Interaction between the min locus and ftsZ.

In Escherichia coli, distinct but similar minicell phenotypes resulting from mutation at the minB locus and increased expression of ftsZ suggested a possible interaction between these genes. A four- to fivefold increase in FtsZ resulting from increased gene dosage was found to suppress the lethality of minCD expressed from the lac promoter. Since increased MinCD did not affect the level of FtsZ, this suggested that MinCD may antagonize FtsZ to inhibit its cell division activity. This possibility was supported by the finding that alleles of ftsZ isolated as resistant to the cell division inhibitor SulA were also resistant to MinCD. Among the ftsZ(Rsa) alleles, two appeared to be completely resistant to MinCD as demonstrated by the lack of an effect of MinCD on cell length and a minicell phenotype observed in the absence of a significant increase in FtsZ. It was shown that SulA inhibits cell division independently of MinCD.     

植物残茬对土壤酸度的影响及其作用机理

土壤强酸性是作物生长的最主要限制因子之一,某些植物残茬可以有效地提高土壤pH,降低活性铝含量,提高作物产量。植物残茬改良土壤酸度的效能因种而异,最高土壤pH升幅可达4.53个单位,多种豆科植物材料可使土壤pH提高2个单位以上,当pH>5时,土壤溶液活性铝降至极低水平,从而消除铝害。植物残茬改良土壤酸度的效能受植物残茬自身特性与土壤特性的影响,而且pH的上升通常在几个月后消失,但这种效能对当季作物有效。植物体内有机酸根的去羧化作用被认为是pH上升的主要机理之一,去羧化机理存在的主要证据是,随着土壤pH升高,植物材料内的可溶性有机成分下降,CO2排放与pH上升高度相关,以及杀菌条件下土壤pH上升速度显著减慢。超量碱机理是植物残茬导致pH上升的又一可能的重要机理,亦即有机盐的作用,有机盐分解转化为碳酸盐,其作用与石灰完全相似,有机盐水解也可导致土壤溶液的碱性反应。铵化作用与硝化作用是高氮植物材料影响土壤酸度的重要机理,有机氮的铵化直接消耗质子,铵的硝化则产生质子,pH的变化与这些氮过程高度相关。含硫植物材料及有机物质分解过程产生的氧化还原条件的变化,也可对土壤pH产生影响,但它们的作用较小。综合来看,去羧化作用机理基于间接证据,没有得到严格验证,超量碱机理可能是土壤pH上升的主要原因,超量碱只能转移,不能制造,含超量碱高的外源性有机材料施入耕地,将是改良土壤酸度,提高作物产量的一种有效途径。     

Alternatively activated macrophages at the recipient site improve fat graft retention by promoting angiogenesis and adipogenesis

The inflammatory response mediated by macrophages plays a role in tissue repair. Macrophages preferentially infiltrate the donor site and subsequently, infiltrate the recipient site after fat grafting. This study aimed to trace host‐derived macrophages and to evaluate the effects of macrophage infiltration at the recipient site during the early stage on long‐term fat graft retention. In our novel mouse model, all mice underwent simulated liposuction and were divided into 2 groups. The fat procurement plus grafting (Pro‐Grafting) group was engrafted with prepared fat (0.3 ml). The pro‐Grafting+M2 group was engrafted with prepared fat (0.3 ml) mixed with 1.0 × 10⁶ GFP+M0 macrophages, and then, 2 ng IL‐4 was injected into the grafts on Day 3. In addition, 1.0 × 10⁶ GFP+M0 macrophages were injected into the tail vein for tracing in the Pro‐Grafting group. As a result, GFP+macrophages first infiltrated the donor site and subsequently infiltrated the recipient site in the Pro‐Grafting group. The long‐term retention rate was higher in the Pro‐Grafting+M2 group (52% ± 6.5%) than in the Pro‐Grafting group (40% ± 3.5%). CD34+ and CD31+ areas were observed earlier, and expression of the adipogenic proteins PPAR‐γ, C/EBP and AP2 was higher in the Pro‐Grafting+M2 group than in the Pro‐Grafting group. The host macrophages preferentially infiltrate the donor site, and then, infiltrate the recipient site after fat grafting. At the early stage, an increase in macrophages at the recipient site may promote vascularization and regeneration, and thereby improve the fat graft retention rate.     

森林凋落物分解重要影响因子及其研究进展

当前 ,森林凋落物分解被放在陆地生态系统碳平衡背景下进行研究 ,认识凋落物分解过程的影响因素和影响机理对理解地表碳平衡具有重要意义。凋落物在分解过程中 ,伴随有养分含量的变化 ,低品质凋落物在分解前期 (可达 2～ 3年 )会从环境中固定养分 ,特别是氮磷养分 ,而在后期则会释放出养分。凋落物本身的养分含量是影响分解速率的重要因素 ,高养分含量的凋落物分解快些 ,阔叶凋落物比针叶凋落物分解快些。有资料显示 ,在总分解率为2 9 4 %的构成中 ,理化因素、微生物因素与土壤动物因素对凋落物分解的贡献率分别为 7 2 %、8 0 %和 14 2 %。不同类型凋落物在分解过程中的土壤动物类群也不同 ,它也是造成凋落物分解速率不同的关键因素 ,通常阔叶树种凋落物分解过程中 ,会有更多的微节肢动物出现。CO2浓度升高将造成植物有机质含碳量与其它养分的比值升高 ,形成低品质的凋落物 ,从而间接影响凋落物分解速率 ,一般认为 ,全球CO2 浓度升高会加强土壤作为碳汇的功能。     

Isolation and characterization of peptide antibiotics LI-F04 and polymyxin B6 produced by Paenibacillus polymyxa strain JSa-9

Paenibacillus polymyxa JSa-9 had been found to produce five cyclic LI-F type antibiotics which were released into culture medium in accordance with our previous report. In this study, another three kinds of antagonistic compounds were extracted from P. polymyxa JSa-9 cell pellets and (or) spores by methanol. Using high performance liquid chromatography (HPLC) method, two antagonistic fractions were separated and collected from the methanol extract. One showed inhibition against Escherichia coli and Staphylococcus aureus, while the other was active against Aspergillus niger and S. aureus. By means of electrospray ionization mass spectroscopy (ESI-MS), infrared spectroscopy (IR), and amino acid analysis, two kinds of compounds from fraction B with molecular masses of 901 and 915 Da were characterized as the linear lipopeptide analogs of antibiotics LI-F04a and LI-F04b, respectively. Another antimicrobial substance from fraction A could be attributed to polymyxin B₆.     

稀土-落叶松单宁配合物的合成及抗真菌活性研究

以稀土(Re~(3+))和落叶松单宁(LT)为原料,采用液相合成法合成了5种廉价的稀土-落叶松单宁(Re~(3+)-LT)配合物,并通过红外光谱、X射线光电子能谱、紫外光谱以及配位数测定确定了配合物的结构.采用牛津杯法、琼脂稀释法测定配合物对黑曲霉、红曲霉、白腐菌、毛霉4种真菌的抑制作用.在抑菌方面,5种配合物对上述4种真菌均具有较强的抑制作用,其抑菌活性大小顺序为Ce~(3+)-LTGd~(3+)-LTLa~(3+)-LTNd~(3+)-LTYb~(3+)-LT,其中Ce~(3+)-LT对4种真菌的最小抑菌浓度分别为:1.6、1.6、0.8和1.6 g·L~(-1);Yb~(3+)-LT对4种真菌的最小抑菌浓度分别为:3.2、1.6、3.2和3.2 g·L~(-1).在杀菌方面,Yb~(3+)-LT的杀菌活性最强,其对4种真菌的最小杀菌浓度分别为:6.4、3.2、3.2和6.4 g·L~(-1).此外,尽管Nd~(3+)-LT和Gd~(3+)-LT具有较强的抑菌活性,但对黑曲霉和毛霉的杀菌作用较弱.     

Nitrogen deprivation induces cross-tolerance of Poa annua callus to salt stress

Alternative respiration pathway (AP) is an important pathway which can be induced by environment stresses in plants. In the present study, we show a new mechanism involving the AP in nitrogen deprivation-induced tolerance of Poa annua callus to salt stress. The AP capacity markedly increased under a 600 mM NaCl treatment or nitrogen deprivation pretreatment and reached a maximum under the nitrogen deprivation pretreatment combined with the NaCl treatment (–N+NaCl). Malondialdehyde (MDA) and H₂O₂ content and Na⁺/K⁺ ratio significantly increased under the 600 mM NaCl treatment but less under the–N+NaCl treatment. Moreover, both the nitrogen deprivation and the NaCl stress stimulated the plasma membrane (PM) H⁺-ATPase activity and increased pyruvate content. The maximal stimulating effect was found under the–N+NaCl treatment. When the AP capacity was reduced by salicylhydroxamic acid (SHAM, an inhibitor of AP), content of MDA and H₂O₂ and Na⁺/K⁺ ratio dramatically increased, whereas PM H⁺-ATPase activity decreased. Moreover, exogenous application of pyruvate produced a similar effect as the nitrogen deprivation pretreatment. The effects of SHAM on the Poa annua callus were counteracted by catalase (a H₂O₂ scavenger) and diphenylene iodonium (a plasma membrane NADPH oxidase inhibitor). Taken together, our results suggest that the nitrogen deprivation enhanced the capacity of AP by increasing pyruvate content, which in turn prevented the Poa annua callus from salt-induced oxidative damages and Na⁺ over-uptake.