Direct measurement of oxygen consumption rates from attached and unattached cells in a reversibly sealed, diffusionally isolated sample chamber

Oxygen consumption is a fundamental component of metabolic networks, mitochondrial function, and global carbon cycling. To date there is no method available that allows for replicate measurements on attached and unattached biological samples without compensation for extraneous oxygen leaking into the system. Here we present the Respiratory Detection System, which is compatible with virtually any biological sample. The RDS can be used to measure oxygen uptake in microliter-scale volumes with a reversibly sealed sample chamber, which contains a porphyrin-based oxygen sensor. With the RDS, one can maintain a diffusional seal for up to three hours, allowing for the direct measurement of respiratory function of samples with fast or slow metabolic rates. The ability to easily measure oxygen uptake in small volumes with small populations or dilute samples has implications in cell biology, environmental biology, and clinical diagnostics.

甲烷氧化菌20Z利用Embden-Meyerhof-Parnas途径高效同化甲烷

为了探究γ-变形菌纲（Gammaproteobacteria）甲烷氧化菌Methylomicrobiumalcaliphilum 20Z的甲烷同化代谢过程。文中整合RNA。seq、LC．MS技术并结合13C标记策略对核酮糖单磷酸途径（Ribulosemonophosphatepathway）及下游途径展开系统组学分析。Malcaliphilum 20Z代谢物组定量分析表明Entner-Doudorofr（EDD）途径的中间代谢物6一磷酸葡萄糖的浓度是（150．95±28．75）μmol／L，2-酮-3-脱氧-6-磷酸葡糖酸浓度低于质谱定量分析检测限，而Embden-Meyerhof-Pamas（EMP）途径中果糖1，6-二磷酸、甘油醛-3-磷酸／二羟丙酮磷酸和磷酸烯醇式丙酮酸的浓度分别是（1142．02±302．88）μmol／L、（1866．76±388．55）μmol／L和（3067．57±898．13）±mol／L。通过EDD和EMP途径的代谢物13C同位素动态富集研究，进一步揭示3位标记丙酮酸丰度是l位标记丙酮酸丰度的4-6倍。最后，基因表达比较分析发现EMP途径的关键基因（如：fbaA、tpiA、gap和pykA）的表达水平（RPKM）分别是2479．2、2493．9、2274．6和1846．0，而EDD途径中基因（如：pgi、eda和edd）的RPKM仅是263．8、341．2和225．4。综合上述结果阐明EMP途径才是Malcaliphilum20Z进行甲烷同化的关键通路。EMP途径代谢功能的全新阐述不但改变对Gammaproteobacteria甲炕氧化菌甲烷同化模式的传统认知，而且为甲烷高效生物催化转化提供重要的理论基础。