Abbas Amina Aicha, Planchon Stella, Jobin Michel, Schmitt Philippe
INRA, UMR408 Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France; Université d'Avignon et des Pays de Vaucluse, UMR408 Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France.
INRA, UMR408 Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France; Université d'Avignon et des Pays de Vaucluse, UMR408 Sécurité et Qualité des Produits d'Origine Végétale, F-84000 Avignon, France.
Food Microbiol. 2014 Sep;42:122-31. doi: 10.1016/j.fm.2014.03.004. Epub 2014 Mar 28.
This study was performed to evaluate the effect of anaerobiosis on the formation of Bacillus cereus spores and their resulting properties. For this purpose, an appropriate sporulation medium was developed (MODs). Sporulation of 18 strains from different phylogenetic groups of B. cereus was studied in MODs medium in aerobiosis and anaerobiosis. In anaerobiosis, sporulation ability was weaker and more heterogeneous than in aerobiosis. Among tested strains, B. cereus AH187 produced the highest level of spores in anaerobiosis. This strain was therefore chosen to study spore properties. Spores produced in anaerobiosis were more resistant to wet heat at 90 °C, 92.5 °C, 95 °C, 97.5 °C and 100 °C. For example, D90 were 21,09 ± 1.70 and 81.87 ± 2.00 for aerobiosis and anaerobiosis conditions, respectively. Spores produced in anaerobiosis have a z-value of 7.70 °C compared with 10.52 °C for spores produced in aerobiosis. Spores produced in anaerobiosis were also more resistant to 1 M NaOH, 1 M nitrous acid and pulsed light at fluences of 0.34 J cm(-2) and 0.49 J cm(-2). No difference in resistance to UV-C, 5% hydrogen peroxide or 0.25 mM formaldehyde was observed between these two conditions. In the presence of L-alanine, spores produced in anaerobiosis germinated more efficiently than spore produced in aerobiosis. No difference in germination was observed with inosine as inducer. No difference in the size of spores produced in the different conditions was observed by transmission electron microscopy. However, spores obtained under anaerobic conditions had a damaged exosporium, or in some cases a completely detached exosporium, unlike spores produced under aerobic conditions. This study shows that few spores are formed under anaerobic condition; nevertheless, this condition has an impact on the spore properties of B. cereus AH 187 strain. Spores obtained under anaerobic condition were more resistant to heat and to some chemical compounds. This is an important feature, considering the risk associated with the presence of this pathogen in thermally processed and packaged food in absence of oxygen.
本研究旨在评估厌氧环境对蜡样芽孢杆菌孢子形成及其特性的影响。为此，开发了一种合适的芽孢形成培养基（MODs）。研究了来自蜡样芽孢杆菌不同系统发育组的18个菌株在MODs培养基中需氧和厌氧条件下的芽孢形成情况。在厌氧环境中，芽孢形成能力比需氧环境中更弱且更具异质性。在测试菌株中，蜡样芽孢杆菌AH187在厌氧环境中产生的孢子水平最高。因此选择该菌株来研究孢子特性。厌氧条件下产生的孢子对90℃、92.5℃、95℃、97.5℃和100℃的湿热更具抗性。例如，在需氧和厌氧条件下，D90分别为21.09±1.70和81.87±2.00。厌氧条件下产生的孢子的z值为7.70℃，而需氧条件下产生的孢子的z值为10.52℃。厌氧条件下产生的孢子对1 M NaOH、1 M亚硝酸以及0.34 J cm(-2)和0.49 J cm(-2)的脉冲光也更具抗性。在这两种条件下，对UV-C、5%过氧化氢或0.25 mM甲醛的抗性没有差异。在L-丙氨酸存在的情况下，厌氧条件下产生的孢子比需氧条件下产生的孢子发芽更有效。以肌苷作为诱导剂时，发芽情况没有差异。通过透射电子显微镜观察，在不同条件下产生孢子的大小没有差异。然而，与需氧条件下产生的孢子不同，厌氧条件下获得的孢子的芽孢衣受损，或在某些情况下芽孢衣完全脱落。本研究表明，在厌氧条件下形成的孢子很少；然而，这种条件会影响蜡样芽孢杆菌AH 187菌株的孢子特性。厌氧条件下获得的孢子对热和某些化合物更具抗性。考虑到在无氧的热加工和包装食品中存在这种病原体所带来的风险，这是一个重要特征。
