Ethanol production at 45 °C by Kluyveromyces marxianus IMB3 during growth on molasses pre-treated with Amberlite® and non-living biomass

The use of high concentrations of molasses as a fermentation feed-stock for ethanol production is normally precluded by the presence of inhibitory compounds. Use of the thermotolerant, ethanol-producing yeast strain Kluyveromyces marxianus IMB3 in fermentations containing high concentrations of molasses resulted in sub-optimal production of ethanol. The results suggested that this was caused by the presence of inhibitory materials rather than an intolerance to increased concentrations of ethanol. In the current study we describe the pretreatment of molasses preparations with either an Amberlite^® monobed mixed ion-exchange resin or non-living microbial biomass from a local distillery. In the study molasses samples diluted to yield a final sugar concentration of 160?g/l were used as the substrate. Control fermentations using the untreated molasses dilutions yielded a maximum ethanol concentration of 40?g/l, representing 49% of the maximum theoretical yield. Fermentations using molasses samples pre-treated with Amberlite^® or non-living biomass yielded maximum ethanol concentrations of 58 and 54?g/l, representing 71 and 66% of the maximum theoretical yield, respectively. The results suggest that pre-treatment brings about removal of toxic or inhibitory materials from the fermentation feed-stock and we believe that such pre-treatments, particularly using the less expensive non-living biomass preparations may find a role in processes concerned with the commercial production of ethanol from molasses using this microorganism.     

A review on coumarins as acetylcholinesterase inhibitors for Alzheimer's disease

Acetylcholinesterase (AChE) enzyme inhibition is an important target for the management of Alzheimer disease (AD) and AChE inhibitors are the main stay drugs for its management. Coumarins are the phytochemicals with wide range of biological activities including AChE inhibition. The scientists have attempted to explore the coumarin template for synthesizing novel AChE inhibitors with additional pharmacological activities including decrease in beta-amyloid (Aβ) deposition and beta-secretase inhibition that are also important for AD management. Most of the designed schemes have involved incorporation of a catalytic site interacting moiety at 3- and 4-positions of the coumarin ring. The present review describes these differently synthesized coumarin derivatives as AChE inhibitors for management of AD.     

rigrag: high-resolution mapping of genic targeting preferences during HIV-1 integration in vitro and in vivo

HIV-1 integration favors recurrent integration gene (RIG) targets and genic proviruses can confer cell survival in vivo. However, the relationship between initial RIG integrants and how these evolve in patients over time are unknown. To address these shortcomings, we built phenomenological models of random integration in silico, which were used to identify 3718 RIGs as well as 2150 recurrent avoided genes from 1.7 million integration sites across 10 in vitro datasets. Despite RIGs comprising only 13% of human genes, they harbored 70% of genic HIV-1 integrations across in vitro and patient-derived datasets. Although previously reported to associate with super-enhancers, RIGs tracked more strongly with speckle-associated domains. While depletion of the integrase cofactor LEDGF/p75 significantly reduced recurrent HIV-1 integration in vitro, LEDGF/p75 primarily occupied non-speckle-associated regions of chromatin, suggesting a previously unappreciated dynamic aspect of LEDGF/p75 functionality in HIV-1 integration targeting. Finally, we identified only six genes from patient samples—BACH2, STAT5B, MKL1, MKL2, IL2RB and MDC1—that displayed enriched integration targeting frequencies and harbored proviruses that likely contributed to cell survival. Thus, despite the known preference of HIV-1 to target cancer-related genes for integration, we conclude that genic proviruses play a limited role to directly affect cell proliferation in vivo.     

Phosphorylation of Enoyl-Acyl Carrier Protein Reductase InhA Impacts Mycobacterial Growth and Survival

InhA, the primary target for the first line anti-tuberculosis drug isoniazid, is a key enzyme of the fatty-acid synthase II system involved in mycolic acid biosynthesis in Mycobacterium tuberculosis. In this study, we show that InhA is a substrate for mycobacterial serine/threonine protein kinases. Using a novel approach to validate phosphorylation of a substrate by multiple kinases in a surrogate host (Escherichia coli), we have demonstrated efficient phosphorylation of InhA by PknA, PknB, and PknH, and to a lower extent by PknF. Additionally, the sites targeted by PknA/PknB have been identified and shown to be predominantly located at the C terminus of InhA. Results demonstrate in vivo phosphorylation of InhA in mycobacteria and validate Thr-266 as one of the key sites of phosphorylation. Significantly, our studies reveal that the phosphorylation of InhA by kinases modulates its biochemical activity, with phosphorylation resulting in decreased enzymatic activity. Co-expression of kinase and InhA alters the growth dynamics of Mycobacterium smegmatis, suggesting that InhA phosphorylation in vivo is an important event in regulating its activity. An InhA-T266E mutant, which mimics constitutive phosphorylation, is unable to rescue an M. smegmatis conditional inhA gene replacement mutant, emphasizing the critical role of Thr-266 in mediating post-translational regulation of InhA activity. The involvement of various serine/threonine kinases in modulating the activity of a number of enzymes of the mycolic acid synthesis pathway, including InhA, accentuates the intricacies of mycobacterial signaling networks in parallel with the changing environment.     

Evolutionary constraint on low elevation range expansion: Defense‐abiotic stress‐tolerance trade‐off in crosses of the ecological model Boechera stricta

Most transplant experiments across species geographic range boundaries indicate that adaptation to stressful environments outside the range is often constrained. However, the mechanisms of these constraints remain poorly understood. We used extended generation crosses from diverged high and low elevation populations. In experiments across low elevation range boundaries, there was selection on the parental lines for abiotic stress‐tolerance and resistance to herbivores. However, in support of a defense‐tolerance trade‐off, extended generation crosses showed nonindependent segregation of these traits in the laboratory across a drought‐stress gradient and in the field across the low elevation range boundary. Genotypic variation in a marker from a region of the genome containing a candidate gene (MYC2) was associated with change in the genetic trade‐off. Thus, using crosses and forward genetics, we found experimental genetic and molecular evidence for a pleiotropic trade‐off that could constrain the evolution of range expansion.     

Phenotype and growth behavior of residual β-catenin-positive hepatocytes in livers of β-catenin-deficient mice

Signaling through the Wnt/β-catenin pathway is a crucial determinant of hepatic zonal gene expression, liver development, regeneration, and tumorigenesis. Transgenic mice with hepatocyte-specific knockout of Ctnnb1 (encoding β-catenin) have proven their usefulness in elucidating these processes. We now found that a small number of hepatocytes escape the Cre-mediated gene knockout in that mouse model. The remaining β-catenin-positive hepatocytes showed approximately 25% higher cell volumes compared to the β-catenin-negative cells and exhibited a marker protein expression profile similar to that of normal perivenous hepatocytes or hepatoma cells with mutationally activated β-catenin. Surprisingly, the expression pattern was observed independent of the cell's position within the liver lobule, suggesting a malfunction of physiological periportal repression of perivenously expressed genes in β-catenin-deficient liver. Clusters of β-catenin-expressing hepatocytes lacked expression of the gap junction proteins Connexin 26 and 32. Nonetheless, β-catenin-positive hepatocytes had no striking proliferative advantage, but started to grow out on treatment with phenobarbital, a tumor-promoting agent known to facilitate the formation of mouse liver adenoma with activating mutations of Ctnnb1. Progressive re-population of Ctnnb1 knockout livers with wild-type hepatocytes was seen in aged mice with a pre-cirrhotic phenotype. In these large clusters of β-catenin-expressing hepatocytes, perivenous-specific gene expression was re-established. In summary, our data demonstrate that the zone-specificity of a hepatocyte's gene expression profile is dependent on the presence of β-catenin, and that β-catenin provides a proliferative advantage to hepatocytes when promoted with phenobarbital, or in a pre-cirrhotic environment.