Hokkaido University · Earth and Planetary Sciences
Professor Koji Yamazaki's research lab specializes in microbial ecology and molecular microbiology, with a focus on thermophilic and acidophilic bacteria, particularly *Alicyclobacillus acidoterrestris*, a major spoilage organism in acidic beverages. The lab investigates the molecular mechanisms of bacterial heat resistance, bacteriocin activity, and rapid detection methods using molecular techniques such as RT-PCR and 16S rRNA gene sequencing. Research also extends to environmental microbiology, including the impact of stratospheric quasi-biennial oscillations on atmospheric dynamics, linking microbial and atmospheric processes through interdisciplinary approaches.
Figures are computed from collected data and may differ slightly.
Thermophilic bacteria isolated from spoiled acidic beverages were identified on the basis of DNA-DNA homology and 16S ribosomal DNA sequence similarity to Alicyclobacillus acidoterrestris. This result suggested that the isolates were a new type of spoilage bacterium in acidic beverages in Japan.
Abstract. The quasi-biennial oscillation (QBO) is quasi-periodic oscillation of the tropical zonal wind in the stratosphere. When the tropical lower stratospheric wind is easterly (westerly), the winter Northern Hemisphere (NH) stratospheric polar vortex tends to be weak (strong). This relation is known as the Holton–Tan relationship. Several mechanisms for this relationship have been proposed, especially linking the tropics with high latitudes through stratospheric pathway. Although QBO impacts
The bacteriocin piscicocin CS526 was inactivated by proteolytic enzymes, was stable at 100 degrees C for 30 min, had a pH range of 2 to 8, and was active against Enterococcus, Listeria, Pediococcus, and Leuconostoc. The N-terminal sequence was YGNGL, not the YGNGV consensus motif common in class IIa bacteriocins (alternate residues underlined). The molecular mass of piscicocin CS526, which had a bactericidal mode of action, was approximately 4,430 Da.
The reverse transcription-polymerase chain reaction (RT-PCR), after a short enrichment culture, was used to detect Alicyclobacillus acidoterrestris in acidic beverages. Two specific primers were selected from the region of V2 and V4 on 16S rRNA gene. With this primer set, 294-bp fragments from A. acidoterrestris could be amplified. The detection limit of the RT-PCR with the FHLP filters was about 10-1 fg of pure total RNA per reaction. Juice samples inoculated with 10(4) cfu of A. acidoterrestri
Molecular mechanism of action of piscicocin CS526 is very similar to that of other pediocin-like bacteriocins, although piscicocin CS526 possesses a unique N-terminal sequence in which Val is substituted for by Leu in the amino acid at position 7.
The influence of divalent cations on the heat resistance of spores of the thermoacidophilic spoilage bacterium Alicyclobacillus acidoterrestris was studied. The heat resistance of A. acidoterrestris spores was not affected by the presence of the different divalent cations (Ca2+, Mg2+, Ba2+, Mn2+ and Sr2+) in the sporulation medium, and by the demineralization or remineralization. And the Ca and Mn contents in A. acidoterrestris spores were scarcely changed by these treatments. However, the heat
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