Rahkila Riitta, Johansson Per, Säde Elina, Paulin Lars, Auvinen Petri, Björkroth Johanna
Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland.
Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
Appl Environ Microbiol. 2015 Apr;81(7):2474-80. doi: 10.1128/AEM.04013-14. Epub 2015 Jan 23.
Leuconostoc gelidum subsp. gasicomitatum is a psychrotrophic lactic acid bacterium (LAB) that causes spoilage of a variety of modified-atmosphere-packaged (MAP) cold-stored food products. During the past 10 years, this spoilage organism has been increasingly reported in MAP meat and vegetable products in northern Europe. In the present study, the population structure within 252 L. gelidum subsp. gasicomitatum strains was determined based on a novel multilocus sequence-typing (MLST) scheme employing seven housekeeping genes. These strains had been isolated from meat and vegetable sources over a time span of 15 years, and all 68 previously detected pulsed-field gel electrophoresis (PFGE) genotypes were represented. A total of 46 sequence types (STs) were identified, with a majority of the strains (>60%) belonging to three major STs, which were grouped into three clonal complexes (CCs) and 17 singletons by Global Optimal eBURST (goeBURST). The results by Bayesian analysis of population structure (BAPS) mostly correlated with the grouping by goeBURST. Admixture analysis by BAPS indicated a very low level of exchange of genetic material between the subpopulations. Niche specificity was observed within the subpopulations: CC1 and BAPS cluster 1 consisted mostly of strains from a variety of MAP meats, whereas vegetable strains grouped together with strains from MAP poultry within CC2 and BAPS cluster 2. The MLST scheme presented in this study provides a shareable and continuously growing sequence database enabling global comparison of strains associated with spoilage cases. This will further advance our understanding of the microbial ecology of this industrially important LAB.
嗜冷明串珠菌产气亚种是一种嗜冷乳酸菌，可导致多种气调包装（MAP）冷藏食品变质。在过去10年中，这种腐败菌在北欧的MAP肉类和蔬菜产品中越来越多地被报道。在本研究中，基于一种采用7个管家基因的新型多位点序列分型（MLST）方案，确定了252株嗜冷明串珠菌产气亚种的种群结构。这些菌株是在15年的时间跨度内从肉类和蔬菜来源中分离出来的，涵盖了所有先前检测到的68种脉冲场凝胶电泳（PFGE）基因型。共鉴定出46种序列类型（STs），大多数菌株（>60%）属于三个主要的STs，通过全局最优eBURST（goeBURST）将它们分为三个克隆复合体（CCs）和17个单态型。贝叶斯种群结构分析（BAPS）的结果与goeBURST的分组大多相关。BAPS的混合分析表明亚种群之间的遗传物质交换水平非常低。在亚种群中观察到生态位特异性：CC1和BAPS聚类1主要由来自各种MAP肉类的菌株组成，而蔬菜菌株与CC2和BAPS聚类2中来自MAP家禽的菌株聚集在一起。本研究中提出的MLST方案提供了一个可共享且不断增长的序列数据库，能够对与腐败案例相关的菌株进行全球比较。这将进一步推动我们对这种具有重要工业意义的乳酸菌微生物生态学的理解。
