TiFN, P.O. Box 557, 6700 AN, Wageningen, The Netherlands.
Department of Applied and Industrial Mycology, Westerdijk Fungal Biodiversity Institute, Uppsalalaan 8, 3584 CT, Utrecht, The Netherlands.
Environ Microbiol. 2020 Mar;22(3):986-999. doi: 10.1111/1462-2920.14791. Epub 2019 Oct 24.
Fungi colonize habitats by means of spores. These cells are stress-resistant compared with growing fungal cells. Fungal conidia, asexual spores, formed by cosmopolitan fungal genera like Penicillium, Aspergillus and Peacilomyces are dispersed by air. They are present in places where food products are stored and as a result, they cause food spoilage. Here, we determined the heterogeneity of heat resistance of conidia between and within strains of Paecilomyces variotii, a spoiler of foods such as margarine, fruit juices, canned fruits and non-carbonized sodas. Out of 108 strains, 31 isolates showed a conidial survival >10% after a 10-min-heat treatment at 59°C. Three strains with different conidial heat resistance were selected for further phenotyping. Conidia of DTO 212-C5 and DTO 032-I3 showed 0.3% and 2.6% survival in the screening respectively, while survival of DTO 217-A2 conidia was >10%. The decimal reduction times of these strains at 60°C (D value) were 3.7 ± 0.08, 5.5 ± 0.35 and 22.9 ± 2.00 min respectively. Further in-depth analysis revealed that the three strains showed differences in morphology, spore size distributions, compatible solute compositions and growth under salt stress. Conidia of DTO 217-A2 are the most heat-resistant reported so far. The ecological consequences of this heterogeneity of resistance, including food spoilage, are discussed.
真菌通过孢子来定殖栖息地。与生长中的真菌细胞相比，这些细胞具有更强的抗应激能力。无性孢子真菌分生孢子，由青霉属、曲霉属和拟青霉属等世界性真菌属形成，通过空气传播。它们存在于储存食品的地方，因此会导致食品变质。在这里，我们确定了变栖曲霉（一种会破坏黄油、果汁、罐装水果和非碳化苏打水等食品的微生物）不同菌株之间和菌株内部的耐热性的异质性。在 108 株菌株中，有 31 株菌株在 59°C 下经过 10 分钟的热处理后，其孢子存活率>10%。选择 3 株具有不同耐热性的孢子进行进一步表型分析。DTO 212-C5 和 DTO 032-I3 的孢子在筛选中分别显示出 0.3%和 2.6%的存活率，而 DTO 217-A2 的孢子存活率>10%。这些菌株在 60°C 下的十进制减少时间（D 值）分别为 3.7±0.08、5.5±0.35 和 22.9±2.00 分钟。进一步深入分析表明，这 3 株菌株在形态、孢子大小分布、相容溶质组成和盐胁迫下的生长方面存在差异。DTO 217-A2 的孢子是迄今为止报道的耐热性最强的孢子。讨论了这种抗性异质性的生态后果，包括食品变质。
