Application of Yersinia kristensenii bacteriocin as a specific marker for the rapid identification of suspected isolates of Yersinia enterocolitica

Out of 143 suspected foods and clinical isolates of the genus Yersinia , 77 isolates were bacteriocin-sensitive and 66 bacteriocin non-sensitive. Of the 77 bacteriocin-sensitive isolates, 72 (93.5%) were identified as Y. enterocolitica and 5 (6.49%) as Y. frederiksenii. Out of 66 bacteriocin non-sensitive suspected isolates, 22 (33.3%) were identified as Yersinia spp. other than Y. enterocolitica and 43 (65.1%) were other Gram-negative bacteria with the exception of one (1.5%) isolate identified as Y. enterocolitica.     

低温对植物叶片中超氧物歧化酶、过氧化氢酶和过氧化氢水平的影响

番茄和鸡蛋果叶片中可提取的SOD活性不受低温的影响。在电泳谱带上SOD主同工酶带被氰化物而不被低温抑制,次同工酶带在低温下不稳定,且活性很低,它的变化不影响总的SOD活性。一些冷敏感植物叶片中CAT活性被低温抑制,而H_2O_3水平在低温下稳定或有增加,这可能使毒性更强的羟基离子(OH·)易于形成。     

Evaluation of the ability of primary selective enrichment to resuscitate heat-injured and freeze-injured Listeria monocytogenes cells.

Resuscitation rates of injured Listeria monocytogenes on conventional selective Listeria enrichment broth and nonselective Trypticase soy broth containing 0.6% yeast extract were compared. Cells were heated to 60 degrees C for 5 min or frozen at -20 degrees C for 7 days. Inoculation of Trypticase soy broth-yeast extract with the stressed cells resulted in growth that was superior to that in Listeria enrichment broth. Injured cells were fully recovered at 6 to 8 h.     

Ribosomal RNA sequence phylogeny is not congruent with ascospore morphology among species in Ceratocystis sensu stricto

The genus Ceratocystis sensu stricto includes important fungal pathogens of woody and herbaceous plants. This genus is distinguished from species in Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore shape has been used extensively in delineating Ceratocystis taxa, which show a large variety of ascospore shapes. Sequence analysis of one region of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA subunit showed that there was a majority of multiple substitutions at nucleotide sites and that there was a low transition/transversion ratio, T = 0.72. Both of these results suggest that these are well established, old species. Ascospore morphology, for the most part, was not congruent with the molecular phylogeny, and the use of morphological characters may be misleading in the taxonomy of these species.      

Nuclear staining with alum hematoxylin

The hematoxylin and eosin stain is the most common method used in anatomic pathology, yet it is a method about which technologists ask numerous questions. Hematoxylin is a natural dye obtained from a tree originally found in Central America, and is easily converted into the dye hematein. This dye forms coordination compounds with mordant metals, such as aluminum, and the resulting lake attaches to cell nuclei. Regressive formulations contain a higher concentration of dye than progressive formulations and may also contain a lower concentration of mordant. The presence of an acid increases the life of the solution and in progressive solutions may also affect selectivity of staining. An appendix lists more than 60 hemalum formulations and the ratio of dye to mordant for each.     

Factors affecting production and activity of phospholipase C by Yersinia enterocotttica

The production of phospholipase C by Yersinia enterocolitica strain SG was optimum at 37†C at pH 6·5. No enzyme activity could be detected when the organism was grown at extreme pH values (pH > 8·5 or <5·0). The enzyme production was maximum when the organism was grown under static conditions in TSB medium. All solvents and salts inhibited the enzyme activity, whereas loss of activity was 95% in presence of methanol (20%) and 99% in presence of sodium azide (0·2 mol/l). The enzyme activity was increased twofold in the presence of cyste-ine and decreased by 98% in the presence of sodium perchlorate (0·2 mol/1).     

Evaluation of the ability of primary selective enrichment to resuscitate heat-injured and freeze-injured Listeria monocytogenes cells.

Resuscitation rates of injured Listeria monocytogenes on conventional selective Listeria enrichment broth and nonselective Trypticase soy broth containing 0.6% yeast extract were compared. Cells were heated to 60 degrees C for 5 min or frozen at -20 degrees C for 7 days. Inoculation of Trypticase soy broth-yeast extract with the stressed cells resulted in growth that was superior to that in Listeria enrichment broth. Injured cells were fully recovered at 6 to 8 h.