Ojala Teija, Laine Pia K S, Ahlroos Terhi, Tanskanen Jarna, Pitkänen Saara, Salusjärvi Tuomas, Kankainen Matti, Tynkkynen Soile, Paulin Lars, Auvinen Petri
Institute of Biotechnology, University of Helsinki, Viikinkaari 4, PO Box 56, FI-00014 Helsinki, Finland.
Institute of Biotechnology, University of Helsinki, Viikinkaari 4, PO Box 56, FI-00014 Helsinki, Finland.
Int J Food Microbiol. 2017 Jan 16;241:39-48. doi: 10.1016/j.ijfoodmicro.2016.09.022. Epub 2016 Sep 26.
Propionibacterium freudenreichii is a commercially important bacterium that is essential for the development of the characteristic eyes and flavor of Swiss-type cheeses. These bacteria grow actively and produce large quantities of flavor compounds during cheese ripening at warm temperatures but also appear to contribute to the aroma development during the subsequent cold storage of cheese. Here, we advance our understanding of the role of P. freudenreichii in cheese ripening by presenting the 2.68-Mbp annotated genome sequence of P. freudenreichii ssp. shermanii JS and determining its global transcriptional profiles during industrial cheese-making using transcriptome sequencing. The annotation of the genome identified a total of 2377 protein-coding genes and revealed the presence of enzymes and pathways for formation of several flavor compounds. Based on transcriptome profiling, the expression of 348 protein-coding genes was altered between the warm and cold room ripening of cheese. Several propionate, acetate, and diacetyl/acetoin production related genes had higher expression levels in the warm room, whereas a general slowing down of the metabolism and an activation of mobile genetic elements was seen in the cold room. A few ripening-related and amino acid catabolism involved genes were induced or remained active in cold room, indicating that strain JS contributes to the aroma development also during cold room ripening. In addition, we performed a comparative genomic analysis of strain JS and 29 other Propionibacterium strains of 10 different species, including an isolate of both P. freudenreichii subspecies freudenreichii and shermanii. Ortholog grouping of the predicted protein sequences revealed that close to 86% of the ortholog groups of strain JS, including a variety of ripening-related ortholog groups, were conserved across the P. freudenreichii isolates. Taken together, this study contributes to the understanding of the genomic basis of P. freudenreichii and sheds light on its activities during cheese ripening.
费氏丙酸杆菌是一种具有重要商业价值的细菌，对于瑞士型奶酪独特的眼状结构和风味的形成至关重要。这些细菌在温暖温度下的奶酪成熟过程中活跃生长并产生大量风味化合物，但在奶酪随后的冷藏过程中似乎也对香气的形成有贡献。在此，我们通过展示费氏丙酸杆菌谢氏亚种JS的2.68 Mbp注释基因组序列，并使用转录组测序确定其在工业奶酪制作过程中的全局转录谱，来加深我们对费氏丙酸杆菌在奶酪成熟中作用的理解。基因组注释共鉴定出2377个蛋白质编码基因，并揭示了几种风味化合物形成的酶和途径。基于转录组分析，在奶酪的温暖和冷藏成熟阶段之间，348个蛋白质编码基因的表达发生了改变。几个与丙酸、乙酸和双乙酰/乙偶姻产生相关的基因在温暖环境中有较高的表达水平，而在冷藏环境中则观察到代谢普遍减缓以及可移动遗传元件的激活。一些与成熟相关和涉及氨基酸分解代谢的基因在冷藏环境中被诱导或保持活跃，表明JS菌株在冷藏成熟过程中也有助于香气的形成。此外，我们对JS菌株和其他10个不同物种的29种丙酸杆菌菌株进行了比较基因组分析，包括费氏丙酸杆菌费氏亚种和谢氏亚种的分离株。预测蛋白质序列的直系同源分组显示，JS菌株近86%的直系同源组，包括各种与成熟相关的直系同源组，在费氏丙酸杆菌分离株中是保守的。综上所述，本研究有助于理解费氏丙酸杆菌的基因组基础，并揭示其在奶酪成熟过程中的活动。
