Nofima Mat AS, Ås, Norway.
PLoS One. 2011 Jan 6;6(1):e16192. doi: 10.1371/journal.pone.0016192.
Subclass IIa bacteriocins have strong antilisterial activity and can control the growth of Listeria monocytogenes in food. However, L. monocytogenes may develop resistance towards such bacteriocins. In this follow-up study, the transcriptomes of a high level (L502-1) and a low level (L502-6) spontaneous sakacin P-resistant mutant strain of L. monocytogenes were compared to the wild-type (L502). The growth of the resistant strains was reduced on mannose but not affected on cellobiose and the transcriptomics was performed during growth on these sugars. The mannose phosphotransferase system (PTS) encoded by the mptACD operon (mpt) is known for transporting mannose and also act as a receptor to class IIa bacteriocins. The mpt was repressed in L502-1 and this is in accordance with abolition of the bacteriocin receptor with resistance to class IIa bacteriocins. In contrast, the mpt was induced in L502-6. Despite the induction of the mpt, L502-6 showed 1,000 times more resistance phenotype and reduced growth on mannose suggesting the mannose-PTS may not be functional in L502-6. The microarray data suggests the presence of other transcriptional responses that may be linked to the sakacin P resistance phenotype particularly in L502-6. Most of commonly regulated genes encode proteins involved in transport and energy metabolism. The resistant strains displayed shift in general carbon catabolite control possibly mediated by the mpt. Our data suggest that the resistant strains may have a reduced virulence potential. Growth sugar- and mutant-specific responses were also revealed. The two resistant strains also displayed difference in stability of the sakacin P resistance phenotype, growth in the presence of both the lytic bacteriophage P100 and activated charcoal. Taken together, the present study showed that a single time exposure to the class IIa bacteriocin sakacin P may elicit contrasting phenotypic and transcriptome responses in L. monocytogenes possibly through regulation of the mpt.
亚类 IIa 细菌素具有很强的抗李斯特菌活性，可以控制食品中李斯特菌的生长。然而，李斯特菌可能会对这种细菌素产生抗性。在这项后续研究中，我们比较了李斯特菌高（L502-1）和低（L502-6）自发 sakacin P 抗性突变株与野生型（L502）的转录组。抗性菌株在甘露糖上的生长受到抑制，但在纤维二糖上不受影响，并且在这些糖上生长时进行了转录组分析。甘露糖磷酸转移酶系统（PTS）由 mptACD 操纵子（mpt）编码，用于运输甘露糖，也作为 IIa 类细菌素的受体。mpt 在 L502-1 中受到抑制，这与对 IIa 类细菌素的抗性导致细菌素受体丧失一致。相反，mpt 在 L502-6 中被诱导。尽管 mpt 被诱导，但 L502-6 表现出 1000 倍的抗性表型，并且在甘露糖上的生长减少，这表明甘露糖-PTS 在 L502-6 中可能不起作用。微阵列数据表明，存在其他转录响应，可能与 sakacin P 抗性表型有关，特别是在 L502-6 中。大多数常见调节基因编码参与运输和能量代谢的蛋白质。抗性菌株表现出普遍的碳分解代谢物控制的转移，可能由 mpt 介导。我们的数据表明，抗性菌株的毒力潜力可能降低。还揭示了生长糖和突变体特异性的反应。这两种抗性菌株在溶菌噬菌体 P100 和活性炭存在下的生长稳定性方面也表现出差异。总的来说，本研究表明，单次接触 IIa 类细菌素 sakacin P 可能会在李斯特菌中引起截然不同的表型和转录组反应，可能通过 mpt 的调节。
