The catabolism of lignin-derived p-methoxylated aromatic compounds by Rhodococcus jostii RHA1

Emergent strategies to valorize lignin, an abundant but underutilized aromatic biopolymer, include tandem processes that integrate chemical depolymerization and biological catalysis. To date, aromatic monomers from C-O bond cleavage of lignin have been converted to bioproducts, but the presence of recalcitrant C-C bonds in lignin limits the product yield. A promising chemocatalytic strategy that overcomes this limitation involves phenol methyl protection and autoxidation. Incorporating this into a tandem process requires microbial cell factories able to transform the p-methoxylated products in the resulting methylated lignin stream. In this study, we assessed the ability of Rhodococcus jostii RHA1 to catabolize the major aromatic products in a methylated lignin stream and elucidated the pathways responsible for this catabolism. RHA1 grew on a methylated pine lignin stream, catabolizing the major aromatic monomers: p-methoxybenzoate (p-MBA), veratrate, and veratraldehyde. Bioinformatic analyses suggested that a cytochrome P450, PbdA, and its cognate reductase, PbdB, are involved in p-MBA catabolism. Gene deletion studies established that both pbdA and pbdB are essential for growth on p-MBA and several derivatives. Furthermore, a deletion mutant of a candidate p-hydroxybenzoate (p-HBA) hydroxylase, ΔpobA, did not grow on p-HBA. Veratraldehyde and veratrate catabolism required both vanillin dehydrogenase (Vdh) and vanillate O-demethylase (VanAB), revealing previously unknown roles of these enzymes. Finally, a ΔpcaL strain grew on neither p-MBA nor veratrate, indicating they are catabolized through the β-ketoadipate pathway. This study expands our understanding of the bacterial catabolism of aromatic compounds and facilitates the development of biocatalysts for lignin valorization.IMPORTANCELignin, an abundant aromatic polymer found in plant biomass, is a promising renewable replacement for fossil fuels as a feedstock for the chemical industry. Strategies for upgrading lignin include processes that couple the catalytic fractionation of biomass and biocatalytic transformation of the resulting aromatic compounds with a microbial cell factory. Engineering microbial cell factories for this biocatalysis requires characterization of bacterial pathways involved in catabolizing lignin-derived aromatic compounds. This study identifies new pathways for lignin-derived aromatic degradation in Rhodococcus, a genus of bacteria well suited for biocatalysis. Additionally, we describe previously unknown activities of characterized enzymes on lignin-derived compounds, expanding their utility. This work advances the development of strategies to replace fossil fuel-based feedstocks with sustainable alternatives.

An indigenous Saccharomyces uvarum population with high genetic diversity dominates uninoculated Chardonnay fermentations at a Canadian winery

Saccharomyces cerevisiae is the primary yeast species responsible for most fermentations in winemaking. However, other yeasts, including Saccharomyces uvarum, have occasionally been found conducting commercial fermentations around the world. S. uvarum is typically associated with white wine fermentations in cool-climate wine regions, and has been identified as the dominant yeast in fermentations from France, Hungary, northern Italy, and, recently, Canada. However, little is known about how the origin and genetic diversity of the Canadian S. uvarum population relates to strains from other parts of the world. In this study, a highly diverse S. uvarum population was found dominating uninoculated commercial fermentations of Chardonnay grapes sourced from two different vineyards. Most of the strains identified were found to be genetically distinct from S. uvarum strains isolated globally. Of the 106 strains of S. uvarum identified in this study, four played a dominant role in the fermentations, with some strains predominating in the fermentations from one vineyard over the other. Furthermore, two of these dominant strains were previously identified as dominant strains in uninoculated Chardonnay fermentations at the same winery two years earlier, suggesting the presence of a winery-resident population of indigenous S. uvarum. This research provides valuable insight into the diversity and persistence of non-commercial S. uvarum strains in North America, and a stepping stone for future work into the enological potential of an alternative Saccharomyces yeast species.

Increased glycosylation of human lens epithelial basement membrane in diabetes mellitus

We studied the nonenzymatic glycosylation of lens epithelial basement membranes (LEBM) of senile cataractous lenses of both diabetic and nondiabetic patients. The human LEBMs were isolated from surgically removed senile cataracts and purified by osmotic lysis and detergent treatments. Glycosylation assay of LEBMs was done using the colorimetric method of Flückiger and Winterhalter. The glycosylation value ranged from 16.39 to 92.56 n mol/mg protein overall, with a mean of 63.54 +/- 24.56 n mol/mg protein for the diabetic specimens and a mean of 29.97 +/- 14.48 n mol/mg protein for the nondiabetic controls (P = 0.009). The study confirms our previous observation of in vivo glycosylation of the LEBM and further establishes that diabetic patients have a twofold increase in the amount of LEBM glycosylation when compared to their nondiabetic counterparts.

The somatostatin receptors SSTR1 and SSTR2 are coupled to inhibition of adenylyl cyclase in Chinese hamster ovary cells via pertussis toxin-sensitive pathways

Somatostatin exerts multiple effects throughout the body by binding to specific somatostatin receptors. Two classes of somatostatin receptors, SRIF1 and SRIF2, have been distinguished biochemically and pharmacologically. Two cDNAs have been recently isolated that encode somatostatin receptors 1 and 2 (SSTR1 and SSTR2, respectively). The pharmacological characteristics of receptors expressing these cDNAs resemble those of the SRIF2 and SRIF1 classes of somatostatin receptors, respectively. We stably expressed the rat homologs of both receptors in Chinese hamster ovary (CHO) cells (type K1). These transfected cell lines recognized the endogenous ligands SS14 and SS28 with high affinity, whereas the synthetic analog MK678 identified only SSTR2. In preparations of CHO-SSTR1 or CHO-SSTR2 cells, SS14 and SS28 inhibited forskolin-stimulated adenylyl cyclase activity by approximately 35%, with ED50 values in the nanomolar range. The adenylyl cyclase inhibition was dependent upon the guanine nucleotide GTP and could be ablated with pertussis toxin preincubation. The present data indicate that SSTR1 and SSTR2 are coupled to inhibition of adenylyl cyclase via pertussis toxin- sensitive G-proteins.

The effect of a diuretic (hydrochlorothiazide) on tear production in humans

The effect of an orally administered diuretic, hydrochlorothiazide, on tear production in 11 normal young human subjects (five men and six women, 18 to 35 years old) was measured in a single-masked study. Schirmer tests with topical anesthetic showed a significant (P = .02) decrease in basal aqueous tear production on days when these subjects were taking the diuretic. The average decrease was 2.1 mm of wetting in five minutes.

Glycosylation in vivo of human lens capsule (basement membrane) and diabetes mellitus

Glycosylation represents a nonenzymatic posttranslational modification of some proteins in vivo. We have investigated possible glycosylation, in vivo, of human lens capsule (basement membrane of lens epithelium) using a colorimetric method. Our study reveals, for the first time, in vivo glycosylation of human lens capsule. Furthermore, the glycosylation of the lens capsule in the diabetics (57.30 +/- 11.26 n moles/mg. protein) is found to be significantly greater than that in their nondiabetic counterparts (29.11 +/- 4.90 n moles/mg. protein) (p less than 0.0005). The present observation represents the first example of increased glycosylation of a basement membrane in the diabetic patients as compared to the nondiabetic controls.

Enhanced NE uptake by isolated hypothalamic storage vesicles of hypertensive rats

The in vitro uptake of 3H-NE by storage vesicles from the hypothalamus of age-matched spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats has been studied using a new reliable procedure for the isolation of biochemically active storage vesicles. In each of 13 paired studies, done in triplicate, storage vesicles of SHR took up more 3H-NE than those of WKY. (The mean difference was 37% more uptake by SHR.) Electron-microscopic examination of normotensive samples showed a concentration of intact synaptic vesicles; whereas SHR subfractions were composed of fragmented membranes that resembled swollen, distorted vesicles. These findings in the brain tissues of SHR parallel our previous results found in SHR peripheral tissues. Taken together, we interpret the results to indicate that the membranes of synaptic vesicles of SHR are altered structurally and biochemically.