Biochemical and Biophysical Investigations of Non-Zinc Dependent Glyoxalase I Enzymes

The principal methylglyoxal (MG)-detoxifying system in most living organisms is the two metalloenzyme Glyoxalase system. Glyoxalase I (GlxI) initially converts the non-enzymatically formed MG-GSH hemithioacetal to the thioester S,D-lactoylglutathione. The hydrolase, Glyoxalase II(GlxII) regenerates GSH and liberates the product D-lactate. Ni2+/Co2+- and Zn2+-activated GlxI enzymes exist in nature. The Ni2+/Co2+-activated GlxI are not active as Zn2+-holoenzymes in spite of the structural similarities to the Zn2+-dependent enzymes. The Zn2+-GlxI enzymes have been investigated heavily relative to the Ni2+/Co2+-activated enzymes, which have been isolated more recently. As part of this study the three GlxI homologs isolated from Pseudomonas aeruginosa were characterized. The homologous genes encode GlxI enzymes of both metal activation type. The Zn2+-activated P. aeruginosa GlxI is difficult to de-metallate compared to the Ni2+/Co2+-activated enzymesreflecting a difference in metal-binding/insertion between the two types of GlxI. The E. coli GlxII was isolated and characterized to determine whether Ni2+/Co2+-activation is a characteristic of the Glx system as a whole in this organism. Inductively coupled plasma mass spectrometry on purified E. coli GlxII confirms that the active protein is a binuclear Zn2+-metalloenzyme. The results to date indicate a detectable isotope effect for the Cd2+-holoenzyme but not the Ni2+-reconstituted enzyme. Chemical crosslinking experiments indicate that the SlyD Ni2+ metallochaperone does not form a complex with E.coli GlxI. This indicates that the E. coli active site is not metallated in vivo by this accessory protein. The principal biophysical experiment in this project was determining of Ni2+-binding stoichiometry for E. coli GlxI by 1H-15N heteronuclear single quantum coherence (HSQC) NMR. The GlxI dimer reorganization ceases when the metal:dimer stoichiometry reaches 0.5 during apoenzyme titration. This finding supports previous studies that indicate half-of-the-sites metal binding in this enzyme

Bioavailability of Macro and Micronutrients Across Global Topsoils: Main Drivers and Global Change Impacts

Understanding the chemical composition of our planet\u27s crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro- and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome-dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling-atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world

Keeping the microbiology lab alive: essential microbiology lab skill development in the wake of COVID-19

NAThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Finding the silver lining during a global pandemic: opportunities for curriculum innovation in microbiology education

N/AThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Bioavailability of macro and micronutrients across global topsoils:Main drivers and global change impacts

Understanding the chemical composition of our planet's crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro‐ and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome‐dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling‐atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world