Phosphorus and Nitrogen Drive the Seasonal Dynamics of Bacterial Communities in Pinus Forest Rhizospheric Soil of the Qinling Mountains.

The temporal distribution patterns of bacterial communities, as an important group in mountain soil, are affected by various environmental factors. To improve knowledge regarding the successional seasonal dynamics of the mountain soil bacterial communities, the rhizospheric soil of a 30-year-old natural secondary Pinus tabulaeformis forest, located in the high-altitude (1900 m a.s.l.) of the temperate Qinling Mountains, was sampled and studied during four different seasons. The bacterial community composition and structure in the rhizospheric soil were studied using an Illumina MiSeq Sequencing platform. Furthermore, the edaphic properties and soil enzymatic activities (urease, phosphatase, and catalase) were measured in order to identify the main impact factors on the soil bacterial community. According to the results, all of the edaphic properties and soil enzymatic activities were significantly affected by the seasonal changes, except for the C/N ratio. Although the biomasses of soil bacterial communities increased during the summer and autumn (warm seasons), their Shannon diversity and Pielou's evenness were decreased. Proteobacteria, Acidobacteria, Actinobacteria, Planctomycetes, and Bacteroidetes were the predominant bacterial groups in all of the soil samples, and the genera of Ktedonobacter, Sphingobium as well as an unclassified member of the Ktedonobacteria were the keystone taxa. The composition and structure of soil bacterial communities were strongly impacted by the edaphic properties, especially the temperature, moisture, ammoniacal nitrogen, available phosphorus and total phosphorus which were the crucial factors to drive the temporal distribution of the soil bacterial community and diversity. In conclusion, the soil temperature, moisture and the nutrients N and P were the crucial edaphic factors for shaping the rhizospheric soil bacterial communities as season and climate change in a P. tabulaeformis forest of Qinling Mountains.

Design and Use of a Low Cost, Automated Morbidostat for Adaptive Evolution of Bacteria Under Antibiotic Drug Selection.

We describe a low cost, configurable morbidostat for characterizing the evolutionary pathway of antibiotic resistance. The morbidostat is a bacterial culture device that continuously monitors bacterial growth and dynamically adjusts the drug concentration to constantly challenge the bacteria as they evolve to acquire drug resistance. The device features a working volume of ~10 ml and is fully automated and equipped with optical density measurement and micro-pumps for medium and drug delivery. To validate the platform, we measured the stepwise acquisition of trimethoprim resistance in Escherichia coli MG 1655, and integrated the device with a multiplexed microfluidic platform to investigate cell morphology and antibiotic susceptibility. The approach can be up-scaled to laboratory studies of antibiotic drug resistance, and is extendible to adaptive evolution for strain improvements in metabolic engineering and other bacterial culture experiments.

The interrelationship between cholinergic pathway in the magnocellular paraventricular nucleus and natriuresis.

The central nervous system is known to play important roles in the regulation of renal sodium excretion. The present study was designed to reveal the interrelationship between cholinergic pathway in the magnocellular paraventricular nucleus (PVN) and the natriuresis induced by brain cholinergic stimuli. The results indicated that urinary sodium excretion was significantly increased at 40 min after intracerebroventricular (ICV) injection of carbachol (CBC). Immunohistochemical studies showed that CBC increased choline acetyltransferase-immunoreactivity (ChAT-IR) in the magnocellular PVN and renal proximal convoluted tubule (PCT), respectively. After pretreatment with atropine, urinary sodium excretion was significantly reduced, and carbachol-increased ChAT-IR in the magnocellular PVN and PCT was also significantly decreased. These results suggested that brain cholinergic stimuli induced the natriuresis and increased the activity of cholinergic neurons in the magnocellular PVN and cholinergic system in the PCT. The blockade of muscarinic receptor completely abolished the natriuresis and partially inhibited carbachol-exerted stimulatory effects in the magnocellular PVN and PCT. To summarize, brain cholinergic pathway and peripheral cholinergic system in kidney were found to contribute to the natriuresis following brain cholinergic stimulation. Our findings revealed novel evidence that PVN was involved in the natriuresis via humoral mechanisms.

Trimethylated chitosan-conjugated PLGA nanoparticles for the delivery of drugs to the brain.

Trimethylated chitosan (TMC) surface-modified poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles (TMC/PLGA-NP) were synthesized as a drug carrier for brain delivery. TMC was covalently coupled to the surface of PLGA nanoparticles (PLGA-NP) via a carbodiimide-mediated link. The zeta potential of TMC/PLGA-NP was about 20mV with a mean diameter around 150nm. 6-coumarin loaded PLGA-NP and TMC/PLGA-NP were injected into the caudal vein of mice, and fluorescent microscopy of brain sections showed a higher accumulation of TMC/PLGA-NP in the cortex, paracoele, the third ventricle and choroid plexus epithelium, while no brain uptake of PLGA-NP was observed. There was no pronounced difference in cell viability between TMC/PLGA-NP and PLGA-NP as shown by MTT assay. Behavioral testing showed that the injection of coenzyme Q(10) loaded TMC/PLGA-NP greatly improved memory impairment, restoring it to a normal level, but the efficacy was slight for loaded PLGA-NP, without TMC conjugation. The senile plaque and biochemical parameter tests confirmed the brain-targeted effects of TMC/PLGA-NP. These experiments show that TMC surface-modified nanoparticles are able to cross the blood-brain barrier and appear to be a promising brain drug delivery carrier with low toxicity.