微生物絮凝剂及其絮凝微生物的研究进展

介绍了近几年来国内外微生物絮凝剂和絮凝微生物的一些发展概况,列举了近几年发现的一些微生物絮凝剂的物质属性和组成,重点讨论了胞外絮凝剂和絮凝酵母的絮凝机理,详细综述了絮凝微生物的遗传学方面的研究进展,分析讨论微生物絮凝剂的应用概况,提出微生物絮凝剂的发展趋势和研究方向。     

Organic matter composition of gravel-stored sediments from salmon-bearing streams

The objective of this project was to evaluate the changing composition and structure of the sediment-associated organic matter (OM) stored in the gravel bed of highly productive salmon-bearing streams and, determine if the OM changes affect the morphology and settling rates of the sediment. In July of 2001, a dozen infiltration gravel bags were buried in the channel bed of O'Ne-eil Creek in northern British Columbia (Canada) to collect fine sediment and the associated organic matter for chemical and morphological analysis. The bags were removed over a 10 week period which incorporated summer low flows, salmon spawning, salmon die-off and the onset of autumn low flow conditions. Our results indicate two visibly different structures in the organic matter film overlying the mineral material of the flocs. A web-like structure was noted during mid-spawn while a film-like covering was observed in pre-spawn and post-fish periods. The strength of the film-like covering is surmised to be associated with the larger gravel-stored floc sizes noted at these times. Chemical analysis of these biofilms indicated higher metal complexation properties during the spawning periods as opposed to before or after salmon were present. The changing OM contributions were associated with changes in floc size, density and settling rates. The physical disturbance to the gravels associated with spawning salmon was also correlated with altered characteristics of the gravel-stored flocs.     

Chitosan functional properties

Chitosan is a partially deacetylated polymer of N-acetyl glucosamine. It is essentially a natural, water-soluble, derivative of cellulose with unique properties. Chitosan is usually prepared from chitin (2 acetamido-2-deoxy β-1,4-D-glucan) and chitin has been found in a wide range of natural sources (crustaceans, fungi, insects, annelids, molluscs, coelenterata etc.) However chitosan is only manufactured from crustaceans (crab and crayfish) primarily because a large amount of the crustacean exoskeleton is available as a by product of food processing. Squid pens (a waste byproduct of New Zealand squid processing) are a novel, renewable source of chitin and chitosan. Squid pens are currently regarded as waste and so the raw material is relatively cheap. This study was intended to assess the functional properties of squid pen chitosan. Chitosan was extracted from squid pens and assessed for composition, rheology, flocculation, film formation and antimicrobial properties. Crustacean chitosans were also assessed for comparison. Squid chitosan was colourless, had a low ash content and had significantly improved thickening and suspending properties. The flocculation capacity of squid chitosan was low in comparison with the crustacean sourced chitosans. However it should be possible to increase the flocculation capacity of squid pen chitosan by decreasing the degree of acetylation. Films made with squid chitosan were more elastic than crustacean chitosan with improved functional properties. This high quality chitosan could prove particularly suitable for medical/analytical applications. This revised version was published online in November 2006 with corrections to the Cover Date.     

茎瘤固氮根瘤菌ORS571鞭毛马达基因fliN与fliM的功能分析

【目的】考察茎瘤固氮根瘤菌ORS571中鞭毛马达蛋白FliN、FliM的编码基因分别缺失的突变体表型,初步探究其功能机理。【方法】本研究采用同源重组和三亲本接合转移的方法构建突变体,测定野生型及突变株的生长曲线、趋化性、胞外多糖的分泌、生物膜的形成及细胞絮凝等表型。【结果】三种菌株的生长速率基本无差,与野生型菌株相比突变株鞭毛结构丧失,趋化能力、分泌的胞外多糖和生物膜形成能力均下降,但相同时间内细胞絮凝程度比野生型明显。【结论】实验表明,鞭毛基因fliN、fliM对茎瘤固氮根瘤菌ORS571鞭毛的形成、趋化运动、胞外多糖的分泌、生物膜的形成及细胞絮凝能力等均有调控作用。     

Sedimentation in Boreal Lakes—The Role of Flocculation of Allochthonous Dissolved Organic Matter in the Water Column

We quantified sedimentation of organic carbon in 12 Swedish small boreal lakes (<0.48 km²), which ranged in dissolved organic carbon (DOC) from 4.4 to 21.4 mg C l⁻¹. Stable isotope analysis suggests that most of the settling organic matter is of allochthonous origin. Annual sedimentation of allochthonous matter per m² lake area was correlated to DOC concentration in the water (R ² = 0.41), and the relationship was improved when sedimentation data were normalized to water depth (R ² = 0.58). The net efflux of C as CO₂ from the water to the atmosphere was likewise correlated to DOC concentration (R ² = 0.52). The losses of organic carbon from the water column via mineralization to CO₂ and via sedimentation were approximately of equal importance throughout the year. Our results imply that DOC is a precursor of the settling matter, resulting in an important pathway in the carbon cycle of boreal lakes. Thus, flocculation of DOC of terrestrial origin and subsequent sedimentation could lead to carbon sequestration by burial in lake sediments.     

植物单宁的絮凝研究

研究了利用超临界CO2萃取技术提取的植物单宁提取液对高岭土悬浊液的絮凝效果。通过烧杯混凝试验进行单因素试验研究,确定了植物单宁对高岭土悬浊液的最佳浓度、投加量、沉淀时间、pH值和温度。试验表明,植物单宁具有一定的絮凝作用,对高岭土悬浊液的絮凝处理效果较好,得到较适宜的絮凝处理条件为：处理浓度20mL／L,投加量60mL,沉淀时间5min,pH值3．0,温度25℃。     

絮凝方法收集产氨短杆菌MA-2、黄色短杆菌MA-3条件的优化

采用壳聚糖作絮凝剂收集富含延胡索酸酶活力的产氨短杆菌MA-2、黄色短杆菌MA-3。研究了絮凝剂加入量及加入时混合方式与时间等因素对延胡索酸酶活力及分离效果的影响,并对壳聚糖絮凝收集产氨短杆菌MA-2、黄色短杆菌MA-3的过程进行了初步分析。     

Characterization of a biofilm-like extracellular matrix in FLO1-expressing Saccharomyces cerevisiae cells

Like bacteria, fungi growing in biofilms are often embedded in a so-called extracellular matrix (ECM), a complex and species-specific mixture of compounds secreted by cells in the biofilm. The precise physiological role of this ECM and its importance for the stress and drug resistance that is so characteristic of biofilms remain vague. Here, we describe the discovery of an ECM produced by flocculating Saccharomyces cerevisiae cells. Although S. cerevisiae has long been believed not to produce an ECM, our results indicate that flocculating cells secrete a mixture of glucose and mannose polysaccharides that surrounds flocculating cells. This matrix impedes the penetration of large molecules into the floc, but does not seem to play a role in the resistance of flocculating cultures to drugs and ethanol. Together, our results provide a new model system to study the formation and biological role of microbial extracellular matrices.     

粟酒裂殖酵母核糖体蛋白RPL21表达不足引发细胞粘附

【目的】随机选择裂殖酵母核糖体蛋白RPL21作为研究对象,分析其表达不足对细胞的影响。【方法】通过同源臂交换的方法,敲除裂殖酵母基因组中RPL21蛋白的编码基因rpl21-1和rpl21-2,观察突变菌株rpl21-1Δ和rpl21-2Δ细胞内的核糖体合成情况以及细胞表型变化。【结果】突变菌株rpl21-1Δ和rpl21-2Δ细胞内总的rpl21(rpl21-1+rpl21-2)表达水平与野生型菌株相比分别减少了66.5%和58.7%,合成的核糖体总量较野生型菌株分别下降了62.8%和50.4%。突变菌株在YEPD液体培养基中培养时发生细胞粘附现象,而基因回补的重组菌株rpl21-1Δ/RPL21-1和rpl21-2Δ/RPL21-2突变株细胞中粘附现象消失。【结论】核糖体蛋白损伤造成核糖体合成受阻,进而引发细胞生长过程中的粘附在粟酒裂殖酵母中是普遍存在的现象。