Expression and function of secreted proteases in commensal lifestyles of Staphylococci

蛋白水解酶是降解或处理其他蛋白质的蛋白质，在所有形式的生命中都具有重要或必要的功能。蛋白水解酶也有助于细菌致病。一些细菌是人类微生物区系的一部分，在那里它们阻止致病细菌的生长。我们的研究将评估一种类似的分泌蛋白水解酶的功能和表达的差异如何有助于两个相关物种的葡萄球菌定植于人类的鼻子。其中，金黄色葡萄球菌只在鼻子上定植，但如果它突破上皮屏障，也会引起严重感染。相比之下，表皮葡萄球菌在人类皮肤上也随处可见，但很少会引起严重感染。重要的是，表皮葡萄球菌分泌的一种蛋白酶，称为ESP，干扰了金黄色葡萄球菌在鼻部定植的能力。令人惊讶的是，金黄色葡萄球菌能够产生一种非常相似的蛋白酶。我们认为，鼻腔中的生长条件向表皮葡萄球菌发出信号，以产生这种酶，以阻止金黄色葡萄球菌的生长，而同样的环境条件指示金黄色葡萄球菌不产生该酶。我们认为，金黄色葡萄球菌只有在进入人体并引起感染时才会产生这种酶，在那里它不必与表皮葡萄球菌竞争。因此，确定指示这些细菌产生或不产生这种蛋白酶的信号，将有助于更好地理解一些细菌是如何被指示致病的，而另一些细菌则对同样的指令做出反应，以维持人类健康。我们将测试每个微生物产生蛋白酶的能力，以响应可能在鼻子或皮肤上遇到的信号，包括酸度、游离脂肪酸的存在和寡肽的可获得性的变化。帮助细菌对这些信号做出反应的传感器蛋白质将被识别，我们将使这些蛋白质失活，以确定细菌如何对它们的丢失做出反应。最后，我们将从每个细菌中分离出蛋白酶，并修改其性质，以便我们能够了解它如何起作用，要么促进表皮葡萄球菌的共生，要么阻止金黄色葡萄球菌的定居。

Proteases are proteins that degrade or process other proteins, and contribute to important or essential functions in all forms of life. Proteases also contribute to the ability of bacteria to cause disease. Some bacteria are part of the human microflora, where they discourage the growth of disease causing bacteria. Our research will evaluate how differences in function and expression of a similar secreted protease contribute to the ability of two related species of Staphylococci to colonize the nose of humans. Of these, Staphylococcus aureus only colonizes the nose, but can also cause severe infections if it breaches the epithelial barrier. In contrast, S. epidermidis is also ubiquitous on human skin, but rarely causes severe infections. Importantly, a secreted protease of S. epidermidis, named Esp interferes with the ability of S. aureus to colonize the nose. Surprisingly, S. aureus is capable of producing a very similar protease. We propose that growth conditions in the nose signal S. epidermidis to produce this protease, to discourage growth of S. aureus, while the same environmental conditions instruct S. aureus not to produce the protease. We believe that S. aureus only produces this protease once it enters the body and causes an infection, where it does not have to compete with S. epidermidis. Consequently, determining the signals that instruct these bacteria to either produce, or not produce this protease, will lead to a better understanding of how some bacteria are instructed to cause disease, and others respond to the same instructions to maintain human health. We will test the ability of each microbe to produce protease in response to signals that may be encountered in the nose or on the skin, including changes in acidity, presence of free fatty acids, and the availability of oligopeptides. Sensor proteins that help the bacteria respond to these signals will be identified, and we will inactivate these proteins to determine how the bacteria respond to their loss. Finally, we will isolate the protease from each bacteria, and modify its properties so that we can understand how it functions to either promote commensalism of S. epidermidis, or alternately to discourage colonization of S. aureus.