verified by crystallographic, spectroscopic, and computational analyses. Treatment of H₃L^pyrroleand H₃L^indolewith divalent transition metal chlorides (M^IICl₂, M=Fe, Cu, Zn) causes one heterocycle to deprotonate and coordinate to the M(II) center, giving rise to tetradentate ligands with two remaining outer‐sphere H‐bond donors. Further ligand deprotonation is observed upon reaction with Ni(II) and Cu(II) salts with weakly coordinating counteranions. The reported complexes highlight the versatility of TACH‐based ligands with pendant H‐bond donors, as the resulting scaffolds can support multiple protonation states, coordination geometries, and H‐bonding interactions. 

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3. Overexpression of RuBisCO form I and II genes in Rhodopseudomonas palustris TIE-1 augments polyhydroxyalkanoate production heterotrophically and autotrophically

   https://doi.org/10.1128/aem.01438-24  

   Ranaivoarisoa, Tahina Onina; Bai, Wei; Karthikeyan, Rengasamy; Steele, Hope; Silberman, Miriam; Olabode, Jennifer; Conners, Eric; Gallagher, Brian; Bose, Arpita (September 2024, Applied and Environmental Microbiology)

   Reguera, Gemma (Ed.)

   ABSTRACT With the rising demand for sustainable renewable resources, microorganisms capable of producing bioproducts such as bioplastics are attractive. While many bioproduction systems are well-studied in model organisms, investigating non-model organisms is essential to expand the field and utilize metabolically versatile strains. This investigation centers onRhodopseudomonas palustrisTIE-1, a purple non-sulfur bacterium capable of producing bioplastics. To increase bioplastic production, genes encoding the putative regulatory protein PhaR and the depolymerase PhaZ of the polyhydroxyalkanoate (PHA) biosynthesis pathway were deleted. Genes associated with pathways that might compete with PHA production, specifically those linked to glycogen production and nitrogen fixation, were deleted. Additionally, RuBisCO form I and II genes were integrated into TIE-1’s genome by a phage integration system, developed in this study. Our results show that deletion ofphaRincreases PHA production when TIE-1 is grown photoheterotrophically with butyrate and ammonium chloride (NH₄Cl). Mutants unable to produce glycogen or fix nitrogen show increased PHA production under photoautotrophic growth with hydrogen and NH₄Cl. The most significant increase in PHA production was observed when RuBisCO form I and form I & II genes were overexpressed, five times under photoheterotrophy with butyrate, two times with hydrogen and NH₄Cl, and two times under photoelectrotrophic growth with N₂. In summary, inserting copies of RuBisCO genes into the TIE-1 genome is a more effective strategy than deleting competing pathways to increase PHA production in TIE-1. The successful use of the phage integration system opens numerous opportunities for synthetic biology in TIE-1.IMPORTANCEOur planet has been burdened by pollution resulting from the extensive use of petroleum-derived plastics for the last few decades. Since the discovery of biodegradable plastic alternatives, concerted efforts have been made to enhance their bioproduction. The versatile microorganismRhodopseudomonas palustrisTIE-1 (TIE-1) stands out as a promising candidate for bioplastic synthesis, owing to its ability to use multiple electron sources, fix the greenhouse gas CO₂, and use light as an energy source. Two categories of strains were meticulously designed from the TIE-1 wild-type to augment the production of polyhydroxyalkanoate (PHA), one such bioplastic produced. The first group includes mutants carrying a deletion of thephaRorphaZgenes in the PHA pathway, and those lacking potential competitive carbon and energy sinks to the PHA pathway (namely, glycogen biosynthesis and nitrogen fixation). The second group comprises TIE-1 strains that overexpress RuBisCO form I or form I & II genes inserted via a phage integration system. By studying numerous metabolic mutants and overexpression strains, we conclude that genetic modifications in the environmental microbe TIE-1 can improve PHA production. When combined with other approaches (such as reactor design, use of microbial consortia, and different feedstocks), genetic and metabolic manipulations of purple nonsulfur bacteria like TIE-1 are essential for replacing petroleum-derived plastics with biodegradable plastics like PHA. 

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4. Eu(II)‐Based Quaternary Chalcogenides with Noncentrosymmetric Structures Stabilized by Site Disorder of d10 Metal Cations

   https://doi.org/10.1002/zaac.202500041  

   Jana, Subhendu; Gabilondo, Eric A; Mongkhonratanachai, Machima; Halasyamani, P Shiv; Maggard, Paul A (June 2025, Zeitschrift für anorganische und allgemeine Chemie)

   Quaternary metal‐chalcogenides combining rare‐earth cations with late transition metal cations are attracting growing attention for their optical properties, such as for solar energy conversion or second harmonic generation. Synthetic explorations of theII₃‐I₂‐IV₂‐Ch₈family (II = Eu;I = Cu or Ag;IV = Si, Ch = S or Se) have yielded Eu₃Ag₂Si₂S₈(1) and Eu₃Cu_1.08(1)Si_2.42(1)Se₈(2). Their structures have been characterized by X‐ray diffraction to form in the noncentrosymmetric space groupI3dand to exhibit two distinct types of mixed‐site occupancies, for the Ag(I) cations in1and mixed Cu(I)/Si(IV) cations in2. In both, the cation disorder occurs to achieve charge balancing with the chalcogenide anions. A high yield of1can be achievedwith optical measurements showing indirect and direct band transitions of ≈2.2(1) and ≈2.4(1) eV, respectively. Its second harmonic generation response is found to be relatively strong, approximately 0.9 × AgGaS₂, confirming its noncentrosymmetric structure. Band structure calculations reveal the valence and conduction band edges stem predominantly from the filled Ag(I)/Cu(I)‐based states and empty Si(IV)‐based states, respectively, with additional contributions from the chalcogenide anions. Calculation results also show that cation disorder facilitates a reduction in the antibonding interactions between the Ag(I)/Cu(I)d‐based and chalcogenidep‐based states. 

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5. Organo‐Functionalized Lacunary Double Cubane‐Type Oxometallates: Synthesis, Structure, and Properties of [(M ^II Cl) ₂ (V ^IV O) ₂ {((HOCH ₂ CH ₂ )(H)N(CH ₂ CH ₂ O))(HN(CH ₂ CH ₂ O) ₂ )} ₂ ] (M=Co, Zn)

   https://doi.org/10.1002/chem.202301389  

   Shuaib, Damola T.; Swenson, LaSalle; Kaduk, James A.; Chang, Tieyan; Chen, Yu‐Sheng; McNeely, James; Khan, M. Ishaque (October 2023, Chemistry – A European Journal)

   Abstract Organofunctionalized tetranuclear clusters [(M^IICl)₂(V^IVO)₂{((HOCH₂CH₂)(H)N(CH₂CH₂O))(HN(CH₂CH₂O)₂)}₂] (1, M=Co,2: M=Zn) containing an unprecedented oxometallacyclic {M₂V₂Cl₂N₄O₈} (M=Co, Zn) framework have been prepared by solvothermal reactions. The new oxo‐alkoxide compounds were fully characterized by spectroscopic methods, magnetic susceptibility measurement, DFT and ab initio computational methods, and complete single‐crystal X‐ray diffraction structure analysis. The isostructural clusters are formed of edge‐sharing octahedral {VO₅N} and trigonal bipyramidal {MO₃NCl} units. Diethanolamine ligates the bimetallic lacunary double cubane core of1and2in an unusual two‐mode fashion, unobserved previously. In the crystalline state, the clusters of1and2are joined by hydrogen bonds to form a three‐dimensional network structure. Magnetic susceptibility data indicate weakly antiferromagnetic interactions between the vanadium centers [J_iso(V^IV−V^IV)=−5.4(1); −3.9(2) cm⁻¹], and inequivalent antiferromagnetic interactions between the cobalt and vanadium centers [J_iso(V^IV−Co^II)=−12.6 and −7.5 cm⁻¹] contained in1. 

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