近日由于公众对细菌造成污染的说法关注过多，很容易让人忽略这样一个事实：如果没有有益菌种的存在和作用，我们的世界将会变得乏味和缺少食物；乳酸菌就属于这一类有益菌种。美国能源部联合基因协会(DOE-JGI)和加州大学戴维斯分校的研究人员们已经确定了9种不同的乳酸菌（LAB）的基因序列，并把这一发现发表在10月17日的美国科学院院刊(http://www.pnas.org/cgi/content /abstract/0607117103v1)中。这些微小的乳酸菌基因信息揭示了乳酸菌是如何依靠其不同的基因功能，有效地从其生存的营养环境中摄取碳、氮元素的；并反映了其生物合成能力的有限范围，使其有望得到更多的工业应用。
乳酸菌在食品和饮料的发酵生产过程中起着重要的作用，每年可带来数百亿美元的市场销售额。乳酸菌通过发酵六碳糖（己糖）来产生乳酸，相关产品种类丰富，包括酒类、腊肠、干酪、发酵面包、腌菜、酸奶、可可饮料和咖啡等。
“能源部联合基因协会对全面研究乳酸菌的贡献非常巨大，”这项研究的高级合作者、加州大学戴维斯分校葡萄栽培与酿造学的助教David Mills说，“破解这些发酵微生物的基因序列将极大地帮助我们了解它们在食品工业中的作用，实现最优化的生产设计。举例来说，更好地了解乳酸菌在干酪成熟中的作用就可以制定出缩短成熟时间的方案，从而节约能源。另外，乳酸菌还可以用于各种生物产品如右旋糖苷和抗菌剂的商业化生产，基因序列的信息则可以帮助发展其在生物能源和其它重要化学品生产方面的应用。”
这一成果的发表是乳酸菌基因联盟在多年的不懈努力中取得的最高成果，该联盟于2001年成立，由至少12个学术团体组成。能源部联合基因协会基因科技项目主任Paul Richardson介绍说，该联盟的研究类目涵盖了工业应用中的多种重要菌属，包括乳球菌、肠球菌、酒球菌、足球菌、链球菌、明串珠菌和乳杆菌。“这些不同菌属的基因序列为研究乳酸菌的糖类代谢和能量转化系统及其演变提供了依据，这有助于确定在产生某种最终产物的过程中起关键作用的酶，这些产物包括醋酸、乳酸、乙醇和二氧化碳。”
“这项研究揭示了乳酸菌的基因和生物信息的特点，必将给食品、健康和农业带来冲击，”荷兰Wageningen食品科学中心的项目主任、微生物学教授Willem M.de Vos说，“这是个壮举，他们公布的乳酸菌基因数据比现有的多几倍，这些丰富和可靠的数据可以帮助其它研究团体更好地了解和提高牛奶、肉类和酒类发酵的引发过程，或应用于养殖工业和其它工业领域。”世界各地的专家对这些新的生物信息的分析将会进一步完善这些基因数据，并提供更多关于微生物基因的学说，包括基因变异的机理和水平基因的获得。
背景资料：
能源部联合基因协会（DOE-JGI）是由美国能源部科学事务所资助，联合了来自能源部的五个国家实验室（Lawrence Berkeley、Lawrence Livermore、Los Alamos、 Oak Ridge和 Pacific Northwest）和斯坦福大学人类基因中心的专家，通过对基因组学的研究来完成能源部关于清洁能源和环境保护方面的研究项目。
英文原文：
Genomic Comparison Of Lactic Acid Bacteria Published
With public concerns at a fevered pitch over the bacterial contamination of spinach, it is easy to lose track of how bland and deprived our world would be without the contribution to our food supply of such benign microbial players as lactic acid-producing bacteria. Researchers from the U.S. Department of Energy Joint Genome Institute (DOE JGI) and the University of California, Davis, and their colleagues have characterized the genome sequences of nine different lactic acid-producing bacteria, or LAB, and have published their findings in the October 17 edition of the Proceedings of the National Academy of Sciences .The small LAB genomes encode a diverse repertoire of genes for efficient carbon and nitrogen acquisition from the nutritionally rich environments they inhabit and reflect a limited range of biosynthetic capabilities promising broad industrial applications.
Lactic acid-producing bacteria play a key role in the production of fermented foods and beverages, accounting for tens of billions of dollars in sales annually. Products constituting a fine repast, such as wine, salami, cheese, sourdough bread, pickles, yogurt, cocoa, and coffee are all enhanced by LAB, which ferment six-carbon sugars, or hexoses, to produce lactic acid.
"DOE JGI's contribution to the whole study of lactic acid bacteria is simply immense," said David Mills, Associate Professor, Viticulture & Enology, University of California, Davis, and senior author on the study. "Access to the genome sequences for these fermentative microorganisms will dramatically increase our understanding of their role in industrial food production, leading to more optimized production schemes. For example, a better understanding of the role of lactic acid bacteria in cheese ripening will result in production strategies that reduce ripening time and thereby save energy. Moreover, lactic acid bacteria are used for production of various commercial bioproducts such as dextran and antimicrobials. The availability of these genome sequences will foster development of additional production schemes for biofuels and other important chemicals."
The publication is the culmination of a multiyear effort by the Lactic Acid Bacteria Genome Consortium, a group of at least a dozen academic organizations formed in 2001. Paul Richardson, DOE JGI Genomic Technologies Program head, said that the functional classification embraced a variety of industrially important genera, including Lactococcus, Enterococcus, Oenococcus, Pediococcus, Streptococcus, Leuconostoc, and Lactobacillus species. "The sequence of these diverse species offered a window into the sugar metabolism and energy conversion systems of LAB, and the evolution of these systems, which helped identify key enzymes involved in the production of end products including acetic acid, lactic acid, ethanol, and CO2."
"This work represents a hallmark in the genomic and bioinformatic characterization of lactic acid bacteria that have an impact on food, health, and agriculture," said Willem M. de Vos, Professor of Microbiology and Program Director of the Wageningen Center for Food Sciences in Holland. "In a heroic effort, their publication more than doubles the number of lactic acid bacterial genomes that are publicly available and provides the research community with a wealth of high-quality data that can be used to understand and improve starter cultures for dairy, meat, and wine fermentations; probiotic cultures; and other industrial applications. The extensive bioinformatic analyses by world experts adds to the impact of the genomic data and provides new hypotheses on how microbial genomes evolve by mechanisms of genomic loss and horizontal gene acquisitions."
