Directed evolution of RhlI to generate new and increased quorum sensing signal molecule catalytic activities

Publication date: Available online 16 November 2019Source: Enzyme and Microbial TechnologyAuthor(s): Biao Zhang, Lili Ren, Dayong Xu, Haonan Wang, Zhuo Chen, Bingrong Zhang, Xin Zeng, Lianhong Sun, Feng LiAbstractQuorum sensing is a population density-dependent gene expression regulation mechanism in bacteria. The substrate specificity of RhlI, an enzyme in the RhlI–RhlR quorum sensing system of Pseudomonas aeruginosa, was explored by directed evolution to gain insight into the molecular mechanisms of quorum sensing. RhlI catalyzes S-adenosyl methionine and butanoyl or hexanoyl acyl carrier protein to form N-butanoyl homoserine lactone (BHL) and or N-hexanoyl homoserine lactone (HHL), respectively, none of which contain 3-oxo groups. We developed high-throughput genetic screening and selection methods to identify RhlI mutants via four rounds of directed evolution and identified RhlI-4M1 as the mutant that generated new catalytic activity and synthesized 3-oxo-hexanoyl homoserine lactone (OHHL) containing the 3-oxo group in Escherichia coli. Additionally, the synthesizing activities of BHL and HHL were improved by 3.98- and 3.01-fold, respectively. RhlI-4M1 contains five amino acid substitutions (A15D, K31R, T92S, Y129 N, and L184Q) and one stop codon (Q193*) mutations. The deletion of nine amino acids in the C-terminus was crucial for OHHL production by RhlI mutants. This work demonstrates that the genetic screen/selection should be useful in the development of a...
Source: Enzyme and Microbial Technology - Category: Biotechnology Source Type: research

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Publication date: Available online 14 December 2019Source: Sensing and Bio-Sensing ResearchAuthor(s): A. Pangajam, K. Theyagarajan, K. DinakaranAbstractA selective electrochemical sensor based on carbon dot (CD)/ZnO nanoroad/PANI nanoassembly has been developed towards the detection of cadmium (II) present in the environmental samples. In this work, a conductive nanocomposite electrode, CDs/ZnO/PANI, was successfully fabricated by polymerizing aniline (PANI) in the presence of carbon dot and Zinc oxide nanorod and followed by coating onto printed carbon sheet. These CDs were nearly spherical with good size distribution and...
Source: Sensing and Bio Sensing Research - Category: Research Source Type: research
Noonan syndrome with multiple giant cell lesions (NS/MGCLS) is a term used to describe a subgroup of people with Noonan syndrome, a rare condition with phenotypic overlap with NS. Once thought to be a specific and separate entity, it is now suggested to be a variant of the NS spectrum. Here we report a 22-year-old patient misdiagnosed as having Rubinstein-Taybi syndrome (microcephaly, congenital heart disease, ventricular septal defect, cryptorchidism, pterygium coli, inguinal hernia, and short stature and neck).
Source: Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics - Category: ENT & OMF Authors: Source Type: research
Publication date: Available online 14 December 2019Source: Journal of Photochemistry and Photobiology B: BiologyAuthor(s): Jiahua Shao, Zheru Ding, Lexiang Li, Yi Chen, Jun Zhu, Qirong QianAbstractArticular cartilage regeneration is a challenging process due to its inadequate ability of self-recovering biological mechanisms. The progresses of cartilage tissue engineering is supported to overwhelmed the repairing difficulties and degenerative diseases. The main goal of the present study is to design biomaterials with suitable physico-chemical, mechanical and biological properties for the carrier of growth factor and improvi...
Source: Journal of Photochemistry and Photobiology B: Biology - Category: Speech-Language Pathology Source Type: research
Publication date: January 2020Source: Colloid and Interface Science Communications, Volume 34Author(s): Tatiane Melo Pereira, Vera Lucia Perussi Polez, Marcelo Henrique Sousa, Luciano Paulino SilvaAbstractGreen synthesis of silver nanoparticles (AgNPs) is already widely used, however, it presents challenges. This work describes a way to modulate the physicochemical characteristics of AgNPs using green synthesis and aqueous extract from different parts of Handroanthus heptaphyllus. The progress of the synthesis reaction, the physicochemical characteristics, and the biological activity against Escherichia coli and Staphyloco...
Source: Colloids and Interface Science Communications - Category: Nanotechnology Source Type: research
Peng Tan The problem of an aging society is becoming increasingly acute. Diseases related to aging also come with it. There are some diseases that people can’t treat fundamentally. Therefore, people try to find a natural ingredient from natural medicine to treat these diseases and improve the quality of life of the elderly. With the screening of a large number of traditional Chinese medicines, we found that polysaccharides from Rehmannia glutinous (PRG) can prolong the lifespan of Caenorhabditis elegans (C. elegans). Neutral polysaccharide is the main component of PRG. In the present study, we used a C. el...
Source: Molecules - Category: Chemistry Authors: Tags: Article Source Type: research
CONCLUSIONS: About one to five patients treated with URS developed an infectious complication and E. Faecalis and E. Coli were the most frequent pathogen isolated. A positive SC is the only independent risk factor for postoperative infection: consequently, an early SC analysis could allow a prompt antibiotic therapy in all patients with positive SC even if mildly symptomatic. PMID: 31833334 [PubMed - as supplied by publisher]
Source: Minerva Urologica e Nefrologica - Category: Urology & Nephrology Tags: Minerva Urol Nefrol Source Type: research
In this study, the CD48 gene of tilapia (Oreochromis niloticus, named On-CD48), was cloned from the head kidney of tilapia. The coding sequences is 654 bp and encoding 217 amino acids. The deduced amino acid sequence of On-CD48 with an estimated molecular weight of 24.4 kDa and a theoretical pI of 5.03. Amino acid alignment indicated that it had two immunoglobulin-like domain conserved region. In healthy tilapia, the On-CD48 could be detected in all the examined tissues and the highest expression level in the spleen. The expression of On-CD48 in the spleen and head kidney was decreased after immunized by formalin-inactiv...
Source: Fish and Shellfish Immunology - Category: Biology Source Type: research
In this study, a microchip electrophoretic method for biosensing E. coli O157:H7 was developed by using E. coli O157:H7 aptamer (apt-E) for specific bacteria recognition together with aptamer-induced catalysed hairpin assembly (CHA) for significantly improving the sensitivity of bacteria detection. Briefly, three nucleic acid strands (apt-E, hairpin H1, and H2) were used in the CHA amplification. Because different quantities of H1/H2 complexes were formed due to the circle amplification induced with different amounts of apt-E and the correlation between the concentrations of apt-E and E. coli O157:H7, E. coli O157:H7 thus ...
Source: Sensors and Actuators B: Chemical - Category: Chemistry Source Type: research
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Source: Sensors and Actuators B: Chemical - Category: Chemistry Source Type: research
Publication date: Available online 5 December 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Hsin-Yao Wang, Chih-Yu Chen, Po-Yu Chu, Yu-Xian Zhu, Chia-Hsun Hsieh, Jang-Jih Lu, Min-Hsien WuAbstractDifferent levels of antibiotic resistance reside in a bacterial clone (heteroresistance) is regarded as an important cause leading to development of superbugs and treatment failure of infectious diseases. However, phenotypical detection of bacterial heteroresistance is not available in current clinical practice or by present analytical tools. To address this issue, we developed an optically induced dielectrophoresis (ODEP...
Source: Sensors and Actuators B: Chemical - Category: Chemistry Source Type: research
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