Two Cases of Multi-antibiotic Resistant Cronobacter spp. Infections of Infants in China＊

Infections by Cronobacter spp. are hazardous to infants since they can lead to neonatal meningitis, bacteremia, and necrotizing enterocolitis. Cronobacter spp. are frequently resistant to 13-1actam derivatives, macrolides, and aminoglycosides. In addition, multi-resistant strains have also been detected. In China, the isolation rate of Cronobacter spp. from commercial powdered infant formula （PIF） or follow-up formula （FUF） is relatively high. Nevertheless, clinical cases of Cronobacter infection have been ignored to date. Here we describe two cases of Cronobacter infection detected at the Wuhan Women and Children Medical Care Center Hospital （Wuhan City, China）. We provide the genomic analysis of the isolates and the antibiotic-resistance profiles of the two strains. The Cronobacter strains identified in this study were not susceptible to third-generation cephalosporins, aminoglycoside, and/or trimethoprim-sulfamethoxazole. Whole genome sequencing revealed various genes known to encode antibiotic resistance. Future studies are needed to determine whether the genes predicted in this study are functional. As with Enterobocter spp., the antibiotic resistance of Cronobocter is a serious issue that requires more attention.

The Survey of Cronobacter spp.(formerly Enterbacter sakazakii) in Infant and Follow-up Powdered Formula in China in 2012

Objective To determine Cronobacter spp. contamination in infant and follow-up powdered formula in China. Methods All of 2282 samples were collected from the retail markets in China from January 2012 to December 2012, and analyzed for Cronobacter spp. by the Chinese National Food Safety Standard. Characterization of the isolates was analyzed by pulsed-field gel electrophoresis（PFGE） with XbaI and Spe I restriction enzymes. Results Cronobacter spp. strains were isolated from 25 samples, and the positive rates in infant powdered formulas and follow-up powdered formulas were 0.90%（10/1011） and 1.18%（15/1271）, respectively. Analysis of variable data regarding different purchasing store formats, seasonality, and production locations as well as comparison of infant versus follow-up formulas did not reveal statistically significant factors. During the sampling period, one of six surveillance zones did exhibit a statistically significant trend towards higher positive rate. PFGE characterization of Cronobacter spp. to elucidate genetic diversity revealed only three pairs of Cronobacter spp. out of 25 having the same PFGE patterns. Conclusion The current investigation indicated a lower positive rate of Cronobacter spp. in the powdered formula in China. This evidence suggested contamination originating from multiple different sources during the manufacturing process.

Food Safety Risks and Contributing Factors of Cronobacter spp.

Cronobacter species are a group of Gram-negative opportunistic pathogens,which cause meningitis,sep-ticemia,and necrotizing enterocolitis in neonates and infants,with neurological sequelae in severe cases.Interest in Cronobacter has increased significantly in recent years due to its high virulence in children.In this review,we summarize the current understanding of the prevalence of Cronobacter species in several important food types.We discuss the response mechanisms enabling persistence in adverse growth con-ditions,as well as its pathogenicity.We emphasize the food safety concerns caused by Cronobacter and subsequent control methods and clinical treatments.

基于改进YOLOv3-SPP算法的道路车辆检测

针对在城市道路场景下视觉检测车辆时,车辆密集和远处车辆呈现小尺度,导致出现检测精度低或者漏检的问题,提出了一种基于改进的YOLOv3-SPP算法,对激活函数进行优化,以DIOU-NMS Loss作为边界框损失函数,增强网络的表达能力。为提高所提算法对小目标和遮挡目标的特征提取能力,引入空洞卷积模块,增大目标的感受野。实验结果表明,所提算法在检测车辆目标时m AP提高了1.79%,也有效减少了在检测紧密车辆目标时出现的漏检现象。

FOSB、SPP1基因表达对经肝动脉介入化疗栓塞术治疗的中晚期肝癌生存期预测价值

目的探讨骨肉瘤原癌基凶同源物B(FOSB)、分泌性磷蛋白1(SPP 1)基因表达对经肝动脉介入化疗栓塞术治疗的中晚期肝癌患者术后生存期的预测价值。方法回顾性分析2016年1月—2017年10月在西安医学院第一附属医院进行诊治的中晚期肝癌患者115例作为研究对象,根据FOSB、SPP 1基因表达水平分为FOSB高表达组(n=52)、FOSB低表达组(n=63)及SPP 1高表达组(n=89)、SPP 1低表达组(n=26)。同时选取115例健康体检者为健康对照组。分析FOSB、SPP 1表达与中晚期肝癌患者临床病理特征的关系。对纳入研究的患者进行为期60个月的随访,Logistics风险回归模型分析影响患者生存期的危险因素。Kaplan-Meier生存曲线分析FOSB、SPP 1表达水平与患者生存预后的关系。结果肝癌患者外周血单个核细胞中FOSB mRNA表达水平明显低于健康对照组,SPP 1 mRNA表达水平明显高于健康对照组,差异具有统计学意义(P<0.05)。FOSB、SPP 1表达在中晚期肝癌患者肿瘤大小、Child-Pugh分级、淋巴转移、BCLC分期方面比较差异具有统计学意义(P<0.05)。单因素分析结果显示,存活组和死亡组在肿瘤大小、Child-Pugh分级、淋巴转移、BCLC分期、FOSB、SPP 1表达方面比较,差异均具有统计学意义(P<0.05)。肿瘤大小、Child-Pugh分级、淋巴转移、BCLC分期、FOSB低表达、SPP 1高表达均为中晚期肝癌患者生存期的独立危险因素(P<0.05)。随访时间60个月,患者生存率为17.39%(20/115),FOSB高表达组中位生存时间为39.7个月,明显高于FOSB低表达组的19.3个月(P<0.05);SPP 1低表达组中位生存时间为40个月,明显高于SPP 1高表达组的18个月(P<0.05)。结论FOSB在中晚期肝癌患者中表达明显下调,SPP 1表达上调,其对预测中晚期肝癌患者肝动脉介入化疗栓塞术治疗生存期具有一定的价值。FOSB、SPP 1有望成为评估介入术治疗患者预后的潜在指标,可协同肿瘤大小、Child-Pugh分级、淋巴转移、BCLC分期等临床指标预测或评估肝癌患者术后生存情况。

Cronobacter spp.,foodborne pathogens threatening neonates and infants

Cronobacter spp.(formerly Enterobacter sakazakii) are special foodborne pathogens. Cronobacter infection can cause necrotizing enterocolitis, sepsis and meningitis in all age groups, especially neonates and infants, with a high fatality of up to 80%, although the infection is rare. Outbreaks of Cronobacter infection are epidemiologically proven to be associated with contaminated powdered infant formula(PIF). Cronobacter spp.can resist dry environments and survive for a long period in food with low water activity. Therefore, Cronobacter spp.have become serious pathogens of neonates and infants, as well as in the dairy industry. In this review, we present the taxonomy, pathogenesis, resistance, detection and control of Cronobacter spp.

SPP1和PD-L1在子宫内膜癌组织中的表达及其预后价值

目的:分析分泌型磷蛋白1(secreted phosphoprotein 1,SPP1)和程序性死亡蛋白配体1(programmed cell death-ligand 1,PD-L1)在子宫内膜癌(endometrial carcinoma,EC)组织中的表达水平及与预后的关系。方法:通过免疫组织化学方法分析SPP1和PD-L1在84例EC组织和61例正常子宫内膜组织中的表达情况,分析SPP1和PD-L1表达与临床病理特征及预后的关系,利用UALCAN分析工具(https://ualcan.path.uab.edu/)分析癌症基因组图谱(The Cancer Genome Atlas,TCGA)数据库中EC组织SPP1和PD-L1 mRNA的表达及与预后的关系。结果:EC组织SPP1阳性表达率高于正常子宫内膜组织(71.43%vs 36.07%,P=0.001),PD-L1阳性表达率低于正常子宫内膜组织(25.00%vs 42.62%,P=0.025);EC组织中,SPP1阳性表达率与组织学分级相关(P<0.05),PD-L1阳性表达率与淋巴结转移相关(P<0.05),SPP1与PD-L1表达呈正相关(列联系数r=0.237,P=0.026);EC组织中,不同SPP1和PD-L1表达患者总生存期无差异(均P>0.05)。TCGA数据库中生物信息学分析显示EC中SPP1 mRNA表达水平显著高于正常子宫内膜组织(P<0.01),PD-L1 mRNA表达水平与正常子宫内膜组织比较,差异无统计学意义(P=0.057);EC组织SPP1 mRNA和PD-L1 mRNA表达水平呈正相关(r=0.350,P<0.05);不同SPP1和PD-L1表达水平患者总生存期无差异(均P>0.05)。结论:SPP1在EC组织中的表达与PD-L1呈正相关,可能共同参与EC免疫微环境调控,SPP1和PD-L1均不是EC独立预后因子。

Genetic Diversity of Jute Mallow (Corchorus spp.) Accessions Based on ISSR Markers

Jute mallow is a nutritious leafy vegetable. The leaves are rich in proteins, vitamins and essential amino acids. Molecular characterization of Jute mallow with focus on improvement of leaf yield is scarcely reported. In the present study, inter sequence simple repeats (ISSR) molecular markers were employed to assess genetic diversity and relationships of 83 accessions of Jute mallow from different parts of Africa and Asia conserved at the World Vegetable Center East and Southern Africa. A total of 89 bands were amplified by 8 ISSR primers. Number of polymorphic bands per primer ranged from 2 to 6 with an average of 2.75 bands per primer. Polymorphic information content (PIC) values ranged from 0.390 to 0.760 with average of 0.53. Average Nei’s gene diversity (h) and Shannon’s information index (I) were 0.335 and 0.494 respectively. The highest pairwise genetic distance was 0.431 observed in a population from East Africa accessions. PC1 and PC2 axis explained 21.69% and 11.66% of the total variation respectively. UPGMA cluster analysis grouped the accessions into six main clusters at genetic similarity coefficient of 0.53 as standard value for classification. These results have important implications for jute mallow breeding and conservation.

Prevalence and Antibiotic Resistance of Urinary Tract Pathogens, with Molecular Identification of Klebsiella pneumoniae, Klebsiella oxytoca, and Acinetobacter spp., Using Multiplex Real-Time PCR

Urinary tract infections (UTIs) caused by uropathogens are a significant public health problem, and their treatment primarily relies on antibiotic therapy. However, the increasing global development of antibiotic resistance necessitates updating diagnostic techniques to ensure higher sensitivity and specificity, especially with advancements in science and medicine. This study aimed to evaluate the prevalence of UTIs and antibiotic resistance profiles through urine culture, as well as to identify Klebsiella pneumoniae, Klebsiella oxytoca, and Acinetobacter spp. in urine samples using a molecular approach with multiplex real-time PCR. From May 3 to July 25, 2023, at the Pietro Annigoni Biomolecular Research Center (CERBA) and Saint Camille Hospital of Ouagadougou (HOSCO), 209 urine samples collected from patients with suspected UTIs were analyzed using both urine culture and multiplex real-time PCR. Among the 209 patients, 52.15% were male and 47.85% female, with an average age of 46.87 ± 21.33 years. Urine cultures revealed an overall UTI prevalence of 23.44%, with a prevalence of 8.13% in men versus 15.31% in women (P = 0.023). The bacterial prevalence rates were as follows: Escherichia coli (12.92%), Klebsiella spp. (7.18%), Enterobacter cloacae (1.44%), Staphylococcus aureus (0.96%), and other bacteria. Klebsiella spp. demonstrated 100% resistance to Amoxicillin and Amoxicillin/Clavulanic Acid, while Escherichia coli showed 96.2% and 65.4% resistance to Amoxicillin and Amoxicillin/Clavulanic Acid, respectively. PCR analysis of the target bacteria revealed mono-infection prevalence rates of Klebsiella pneumoniae (10.39%), Klebsiella oxytoca (7.79%), and Acinetobacter spp. (7.79%), along with a co-infection prevalence rate of Klebsiella pneumoniae/Acinetobacter spp. (1.30%). This study demonstrated that PCR, with its high sensitivity and specificity, could effectively distinguish Klebsiella pneumoniae from Klebsiella oxytoca and detect Acinetobacter spp. in less than 24 hours—something urine culture alone could not achieve. The relative ease of automating urine PCR testing, combined with its diagnostic accuracy and rapid turnaround time, makes it a valuable addition to modern medical practice for the laboratory diagnosis of UTIs.

Effect of dissolved organic nitrogen on the bloom of Prorocentrum donghaiense and Karenia spp. in the East China Sea coastal waters

Understan ding the mechanism of harmful algal bloom formation is vital for effectively preventing algal bloom outbreaks in coastal environments.Karenia spp.blooms in the East China Sea show a significant correlation with nutrient regimes.However,the impact of key components of nutrients,especially dissolved organic nitrogen(DON),on the blooms of Karenia spp.is not clear.Quantitative research is still lacking.In this study,the cruise observations,field mesocosm-flask culture experiments,and a multinitrogen-tri-phytoplankton-detritus model(NTPD) are combined to reveal the quantitative influence of nutrient regimes on the shift of Prorocentrum donghaiense and Karenia spp.in the East China Sea.It has a synchronism rhythm of diatom-P.donghaienseKarenia spp.-diatom loop in the field culture experiment,which is consistent with the results of the cruise observation.The results showed that the processes of terrigenous DON(TeDON) and dissolved inorganic nitrogen(DIN:NO_(3)^(-)-N,NH_(4)^(+)-N) absorption promoted P.donghaiense to become the dominant algae in the community;whereas the processes of DON from P.donghaiense absorption promoted Karenia spp.to become the dominant algae in ambient DIN exhaustion.In addition,the three-dimensional fluorescence components of humus C,tyrosine and fulvic acid can indicate the processes of growth and extinction of P.donghaiense and Karenia spp.,respectively.This study infers that P.donghaiense and Karenia spp.regime shift mechanism associated with the nutrient regime in coastal waters,which provides a scientific basis for the environmental management of coastal eco system health.

Strawberry (Fragaria spp.): Cultivation, Production, Consumption, and Marketing in Cameroon

Strawberry (Fragaria spp.) is one of the most important fruits classified as exotic fruits imported into Cameroon. To have an inventory of its cultivation in Cameroon, a survey study was carried out among eight farms of Fragaria spp. from January 2021 to February 2022. The plant was introduced in Cameroon in 2018. There are 13 varieties of Fragaria spp. currently cultivated. Among these 13 varieties, eleven are hybrids of Fragaria x ananassa (“Amiga”, “Amine”, “Camarosa”, “Chandler”, “Charlotte”, “Elsanta”, “Gariguette”, “Madame Moutot”, “Ostara”, “Ruby gem” and “San Andreas”), and two of the hybrids of Fragaria vesca (“Maestro” and “Mara des bois”). The cropping system, irrigation system, and type of fertilizers applied differ from one strawberry farm to another. Biofertilizers (such as mycorrhizal), inorganic and organic fertilizers are actually used to improve production. The potential annual production of strawberries from January 2021 to February 2022, estimated based on the survey data, was 21.216 tons for all growers. Among these eight production farms, the Lolodorf BIO Farm presents 6000 kg (six tons) of strawberries and 100,000 stolons (seedlings) produced, from seven varieties of Fragaria spp. cultivated, with 6 varieties which are hybrids variety Fragaria x ananassa (“Amiga”, “Amine”, “Chandler”, “Gariguette”, “Madame Moutot”, and “Ruby gem”), and one which is a hybrid of Fragaria vesca (“Mara des bois”). Certain diseases were also observed and recorded depending on the growing areas.

Botulinum toxin type A-targeted SPP1 contributes to neuropathic pain by the activation of microglia pyroptosis

BACKGROUND Neuropathic pain(NP)is the primary symptom of various neurological condi-tions.Patients with NP often experience mood disorders,particularly depression and anxiety,that can severely affect their normal lives.Microglial cells are as-sociated with NP.Excessive inflammatory responses,especially the secretion of large amounts of pro-inflammatory cytokines,ultimately lead to neuroinflam-mation.Microglial pyroptosis is a newly discovered form of inflammatory cell death associated with immune responses and inflammation-related diseases of the central nervous system.METHODS Two models,an in vitro lipopolysaccharide(LPS)-stimulated microglial cell model and a selective nerve injury model using BTX-A and SPP1 knockdown treatments,were used.Key proteins in the pyroptosis signaling pathway,NLRP3-GSDMD,were assessed using western blotting,real-time quantitative polymerase chain reaction,and immunofluorescence.Inflammatory factors[interleukin(IL)-6,IL-1β,and tumor necrosis factor(TNF)-α]were assessed using enzyme-linked immuno-sorbent assay.We also evaluated microglial cell proliferation and apoptosis.Furthermore,we measured pain sensation by assessing the delayed hind paw withdrawal latency using thermal stimulation.RESULTS The expression levels of ACS and GSDMD-N and the mRNA expression of TNF-α,IL-6,and IL-1βwere enhanced in LPS-treated microglia.Furthermore,SPP1 expression was also induced in LPS-treated microglia.Notably,BTX-A inhibited SPP1 mRNA and protein expression in the LPS-treated microglia.Additionally,depletion of SPP1 or BTX-A inhibited cell viability and induced apoptosis in LPS-treated microglia,whereas co-treatment with BTX-A enhanced the effect of SPP1 short hairpin(sh)RNA in LPS-treated microglia.Finally,SPP1 depletion or BTX-A treatment reduced the levels of GSDMD-N,NLPRP3,and ASC and suppressed the production of inflammatory factors.CONCLUSION Notably,BTX-A therapy and SPP1 shRNA enhance microglial proliferation and apoptosis and inhibit microglial death.It improves pain perception and inhibits microglial activation in rats with selective nerve pain.

Multidrug-Resistant of Escherichia coli and Salmonella spp. Strains in Chicken Feces Intended for Consumption in Open Spaces of Ouagadougou, Burkina Faso

Resistant bacteria can be transmitted to humans through feces or contaminated meat from local chickens. Bacterial strains were isolated from the intestinal contents of 400 local chicken samples from various sales sites. These strains were then characterized using bacteriological and biochemical methods to identify resistant strains. In a study conducted in Ouagadougou, we systematically collected chicken fecal samples from 20 locations across the city, followed by isolation and identification of Salmonella spp. using specific enrichment and culture methods, as well as Escherichia coli. Bacterial strains were characterized using antibiotic resistance profiles were determined through agar diffusion tests, revealing sensitivity or resistance to a range of antibiotics based on established scientific criteria. The results showed that out of the 400 samples collected, 81.25% and 63.5% were contaminated by Escherichia coli and Salmonella spp., respectively. Among these, 86.15% of identified Escherichia coli and 50.78% of Salmonella spp. displayed resistance to at least one tested antibiotic. Among 280 Escherichia coli isolates identified resistant to at least one antibiotic, 31.07% were resistant to cefotaxime (CTX), 20.35% to ceftazidime (CAZ), 21.07% to ceftriaxone (CTR), 75% to amoxicillin clavulanic acid (AMC), 23.57% aztreoname (ATM) and 27.14% were resistant to imipenem (IMP). In the case of the 129 Salmonella spp. isolates resistant to at least one tested antibiotic, 34.88% were resistant to CTX;41.08% to CAZ;35.65% to CTR, 92% to AMC, 39.53% to ATM and finally 47.28% were resistant to IMP. Our study revealed high prevalence of resistance in bacterial strains isolated from local chickens sold outdoors in Ouagadougou. These findings raise significant public health concerns, due to the possible transmission of these resistant strains to humans through the consumption of contaminated meat, thus complicating the treatment of bacterial infections.

基于SPPs的二维多凹槽结构MIM波导透射特性的研究

不规则结构对波导的传播特性有着很大的影响,但对于MIM(Metal-Insulator-Metal,金属-介质-金属型)波导双边矩形槽并添加多凹槽结构对传播特性的影响方面的研究尚少。在研究内嵌凹槽位置对MIM波导透射特性影响的基础上,提出了在双矩形波导模型基础的内部添加多凹槽结构来影响波导的透射特性,并对波长与透射的关系及不同凹槽位置、不同凹槽数目的电场模图进行了对比分析。在凹槽位置改变时,Fano共振峰位置发生了移动,在小波长区域共振峰的数目也有所改变。随着上凹槽位置的增大,最大透射峰位置发生了蓝移,透射强度也有一定的增强;增加凹槽对数,得到波长与透射特性的关系曲线发生了改变,随着凹槽对数的增加,Fano共振峰的位置发生了一定的红移,且在小波长600~1 000 nm区域,Fano共振峰数目及透射峰值均发生了变化。这些研究结果可为预测金属缝隙波导制备过程中小尺度、多凹槽局部缺陷结构对其传播特性的影响提供理论依据。

差分码偏差产品对BDS-3多频SPP影响分析

为分析不同差分码偏差(differential code bias,DCB)产品对BDS-3多频伪距单点定位(single point positioning,SPP)的影响,基于IGS跟踪站实测数据,对比分析CAS产品、DLR产品、GBM产品解算B1C/B2a、B1I/B3I、B1C/B2a/B3I、B1I/B2a/B3I伪距单点定位精度的影响。试验结果表明:采用CAS产品解算BDS-3双频和三频伪距单点定位精度较优;采用DLR产品解算B1I/B3I和B1I/B2a/B3I伪距单点定位精度较优,但低于CAS产品;采用DLR产品和GBM产品解算B1C/B2a和B1C/B2a/B3I伪距单点定位精度较差,E、N、U 3个方向精度均低于7 m;无论采用哪种产品,三频伪距单点定位精度均优于双频伪距单点定位精度,且提升量较优。

SPP1、OLR1在宫颈癌的表达及临床意义

观察SPP1(分泌型磷酸蛋白1)、OLR1(氧化低密度脂蛋白受体1)在正常宫颈及宫颈癌中的表达情况,探讨二者与宫颈癌相关临床病理资料及预后的关系。方法 选取2021年01月至2023年01月就诊于包头市肿瘤医院的48例宫颈癌患者为病例组,获取同一时间就诊于该院的48例正常宫颈组织为对照组。应用免疫组化法检测SPP1、OLR1在上述两组的表达情况,初步探讨SPP1和OLR1与宫颈癌患者的关系及二者之间的相关性;采用生物信息学分析对比宫颈癌及正常宫颈中SPP1、OLR1的表达,并分析其与宫颈癌患者生存预后的关系。结果 癌组织中SPP1、OLR1阳性表达率高于正常组织(P<0.05);SPP1的表达与癌组织淋巴结转移、分化程度及FIGO具有相关性(P<0.05);OLR1的表达与癌组织淋巴结转移和分化程度具有相关性(P<0.05);在癌组织中,SPP1和OLR1的表达呈正相关(r=0.423,P=0.007)。与SPP1低表达相比,高表达患者的生存率更低(P<0.05);宫颈癌患者的预后不良与SPP1、OLR1的T分期、N分期相关(P<0.05)。结论 宫颈癌组织的发生发展可能与SPP1、OLR1密不可分,检测这两种蛋白对宫颈癌的发生、发展及预后有一定的帮助。

胶州湾聚球菌(Synechococcus spp.)蓝细菌的分布及其对初级生产力的贡献

自2002—2004年应用表面荧光显微镜计数法对胶州湾聚球菌(Synechococcusspp.)蓝细菌的季节变化、月变化及其对浮游植物总初级生产力的贡献进行调查研究。结果显示,胶州湾Synechococcusspp.丰度处于0.16×104—21×104cells/ml之间,最大与最小值之间相差约两个数量级,其中夏天Synechococcusspp.丰度最高,春、秋季相当,冬季最低。夏季Synechococcusspp.丰度平均值约是冬季的3—4倍。Synechococcusspp.的季节变化呈现一定周期性。Synechococcusspp.月最高值(21×104cells/ml)出现在8月的B2站表层,最低值(0.15×104cells/ml)出现在12月A1站表层。对18个月的胶州湾Synechococcusspp.水平分布进行分析,结果显示,河口和近岸区域Synechococcusspp.丰度相对较高。以D8站为典型站位对Synechococcusspp.垂直分布进行的分析发现,不同季节Synechococcusspp.最大值出现的水深不同。胶州湾Synechococcusspp.在总浮游植物生物量中所占的比例在0.2%—77%之间,平均为4.7%。此外,对2003—2004年温度与Syne-chococcusspp.丰度的相关性分析中发现,两者呈正线性相关(相关系数达0.6)。

食蚊鱼(Gambusia spp.)入侵生态学研究进展

食蚊鱼(Gambusia spp.)是原产于北美洲的著名入侵物种,它对蚊类幼虫具有很强的捕食压力,被作为疟疾防治生物工具而在全世界温带和热带地区扩散。近20多年来的研究认为,食蚊鱼通过食物竞争和捕食等机制威胁引入地的无脊椎动物、鱼类、两栖类的生存,显著影响引入地的生物多样性。它们具有广泛的生境适应性、生长迅速、卵胎生、高生殖率、对生殖生态条件无特殊要求等特点。另外,它们的个体野外寿命不超过2 a,种群更新速度快,种群内形成春季和夏季两个繁殖群体,并具有不同的繁殖生物学特点,因而形成复杂的世代结构。遗传上,雌鱼具有混交及能长期贮存精子的特点,能快速建立种群并克服奠基效应。这些种群通过快速适应性进化而形成一定规模的地理群体。当前,由于食蚊鱼在预防疟疾的工作中仍具有不可替代的作用,它会借助于人力的作用而继续扩散。为减轻它对非目标地区和非目标生物的影响,应进一步深入开展其入侵生态学研究。

Paenibacillus spp.BD3526发酵小麦麸皮生产凝乳酶

对Paenibacillus spp.BD3526凝乳酶的发酵条件和凝乳性能进行了研究,探讨了不同培养基、发酵时间、碳源、氮源和装液量对凝乳酶活力和活菌数的影响,并与商业化的小牛皱胃酶、重组凝乳酶、Rhizomucor miehei来源凝乳酶进行凝乳性能比较。实验结果表明:发酵时间、碳源、氮源和装液量对BD3526凝乳酶活力(milkclotting activity,MCA)和蛋白水解活力(proteolytic activity,PA)均有不同程度的影响。选用小麦麸皮培养基进行发酵至24 h时,MCA达到最大至3 279.76±67.11 SU/m L,凝乳性能强,PA值在整个发酵期间变化不大;添加碳源或氮源会不同程度地降低MCA值;装液量为30 m L时,发酵上清液中菌体浓度最高、MCA达到6 000 SU/m L。与商业化的凝乳酶相比,BD3256凝乳酶在凝乳过程中未使凝乳块产生过度水解,也无乳清析出现象,具有应用到干酪生产中的潜力。

Trichoderma spp.对樟子松枯梢病病原菌的影响

通过Trichoderma属 3个菌株与樟子松枯梢病菌 (Sphaeropsissapinea)对峙培养试验的结果表明 :Tri chodermaviride1,Trichodermaviride 2及Trichodermaharzianum对樟子松枯梢病病原菌都有抑制效果 ,其中Trichodermaviride 2对病原菌的相对抑制效果最好 ,且其相对抑制效果随着时间的增加而增长 ,在 4 0h达到最高 ,为 73.5 5。Trichodermaviride 1和Trichodermaharzianum对病原菌的相对抑制效果在 16h达到最高 ,分别为 4 .86及 2 .5 9。