Rapid detection of tdh and trh mRNAs of Vibrio parahaemolyticus by the transcription-reverse transcription concerted (TRC) method

Enzymatic characterization of human immunodeficiency virus type 1 reverse transcriptase for use in cDNA synthesis

The aim of this study is to explore the advantages of using human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) in cDNA synthesis. Recombinant HIV-1 group M (HIV-1 M) RT and HIV-1 group O (HIV-1 O) RT were produced in an Escherichia coli expression system. In the incorporation of dTTP into poly(rA)-p(dT)(15) (T/P), the K (m) values for dTTP of HIV-1 M RT and HIV-1 O RT were 8 and 12 % of that of Moloney murine leukemia virus (MMLV) RT, respectively, and the K (m) values for T/P were 25 and 23 % of that of MMLV RT, respectively. Compared with MMLV RT, HIV-1 M RT and HIV-1 O RT were less susceptible to formamide, which is frequently used for cDNA synthesis with a G + C-rich RNA to improve specificity. The high substrate affinity and low susceptibility to formamide of HIV-1 RT might be advantageous for its use in cDNA synthesis.

Evaluation of the Compact Dry VP method for screening raw seafood for total Vibrio parahaemolyticus

Compact Dry VP (CDVP) is a ready-to-use method for enumerating Vibrio parahaemolyticus in food. The presterilized plates contain a culture medium comprising peptone, NaCl, bile salts, antibiotics, chromogenic substrates, and polysaccharide gum as a cold water-soluble gelling. After diluting raw seafood samples in a phosphate-buffered saline solution, a 1-ml aliquot was inoculated onto the center of the plate and allowed to diffuse by capillary action. Blue-green colonies forming on the plates were counted after 18 to 20 h of incubation at 35 degrees C. A total of 85 V. parahaemolyticus strains (62 tdh+ strains and 23 tdh- strains) were studied for inclusivity, 81 (95.3 %) of which produced blue-green colonies. When 97 strains (14 strains of Vibrio spp., 33 strains of coliform bacteria, and 50 strains of noncoliform bacteria) were assessed for exclusivity, 10 strains of Vibrio spp. produced non-blue-green colonies, and 87 strains failed to grow. The CDVP and U.S. Food and Drug Administration Bacteriological Analytical Manual (FDA-BAM) methods were compared with the use of four different types of raw seafood that were inoculated with four different V. parahaemolyticus strains. For raw tuna and oysters, the FDA-BAM colony lift method was used, whereas the FDA-BAM most-probable-number method was used for salmon and scallop. The linear correlation coefficients between the CDVP and FDA-BAM methods were 0.99 for fresh raw tuna, 0.95 for fresh raw oysters, 0.95 for frozen raw salmon, and 0.95 for frozen raw scallops. These results suggest that the CDVP method is useful for screening raw seafood for V. parahaemolyticus.

Comparison of the thermal stabilities of reverse transcriptases from avian myeloblastosis virus and Moloney murine leukaemia virus

Reverse transcriptases (RTs) from avian myeloblastosis virus (AMV) and Moloney murine leukaemia virus (MMLV) have been most extensively used as a tool for conversion of RNA to DNA. In this study, we compared the thermal stabilities of AMV RT and MMLV RT by observing their irreversible thermal inactivation. The temperatures reducing initial activity by 50% in 10-min incubation, T(50), of AMV RT were 47 degrees C without the template-primer (T/P), poly(rA)-p(dT)(12-18), and 52 degrees C with the T/P (28 microM). T(50) of MMLV RT were 44 degrees C without the T/P and 47 degrees C with the T/P (28 microM). Unexpectedly, AMV RT was considerably activated when incubated with the T/P at 45 and 48 degrees C. Such activation was not observed in MMLV RT. These results suggest that AMV RT and MMLV RT are different in the following: (i) The intrinsic thermal stability of AMV RT is higher than that of MMLV RT; (ii) AMV RT is activated by thermal treatment with the T/P at 45-48 degrees C; and (iii) AMV RT is stabilized by the T/P more potently than MMLV RT. Thermodynamic analysis indicates that thermal inactivation of AMV RT and MMLV RT is due to the large entropy change of activation for thermal inactivation.