Abteilung für Mikrobiologie, ZIEL, Technische Universität München, D-85354 Freising, Germany.
J Dairy Sci. 2010 Oct;93(10):4497-505. doi: 10.3168/jds.2010-3244.
The microbial surface ripening consortia of 49 soft cheeses were investigated with respect to their inhibition of Listeria monocytogenes. When L. monocytogenes EGDe (serovar 1/2a) was cultivated in cell-free supernatants obtained from consortia grown for 8 h in liquid medium, a strong bactericidal activity was observed in several cases. The cell-free supernatants of 2 of these consortia (I and II) reduced an initial L. monocytogenes inoculum of 5 × 10(7) cfu/mL to zero after 24 h of incubation. No inhibitory substances could be washed off the complex consortia when incubated for a 10-min period. A taxonomical analysis of the antilisterial consortia I and II using Fourier transform infrared spectroscopy yielded a considerable species diversity, with lactic acid bacteria increasing strongly during the 8-h cultivation. Therefore, 23 lactic acid bacteria bacteriocin genes were assayed using specific PCR primers, identifying 3 bacteriocin genes in both microbial communities. However, no transcription of these genes was found on cheese surfaces or in consortia propagated in liquid culture. Individual lactic acid bacteria isolates of consortia I and II displayed no or only weak inhibition of L. monocytogenes on solid medium. The complex cell-free supernatants I and II, in contrast, exhibited an unusually broad inhibitory spectrum, killing L. monocytogenes ssp., Bacillus spp., Staphylococcus aureus, as well as gram-negative bacteria such as Escherichia coli DH5α and Salmonella enterica serovar Typhimurium. Inhibition could not be abolished by heating to 100°C or by proteinase K treatment. Initial purification of an inhibitory substance from consortium I by solid-phase extraction and HPLC indicates the presence of rather small, extremely stable compounds, which, most probably, are not bacteriocins.
研究了 49 种软奶酪的微生物表面成熟共生体，以研究它们对李斯特菌（Listeria monocytogenes）的抑制作用。当李斯特菌 EGDe（血清型 1/2a）在液体培养基中培养 8 小时的无细胞上清液中培养时，在几种情况下观察到强烈的杀菌活性。这两种共生体（I 和 II）的无细胞上清液在 24 小时的孵育后将初始李斯特菌接种物 5×10(7)cfu/mL 降低至零。当孵育 10 分钟时，不能从复杂的共生体上洗掉抑制物质。使用傅里叶变换红外光谱法对具有抗李斯特菌作用的共生体 I 和 II 进行分类分析，得到了相当大的物种多样性，在 8 小时的培养过程中，乳酸杆菌的数量明显增加。因此，使用特异性 PCR 引物检测了 23 种乳酸菌细菌素基因，在两个微生物群落中均鉴定出 3 种细菌素基因。然而，在奶酪表面或在液体培养基中繁殖的共生体中未发现这些基因的转录。共生体 I 和 II 的单个乳酸细菌分离株在固体培养基上对李斯特菌的抑制作用不明显或仅微弱。相反，复杂的无细胞上清液 I 和 II 表现出异常广泛的抑制谱，可杀死李斯特菌 ssp.、芽孢杆菌、金黄色葡萄球菌以及革兰氏阴性菌，如大肠杆菌 DH5α 和肠炎沙门氏菌血清型 Typhimurium。加热至 100°C 或用蛋白酶 K 处理不能消除抑制作用。用固相萃取和 HPLC 从共生体 I 中初步纯化抑制物质表明存在相当小的、极其稳定的化合物，这些化合物很可能不是细菌素。
