Bacteriophages and plasmids in streptococcus thermophilus

乳制品行业是我们的遗产和经济的重要组成部分。它是加拿大农业食品经济的第四大部门。2007年，奶牛养殖业的收入为52亿加元，乳制品加工商的销售额为116亿加元，占加拿大食品和饮料行业所有加工销售额的15%。超过38，000名加拿大人在14，660个奶牛场工作，另有超过22，000人在445个奶牛场工作。这使得乳制品行业成为食品行业的第二大雇主。目前我国生产的奶酪超过450种。2007年，加拿大奶酪产量达到创纪录的水平，达到403，828吨，比2006年增加4.4%。同样，酸奶产量达到251，672吨的历史最高水平，比2006年增长了3.3%。没有迹象表明这种趋势会很快改变。然而，我们的乳制品行业面临着国内和国际市场的激烈竞争，必须提供高质量的产品。奶酪和酸奶的工业生产需要用精心挑选的细菌细胞（称为发酵剂）接种牛奶，以控制发酵并获得优质产品。发酵剂是一种细菌的组合，其中嗜热链球菌是最重要的菌种之一。进行发酵剂培养对于获得高质量的产品至关重要。

The dairy industry is a significant part of our heritage and of our economy. It is the fourth largest sector of the Canadian agri-food economy. In 2007, dairy farming generated receipts of $5.2 billion and sales from dairy processors amounted to $11.6 billion, accounting for 15% of all processing sales in the Canadian food and beverage sector. Over 38,000 Canadians are working on 14,660 dairy farms, and over 22,000 others are employed in 445 dairy plants. This makes the dairy sector the second largest employer in the food industry. More than 450 cheeses are now produced in our country. In 2007, Canadian cheeses were produced at a record level, reaching 403,828 tons, an increase of 4.4% from 2006. Similarly, yogurt production reached an all-time high of 251,672 tons, an increase of 3.3% from 2006. There is no indication that this trend will change soon. However, our dairy industry is facing intense competitions on the national and international markets and must deliver high-quality products. The industrial manufacture of cheese and yogurt requires the inoculation of milk with carefully selected bacterial cells (known as starter culture) in order to control the fermentation and to obtain quality products. The starter culture is a combination of bacteria, of which Streptococcus thermophilus is one of the most important species. Performing starter cultures are critical to obtain high-quality products.