Caseinolysis in cheese by Enterobacteriaceae strains of dairy origin

AIMS: To study the effect of Enterobacteriaceae strains of dairy origin on caseins under cheese manufacture and ripening conditions. METHODS AND RESULTS: Strains belonging to the genera Enterobacter, Escherichia, Hafnia and Serratia were isolated from fresh raw milk cheeses. Residual caseins in cheeses made from milk individually inoculated with 10 strains of Enterobacteriaceae were determined by capillary electrophoresis. Hierarchical cluster analysis of strains based on data of residual caseins grouped together strains from the same genus, excepting Hafnia strains, which were separated into two groups. Serratia was the most proteolytic genus in our study. Preferences for degradation of casein fractions differed among the four genera studied. CONCLUSIONS: Enterobacteriaceae strains posses proteolytic systems active on all casein fractions under cheese manufacture and ripening conditions. The effects on caseins were similar for strains belonging to the same genus. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of Enterobacteriaceae in cheeses may affect proteolysis during ripening. Assays of Enterobacteriaceae proteolytic activity on milk agar plates may underestimate their caseinolytic activity in cheese.     

Enterobacteriaceae facilitate the anaerobic degradation of glucose by a forest soil

Anoxic micro zones that occur in soil aggregates of oxic soils may be temporarily extended after rainfall and thus facilitate the anaerobic degradation of organic compounds in soils. The microbial degradation of glucose by anoxic slurries of a forest soil yielded acetate, CO₂, H₂, succinate, and ethanol, products indicative of mixed acid fermentation. Prokaryotes involved in this process were identified by time-resolved 16S rRNA gene-targeted stable isotope probing with [¹³C-U]-glucose. All labeled phylotypes from the ¹³C-enriched 16S rRNA gene were most closely related to Rahnella and Ewingella , enterobacterial genera known to catalyze mixed acid fermentation. These results indicate that facultative aerobes, in particular Enterobacteriaceae , (1) can outcompete obligate anaerobes when conditions become anoxic in forest soils and (2) may be involved in the initial decomposition of monosaccharides in anoxic micro zones of aerated forest soils.     

Prevalence of plasmid-mediated quinolone resistance determinants among oxyiminocephalosporin-resistant Enterobacteriaceae in Argentina

High quinolone resistance rates were observed among oxyiminocephalosporin-resistant enterobacteria. In the present study, we searched for the prevalence of plasmid-mediated quinolone resistance (PMQR) genes within the 55 oxyiminocephalosporin-resistant enterobacteria collected in a previous survey. The main PMQR determinants were aac(6'')-Ib-cr and qnrB, which had prevalence rates of 42.4% and 33.3%, respectively. The aac(6'')-Ib-cr gene was more frequently found in CTX-M-15-producing isolates, while qnrB was homogeneously distributed among all CTX-M producers.     

Demonstration of formaldehyde dehydrogenase activity in formaldehyde-resistant Enterobacteriaceae

Clinical isolates of different Enterobacteriaceae strains and genetically modified variants which were resistant to the disinfectant formaldehyde were investigated. In cell-free extracts of all formaldehyde-resistant strains a glutathione-dependent formaldehyde dehydrogenase activity was demonstrated. In contrast cell extracts from formaldehyde sensitive strains did not show any formaldehyde dehydrogenase activity. The enzymatic degradation of formaldehyde seems to play an important role in formaldehyde resistance.     

Taxonomy of Toxoplasma*

SYNOPSIS. After reviewing reports of the hosts, structure and life cycle of Toxoplasma, the genus is placed in the apicomplexan family Eimeriidae and the following 7 species are recognized: Toxoplasma gondii (Nicolle & Manceaux) (type species) from about 200 species of mammals and birds, with oocysts in felids; Toxoplasma alencari (Da Costa & Pereira) from the frog Leptodactylus ocellatus; Toxoplasma brumpti Coutelen from the iguana Iguana tuberculata; Toxoplasma colubri Tibaldi from the snakes Coluber melanoleucus and Coluber viridiflavus; Toxoplasma hammondi (Frenkel & Dubey) (a new combination for Hammondia hammondi) from the house mouse with oocysts in the domestic cat; Toxoplasma ranae Levine & Nye from the leopard frog Rana pipiens; and Toxoplasma serpai Scorza, Dagert & Iturriza Arocha from the toad Bufo marinus.     

Metabolism of L(−)-carnitine by Enterobacteriaceae under aerobic conditions

Different Enterobacteriaceae, such as Escherichia coli, Proteus vulgaris and Proteus mirabilis, are able to convert L(-)-carnitine, via crotonobetaine, into gamma-butyrobetaine in the presence of carbon and nitrogen sources under aerobic conditions. Intermediates of L(-)-carnitine metabolism (crotonobetaine, gamma-butyrobetaine) could be detected by thin-layer chromatography. In parallel, L(-)-carnitine dehydratase, carnitine racemasing system and crotonobetaine reductase activities were determined enzymatically. Monoclonal antibodies against purified CaiB and CaiA from E. coli O44K74 were used to screen cell-free extracts of different Enterobacteriaceae (E. coli ATCC 25922, P. vulgaris, P. mirabilis, Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae) grown under aerobic conditions in the presence of L(-)-carnitine.     

三种菟丝子的数值分类学

选取３３个形态学性状,应用不加权虎术平均配对法,对惧到的３种菟丝子的２４个居群进行了数值分类学研究,结果表明：（１）日本菟丝子与大花菟丝子亲缘关系较近,两者与中国菟丝子之间关系较疏远,聚类结果献技Ｙｕｎｃｋｅｒ对菟丝子属的分类处理;（２）日本菟丝子和大花菟丝子种内都存在遗传多样性,根据聚类结果将日本菟丝子分成２个变种,将大花菟丝子分成３个变种。     

不同时期肠杆菌科细菌产ESBLS及耐药性的监测

目的对不同时期肠杆菌科细菌产超广谱β-内酰胺酶（ESBLS）及耐药性进行监测。方法采用生物梅里埃ATB药敏试验板测定肠杆菌科细菌中大肠埃希菌和肺炎克雷伯菌对抗生素的敏感性,同时用表型确证法检测ESBLS。结果肠杆菌科细菌2006-2008年与2009-2011年两个时期相比,ESBLS的检出率增长近50%。对亚胺配南、头孢吡肟、头孢西丁耐药率较低,对哌拉西林/他唑巴坦、阿米卡星的耐药率次之,对其他β-内酰胺类、氨基糖苷类、喹诺酮类及磺胺类抗生素的耐药率较高,且两个时期相比耐药率增加明显,差异具有统计学意义（P〈0.05）。结论临床产ESBLS菌株不断增多,多重耐药现象越来越严重,临床实验室应当把ESBLS的检测作为常规监测工作,有效指导临床选用抗菌药物。     

糖多孢菌属的多相分类

在糖多孢菌属的分类学研究中,最初是根据形态特征、培养特征及生理生化特征等表观分类学指征进行研究。随着“多相分类”方法的广泛应用,化学分类和分子分类在糖多孢菌属的分类学研究中起到越来越重要的作用。糖多孢菌是寻找新的生物活性物质的重要菌源,某些种能产生重要的生物活性物质,如抗生素、酶类、维生素、藻类促生长因子、纤维素降解促进因子、免疫抑制剂等。     

Characterisation of local isolates of Enterobacteriaceae from Turkey

20 local isolates of enterics belonging to the genera Salmonella, Enterobacter, Proteus, Citrobacter from human, chicken and/or egg were characterised for their antibiotic resistance patterns, plasmid profiles, phage types, outer membrane proteins, and lipopolysaccharide patterns. Relatedness of these characteristics for epidemiological analysis was assessed. 18 (90%) strains were resistant to at least one antibiotic and those (multi-drug resistant ones) resisting to two or more antibiotics constituted 50% of all isolates. A common 54 kb plasmid was harboured by 55% of the isolates. 14 isolates showed smooth type lipopolysaccharide. 60% of the 20 isolates contained outer membrane proteins in a molecular weight range of 34.6 to 30.6 kDa. The data reveal the lack of correlation between the characteristics investigated.     

座壳孢属真菌的分类研究

对昆虫病原真菌座壳孢的功能、资源调查、经典分类发展历程及其传统分类存在的问题、以及应用现代分子生物学方法研究座壳孢的系统发育等进行了回顾和总结,旨在为澄清该属真菌的种类及其系统发育关系提供科学依据。     

Genome Reduction Promotes Increase in Protein Functional Complexity in Bacteria

Obligate pathogenic and endosymbiotic bacteria typically experience gene loss due to functional redundancy, asexuality, and genetic drift. We hypothesize that reduced genomes increase their functional complexity through protein multitasking, in which many genes adopt new roles to counteract gene loss. Comparisons of interaction networks among six bacteria that have varied genome sizes (Mycoplasma pneumoniae, Treponema pallidum, Helicobacter pylori, Campylobacter jejuni, Synechocystis sp., and Mycobacterium tuberculosis) reveal that proteins in small genomes interact with proteins from a wider range of functions than do their orthologs in larger genomes. This suggests that surviving proteins form increasingly complex functional relationships to compensate for genes that are lost.     

放线菌的分子分类

在放线菌分类学研究中,最初是根据形态特征、生理生化特征等表观分类学特征进行研究。随着分子生物学的飞速发展,放线菌的分类鉴定亦从传统的表型分类进入到各种基因型分类水平。分子分类在放线菌分类研究中起到越来越重要的作用,目前放线菌的分子分类研究主要包括:G Cmol%测定、DNA杂交、核酸结构分析以及DNA指纹图谱分析等方面。     

肠杆菌科细菌肺部感染病原菌分布与耐药性监测

目的了解浙江龙游县人民医院肠杆菌科细菌肺部感染病原菌分布及耐药性,为临床合理使用抗菌药物提供依据。方法采用纸片扩散法对病原菌进行药敏试验,并进行ESBLs检测,按CLSI 2012年标准判定药敏结果,用WHONET 5.6软件分析结果。结果痰培养共分离出371株肠杆科细菌,主要为肺炎克雷伯菌、大肠埃希菌和阴沟肠杆菌,产ESBLs菌阳性率高,对碳青霉烯类抗菌药物耐药率低,均在10.00%以下,其他药物均有不同程度耐药,测试抗菌药物的耐药率差异有统计学意义（P〈0.05）。结论临床常见肠杆菌科细菌耐药率高,开展病原菌耐药性监测,对指导临床抗感染治疗合理选择抗菌药物具有重要意义。     

根瘤菌多相分类的研究进展

根瘤菌可以入侵豆科植物形成根瘤或茎瘤,并可固定空气中的氮为其宿主植物提供必需的氮素营养。根瘤菌的分类系统可分为早期根瘤菌的分类系统和现代根瘤菌的分类系统两个阶段。根瘤菌的多相分类技术包括表型的分群方法和遗传型的分群方法两大类。     

Phylogenetic analysis of enteric species of the family Enterobacteriaceae using the oriC-locus

Phylogenetic analysis of 38 enteric species belonging to the Enterobacteraceae family was carried out using the non-coding locus oriC, the chromosomal replication origin. The oriC loci were amplified with conserved oligonucleotides and the PCR fragments were sequenced directly. The results establish a phylogenetic tree for the classification of different species of the genera Escherichia, Shigella, Salmonella, Enterobacter, Citrobacter, Klebsiella, Raoultella, Kluyvera, Cedecea and Buttiauxella. Functional important protein-binding sites located in oriC are well conserved throughout the enteric group. More over, due to a high overall divergence value phylogenetic trees were robust and well supported by bootstrap analysis. In comparison with 16S rDNA analysis, the oriC sequences indicated a greater evolutionary divergence for bacteria. We propose that the oriC locus might be a suitable phylogenetic marker for the identification and classification of bacteria, in particular for closely related species.     

Comparison of disc diffusion, Etest and agar dilution for susceptibility testing of colistin against Enterobacteriaceae

Aims: In this study, we compared different methods of colistin susceptibility testing, disc diffusion, agar dilution and Etest using a set of Enterobacteriaceae isolates that included colistin‐resistant strains. Methods and results: Susceptibility of 200 clinical isolates of Enterobacteriaceae to colistin was tested to compare agar dilution (reference method), disc diffusion (50 and 10 μg) and Etest. MICs (minimum inhibitory concentrations) were interpreted using the criteria established by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Colistin exhibited excellent activity against Escherichia coli and E. cloacae (MIC₉₀ = 0·5 mg l^?1). In contrast, colistin was less active against Klebsiella pneumoniae (MIC₉₀ = 16 mg l^?1). Resistance rates varied from 0% in E. coli to 1·8% in E. cloacae and 13% in K. pneumoniae. High rates of very major errors were observed in the disc diffusion test using either the criteria of the Comité de l’antibiogramme de la Société Française de Microbiologie (CA‐SFM) or the criteria of the Clinical and Laboratory Standards Institute (CLSI), respectively, 3·5 and 2·5%. When the criteria of Gales et al. were applied, the number of very major errors was reduced to one (0·5%). The Etest showed good concordance with agar dilution method. Conclusion: Disc susceptibility testing methods are unreliable on detecting colistin resistance. MIC should be determined to confirm the susceptibility results by disc diffusion. Significance and Impact of the study: We recommend the determination of MIC by Etest for all multidrug‐resistant Enterobacteriaceae when colistin is required for the treatment.     

植物分子分类与鉴定综述

以高等植物为对象,首先从ｎＤＮＡ、ｃｐＤＮＡ、ｍｔＤＮＡ三方面对植物分子分类与鉴定的分子基础进行综述,然后阐述ＲＦＬＰ、ＲＡＰＤ、ＡＦＬＰ及ＳＳＲ等分子分类方法的特点及应用。     

一株拮抗链霉菌的鉴定及其多相分类特征

通过16S r RNA基因序列分析一株拮抗放线菌JXNU03的系统发育关系,通过生理生化试验分析其生理生化特征,利用菌丝生长率法和杯碟法测定其拮抗活性。结果发现,放线菌JXNU03在高氏一号培养基上培养时,基内菌丝发达,分支多且不断裂,气生菌丝发育良好,孢子丝直形或螺旋状,孢子表面带刺,细胞水解液中检测到葡萄糖,未检测出特征性糖,糖类型属于C型,细胞壁氨基酸中含有L,L-DAP,属于细胞壁Ⅰ型,16S r RNA基因序列与灭癌素链霉菌的同源性高达98%,其发酵液对革兰氏阳性细菌、革兰氏阴性细菌、酵母菌和霉菌等都具有较强的拮抗作用。因此放线菌JXNU03被鉴定为灭癌素链霉菌,记为灭癌素链霉菌JXNU03(Streptomyes gancidicus JXNU03),是一株对细菌、酵母菌和霉菌均有较强拮抗活性的链霉菌,具有潜在开发价值。     

Taxonomy of some common Amphidinium species

The taxonomic status of several well known species belonging to the genus Amphidinium (Dinophyceae) has been re-examined. Studies in culture and observations on the micro-anatomy of these organisms suggest that the number of species can be reduced to two, A. klebsii and A. carterae. They may be distinguished on the basis of fundamental differences in chloroplast morphology.