YpdA,a putative bacillithiol disulfide reductase,contributes to cellular redox homeostasis and virulence in Staphylococcus aureus

The intracellular redox environment of Staphylococcus aureus is mainly buffered by bacillithiol (BSH), a low molecular weight thiol. The identity of enzymes responsible for the recycling of oxidized bacillithiol disulfide (BSSB) to the reduced form (BSH) remains elusive. We examined YpdA, a putative bacillithiol reductase, for its role in maintaining intracellular redox homeostasis. The ypdA mutant showed increased levels of BSSB and a lower bacillithiol redox ratio vs. the isogenic parent, indicating a higher level of oxidative stress within the bacterial cytosol. We showed that YpdA consumed NAD(P)H; and YpdA protein levels were augmented in response to stress. Wild type strains overexpressing YpdA showed increased tolerance to oxidants and electrophilic agents. Importantly, YpdA overexpression in the parental strain caused an increase in BSH levels accompanied by a decrease in BSSB concentration in the presence of stress, resulting in an increase in bacillithiol redox ratio vs. the vector control. Additionally, the ypdA mutant exhibited decreased survival in human neutrophils (PMNs) as compared with the parent, while YpdA overexpression protected the resulting strain from oxidative stress in vitro and from killing by human neutrophils ex vivo. Taken together, these data present a new role for YpdA in S. aureus physiology and virulence through the bacillithiol system.     

单细胞测序方法研究进展

近年来,高通量测序技术(Next-generation sequencing,NGS)快速发展,已广泛应用于生命科学各个领域,但传统的混合细胞测序(Bulk cell sequencing)检测的是细胞群体的总平均反应,无法反应每个细胞的真实情况,这会影响研究者对细胞功能认知的准确性。单细胞测序技术(Single cell sequencing,sc-Seq)的出现,从一定程度上解决了传统测序固有的缺陷。单细胞测序是针对单个细胞的RNA或DNA进行测序,能够准确测出单个细胞的基因结构和表达状态,从而分析相同表型细胞的异质性。本文首先介绍单细胞测序的原理、测序类型和测序平台,有助于理解单细胞测序和在进行科研项目时设计合适的项目方案。进一步介绍单细胞转录组测序的分析流程和各种常用的分析工具或软件,并重点阐述单细胞转录组测序分析中的细胞聚类和拟时序分析的原理和研究进展,为进行单细胞转录组测序数据分析提供参考。最后,本文简述了单细胞测序研究热度、单细胞测序的应用、挑战和展望等,有助于更全面地认识单细胞测序。     

关联维数法在皮肤激光散斑测量中的应用

本文采用关联维数方法研究了皮肤厚度对皮肤激光散斑测量的影响。计算了６种模拟皮肤厚度情况下的生物散斑关联维数。结果表明,维数随皮肤厚度的增加而减小,而且重复性很好。这说明,关联维数方法可以应用在皮肤激光散斑的研究中     

脂肪间充质干细胞来源外泌体的功能

外泌体是细胞外膜质纳米囊泡,将蛋白质、核酸(DNA和RNA)转运到靶细胞中,介导局部和系统的细胞间通信,从而改变受体细胞的行为.这些小泡在许多生物功能中发挥重要作用,如脂肪合成、免疫调节、神经再生和肿瘤调节等.脂肪间充质干细胞目前被认为是细胞治疗和再生医学领域中一种功能丰富的工具,可产生和分泌多种外泌体,继承细胞的多种...     

The Development of a Novel Form of Mouse Cage Enrichment

This article describes the design and testing of a novel form of mouse cage enrichment. A cage insert was designed and developed to fulfill a number of enrichment goals pertaining to its effectiveness and practicality (i.e., to improve the environment of mice in laboratories while causing the minimum of interference to the husbandry and care procedures carried out by animal care staff). Behavioral and physical parameters were used over an 8-week period to assess effectiveness, with subjective opinions of cage cleaning staff and physical examinations of the inserts after cleaning being used to assess practicality. Results show that the insert was both a practical and effective form of mouse enrichment which produced a number of enriching effects without adversely affecting the animals, their environment, or the husbandry and care procedures.     

A novel sulfonylurea receptor family member expressed in the embryonic Drosophila dorsal vessel and tracheal system.

Sulfonylurea receptors (SURx) are required subunits of the ATP-sensitive potassium channel. SURx alone is electrophysiologically inert. However, when SURx is combined with an inward rectifier Kir6.2 subunit, ATP-sensitive potassium channel activity is generated. We report the identification, characterization, and localization of Dsur, a novel Drosophila gene that is highly related to the vertebrate SUR family. The Dsur coding sequence contains structural features characteristic of the ABC transporter family and, in addition, harbors 1.7 kilobases of a distinctive sequence that does not share homology with any known gene. When Dsur alone is expressed in Xenopus oocytes glibenclamide-sensitive potassium channel activity occurs. During Drosophila embryogenesis, the Dsur gene is specifically expressed in the developing tracheal system and dorsal vessel. Studies of the Drosophila genome support that only a single Dsur gene is present. Our data reveal conservation of glibenclamide-sensitive potassium channels in Drosophila and suggest that Dsur may play an important role during Drosophila embryogenesis. The lack of gene duplication in the Drosophila system provides a unique opportunity for functional studies of SUR using a genetic approach.     

Impact of antennectomy, eye blinding and tibial comb coating on the predatory behaviour of Rhynocoris kumarii Ambrose and Livingstone (Het., Reduviidae) on Spodoptera litura Fabr. (Lep., Noctuidae)

The predaceous reduviid Rhynocoris kumarii uses its antennae, eyes and tibial comb to predate tobacco cutworm Spodoptera litura (Fabr). A delayed arousal response was observed in the antennectomized, eye blinded and tibial comb-coated predators. The predators whose entire antennae had been removed showed significant delayed approach but the approach response was not affected significantly in the blinded and tibial comb-coated reduviid predators. Capturing response was significantly affected in pedicel and entire antennae-removed predators, and blinded and tibial comb-coated predators. Antennectomy, eye blinding and tibial comb coating did not cause any impact in the act of paralysing the prey. Progressive reduction in sucking duration and the number of sucking sites were observed as a function of sequential segment-wise removal of antennae. A reduction in the sucking duration and number of sucking sites were also observed in blinded and tibial comb coated predators.     

Contemporaneous N(2) Fixation and Oxygenic Photosynthesis in the Nonheterocystous Mat-Forming Cyanobacterium Lyngbya aestuarii

The nonheterocystous filamentous cyanobacterial genus Lyngbya is a widespread and frequently dominant component of marine microbial mats. It is suspected of contributing to relatively high rates of N(2) fixation associated with mats. The ability to contemporaneously conduct O(2)-sensitive N(2) fixation and oxygenic photosynthesis was investigated in Lyngbya aestuarii isolates from a North Carolina intertidal mat. Short-term (<4-h) additions of the photosystem II (O(2) evolution) inhibitor 3(3,4-dichlorophenyl)-1,1-dimethylurea stimulated light-mediated N(2) fixation (nitrogenase activity), indicating potential inhibition of N(2) fixation by O(2) production. However, some degree of light-mediated N(2) fixation in the absence of 3(3,4-dichlorophenyl)-1,1-dimethylurea was observed. Electron microscopic immunocytochemical localization of nitrogenase, coupled to microautoradiographic studies of CO(2) fixation and cellular deposition of the tetrazolium salt 2,4,5-triphenyltetrazolium chloride, revealed that (i) nitrogenase was widely distributed throughout individual filaments during illuminated and dark periods, (ii) CO(2) fixation was most active in intercalary regions, and (iii) daylight 2,4,5-triphenyltetrazolium chloride reduction (formazan deposition) was most intense in terminal regions. Results suggest lateral partitioning of photosynthesis and N(2) fixation during illumination, with N(2) fixation being confined to terminal regions. During darkness, a larger share of the filament appears capable of N(2) fixation.