一种新的频繁子树挖掘算法研究与实现

为提高频繁子树挖掘算法效率,结合原有频繁子树挖掘算法FSubtreeM的相关技术提出了新的全局树引导结构及其相关引理,并证明了其正确性.最后提出了新的频繁子树挖掘算法FSM_CGTG,并通过实验证明了该算法在现实数据集上的有效性且比现有频繁子树挖掘算法FSubtreeM性能优越.     

Hanseniaspora opuntiae, Saccharomyces cerevisiae, Lactobacillus fermentum, and Acetobacter pasteurianus predominate during well-performed Malaysian cocoa bean box fermentations,underlining the importance of these microbial species for a successful cocoa bean fermentation process

Two spontaneous Malaysian cocoa bean box fermentations (one farm, two plantation plots) were investigated. Physical parameters, microbial community dynamics, yeast and bacterial species diversity [mainly lactic acid bacteria (LAB) and acetic acid bacteria (AAB)], and metabolite kinetics were monitored, and chocolates were produced from the respective fermented dry cocoa beans. Similar microbial growth and metabolite profiles were obtained for the two fermentations. Low concentrations of citric acid were found in the fresh pulp, revealing low acidity of the raw material. The main end-products of the catabolism of the pulp substrates glucose, fructose, and citric acid by yeasts, LAB, and AAB were ethanol, lactic acid, acetic acid, and/or mannitol. Hanseniaspora opuntiae, Lactobacillus fermentum, and Acetobacter pasteurianus were the prevalent species of the two fermentations. Saccharomyces cerevisiae, Lactobacillus plantarum, Lactobacillus pentosus, and Acetobacter ghanensis were also found during the mid-phase of the fermentation processes. Leuconostoc pseudomesenteroides and Acetobacter senegalensis were among the prevailing species during the initial phase of the fermentations. Tatumella saanichensis and Enterobacter sp. were present in the beginning of the fermentations and they could be responsible for the degradation of citric acid and/or the production of gluconic acid and lactic acid, respectively. The presence of facultative heterofermentative LAB during the fermentations caused a high production of lactic acid. Finally, as these fermentations were carried out with high-quality raw material and were characterised by a restricted microbial species diversity, resulting in successfully fermented dry cocoa beans and good chocolates produced thereof, it is likely that the prevailing species H. opuntiae, S. cerevisiae, Lb. fermentum, and A. pasteurianus were responsible for it.     

Genotypic diversity of bacteria and yeasts isolated from Tibetan kefir

In this study, we have investigated the intraspecies genotypic diversity of bacteria and yeasts isolated from Tibetan kefir via the (GTG)₅‐REP‐PCR technology. According to the cluster analysis of generated fingerprints, forty‐nine bacterial isolates were grouped into nine clusters and formed thirteen genotypes, and twenty‐two yeast isolates were grouped into two clusters and formed two genotypes. It's worth noting that isolates of Lactobacillus kefiranofaciens, Streptococcus thermophilus, Lactobacillus kefiri and Lactobacillus paracasei exhibited the intraspecies genotypic diversity, whereas isolates of Saccharomyces cerevisiae and Kazachstania unispora did not exhibit. These results confirmed that bacterial isolates possessed higher level of intraspecies genotypic diversity than yeast isolates studied in this research. These findings revealed that (GTG)₅‐REP‐PCR was an efficient and sensitive molecular typing tool for revealing the intraspecies genotypic diversity among the bacterial isolates originated from Tibetan kefir.     

不应忽视GTG起爆药对环境的永久危害

文章列举数据说明了用GTG作雷管起爆药，爆炸后所产生的重金属氧化物的毒性及其对环境、人体的危害，提出用GTG取代DDNP不符合可持续发展战略的观点。提出科技开发和立项时，应进行环境影响评价的科研思路。     

GTG banding pattern on human metaphase chromosomes revealed by high resolution atomic-force microscopy

Surface topography of human metaphase chromosomes following GTG banding was examined using high resolution atomic force microscopy (AFM). Although using a completely different imaging mechanism, which is based on the mechanical interaction of a probe tip with the chromosome, the observed banding pattern is comparable to results from light microscopy and a karyotype of the AFM imaged metaphase spread can be generated. The AFM imaging process was performed on a normal 2 n  = 46, XX karyotype and on a 2 n  = 46, XY, t(2;15)(q23;q15) karyotype as an example of a translocation of chromosomal bands.     

Phenotypic and genotypic characterization of foodborne bacteria isolated from Sinop Province,Turkey

In this study, genotypic and phenotypic characteristics of the strains, antibiotic susceptibility, and antibiotic resistance genes of the Escherichia coli, Bacillus cereus, Listeria spp., and Salmonella spp. isolated from various animal foods in Sinop province were determined. Resistance percentages of the isolated strains to the antibiotics penicillin, vancomycin, clindamycin, tetracycline, ampicillin/sulbactam, gentamicin, ciprofloxacin, and chloramphenicol were 87.8, 71.9, 69.7, 63.4, 27.5, 23.1, 20.9, and 13.4%, respectively. Antibiotic resistance genes tetA, bla_CMY-2, and cat1 were found in 45, 21.25, and 6.25% of all the strains, respectively. The virulence genes were also investigated in the isolated in E. coli strains; the eae gene was found in 13.1% of the strains, while the stx1 was not identified in any strains. As a result, we can say that SDS-PAGE method may provide discrimination at species level; however, surveys at subspecies level demand molecular approaches such as ERIC and (GTG)₅-PCR. In addition, we can suggest that molecular techniques may be especially helpful in the rapid identification of multidrug-resistant and isolates with virulence genes. This study has revealed that the investigated bacteria in animal foods is a significant reservoir of resistance genes.     

GTG种衣剂在烟草种子包衣生产中的应用试验

为进一步提高我国烟草包衣种子质量,进行了常规种衣剂和进口GTG种衣剂的不同配比试验。结果表明:GTG种衣剂生产的包衣丸化种子裂解度、裂解时间、强度、均匀度等外观质量综合指标优于常规种衣剂;不同配比的GTG种衣剂,生产的烟草包衣种子的外观质量也存在差异,以50%GTG种衣剂 50%国产种衣剂及辅料生产的烟草包衣丸化种子综合质量较好。     

Spontaneous organic cocoa bean box fermentations in Brazil are characterized by a restricted species diversity of lactic acid bacteria and acetic acid bacteria

Spontaneous organic cocoa bean box fermentations were carried out on two different farms in Brazil. Physical parameters, microbial growth, bacterial species diversity [mainly lactic acid bacteria (LAB) and acetic acid bacteria (AAB)], and metabolite kinetics were monitored, and chocolates were produced from the fermented dry cocoa beans. The main end-products of the catabolism of the pulp substrates (glucose, fructose, and citric acid) by yeasts, LAB, and AAB were ethanol, lactic acid, mannitol, and/or acetic acid. Lactobacillus fermentum and Acetobacter pasteurianus were the predominating bacterial species of the fermentations as revealed through (GTG)₅-PCR fingerprinting of isolates and PCR-DGGE of 16S rRNA gene PCR amplicons of DNA directly extracted from fermentation samples. Fructobacillus pseudoficulneus, Lactobacillus plantarum, and Acetobacter senegalensis were among the prevailing species during the initial phase of the fermentations. Also, three novel LAB species were found. This study emphasized the possible participation of Enterobacteriaceae in the cocoa bean fermentation process. Tatumella ptyseos and Tatumella citrea were the prevailing enterobacterial species in the beginning of the fermentations as revealed by 16S rRNA gene-PCR-DGGE. Finally, it turned out that control over a restricted bacterial species diversity during fermentation through an ideal post-harvest handling of the cocoa beans will allow the production of high-quality cocoa and chocolates produced thereof, independent of the fermentation method or farm.     

GTG型火雷管技术研究

文章介绍了GTG型火雷管技术,对该雷管的装药结构、GTG起爆药和KG点火药的极限装药量、耐压性、相容性和可靠性等方面的结果进行了全面的介绍.研究结果表明,用KG作点火药、GTG起爆药作为普通纸壳火雷管的装药是可行的.GTG型火雷管比DDNP起爆药雷管性能可靠,消除了污染,比非起爆药火雷管装配工艺简单,安全性、可靠性、环保性都有所提高,该技术能够满足工业化生产使用要求.     

Effect of growth media on natural starter culture composition and performance evaluated with a polyphasic approach

Three lyophilised scotta innesto natural starter cultures for Pecorino Romano PDO cheese, collected in the 1960s, were revitalised. The influence of M17 and MRS media, compared with the traditional scotta medium, on the microbiota rep‐PCR pattern, acidification ability, and viable cell concentration was investigated with the aim of testing the effects of alternative growth media to scotta, which does not enable high cell concentration. The cocci:bacilli ratio, the cultures’ acidification ability, as well as their molecular fingerprint, were affected by the cultivation medium. The development of a new medium that does not affect the cultures’ characteristics while increasing viable cell concentration, would be desirable.