Comparative Studies on Enrichment And Selective Media for Isolation of Salmonellae from Faecal Specimens

Enrichment media (tetrathionate, selenite and Rapp ap ort broths) and selective media (desoxycholate citrate agar and brilliant green agar) were tested in different combinations to ascertain their capacity for isolation of salmonella bacteria. The material consisted of 299 samples of cattle faeces from two herds infected with salmonella (Table 1), and of 111 artificially contaminated samples of pig faeces (Table 3). The tetrathionate and selenite broths were equally useful for the material as a whole, whereas the results varied between different species of salmonella which is of great practical interest. The number of salmonella isolations was much lower when enrichment with Rappaport broth was used. The rate of salmonella isolations can often be increased by parallel enrichments with two different media. Of the selective agar media tested, brilliant green agar was superior to desoxycholate citrate agar.     

Form of Selenium in Selenite Enrichment Media for Isolation of Salmonellae

Selenite-F and selenite-cystine media, commercially available for the routine isolation of salmonellae, were treated by anion exchange chromatography to separate the selenium from other components of the media. A chemical assay, based on an ascorbic acid reduction, showed that the selenium was all in the form of selenite.     

Physicochemical Studies on Sulfated Polysaccharides Extracted from Seaweeds at Various Temperatures

Sulfated polysaccharides (SPS) were extracted from three species of seaweeds of Ulvacea (Ulva pertusa, Ulva conglobata and Entromorpha prolifera) for 4 hr at various temperatures and their physicochemical properties were studied using viscometric and equilibrium sedimentation measurements in order to determine the optimum extracting condition.

Sulfated polysaccharides extracted at various temperatures from the seaweed of U. pertusa had the same physicochemical properties, while the larger molecular components of SPS was not extracted from U. conglobata and E. prolifera, at the low temperature of 30~40°C. This was confirmed by analyses of their viscosity and molecular weight and by gel filtration chromatography, in which each SPS showed two or three peaks.

The larger molecular component of SPS could be extracted at the high temperature of 80~90°C in the thermostable form.     

Patterns of Community Change among Ammonia Oxidizers in Meadow Soils upon Long-Term Incubation at Different Temperatures

The effect of temperature on the community structure of ammonia-oxidizing bacteria was investigated in three different meadow soils. Two of the soils (OMS and GMS) were acidic (pH 5.0 to 5.8) and from sites in Germany with low annual mean temperature (about 10°C), while KMS soil was slightly alkaline (pH 7.9) and from a site in Israel with a high annual mean temperature (about 22°C). The soils were fertilized and incubated for up to 20 weeks in a moist state and as a buffered (pH 7) slurry amended with urea at different incubation temperatures (4 to 37°C). OMS soil was also incubated with less fertilizer than the other soils. The community structure of ammonia oxidizers was analyzed before and after incubation by denaturing gradient gel electrophoresis (DGGE) of the amoA gene, which codes for the α subunit of ammonia monooxygenase. All amoA gene sequences found belonged to the genus Nitrosospira. The analysis showed community change due to temperature both in moist soil and in the soil slurry. Two patterns of community change were observed. One pattern was a change between the different Nitrosospira clusters, which was observed in moist soil and slurry incubations of GMS and OMS. Nitrosospira AmoA cluster 1 was mainly detected below 30°C, while Nitrosospira cluster 4 was predominant at 25°C. Nitrosospira clusters 3a, 3b, and 9 dominated at 30°C. The second pattern, observed in KMS, showed a community shift predominantly within a single Nitrosospira cluster. The sequences of the individual DGGE bands that exhibited different trends with temperature belonged almost exclusively to Nitrosospira cluster 3a. We conclude that ammonia oxidizer populations are influenced by temperature. In addition, we confirmed previous observations that N fertilizer also influences the community structure of ammonia oxidizers. Thus, Nitrosospira cluster 1 was absent in OMS soil treated with less fertilizer, while Nitrosospira cluster 9 was only found in the sample given less fertilizer.     

Effects of a High Magnetic Field at Different Osmotic Pressures and Temperatures on Multiplication of Saccharomyces cerevisiae

The application of a yeast as a biosystem for determining the effects of a high magnetic field and other physical phenomena was studied. Multiplication of Saccharomyces cerevisiae was observed during exposure to a magnetic field of 4,600 gauss. Cell populations were determined at 24-, 48-, and 72-hr intervals, and possible interactions between the magnetic field and other environmental parameters, such as time, temperature, and osmotic pressure, were considered statistically. The main effect of the high magnetic field was a significant reduction of cell multiplication during each time interval. Significant interactions were found to occur between temperature and the magnetic field at 24 hr, and between temperature and osmotic pressure at each sampling interval. Synergistic effects of the magnetic field and osmotic pressure at both 28 and 38 C were nonsignificant.     

Induction of Nonpigmented Variants of Erwinia herbicola by Incubation at Supraoptimal Temperatures

As with other inducible enzymes, the induced synthesis of l-arabinose isomerase (l-arabinose ketol isomerase, EC 5.3.1.4) in Salmonella typhimurium is subject to catabolite repression. Of the three catabolite repressors tested, glucose produces maximum repression. Analogues of catabolite repressors like 2-deoxy-d-glucose and d-fucose also inhibit the synthesis of the enzyme. The catabolite repression is completely reversed in the presence of 1.5 x 10(-3)m cyclic 3',5'-adenosine monophosphate (AMP). The maximum repression is produced in glucose-grown cells in glucose-containing induction medium. Cyclic 3',5-AMP reverses this repression provided that the cells are treated with ethylenediaminetetraacetic acid (EDTA). In normal cells, cyclic 3',5'-AMP has no effect on the induction but in EDTA-treated cells the cyclic nucleotide enhances synthesis of the enzyme. The inhibition produced by d-fucose cannot be reversed by cyclic 3',5'-AMP. d-Fucose competes with the inducer l-arabinose in some step(s) involved in the process of induction.     

食品中沙门菌培养条件的研究

目的选用5种常用培养基,对沙门菌进行培养试验,比较其增菌效果。方法以5种培养基对沙门菌进行静止需氧培养和静止厌氧培养实验,观察pH对沙门菌生长的影响,并在已选定的最佳条件下进行模拟样品实验。结果得出样品中沙门菌的最低检出限。结论该研究为提高进出口食品中沙门菌的检出率奠定了基础。     

A Comparison of Methods for the Enrichment of Salmonellae from Sheep Faeces

S ummary : A 10-tube MPN technique was used to test the efficiency of nutrient, tetrathionate, mannitol-selenite and mannitol-selenite-cystine broths as enrichment media for detecting salmonellae. Small numbers of broth grown salmonellae could be detected in all 4 media in the presence of 5% of sheep faeces. In naturally infected sheep faeces small numbers of salmonellae were not detected with either nutrient or tetrathionate broths. With mannitol-selenite the sensitivity of salmonella detection increased with both incubation temperature (37–43°) and the addition of faeces. The most sensitive and reliable medium for detecting salmonellae in naturally infected sheep faeces was mannitol-selenite-cystine broth. Neither incubation temperature (37–43°) nor the addition of faeces had a statistically significant effect on its sensitivity.     

The Effect of Various Media on the Growth Responses of Different Clones of Carrot Explants

The induction of growth in otherwise quiescent tissue explantedfrom carrot root has been investigated with reference to theeffects of different kinds of growth-promoting substances addedas supplements to a basal medium, singly and in combination.The effects of these media upon different clones of carrot explantsare described. The idiosyncrasies of different clones of explantswere detected by their responses measured by the incidence ofcell division, the extent of cell enlargement, and by theirnucleic acid content. The basal medium which contains salts,sugar, and vitamins supported only a minimal amount of growth;the basal medium supplemented with casein hydrolysate and coconutmilk (10 per cent by volume) supported the highest level ofgrowth obtained in any of the treatments tried. The active componentsof the coconut milk (AF_cm) when refined required the furtherparticipation of either indole-3yl-acetic acid (IAA) or inositol,and were further stimulated by casein hydrolysate (CH). Thusthe over-all stimulus of the coconut milk comprised two parts—nowrecognized as growth-promoting systems I and II, respectively.The effects of System I were mediated by appropriate combinationsof inositol and the corresponding active growth-promoting factors(AF₁) which were, in turn, represented by a purified factorpreviously isolated from Aesculus (AF₂). System I induced bothcell division and cell enlargement in balance, whereas SystemII stimulated internal cell division more than cell enlargement.The effects of System II were mediated by appropriate combinationsof IAA and active growth-promoting factors (AF₂), which wererepresented by the substance zeatin. The maximum growth of anygiven clone of carrot explants isolated from a given carrotroot was only supported by exogenous requirements, over andabove a basal nutrient medium, which meet its specific endogenouslimitations. The paper shows how these limitations may be diagnosed,and discusses the over-all growth stimulus due to coconut milkin terms of the partial responses elicited by the known componentsof Systems I and II.     

Chromosome Replication and Cell Division in Escherichia coli at Various Temperatures of Growth

The effect of temperature on the growth rate and the pattern of chromosome replication during the division cycle of Escherichia coli B/r growing in various media was investigated. The time between divisions, the time for a round of replication (C), and the time between completion of a round and cell division (D) were threefold longer at 21 C than at 37 C. At all temperatures and in all media, D equalled one-half C, suggesting that a common mechanism controls chromosome replication and the progression of the cell toward division after completion of a round of replication.     

The Effects of Various Incubation Temperatures, Particulate Isolation, and Possible Role of Calmodulin on the Activity of the Base Exchange Enzymes of Rat Brain

The involvement of calmodulin in the choline, ethanolamine, and serine exchange activities of rat brain microsomes was investigated. Calmodulin stimulated choline exchange activity to a greater extent than ethanolamine and serine exchange activities. The three base exchange activities were inhibited by antipsychotic drugs believed to prevent calmodulin interaction, but not by calmodulin-binding protein. The solutions employed for tissue homogenization and subsequent isolation of microsomes greatly influenced the base exchange activities. The process of resuspending isolated microsomes and recentrifugation, or "washing," produced major losses of detectable activity. The base exchange enzyme activities were maximal at 45 degrees, and Arrhenius plots revealed a common transition temperature of 31 degrees. The activation energies for the base exchange reactions decreased at temperatures above the observed transition temperature. Kinetic data, Km and Vmax, for the base exchange activities at 27, 37, and 45 degrees are presented.     

孵育时间在二氧化钛选择性富集磷酸化肽中的影响

目的:旨在探索孵育时间在二氧化钛选择性富集磷酸化肽中的影响。方法:以大肠杆菌BL21(DE3)为材料,预实验确定二氧化钛磁珠与肽段之间的最适比例,之后在此比例下继续探究不同孵育时间条件下的富集效果,以观察孵育时间在二氧化钛富集体系中的影响。结果:预实验确定磁珠与肽段之间最适比例为3 :1,在此比例下发现随着孵育时间的增加其富集效率会逐渐降低,最后确定大肠杆菌中最适孵育时间为5min。结论:孵育时间在大肠杆菌二氧化钛富集体系中对富集效果有明显的影响,并且呈负相关。推测不同样品的最佳孵育时间与样品种属有关。     

Evaluation of Culture Media for the Isolation of Salmonellae from Feces

Serial passage of the 64-2389 strain of type 3 parainfluenza virus in cercopithecus monkey kidney tissue cultures at low temperatures resulted in the selection of a variant which had a higher efficiency of plaque formation at 25 C than the parent line grown at 37 C. The cold variant, unlike the parent strain, plaqued readily at 25 C, and at 37 C it produced significantly larger plaques. Virus titers of the cold variant in hamster lungs were significantly lower and this was probably caused by the stimulation of interferon by the cold variant during the early phase of the infection. The cold variant, like the virus grown at 37 C, also induced the synthesis of interferon late in the infection. Hamsters responded to the intranasal inoculation of each virus line by the development of hemagglutinating-inhibiting antibodies in the sera.