Whole-genome assembly of A02 bacteria involved in nitrogen fixation within cassava leaves.

The endophytic nitrogen (N)-fixing bacterium A02 belongs to the genus Curtobacterium (Curtobacterium sp.) and is crucial for the N metabolism of cassava ( Manihot esculenta Crantz). We isolated the A02 strain from cassava cultivar SC205 and used the 15N isotope dilution method to study the impacts of A02 on growth and accumulation of N in cassava seedlings. Furthermore, the whole genome was sequenced to determine the N-fixation mechanism of A02. Compared with low N control (T1), inoculation with the A02 strain (T2) showed the highest increase in leaf and root dry weight of cassava seedlings, and 120.3 nmol/(mL·h) was the highest nitrogenase activity recorded in leaves, which were considered the main site for colonization and N-fixation. The genome of A02 was 3,555,568 bp in size and contained a circular chromosome and a plasmid. Comparison with the genomes of other short bacilli revealed that strain A02 showed evolutionary proximity to the endophytic bacterium NS330 (Curtobacterium citreum) isolated from rice (Oryza sativa) in India. The genome of A02 contained 13 nitrogen fixation (nif) genes, including 4 nifB, 1 nifR3, 2 nifH, 1 nifU, 1 nifD, 1 nifK, 1 nifE, 1 nifN, and 1 nifC, and formed a relatively complete N fixation gene cluster 8-kb long that accounted for 0.22% of the whole genome length. The nifHDK of strain A02 (Curtobacterium sp.) is identical to the Frankia alignment. Function prediction showed high copy number of the nifB gene was related to the oxygen protection mechanism. Our findings provide exciting information about the bacterial genome in relation to N support for transcriptomic and functional studies for increasing N use efficiency in cassava.

[Cytotoxicity evaluation of the disposable medical syringe piston].

When some testing institutions performed biological evaluation to the disposable medical syringe piston, cytotoxicity was found. According to the biological evaluation testing Selection Guide proposed by Ministry of Health and the Comments of Sample Provider, We performed biological evaluation to one sample by using 5 tests of basic biological evaluation. Cytotoxicity was found, which was probably caused by the residue of the lotion. This research provides reference for objective evaluation of disposable medical syringe piston and safe guarantee of the product.

An in vitro and in vivo study of the brain-targeting effects of an epidermal growth factor-functionalized cholera toxin-like chimeric protein.

The development of neuroprotective drugs has proven to be extremely difficult because of the blood-brain barrier. Intranasal administration is thought to transport the drug from the nasal cavity along the olfactory and trigeminal nerves to the brain, thus bypassing the blood-brain barrier. However, macromolecular protein drugs have low delivery efficiency via this route in general. We hypothesized that an innocuous cholera toxin-like chimeric protein could better enhance the efficiency of protein delivery through the intranasal route. To test this hypothesis, we designed an enhanced green fluorescent protein (EGFP) chimera to evaluate the effect of the cholera toxin (CT) as a carrier for drug delivery into the brain. Then, the EGFP was replaced with epidermal growth factor (EGF) in the chimeric protein, and the therapeutic effect of the new chimeric protein was studied in an LPS-induced neuritis mouse model. The results suggest that the CT-like chimeric protein can bypass the blood-brain barrier and enter the brain in approximately 30 min. This EGF chimeric protein can effectively protect the spatial cognitive ability of and confer anti-anxiety protection to mice. The results indicate that cholera toxin-like chimeric proteins are potential tools for effectively delivering macromodecular drugs into the brain through intranasal administration.