Characterization of an aspartate aminotransferase encoded by YPO0623 with frequent nonsense mutations in .

, the causative agent of plague, is a genetically monomorphic bacterial pathogen that evolved from approximately 7,400 years ago. We observed unusually frequent mutations in YPO0623, mostly resulting in protein translation termination, which implies a strong natural selection. These mutations were found in all phylogenetic lineages of , and there was no apparent pattern in the spatial distribution of the mutant strains.

Regulatory Functions of PurR in : Orchestrating Diverse Biological Activities.

The bacterium has developed various strategies to sense and respond to the complex stresses encountered during its transmission and pathogenic processes. PurR is a common transcriptional regulator of purine biosynthesis among microorganisms, and it modulates the transcription level of the operon to suppress the production of hypoxanthine nucleotide (IMP). This study aims to understand the functions and regulatory mechanisms of in .

Anti-inflammatory phenolics and phenylpropanoids from Praxelis clematidea.

Praxelis clematidea (Asteraceae) is a noxious invasive exotic plant in southern China, and it has caused great damage to ecological conditions and serious financial losses. In this study, four new phenolics (1, 2, 7, 8), and two new phenylpropanoids (3, 4), along with seventeen known compounds were separated and purified from the whole plant of P. clematidea.

Effect of iron salt type and dosing mode on Fenton-based pretreatment of rice straw for enzymatic hydrolysis.

Fenton-based processes with four different iron salts in two different dosing modes were used to pretreat rice straw (RS) samples to increase their enzymatic digestibility. The composition analysis shows that the RS sample pretreated by the dosing mode of iron salt adding into HO has a much lower hemicellulose content than that pretreated by the dosing mode of HO adding into iron salt, and the RS sample pretreated by the chloride salt-based Fenton process has a much lower lignin content and a slightly lower hemicellulose content than that pretreated by the sulphate salt-based Fenton process. The higher concentration of reducing sugar observed on the RS sample with lower lignin and hemicellulose contents justifies that the Fenton-based process could enhance the enzymic hydrolysis of RS by removing hemicellulose and lignin and increasing its accessibility to cellulase.

Ultrasound-assisted alkaline pretreatment for enhancing the enzymatic hydrolysis of rice straw by using the heat energy dissipated from ultrasonication.

Rice straw samples were exposed to ultrasound-assisted alkaline (NaOH) pretreatment by using the heat energy dissipated from ultrasonication to increase their enzymatic digestibility for saccharification. The characterization shows that the pretreatment could selectively remove lignin and hemicellulose without degrading cellulose, and increase porosity and surface area of rice straw. The porosity, surface area and cellulose content of rice straw increased with the increasing concentration of NaOH used.

Pretreatment of rice straw by ultrasound-assisted Fenton process.

Fenton's reagent, ultrasound, and the combination of Fenton's reagent and ultrasound were used to pretreat rice straw (RS) to increase its enzymatic digestibility for saccharification. The characterization shows that compared with ultrasound, Fenton's reagent pretreatment was more efficient in increasing the specific surface area and decreasing the degree of polymerization (DP) of RS. The enzymatic hydrolysis results showed that the RS pretreated by ultrasound-assisted Fenton's reagent (U/F-RS), which exhibited the largest specific surface area and the lowest DP value, had the highest enzymatic activity, and the amount of reducing sugar released from U/F-RS at 48h of enzymatic saccharification is about 4 times as large as that from raw RS and 1.