嗜酸乳杆菌在不同pH条件下生长和存活情况的研究

以豆汁为基质,研究了嗜酸乳杆菌（Ｌａｃｔｏｂａｃｉｌｌｕｓ ａｃｉｄｏｐｈｉｌｕｓ）在不同ＰＨ值的发酵基质和保存基质下的生长和存活情况。结果表明：嗜酸乳杆菌适宜生长的ＰＨ值在５．７左右,然而经过１０周保存实验,在较低ＰＨ值（４．５）培养的嗜酸乳杆菌存活率最高,在最适生长ＰＨ值（５．７）的菌活率却最低。将培养好的嗜酸乳杆菌置于不同ＰＨ值的豆汁中进行保存实验,偶然ＰＨ值对活菌的存活有一定的影响,但影响     

健康长寿老人肠道双歧杆菌鉴定

为研制食品双歧杆菌制剂,从健康长寿老人肠道正常菌群分离并鉴定具有较高生物活性及保健作用的双歧杆菌菌株。对３０份未明菌株标本,进行了分离,纯化,鉴定,经生物学特性,生化试验,同时做代谢产物分析,各菌均产生乙酸和乳酸为主。还做了ＤＮＡ（Ｇ＋Ｃｍｏｌ％）含量测定,测定值在５６～６３范围。而确定３株为婴儿双歧、５株为青春双歧,共选出８株双歧杆菌,为选育优良的双歧杆菌菌株提供了依据。     

有机酸处理对羊肉贮藏品质的影响

采用3种有机酸（乙酸、乳酸、柠檬酸）处理后的羊肉样品与对照组,在0～4℃条件下贮藏,分别在不同的贮藏时间点,同时取样测定各处理样品的pH值、色泽、汁液损失和菌落总数,分析乙酸、乳酸和柠檬酸处理对羊肉贮藏品质指标的影响。结果表明：2%的乙酸、2%乳酸和2%柠檬酸处理能够有效地抑制贮藏过程中杂菌的繁殖,维持样品较低pH值水平和缓慢上升速度,同时提高羊肉贮藏过程中汁液损失率;乙酸、乳酸、柠檬酸处理对羊肉色泽L*值和a*值的影响较小,但b*值较对照组增加;乙酸、乳酸和柠檬酸处理能够有效延长羊肉的保质期。     

爱灵生乐（2036）螺旋藻双歧胶囊对抗生素相关性腹泻小鼠的治疗作用

目的采用盐酸林克霉素诱发小鼠相关性腹泻模型,观察螺旋藻、婴儿型双歧杆菌及其混合物爱灵生乐（2036）螺旋藻双歧胶囊（胶囊内容物,含婴儿型双歧杆菌、螺旋藻,下同）对抗生素相关性腹泻小鼠的治疗作用。方法经口投予盐酸林克霉素0.15 g/（d.鼠）,连续3 d,然后经口分别给予螺旋藻、双歧杆菌及爱灵生乐（2036）螺旋藻双歧胶囊1.66 g/（kg.b.w）,连续5 d。结果经口投予螺旋藻、婴儿型双歧杆菌及爱灵生乐（2036）螺旋藻双歧胶囊1.66 g/（kg.b.w）,连续5 d,能有效改善盐酸林克霉素诱发的小鼠相关性腹泻症状,特别是给予爱灵生乐（2036）螺旋藻双歧胶囊组,可有效治疗盐酸林克霉素诱发小鼠相关性腹泻。结论螺旋藻与双歧杆菌复合制剂对抗生素相关性腹泻有明确治疗作用。     

产朊假丝酵母利用不同有机酸作碳源的研究

分别通过不同有机酸为惟一碳源,研究了产朊假丝酵母（Candida utilis）能够利用的有机酸的种类,旨在为微生物的基础研究和应用基础研究提供部分依据。分别通过对培养时间和菌体在不同有机酸合成培养基中OD值进行统计分析,发现培养时间和柠檬酸、乳酸、琥珀酸、L-苹果酸培养基的OD值极显著相关（P〈0.01）;培养时间和乙酸、酒石酸、富马酸和草酸培养基的OD值无相关性。通过对比菌体培养前后有机酸合成培养基pH值的变化发现乙酸、酒石酸、富马酸和草酸合成培养基的pH值没有明显变化,而苹果酸、乳酸、琥珀酸和柠檬酸为碳源的合成培养基的pH值均明显增大。从而说明产朊假丝酵母能利用L-苹果酸、乳酸、琥珀酸、柠檬酸为碳源,而不能利用乙酸、酒石酸、草酸、富马酸为碳源。     

重症急性胰腺炎患者肠黏膜屏障损伤与血清二胺氧化酶和TLR9水平及肠道菌群和其代谢产物的相关性

探究重症急性胰腺炎患者肠黏膜屏障损伤与血清二胺氧化酶（DAO）、Toll样受体9（TLR9）水平及肠道菌群和其代谢产物的相关性,为该类患者的治疗提供参考。

选取2020年1月至2022年1月在我院进行诊疗的急性胰腺炎患者107例为研究组,根据其病情严重程度将其分为轻中症组（n=51）和重症组（n=56）。另选同期50例在我院进行健康体检的志愿者纳入对照组。比较各组对象不同时间点的血清DAO和TLR9水平、肠黏膜屏障损伤指标（内毒素、D-乳酸、乳果糖/甘露醇比值）、肠道菌群情况及肠道菌群代谢产物水平。

与对照相比较,研究组患者的血清DAO、TLR9、内毒素、D-乳酸水平和乳果糖/甘露醇比值以及肠道肠球菌、酵母菌数量均显著升高,肠道双歧杆菌、消化球菌、乳杆菌数量以及丙酸、丁酸、乙酸水平均显著降低（均P＜0.05）。重症组和轻中症组患者入院24 h、48 h、72 h时的血清DAO、TLR9水平呈现为先升高后降低的趋势,且重症组患者各时间点的血清DAO、TLR9水平均高于轻中症组（均P＜0.05）。重症组和轻中症组患者入院24 h、48 h、72 h时的内毒素、D-乳酸水平及乳果糖/甘露醇比值均呈现先升高后降低的趋势,且重症组患者各时间点的内毒素、D-乳酸水平及乳果糖/甘露醇比值均高于轻中症组（均P＜0.05）。患者内毒素水平与DAO、TLR9水平、双歧杆菌、消化球菌、乳杆菌、乙酸、丁酸水平均呈正相关（均P＜0.05）,与肠球菌、酵母菌数量均呈负相关（均P＜0.05）,与丙酸水平无显著相关性（P＞0.05）。患者D-乳酸水平与双歧杆菌、消化球菌、乳杆菌、乙酸、丁酸、肠球菌、酵母菌水平均无显著相关性（P＞0.05）,与DAO、TLR9、丙酸水平均呈正相关（均P＜0.05）。乳果糖/甘露醇比值与双歧杆菌、消化球菌、乳杆菌、乙酸水平均呈负相关（均P＜0.05）,与DAO、TLR9、酵母菌、丁酸水平均呈正相关（均P＜0.05）,与丙酸水平无显著相关性（P＞0.05）。

重症急性胰腺炎患者肠黏膜屏障损伤更重,血清DAO、TLR9、内毒素、D-乳酸水平及乳果糖/甘露醇比值均显著升高,同时患者的肠黏膜屏障损伤程度与其血清DAO、TLR9水平、肠道菌群数量及代谢产物水平具有相关性。

     

人源双歧杆菌的分离纯化及鉴定

利用改良的乳酸细菌（MRS）培养基从健康人群的粪便中进行双歧杆菌的分离筛选。结果表明：在添加有5-溴-4-氯-3-吲哚-β-D-半乳糖苷（X-Gal）的MRS培养基上双歧杆菌的菌落呈典型的乳白色并带有蓝色,其他菌株的菌落呈白色或深蓝色。实验共分离出10株疑似菌株,经生理生化试验和Biolog自动微生物分析系统鉴定,结果发现其中4株为双歧杆菌,这4株菌中有3株为两歧双歧杆菌,1株为长双歧杆菌。和传统MBS培养基相比较,改良MRS培养基能显著提高筛选效率。     

双歧杆菌三联活菌胶囊对化疗相关性腹泻患者肠黏膜屏障功能的保护作用

目的探讨双歧杆菌三联活菌胶囊对化疗相关性腹泻患者肠黏膜屏障功能的保护作用。方法选取78例化疗相关性腹泻患者,采用随机数字表将患者分为观察组（n=39例）和对照组（n=39例）。两组患者均常规予以补液,维持水电解质平衡及口服思密达3g,3次／d。观察组患者在此基础上加用双歧杆菌三联活菌胶囊420mg,3次／d。对照组除不使用双歧杆菌三联活菌胶囊外余治疗同观察组。观察两组患者治疗前和治疗3d后血清内毒素和和D-乳酸水平的变化,并比较其临床效果。结果治疗3d后,两组患者内毒素和和D-乳酸水平均有明显下降（P〈0．05或P〈0．01）,且观察组下降值明显大于对照组（P〈0．05）;同时观察组患者临床总有效率为92．31％,明显优于对照组的74．36％（x^2=4．52,P〈0．05）。结论双歧杆菌三联活菌胶囊治疗化疗相关性腹泻具有较好的临床效果,其作用机制可能是通过降低血清内毒素和D-乳酸水平,保护和改善改善肠黏膜屏障功能,从而恢复患者的肠功能。     

乳杆菌对致病性大肠杆菌K88和O138体外存活抑制的动力学研究

研究了一株分离自断奶仔猪小肠黏膜的肠乳杆菌L1（Lactobacillus intestinalis）体外发酵特性,及其代谢产物对病原性大肠杆菌Escherichia coli K88和O138存活的影响。体外发酵结果表明：发酵12h后,L,菌液pH值迅速降至3．90,并产生大量乳酸,为104．08mmol／L。L1菌株代谢产物对K88和O138体外生长抑制的动力学研究表明：L1菌株代谢产物对K88和O138存活具有很强的抑制作用;L1菌株发酵液与含相同浓度乳酸的自制培养液比较结果表明：乳酸在L1菌株代谢物对K88和O138存活抑制中发挥了主要作用：K88和O138对pH4．5的MRS培养液具有一定的耐受能力。     

双歧杆菌的免疫调节作用研究进展(上)

双歧杆菌是人和动物肠道的优势菌群 ,是维持宿主健康最重要的细菌。母乳喂养的婴儿比奶瓶喂养者具有更多的双歧杆菌 ,对腹泻肠道感染的易感性更低。在老年人双歧杆菌数量减少 ,而梭菌数量增加。双歧杆菌是革兰阳性、厌氧、无动力、无芽胞的杆菌 ,呈 Y或 V形。传统的 ,双歧杆菌被看做乳酸菌 (lactic acid bacteria,L AB)的成员 ,但其发酵糖类的主要终产物为乙酸 :乳酸 3∶ 2。DNA中 G+C的摩尔百分比为 5 5 %～ 6 4%。根据 DNA- DNA杂交和糖发酵试验 ,目前双歧杆菌属有 32个种。因双歧杆菌的有益作用 ,常被选做益生菌 (probiotic)。益…     

Greenhouse-Selected Resistance to Cry3Bb1-Producing Corn in Three Western Corn Rootworm Populations

Transgenic corn producing the Bacillus thuringiensis (Bt) toxin Cry3Bb1 has been useful for controlling western corn rootworm, Diabrotica virgifera virgifera LeConte, one of the most economically important crop pests in the United States. However, rapid evolution of resistance by this beetle to Bt corn producing Cry3Bb1 has been reported previously from the laboratory, greenhouse, and field. Here we selected in the greenhouse for resistance to Cry3Bb1 corn in three colonies of WCR derived from Kansas, Minnesota, and Wisconsin, respectively. Three generations of rearing on Cry3Bb1 corn significantly increased larval survival on Cry3Bb1 corn, resulting in similar survival in the greenhouse for selected colonies on Cry3Bb1 corn and isoline corn that does not produce Bt toxin. After four to seven generations of rearing on Cry3Bb1 corn, survival in the field on Cry3Bb1 corn relative to isoline corn more than doubled for selected colonies (72%) compared with control colonies (33%). For both selected and control colonies, survival in the field was significantly lower on Cry3Bb1 corn than on isoline corn. On isoline corn, most fitness components were similar for selected colonies and control colonies. However, fecundity was significantly lower for selected colonies than control colonies, indicating a fitness cost associated with resistance. The rapid evolution of resistance by western corn rootworm to Bt corn reported here and previously underlines the importance of effective resistance management for this pest.     

Effects of adult emergence timing on susceptibility and fitness of Cry3Bb1‐resistant western corn rootworms

Field‐evolved resistance by the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte to the Cry3Bb1 trait expressed in maize, has been documented in areas of Nebraska USA. Currently, only limited information is available on life‐history traits of Cry3Bb1‐resistant field populations. Therefore, the Gassmann on‐plant bioassay was used to investigate the potential variability among four Cry3Bb1‐resistant WCR field collections made in 2011–2012 by focusing on the key parameters: larval survival, developmental stage and weight with specific emphasis on the impact of adult emergence timing on these parameters in subsequent progeny. Key results: In three of four collections, the susceptibility of larval progeny from adults that emerged early or late within a generation from Cry3Bb1 plants was similar. Each of the three collections exhibited complete resistance; that is, survival on Cry3Bb1 plants was greater or equal to survival on non‐Bt isoline plants. Bioassays from an additional field collection from one site 2 years (2013) after the original collection (2011) (both from Cry3Bb1 maize) indicated that resistance to Cry3Bb1 was maintained over time at the site despite Bt trait rotation in 2012. In general, comparative WCR life‐history parameter data from Cry3Bb1 and isoline maize indicate that fitness of field collections exhibiting complete resistance was similar on each hybrid. The mean proportion of larvae in third instar and mean weight of larvae recovered in bioassays from progeny of early‐ and late‐emerged adults was not significantly affected by emergence period. This suggests that delays in development and associated mean adult emergence commonly observed in populations that are susceptible to Cry3Bb1 may become smaller as populations become resistant to Cry3Bb1. Results from this article will inform Cry3Bb1 resistance mitigation efforts and contribute to the development of sustainable WCR management programmes.     

Characterization and carbon metabolism in fungi pathogenic to Triatoma infestans, a chagas disease vector

The pathogenicity of Metarhizium anisopliae (Ma) and Beauveria bassiana (Bb) isolates against Triatoma infestans, the major vector of Chagas disease in Argentina is reported. A 100% mortality was achieved with mean lethal times varying form 5.8 (Ma6) to 7.7 (Bb5) or 11.1 days (Bb10). The fatty acid, hydrocarbon, and total lipid patterns were compared for glucose-grown and alkane-grown Bb10 cultures. The alkane-grown cells showed a lipid pattern different from that of glucose-grown cells, with triacylglyercol as the major lipid fraction, whereas sterols prevailed in the glucose-grown cells. A significant reduction in the relative amounts of linoleic acid diminished the unsaturated/saturated fatty acid ratio for alkane-grown cells; in addition, large amounts of heptacosanoic and eicosanoic acids were detected in the saturated fraction. The hydrocarbon profile of Bb10 showed a saturated chain length distribution,with a marked prevalence for straight chains, ranging from n-C18 to n-C37 in the carbon skeleton, with n-C22 as the major component. Alkane-grown cells showed no qualitative changes in their hydrocarbon fraction, but a similar ratio for odd/even carbon chains. After 48-h incubation assays,[1-(14)C]acetate uptake was largely diminished following a period of alkane growth induction. Glucose-grown cells readily incorporated 19% of the labelinto phospholipids, hydrocarbons, triacylglycerols, and free fatty acids. In contrast, incorporation was reduced to 5.3% for alkane-grown cells, accounting only for phospholipid synthesis.     

Leukocyte complement: interleukin-like properties of factor Bb

It has been previously shown that the activated form of Factor B (Factor Bb) of the alternative pathway of complement activation stimulates monocyte spreading and killing of xenogenic erythrocytes and staphylococci. Factor Bb also stimulates lymphocyte blastogenesis in vitro, and native (uncleaved) Factor B is a major constitutive product of murine macrophages. To evaluate the possible "monokine" or "lymphokine"-like properties of Factor Bb, a radioimmunoassay was developed to measure the quantities of Factor B in phytohemagglutinin (PHA)-mitogen-stimulated cultures of human peripheral blood mononuclear cells. Nonstimulated mononuclear cell cultures from human peripheral blood (containing 10-14% monocytes and greater than 85% lymphocytes) at a density of 3 X 10(6) cells/ml (in serum-free medium) released less than 7 X 10(-10) M/liter (60 ng/ml) of Factor B antigen in 24 hr at 37 degrees C, and when mononuclear cells were stimulated with PHA mitogen in serum-free medium, the levels of Factor B antigen in media at 24 hr were significantly higher 1-3 X 10(-8) M/liter (0.9-2.8 micrograms/ml). The molecular size of Factor B in these media was 50-65 kDa by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a size appropriate for Factor Bb (60 kDa). Since pathological effects of macrophages in autoimmune disease may result from the release of lysosomal hydrolases, the effects of purified Factor Bb on mononuclear phagocytes were investigated in an in vitro system of murine peritoneal exudate macrophages. Factor Bb induced secretion of marker lysosomal hydrolases N-acetyl-beta-D-glucosaminidase (hexosaminidase) and beta-glucuronidase from thioglycollate-elicited murine peritoneal exudate macrophages in a dose-response and kinetic manner. Hydrolase release was induced in serum-free medium without a known particulate activator at a concentration of 80-200 nM (5-13 micrograms/ml) Factor Bb. Maximal release occurred in 3-5 hr at 37 degrees C and extracellular enzyme activity of hexosaminidase and glucuronidase increased as intracellular enzyme levels decreased, suggesting that Factor Bb triggers release of these enzymes from intracellular lysosomal pools. These results provide an example of a complement protein which is synthesized, released, and activated during mononuclear cell culture and which induces release of lysosomal enzymes from macrophages. In conventional terminology, Factor B or Factor Bb might be termed a "lymphokine," "monokine," or "interleukin".     

Isolation, characterization and N-terminal sequences of the CNBr-cleavage peptides from human complement Factor B. Localization of a free thiol group and a sequence defining the site cleaved by factor D.

Nine CNBr-cleavage peptides from Factor B (a component of the alternative pathway of complement) were isolated. Each was characterized by amino acid analysis and automated Edman degradation. One peptide contained a methionyl bond resistant to cleavage by CNBr. The number of CNBr-cleavage peptides is in agreement with the results of amino acid analysis of Factor B and the fragments Ba and Bb. A total of 358 unique residues were identified from the N-terminal sequences of the CNBr-cleavage peptides. These represent approx. 50% and 60% of the total residues of Factor B and fragment Bb respectively. Alignment of two CNBr-cleavage peptides (CB-VIc and CB-IV) provided a continuous segment of 140 residues. This sequence contained the site cleaved by Factor D to generate the Ba and Bb fragments during the activation of complement. Peptide CB-IV contained a free thiol group at a position corresponding to residue 33 of fragment Bb. Amino sugar analyses of Factor B and of fragments Bb and Ba indicated that all the carbohydrate structures of factor B are N-linked to asparagine through N-acetylglucosamine. The two carbohydrate-attachment sites of the Bb fragment were identified.     

Proteomic studies of B16 lines: involvement of annexin A1 in melanoma dissemination

To identify proteins involved in melanoma metastasis mechanisms, comparative proteomic studies were undertaken on B16F10 and B16Bl6 melanoma cell lines and their subsequent syngenic primary tumours as pulmonary metastases were present only in the mice bearing a B16Bl6 tumour. 2DE analyses followed by MALDI-TOF identification showed variations of 6 proteins in vitro and 13 proteins in vivo. Differential expressed proteins in tumours were related to energy production and storage. Two differentially expressed proteins which had not been previously associated to melanoma progression, annexin A1 (ANXA1) and creatine kinase B (CKB), were found both in cells and in tumours. To characterize ANXA1 involvement in melanoma B16 dissemination, we reduced ANXA1 protein level by siRNA and observed a significant decrease of B16Bl6 cell invasion through Matrigel coated chambers. We further demonstrated that the presence of several formyl peptide receptors (FPR1, FPRrs1 and 2) revealed by qRT-PCR, played a role in B16 invasion: incubation of B16Bl6 cells with the FPR agonist (fMLP) or antagonist (tBOC) enhanced or decreased Matrigel coated chamber invasion respectively, with a correlation of ANXA1 levels in both treatments. As ANXA1 could bind to FPRs, this should amplify invasion and enhance melanoma dissemination.     

Influence of calcareous soil on Cry3Bb1 expression and efficacy in the field

Greater than expected injury by western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) to Cry3Bb1 expressing maize hybrids (Zea mays L.) has been reported in southwestern Nebraska. Affected areas of some fields are often associated with high pH calcareous soils where maize growth is poor and iron chlorosis is common. As part of a comprehensive study to understand potential causes of unexpected injury, experiments were conducted during 2013 and 2014 to ascertain whether the calcareous soil conditions and associated poor maize growth negatively affect the expression of Cry3Bb1. Quantitative determination of Cry3Bb1 protein expression levels in root tissues was carried out on plants at V5–V6 growth stage using the enzyme-linked immunosorbent assay. Cry3Bb1 and non-Bt near isoline maize hybrids were artificially infested with Cry3Bb1-susceptible WCR eggs to measure survival and efficacy of Cry3Bb1 maize in calcareous and non-calcareous soils. Results showed that there was not a significant difference in expression of Cry3Bb1 protein between plants from calcareous and non-calcareous soils (18.9–21.2 µg/g fresh weight). Western corn rootworm survival was about sevenfold greater from the non-Bt isoline than Cry3Bb1 maize indicating that Cry3Bb1 performed as expected when infested with a Cry3Bb1 susceptible rootworm population. When survival from calcareous and non-calcareous soils was compared, no significant differences were observed in each soil. A significant positive correlation between soil pH and expression of Cry3Bb1 protein in roots was detected from samples collected in 2014 but not in 2013. No such correlation was found between soil pH and survival of WCR. Results suggest that Cry3Bb1 expression levels were sufficient to provide adequate root protection against WCR regardless of soil environment, indicating that lowered Cry3Bb1 expression is not a contributing factor to the greater than expected WCR injury observed in some southwestern Nebraska maize fields.     

The lipid component of lipoproteins from Borrelia burgdorferi: structural analysis, antigenicity, and presentation via human dendritic cells

The spirochaetal bacteria Borrelia burgdorferi (Bb) is the tick-borne causative agent of lyme disease. The major membrane immunogens of Bb are outer surface proteins. The lipid component of these lipoproteins is relevant for the immunogenicity of Bb-lipoproteins. To characterize the antigenic properties, the native lipid component of lipoproteins was isolated and the detailed molecular structure was analyzed. The molecular structure of the lipoprotein-lipid component turned out to be S(propane-2',-3'diol)-3-thio-2-aminopropanic acid (S-glyceryl-cysteine) with one ester-linked fatty acid, one acetyl group, and one N-terminal amide-bound fatty acid. Fatty acid analysis of the lipid component indicated a heterogeneous composition comprising C16:0, C18:0, C18:1, C18:2, and C 20:0. The antigenicity was tested with in vitro bioassays using human blood-derived dendritic cells (DCs) as antigen-presenting cells and autologous Bb-specific T-cells. We found that human DCs present the lipid component of Bb-lipoproteins via MHC class II inducing an antigen-specific T-cell immune response in vitro.     

THE ISOLATION AND PROPERTIES OF LARGE BASIC PEPTIDES FROM BOVINE SPINAL CORD

Abstract— Two basic peptides (B1 and B2) were derived from bovine spinal cord following in situ proteolysis at 37°C for 10–24 h. These peptides do not arise as degradation products from the A1 protein as shown by amino acid composition and end group analysis; rather they appear to originate from some larger basic protein in the spinal cord having similarities to the P2 protein, a basic protein found in peripheral nerve myelin. The peptides were purified following defatting, acid extraction, and ammonium sulphate fractionation, by chromatography on Amberlite IRC-50 resin using guanidinium chloride. The peptides, found generally in a 4:1 ratio of B1 to B2, appeared homogeneous on gel electrophoresis and immunodiffusion. Approximately 25–60 mg of peptides was obtained per 100 g wet spinal cord.
In contrast to the basic A1 protein from myelin, neither of these peptides nor their pepsin digests were encephalitogenic. They do not cross-react immunologically with the basic A1 protein, but cross-react with each other. These peptides further differ from the A1 protein in their tryptic peptide map, size (B1, 63 residues; B2, 54 residues), and composition particularly the high lysine: arginine ratio, and low histidine content. Like the A1 protein, however, they contain a tryptophan residue and a blocked NH₂-terminal amino acid; peptide Bl has COOH-terminal valine. It was concluded that the basic peptides represent a fragment of a hitherto unidentified protein(s) of the nervous system.     

Western corn rootworm and Bt maize: challenges of pest resistance in the field

Crops genetically engineered to produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) manage many key insect pests while reducing the use of conventional insecticides. One of the primary pests targeted by Bt maize in the United States is the western corn rootworm, Diabrotica virgifera virgifera LeConte. Beginning in 2009, populations of western corn rootworm were identified in Iowa, USA that imposed severe root injury to Cry3Bb1 maize. Subsequent laboratory bioassays revealed that these populations were resistant to Cry3Bb1 maize, with survival on Cry3Bb1 maize that was three times higher than populations not associated with such injury. Here we report the results of research that began in 2010 when western corn rootworm were sampled from 14 fields in Iowa, half of which had root injury to Cry3Bb1 maize of greater than 1 node. Of these samples, sufficient eggs were collected to conduct bioassays on seven populations. Laboratory bioassays revealed that these 2010 populations had survival on Cry3Bb1 maize that was 11 times higher and significantly greater than that of control populations, which were brought into the laboratory prior to the commercialization of Bt maize for control of corn rootworm. Additionally, the developmental delays observed for control populations on Cry3Bb1 maize were greatly diminished for 2010 populations. All 2010 populations evaluated in bioassays came from fields with a history of continuous maize production and between 3 and 7 y of Cry3Bb1 maize cultivation. Resistance to Cry34/35Ab1 maize was not detected and there was no correlation between survival on Cry3Bb1 maize and Cry34/35Ab1 maize, suggesting a lack of cross resistance between these Bt toxins. Effectively dealing with the challenge of field-evolved resistance to Bt maize by western corn rootworm will require better adherence to the principles of integrated pest management.