Researchers have identified a new ally in the war against tooth decay: an enzyme produced by a mouth bacterium that prevents plaque formation. The finding could eventually lead to the development of toothpaste that harnesses the body‘s own plaque-fighting tools.  

 在对抗蛀牙的斗争中，研究人员找到了一个新的联盟：一种口腔细菌产生的酶可以防止牙斑的形成。该发现最终可能会有助于开发出一种牙膏，该牙膏可以利用人们自身的武器抗击牙斑。

 The human mouth is awash with bacteria. More than 700 species thrive in the hot, moist conditions, including Streptococcus mutans, one of the main components of plaque. Clinging to the teeth in thin layers called biofilms, S. mutans digests sugars and produces acids that can eat into enamel and cause cavities. Other bacteria are more gracious guests. In 2009, for example, scientists found that S. salivarius, a type of bacterium found on the tongue and other soft tissues in the mouth, decreases the buildup of S. mutans biofilms.

 人类的口腔充满着细菌。在湿热的条件下，会有700多种细菌在口腔中茁壮成长，包括变形链球菌，这是牙斑的主要成分之一。变形链球菌一层一层地吸附在牙齿上，形成所谓的“生物膜”。它们消耗糖类，产生酸，腐蚀牙齿的釉层，造成牙洞。其他的细菌就像更为亲善一些的客人。例如，2009年科学家们发现唾液链球菌可以减少变形链球菌生物膜的积累，这种链球菌存在于口腔中舌和其他软组织上。

 Hidenobu Senpuku, a biologist at the National Institute of Infectious Diseases in Tokyo, and colleagues wanted to know what substance conferred S. salivarius‘s cavity-fighting powers. Using chromatography, a method that divides the molecules in a mixture based on charge or size, they separated out individual proteins from samples of the microbe. The scientists then mixed each kind of protein with S. mutanscells and measured which cultures grew the smallest amount of biofilm on plates in the lab. The protein FruA, an enzyme that breaks apart complex sugars, was the most powerful biofilm blocker.

 东京市日本国家传染病研究院的生物学家千福秀信及同事想了解一下是什么物质赋予了唾液链球菌抗蛀牙的威力。研究人员利用层析法——一种根据电荷或大小将混合物中的各种分子分离开来的方法，把各种不同的蛋白质从唾液链球菌的样品中分离出来。然后，研究人员将每一种蛋白跟变形链球菌混合，测量一下哪一种培养方式在实验室的薄片上形成的生物膜最薄。蛋白质FruA是一种可以分解复合糖的酶，它是威力最大的生物膜阻滞剂。

 The researchers also found that a form of FruA, produced by the common fungusAspergillus niger and available off-the-shelf, stymies plaque equally well. This commercial FruA worked despite the fact that its amino acid sequence is somewhat different from that of S. salivarius FruA. That might speed the development of toothpastes that include FruA, says Senpuku.

 研究人员还发现，有一种形式的FruA，是由普通真菌黑曲霉产生的，是唾手可得的现成产品，在阻止牙斑形成方面有着同样好的效果。尽管这种商业FruA的氨基酸序列跟唾液链球菌FruA的氨基酸序列在某种程度上存在差异，但是商业FruA仍然奏效。千福秀信表示，这样可能会使含有FruA的牙膏得到快速的开发。

 The findings, reported in Applied and Environmental Microbiology, are not a license to eat all the candy you want, however. When researchers increased the concentration of sucrose, a type of sugar, in mixtures containing S. salivarius FruA andS. mutans, the beneficial bacterium lost its ability to prevent biofilm formation. The authors write that this observation may help explain why a 1996 study found that FruA contributed to cavity formation in rats.

 这些发现报道在《应用与环境微生物学》杂志上，然而，这并不意味着准许你去吃所有你想吃的糖。当研究人员在唾液链球菌FruA和变形链球菌的混合物中增加蔗糖的浓度之后，这种有益的细菌失去了阻止生物膜形成的能力。研究论文的作者们写道：该观测结果可以解释为何1996年的一项研究发现FruA在老鼠中促进了牙洞的形成。

 Mary Ellen Davey, a microbiologist at the Forsyth Institute in Cambridge, Massachusetts, agrees that the findings could spur the development of better toothpaste. But she says that won‘t be an easy task. Finding "the formulation that would ‘guarantee‘ that the enzyme remained enzymatically active on the shelf of your favorite drug store is a big challenge," she says.

 马萨诸塞州剑桥市福尔塞斯研究院的微生物学家玛丽·埃伦·戴维同意该发现可能会促使更高质量的牙膏得到开发。但是，她说开发任务不会那么容易。“一个巨大的挑战是：找到一个配方，保证这种酶在你最喜欢的杂货店货架上仍然保持酶的活性，”戴维说。