Bacteriological Survey of Insect Products in Japan.

A microbiological study was conducted on 41 insect product samples (29 raw frozen [21 domestic and 8 imported], 10 powdered, and 2 processed), which were commercially available in Japan. The total aerobic count for raw frozen insects was 5.61 log cfu/g (range: 2.52-8.40), whereas the powdered insect count was 2.89 log cfu/g (range: 1.00-4.57). The bacterial count was significantly higher in raw frozen insects (p < 0.05). The coliform count for the raw frozen insects ranged from <1 to 6.90 log cfu/g, and that for the powdered insects ranged from <1 to 1.00 log cfu/g. The number of samples with values above the detection limit was significantly higher in raw frozen insects (p < 0.05). The detection frequencies of aerobic spores (<1-4.63 log cfu/g), anaerobic spores (<0-4.40 log cfu/g), and Bacillus cereus (<1.7-3.83 log cfu/g) showed no sample type-related significant difference. Listeria spp. was isolated from four samples of raw frozen insects, one of which was Listeria monocytogenes. We did not detect any of the following: Salmonella spp., Shiga toxin-producing E. coli (STEC), Campylobacter jejuni/coli, or pathogenic Yersinia. We isolated insect products retailed in Japan harboring food poisoning bacteria, including L. monocytogenes and B. cereus. In particular, raw frozen products displayed high levels of hygienic indicator bacteria.

ADP-Ribose Pyrophosphatase Reaction in Crystalline State Conducted by Consecutive Binding of Two Manganese(II) Ions as Cofactors.

Adenosine diphosphate ribose pyrophosphatase (ADPRase), a member of the Nudix family proteins, catalyzes the metal-induced and concerted general acid-base hydrolysis of ADP ribose (ADPR) into AMP and ribose-5'-phosphate (R5P). The ADPR-hydrolysis reaction of ADPRase from Thermus thermophilus HB8 (TtADPRase) requires divalent metal cations such as Mn(2+), Zn(2+), or Mg(2+) as cofactors. Here, we report the reaction pathway observed in the catalytic center of TtADPRase, based on cryo-trapping X-ray crystallography at atomic resolutions around 1.0 Å using Mn(2+) as the reaction trigger, which was soaked into TtADPRase-ADPR binary complex crystals. Integrating 11 structures along the reaction timeline, five reaction states of TtADPRase were assigned, which were ADPRase alone (E), the ADPRase-ADPR binary complex (ES), two ADPRase-ADPR-Mn(2+) reaction intermediates (ESM, ESMM), and the postreaction state (E'). Two Mn(2+) ions were inserted consecutively into the catalytic center of the ES-state and ligated by Glu86 and Glu82, which are highly conserved among the Nudix family, in the ESM- and ESMM-states. The ADPR-hydrolysis reaction was characterized by electrostatic, proximity, and orientation effects, and by preferential binding for the transition state. A new reaction mechanism is proposed, which differs from previous ones suggested from structure analyses with nonhydrolyzable substrate analogues or point-mutated ADPRases.