Beer-spoilage by lactic acid bacteria

啤酒是细菌的恶劣环境，因为高二氧化碳和低O2水平，酸性pH，低营养水平，以及具有抗菌作用的乙醇和啤酒花化合物。啤酒中的细菌，最常见的是乳杆菌和小球菌属，通常会污染啤酒。因为这些细菌是产乳酸的，所以它们被称为乳酸菌(LAB)。拟议的研究有两个相辅相成的目标。第一个是定义允许LAB在啤酒中生长的遗传学，即在不锈钢上形成啤酒喂养的生物膜。二是利用遗传信息设计更好的啤酒腐败实验室快速检测鉴定方法。 在支持啤酒生长的基因中，我们已经证明只有HorA和BSRA分别与能够在啤酒中生长的Lab和Pedio价球菌有强烈的关联。然而，许多啤酒腐败实验室都没有这两种基因，这意味着需要其他基因来处理啤酒中的六个生长限制因素。作为确定啤酒中实验室生长所需基因的基础，我们已经完成了黄皮链球菌的基因组序列(包括8个质粒)。我们建议对另外四个啤酒腐败实验室的基因组进行测序。然后，五个啤酒腐败菌的蛋白质将与14个非啤酒腐败实验室的蛋白质进行比较，这些实验室的基因组序列是公开的(使用美国同事开发的软件)，结果表明啤酒中的实验室生长所需的基因。接下来，我们将确定在啤酒和培养基(自由漂浮和作为表面附着的生物膜)中生长时，哪些基因会表达，这也将指出在啤酒中或在啤酒喂养的生物膜中生长所需的基因。所有的生物膜工作都将使用不锈钢作为生长面，因为这是啤酒厂实验室遇到的表面。随后，我们将评估在啤酒或啤酒喂养的生物膜中生长过程中选择性表达的单个基因如何用于抵抗乙醇或啤酒花化合物，或发酵啤酒中特定的残留碳源。最终将评估啤酒中生长所需的基因，作为基于核酸的检测的目标，用于啤酒腐败实验室的快速检测/鉴定。

Beer is a harsh environment for bacteria due to high CO2 & low O2 levels, acidic pH, low nutrient levels, & ethanol & hops compounds which are antimicrobial. Firmicutes bacteria, most commonly Lactobacillus & Pediococcus isolates, generally contaminate beer. As these bacteria are lactic acid producers, they are called lactic acid bacteria (LAB). The proposed research has two complementary objectives. The 1st is to define the genetics that allow LAB to grow in beer & as a beer-fed biofilm on stainless steel. The 2nd is to apply the genetics information to design better methods for rapid detection & identification of beer-spoilage LAB. Of genes suggested to support growth in beer, we have shown that only horA and bsrA are strongly associated with LAB and pediococci able to grow in beer, respectively. Many beer-spoilage LAB have neither gene, however, meaning other genes are needed to deal with the six growth constraints in beer. As a basis for determining the genes needed for LAB growth in beer, we have completed the genome sequence of Pediococcus claussenii (including eight plasmids). We propose sequencing the genomes of four additional beer-spoilage LAB. Proteins of the five beer-spoilage bacteria then will be compared against the proteins of fourteen non-beer-spoilage LAB whose genome sequences are publicly available (with software developed by U. of S. colleagues), with the results indicating genes required for LAB growth in beer. We will next determine which genes are expressed when P. claussenii is grown in beer & in medium (both free-floating & as a surface-adherent biofilm) which will also point to genes needed for growth in beer or in a beer-fed biofilm. All biofilm work will use stainless steel as the growth surface as this is the surface encountered by LAB in breweries. Subsequently, we will assess how individual genes selectively expressed during growth in beer or beer-fed biofilm are used, for example, to resist ethanol or hops compounds, or ferment specific residual carbon sources in beer. Genes required by LAB for growth in beer ultimately will be assessed for use as targets in nucleic acid-based assays for rapid detection/identification of beer-spoilage LAB.