Studies of magnesium and manganese interactions with gluconate and 1,5-gluconolactone

Metabolomic and cultivation insights into the tolerance of the spacecraft-associated Acinetobacter toward Kleenol 30, a cleanroom floor detergent

Introduction

Stringent cleaning procedures during spacecraft assembly are critical to maintaining the integrity of life-detection missions. To ensure cleanliness, NASA spacecraft are assembled in cleanroom facilities, where floors are routinely cleansed with Kleenol 30 (K30), an alkaline detergent.

Methods

Through metabolomic and cultivation approaches, we show that cultures of spacecraft-associated Acinetobacter tolerate up to 1% v/v K30 and are fully inhibited at ≥2%; in comparison, NASA cleanrooms are cleansed with ~0.8-1.6% K30.

Results

For A. johnsonii 2P08AA (isolated from a cleanroom floor), cultivations with 0.1% v/v K30 yield (1) no changes in cell density at late-log phase, (2) modest decreases in growth rate (~17%), (3) negligible lag phase times, (4) limited changes in the intracellular metabolome, and (5) increases in extracellular sugar acids, monosaccharides, organic acids, and fatty acids. For A. radioresistens 50v1 (isolated from a spacecraft surface), cultivations yield (1) ~50% survivals, (2) no changes in growth rate, (3) ~70% decreases in the lag phase time, (4) differential changes in intracellular amino acids, compatible solutes, nucleotide-related metabolites, dicarboxylic acids, and saturated fatty acids, and (5) substantial yet differential impacts to extracellular sugar acids, monosaccharides, and organic acids.

Discussion

These combined results suggest that (1) K30 manifests strain-dependent impacts on the intracellular metabolomes, cultivation kinetics, and survivals, (2) K30 influences extracellular trace element acquisition in both strains, and (3) K30 is better tolerated by the floor-associated strain. Hence, this work lends support towards the hypothesis that repeated cleansing during spacecraft assembly serve as selective pressures that promote tolerances towards the cleaning conditions.

Magnesium(II) d-Gluconate Complexes Relevant to Radioactive Waste Disposals: Metal-Ion-Induced Ligand Deprotonation or Ligand-Promoted Metal-Ion Hydrolysis?

The complexation equilibria between Mg2+ and d-gluconate (Gluc-) ions are of particular importance in modeling the chemical speciation in low- and intermediate-level radioactive waste repositories. NMR measurements and potentiometric titrations conducted at 25 °C and 4 M ionic strength revealed the formation of the MgGluc+, MgGlucOH0, MgGluc(OH)2-, and Mg3Gluc2(OH)40 complexes. The trinuclear species provides indirect evidence for the existence of multinuclear magnesium(II) hydroxido complexes, whose formation was proposed earlier but has not been confirmed yet. Additionally, speciation calculations demonstrated that MgCl2 can markedly decrease the solubility of thorium(IV) at low ligand concentrations. Regarding the structure of MgGluc+, both IR spectra and density functional theory (DFT) calculations indicate the monodentate coordination of Gluc-. By the potentiometric data, the acidity of the water molecules is higher in the MgGluc+ and MgGlucOH0 species than in the Mg(H2O)62+ aqua ion. On the basis of DFT calculations, this ligand-promoted hydrolysis is caused by strong hydrogen bonds forming between Gluc- and Mg(H2O)62+. Conversely, metal-ion-induced ligand deprotonation takes place in the case of calcium(II) complexes, giving rise to salient variations on the NMR spectra in a strongly alkaline medium.

Solid-state hydrolysis of cellulose and methyl α- and β-d-glucopyranosides in presence of magnesium chloride

Solid-state hydrolysis proceeded with cellulose and methyl alpha- and beta-D-glucopyranosides in the presence of hydrated magnesium chloride. This reaction was effective even at >100 degrees C since the hydrated water, which is held by MgCl(2) up to >200 degrees C, is utilized as a nucleophile. Excess water made this reaction ineffective due to the competition between water and sugar oxygen atoms in coordinating with Mg(2+), a Lewis acid. Consequently, this hydrolysis reaction is characteristic of solid-state reactions.

Sugar interaction with metals in aqueous solution: indirect determination from infrared and direct determination from nuclear magnetic resonance spectroscopy

In this article, mid-infrared Fourier transform (Mid-FT-IR) and carbon thirteen nuclear magnetic resonance (13C NMR) spectroscopy have been used to determine possible interactions between sucrose and various alkali or alkaline earth metals in aqueous solution. In the presence of these metals, significant shifts in the absorption bands of sucrose were noted by mid-FT-IR coupled with principal component analysis (PCA). These shifts were explained on the basis of weakening of the H-bond network between sucrose and water and possible interactions between sucrose and the metal ion. Factorial maps were established and the spectral patterns obtained show that these interactions vary according to the nature of the metal ion. 13C NMR analysis showed that the carbon atoms of sucrose undergo shielding or deshielding in the presence of metal ions in aqueous solutions. Two factors were invoked to account for the variation of chemical shifts: the rupture of hydrogen bonds due to hydration of the metal ion and the possible coordination of the metal ion to the oxygen atoms of sucrose.