改良K-B法用于副溶血性弧菌耐药性检测

K-B纸片法是最为广泛的细菌药敏测定方法之一,针对常见的食源性致病菌副溶血性弧菌,对K-B纸片法进行优化和改良。通过建立OD-菌数对应公式以代替传统的麦氏比浊方法,并根据抑菌圈判别结果的差异,选择了标准一次性平皿(9 cm×9 cm),同时对比3种不同的涂布方法,得出定量300μL棉拭子涂布方法变异系数(CV)最小,最后通过8株野生副溶血性弧菌的耐药性检测,表明改良K-B法与传统方法的实验结果基本保持一致。从而建立了一种更高效、更快捷的细菌耐药性测量方法,可应用于副溶血性弧菌的耐药性检测。     

The wax glands and wax secretion of Matsucoccus matsumurae at different development stages

In this paper, the wax secretions and wax glands of Matsucoccus matsumurae (Kuwana) at different instars were investigated using light microscopy, scanning electron microscopy and transmission electron microscopy. The first and second instar nymphs were found to secrete wax filaments via the wax glands located in the atrium of the abdominal spiracles, which have a center open and a series of outer ring pores. The wax gland of the abdominal spiracle possesses a large central wax reservoir and several wax-secreting cells. Third-instar male nymphs secreted long and translucent wax filaments from monolocular, biolocular, trilocular and quadrilocular pores to form twine into cocoons. The adult male secreted long and straight wax filaments in bundles from a group of 18–19 wax-secreting tubular ducts on the abdominal segment VII. Each tube duct contained five or six wax pores. The adult female has dorsal cicatrices distributed in rows, many biolocular tubular ducts and multilocular disc pores with 8–12 loculi secreting wax filaments that form the egg sac, and a rare type wax pores with 10 loculi secreting 10 straight, hollow wax filaments. The ultrastructure and cytological characteristics of the wax glands include wax-secreting cells with a large nucleus, multiple mitochondria and several rough endoplasmic reticulum. The functions of the wax glands and wax secretions are discussed.     

The effect of antiapoptosis genes on clarification performance

Optimal bioreactor harvest time is typically determined based on maximizing product titer without compromising product quality. We suggest that ease of downstream purification should also be considered during harvest. In this view, we studied the effect of antiapoptosis genes on downstream performance. Our hypothesis was that more robust cells would exhibit less cell lysis and thus generate lower levels of cell debris and host‐cell contaminants. We focused on the clarification unit operation, measuring postclarification turbidity and host‐cell protein (HCP) concentration as a function of bioreactor harvest time/cell viability. In order to mimic primary clarification using disk‐stack centrifugation, a scale‐down model consisting of a rotating disk (to simulate shear in the inlet feed zone of the centrifuge) and a swinging‐bucket lab centrifuge was used. Our data suggest that in the absence of shear during primary clarification (typical of depth filters), a 20–50% reduction in HCP levels and 50–65% lower postcentrifugation turbidity was observed for cells with antiapoptosis genes compared to control cells. However, on exposing the cells to shear levels typical in a disk‐stack centrifuge, the reduction in HCP was 10–15% while no difference in postcentrifugation turbidity was observed. The maximum benefit of antiapoptosis genes is, therefore, realized using clarification options that involve low shear, <1 × 10⁶ W/m³ and minimal damage to the cells. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:100–107, 2014     

Melittin-Lipid interaction: A comparative study using liposomes, micelles and bilayerdisks

Comparison of melittin interaction with liposomes, bilayer disks and micelles showed that melittin binding to lipid aggregates is largely dictated by the amount of highly curved areas in the aggregates. The PEG-stabilised bilayer disks were characterised by a combination of small angle neutron scattering, cryo-transmission electron microscopy and dynamic light scattering. Importantly, the theoretically foreseen partial segregation of the lipid components, important for maintaining the structure of the bilayer disk, was confirmed. Steady state fluorescence spectroscopy indicated that melittin mainly resides at the rim of the bilayer disks. Results of the present study help increase the understanding of the mechanisms behind, and the physico-chemical factors affecting, melittin-lipid interaction. We suggest that bilayer disks, due to their stable structure, constitute interesting vehicles for transport of peptides that have high propensity to associate with lipid surfaces of high curvature.     

Production of oligoglucuronans using a monolithic enzymatic microreactor

A glucuronan lyase (EC 4.2.2.14) was immobilized on a monolithic Convective Interaction Media (CIM((R))) disk. The immobilization yield was equal to 29% of the initial activity and 35% of the initial protein amount. Degradations of three glucuronans with various O-acetylation degrees were investigated and compared with degradations using free enzyme. The immobilized glucuronan lyase was inhibited by the O-acetylation degree like the free enzyme. (1)H NMR analyses were used to study the O-acetylation degree of oligoglucuronans and demonstrated that the average degrees of polymerization were inclusive between 4 and 13 after 24h of degradation. This first immobilization of a glucuronan lyase constitutes a new tool to produce oligoglucuronans.     

Direct catalytic electrochemistry of sulfite dehydrogenase: Mechanistic insights and contrasts with related Mo enzymes

Under hydrodynamic electrochemical conditions with slow cyclic voltammetry sweep rates we have been able to probe catalytic events at the molybdenum active site of sulfite dehydrogenase (SDH) from Starkeya novella adsorbed on an edge plane graphite electrode within a polylysine film. The electrochemically driven catalytic behaviour of SDH mirrors that seen in solution assays suggesting that the adsorbed enzyme retains its native activity. However, at high sulfite concentrations, the voltammetric waveform transforms from the expected sigmoidal profile to a peak-shaped response, similar to that reported for the molybdenum enzymes DMSO reductase and nitrate reductase (NarGHI and NapAB) where a redox reaction at the active site has been associated with a switch to lower activity at high overpotentials. This is the first time a similar phenomenon has been observed in a Mo-containing oxidase/dehydrogenase, which raises a number of interesting mechanistic problems. The potential at which the activity of SDH becomes attenuated only emerges at saturating substrate conditions and occurs at a potential (ca. + 320mV vs NHE) well removed from any known redox couple in the enzyme. These results cannot be explained by the same mechanism adopted for DMSO reductase and nitrate reductase catalysis.     

Characterization of cotton fabric scouring by FT-IR ATR spectroscopy

FT-IR attenuated total reflectance (ATR) spectroscopy has been used for the fast characterization of cotton fabric scouring process. The greige and the scoured cotton fabrics showed very similar FT-IR spectrum in transmission mode because the bulk composition of the fabrics are similar. However, FT-IR ATR spectroscopy can provide information about the surface of a fabric. By examination of C–H stretching region at 2800–3000 cm⁻¹, the amount of waxes left on the fabric can be estimated. The presence of pectins and/or waxes can also be probed by observation of carbonyl peak induced by the HCl vapor treatment on the fabric. Based on these changes of FT-IR ATR spectra, the scouring process has been characterized.     

花生种皮蜡质和角质层与黄曲霉侵染和产毒的关系

黄曲霉侵染花生的研究表明,种皮破损的黄曲霉毒素含量显著高于种皮完整的,种皮对黄曲霉侵染和产毒起着重要屏障作用。采用氯仿去除种皮蜡质,用KOH或角质酶去除种皮角质层后,种子黄曲霉感染率和黄曲霉毒素含量显著提高。种皮蜡质和角质层同时去除的与种皮破损的黄曲霉感染率和毒素含量差异不显著,表明种皮的抗性成份主要是蜡质和角质层。种皮蜡质含量测定和种皮表面扫描电镜观察表明,蜡质的含量和角质层的厚度与品种的抗性有关。抗性品种种皮蜡质含量显著高于感病品种。种皮蜡质提取物在体外抑菌效果不显著。说明蜡质的抗性作用主要是物理性阻止黄曲霉菌的穿透。