Corynebacterium glutamicum as an indicator for environmental cobalt and silver stress–A proteome analysis

Cobalt and silver are toxic for cells, but mechanisms of this toxicity are largely unknown. Analysis of Corynebacterium glutamicum proteome from cells grown in control and cobalt or silver enriched media was performed by two dimensional gel electrophoresis (2DE) followed by mass spectrometry. Our results indicate that the cell adapted to cobalt stress by inducing five defense mechanisms: Scavenging of free radicals, promotion of the generation of energy, reparation of DNA, reparation and biogenesis of Fe-S cluster proteins and supporting and reparation of cell wall. In response to the detoxification of Ag⁺ many proteins were up-regulated, which involved reparation of damaged DNA, minimizing the toxic effect of reactive oxygen species (ROS) and energy generation. Overexpression of proteins involved in cell wall biosynthesis (1,4-alpha-glucan branching enzyme and nucleoside-diphosphate-sugar epimerase) upon cobalt stress and induction of proteins involved in energy metabolism (2-methylcitrate dehydratase and 1, 2-methylcitrate synthase) upon silver demonstrate the potential of these enzymes as biomarkers of sub-lethal Ag⁺ and Co toxicity.     

细菌SOD对微生物紫外光辐射损伤的恢复作用

将培养至对数中期的大肠杆菌、钝齿棒杆菌和啤酒酵母等３种微生物的细胞适度稀释液，分别涂布于培养皿上使受紫外光照射，在细胞受辐射后死亡率大于９０％时停止照射，立即加入一定剂量的细菌超氧化物岐化酶（ＳＯＤ），以观察ＳＯＤ对微生物活力的恢复效应．结果表明，ＳＯＤ可使受辐照的细胞存活率显著提高，且量效关系明显，而照前添加ＳＯＤ则无上述效应．检测表明，紫外光照射可引发细菌的超弱发光，且该种超弱发光可因氧气的充入而瞬间增强，鲁米诺也能增强这种超弱发光，加入甘露醇对发光无影响．当紫外光照射后加入ＳＯＤ能使发光强度大为减弱，表明此种超弱发光与的活动有关，并对ＳＯＤ拮抗紫外线杀菌的机理作了讨论．     

温度和溶菌酶敏感菌株的L-谷氨酸合成

用温度敏感型菌株发酵生产L-谷氨酸不存在生物素亚适量问题,因此该方法在国际上被广泛使用.通常采用对出发菌株进行传统诱变的方法获得温度敏感型菌株.以谷氨酸棒杆菌CICC 10226为出发菌株,先克隆其ItsA基因,然后通过基因敲除的方法构建了突变菌株Corynebacterium glutamicum WT ΔL,该菌株同时具有温度敏感性和溶菌酶敏感性.经透射式电子显微镜观察发现,于38℃培养的突变株细胞与在30℃培养的同一种细胞相比,细胞明显增大,而出发菌株无该现象.发酵试验表明,在生物素过量的情况下,在发酵进入细胞产酸期后通过将发酵温度从原来的30℃提高到38℃,温度敏感突变株的产酸量增加近5倍.如果在发酵培养基巾添加适量的琥珀酸和乙酸,该菌株与不添加的在30℃培养的对照相比,产酸量增加近6.5倍.对于野生型出发菌株而言,在生物素过量的情况下,无论是否采用变温发酵方法都几乎不产酸.说明温度敏感突变株即使在生物素过量的情况下也能通过变温发酵诱导其合成并分泌产生L-谷氨酸.图10表1参13     

谷氨酸棒杆菌合成新型生物絮凝剂分批发酵过程的溶氧控制模式

在3L发酵罐上系统研究溶氧水平对谷氨酸棒杆菌菌体生长及新型生物絮凝剂REA 11合成的影响,提出生物絮凝剂REA 11合成的分阶段供氧控制策略:发酵过程0～16h维持体积传氧系数kLa为100h-1,16h后降低kLa为40h-1至发酵结束,整个发酵过程通气量保持在1L·L-1·min-1.采用该分阶段供氧控制策略,生物絮凝剂最终产量达到900mg·L-1,发酵周期缩短到30h,比恒定kLa为40h-1条件下的REA 11产量(549mg·L-1)提高了64%,产率提高了45%,生产强度也比kLa恒定为40h-1,100h-1和200h-1的分批发酵过程分别提高了81 2%,120%和420%,实现了高细胞生长速率和高产物产率的统一.     

高效降酚菌株JY03的筛选及其降解特性研究

从绝缘材料厂排放的工业废水中分离得到一株能高效降解苯酚的菌株JY03,最高可耐受1.5 g/L的苯酚。通过形态观察、生理生化分析和16S rRNA序列分析,初步鉴定该菌属于棒状杆菌属（Corynebacterium sp.JY03）。JY03对苯酚降解最适条件为pH 7.5,温度32℃,苯酚浓度为0.6 g/L,时间为...     

氮源及其添加模式对钝齿棒杆菌JDN28-75合成L-精氨酸的影响

氮源是微生物过量合成L-精氨酸的重要营养因子之一,不同氮源对钝齿棒杆菌JDN28-75合成L-精氨酸的影响研究结果表明,硫酸铵为合适的氮源.不同初始硫酸铵浓度对JDN28-75产L-精氨酸的影响研究结果表明,氮源浓度过高或不足,都会使最终L-精氨酸产量有所降低.低浓度的硫酸铵虽然有利于菌体生长,但对L-精氨酸的合成明显不利,同时糖酸转化率也较低;而高浓度的硫酸铵尽管不利于细胞的生长且造成发酵结束时残糖含量过高,却有利于细胞合成L-精氨酸且实际耗糖的糖酸转化率维持在一个较高的水平.初始硫酸铵浓度为60 g/L时,对JDN28-75菌体的生长有明显的抑制作用,最终发酵液中剩余的硫酸铵也较多(大于30 g/L),但高浓度的硫酸铵是L-精氨酸合成所必需的.在上述研究结果的基础上,确定了初始硫酸铵浓度为20 g/L条件下的补氮策略,比较了4种不同的硫酸铵补加模式对产L-精氨酸的影响,结果表明,在总的硫酸铵浓度相同的情况下,采取分批、低浓度添加氮源的方式既可以有效解除发酵前期高浓度硫酸铵对菌体生长的抑制作用,又可以有效维持发酵中后期体系中菌体合成L-精氨酸所需的较高比例的氮源.最后,在5 L全自动发酵罐中采用20 g/L的初始硫酸铵浓度,连续流加25%的氨水来控制发酵体系pH及补加氮源,L-精氨酸的产量可以达到31.7 g/L,较对照组的产酸量(26.0 g/L)提高了21.9%.图4表2参11     

A novel bioremediation strategy for petroleum hydrocarbon pollutants using salt tolerant Corynebacterium variabile HRJ4 and biochar

The present work aimed to develop a novel strategy to bioremediate the petroleum hydrocarbon contaminants in the environment. Salt tolerant bacterium was isolated from Dagang oilfield, China and identified as Corynebacterium variabile HRJ4 based on 16S rRNA gene sequence analysis. The bacterium had a high salt tolerant capability and biochar was developed as carrier for the bacterium. The bacteria with biochar were most effective in degradation of n-alkanes (C16, C18, C19, C26, C28) and polycyclic aromatic hydrocarbons (NAP, PYR) mixture. The result demonstrated that immobilization of C. variabile HRJ4 with biochar showed higher degradation of total petroleum hydrocarbons (THPs) up to 78.9% after 7-day of incubation as compared to the free leaving bacteria. The approach of this study will be helpful in clean-up of petroleum-contamination in the environments through bioremediation process using eco-friendly and cost effective materials like biochar.     

Desulfurization of dibenzothiophene by a newly isolated Corynebacterium sp. ZD-1 in aqueous phase

IntroductionEmissionofsulfur oxidestotheatmospherethroughcombustionoffossilfuelisamainreasonthatcausesseriousenvironmentalproblemsuchasacidrain.Asthecrisisofenergysourcebecomeworse ,mineoffossilfuelwithhighsulfurcontentsisinevitable.Butthedemandofmiddle d…