The D-Lactate Dehydrogenase from Sporolactobacillus inulinus Also Possessing Reversible Deamination Activity

Hydroxyacid dehydrogenases are responsible for the conversion of 2-keto acids to 2-hydroxyacids and have a wide range of biotechnological applications. In this study, a D-lactate dehydrogenase (D-LDH) from a Sporolactobacillus inulinus strain was experimentally verified to have both the D-LDH and glutamate dehydrogenase (GDH) activities (reversible deamination). The catalytic mechanism was demonstrated by identification of key residues from the crystal structure analysis and site-directed mutagenesis. The Arg²³⁴ and Gly⁷⁹ residues of this enzyme play a significant role in both D-LDH and GDH activities. His²⁹⁵ and Phe²⁹⁸ in DLDH744 were identified to be key residues for lactate dehydrogenase (LDH) activity only whereas Tyr¹⁰¹ is a unique residue that is critical for GDH activity. Characterization of the biochemical properties contributes to understanding of the catalytic mechanism of this novel D-lactate dehydrogenase enzyme.     

A hybrid anaerobic solid-liquid bioreactor for food waste digestion

A hybrid anaerobic solid-liquid (HASL) bioreactor is an enhanced two-phase anaerobic system, that consists of a solid waste reactor as the acidification reactor and a wastewater reactor, i.e. an upflow anaerobic sludge blanket (UASB) reactor as the methanogenic reactor. Food waste digestion in HASL bioreactors with pre-acidification and HASL operation stages was investigated in two separate runs. After 8 days of pre-acidification in Run A and 4 days in Run B, total volatile fatty acid (TVFA) and chemical oxygen demand (COD) concentrations in the leachates of both acidification reactors were similar. During HASL operation stage, TVFA and COD removal in the methanogenic phase were 77–100% and 75–95%, respectively. Some 99% of the total methane generated was from the methanogenic phase with a content of 68–70% methane. At the end of operation, about 59–60% of the added volatile solids (VS) were removed with a methane yield of 0.25 l g^–1 VS.     

Single-cell landscape of the ecosystem in early-relapse hepatocellular carcinoma

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Negative regulation of AMPK signaling by high glucose via E3 ubiquitin ligase MG53

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Transplantation of Oligodendrocyte Precursor Cells Improves Locomotion Deficits in Rats with Spinal Cord Irradiation Injury

Demyelination contributes to the functional impairment of irradiation injured spinal cord. One potential therapeutic strategy involves replacing the myelin-forming cells. Here, we asked whether transplantation of Olig2⁺-GFP⁺-oligodendrocyte precursor cells (OPCs), which are derived from Olig2-GFP-mouse embryonic stem cells (mESCs), could enhance remyelination and functional recovery after spinal cord irradiation injury. We differentiated Olig2-GFP-mESCs into purified Olig2⁺-GFP⁺-OPCs and transplanted them into the rats’ cervical 4–5 dorsal spinal cord level at 4 months after irradiation injury. Eight weeks after transplantation, the Olig2⁺-GFP⁺-OPCs survived and integrated into the injured spinal cord. Immunofluorescence analysis showed that the grafted Olig2⁺-GFP⁺-OPCs primarily differentiated into adenomatous polyposis coli (APC⁺) oligodendrocytes (54.6±10.5%). The staining with luxol fast blue, hematoxylin & eosin (LFB/H&E) and electron microscopy demonstrated that the engrafted Olig2⁺-GFP⁺-OPCs attenuated the demyelination resulted from the irradiation. More importantly, the recovery of forelimb locomotor function was enhanced in animals receiving grafts of Olig2⁺-GFP⁺-OPCs. We concluded that OPC transplantation is a feasible therapy to repair the irradiated lesions in the central nervous system (CNS).     

Clonal Expansion of the Pseudogymnoascus destructans Genotype in North America Is Accompanied by Significant Variation in Phenotypic Expression

Pseudogymnoascus destructans is the causative agent of an emerging infectious disease that threatens populations of several North American bat species. The fungal disease was first observed in 2006 and has since caused the death of nearly six million bats. The disease, commonly known as white-nose syndrome, is characterized by a cutaneous infection with P. destructans causing erosions and ulcers in the skin of nose, ears and/or wings of bats. Previous studies based on sequences from eight loci have found that isolates of P. destructans from bats in the US all belong to one multilocus genotype. Using the same multilocus sequence typing method, we found that isolates from eastern and central Canada also had the same genotype as those from the US, consistent with the clonal expansion of P. destructans into Canada. However, our PCR fingerprinting revealed that among the 112 North American isolates we analyzed, three, all from Canada, showed minor genetic variation. Furthermore, we found significant variations among isolates in mycelial growth rate; the production of mycelial exudates; and pigment production and diffusion into agar media. These phenotypic differences were influenced by culture medium and incubation temperature, indicating significant variation in environmental condition - dependent phenotypic expression among isolates of the clonal P. destructans genotype in North America.     

Novel Inhibitors of Staphylococcus aureus Virulence Gene Expression and Biofilm Formation

Staphylococcus aureus is a major human pathogen and one of the more prominent pathogens causing biofilm related infections in clinic. Antibiotic resistance in S. aureus such as methicillin resistance is approaching an epidemic level. Antibiotic resistance is widespread among major human pathogens and poses a serious problem for public health. Conventional antibiotics are either bacteriostatic or bacteriocidal, leading to strong selection for antibiotic resistant pathogens. An alternative approach of inhibiting pathogen virulence without inhibiting bacterial growth may minimize the selection pressure for resistance. In previous studies, we identified a chemical series of low molecular weight compounds capable of inhibiting group A streptococcus virulence following this alternative anti-microbial approach. In the current study, we demonstrated that two analogs of this class of novel anti-virulence compounds also inhibited virulence gene expression of S. aureus and exhibited an inhibitory effect on S. aureus biofilm formation. This class of anti-virulence compounds could be a starting point for development of novel anti-microbial agents against S. aureus.     

In Vivo Residue-specific Histone Methylation Dynamics

Methylation of specific histone residues is capable of both gene activation and silencing. Despite vast work on the function of methylation, most studies either present a static snapshot of methylation or fail to assign kinetic information to specific residues. Using liquid chromatography-tandem mass spectrometry on a high-resolution mass spectrometer and heavy methyl-SILAC labeling, we studied site-specific histone lysine and arginine methylation dynamics. The detection of labeled intermediates within a methylation state revealed that mono-, di-, and trimethylated residues generally have progressively slower rates of formation. Furthermore, methylations associated with active genes have faster rates than methylations associated with silent genes. Finally, the presence of both an active and silencing mark on the same peptide results in a slower rate of methylation than the presence of either mark alone. Here we show that quantitative proteomic approaches such as this can determine the dynamics of multiple methylated residues, an understudied portion of histone biology.