Like other microbes that live on or in the human body, the bacteria that inhabit the upper respiratory tract, in particular the nasal cavity, have evolved to survive in an environment that presents a number of physical and chemical challenges; these microbes are constantly bombarded with nutritional fluctuations, changes in humidity, the presence of inhaled particulate matter (odorants and allergens), and competition with other microbes. Indeed, only a specialized set of species is able to colonize this niche and successfully contend with the host’s immune system and the constant threat from competitors. To this end, bacteria that live in the nasal cavity have evolved a variety of approaches to outcompete contenders for the limited nutrients and space; broadly speaking, these strategies may be considered a type of “bacterial warfare.” A greater molecular understanding of bacterial warfare has the potential to reveal new approaches or molecules that can be developed as novel therapeutics. As such, there are many studies within the last decade that have sought to understand the complex polymicrobial interactions that occur in various environments. Here, we review what is currently known about the age-dependent structure and interbacterial relationships within the nasal microbiota and summarize the molecular mechanisms that are predicted to dictate bacterial warfare in this niche. Although the currently described interactions are complex, in reality, we have likely only scratched the surface in terms of a true understanding of the types of interbacterial competition and cooperation that are thought to take place in and on the human body.

中文翻译：

---

朋友或敌人：鼻腔内的细菌竞争

与生活在人体表面或体内的其他微生物一样，栖息在上呼吸道（尤其是鼻腔）的细菌已经进化到能够在存在许多物理和化学挑战的环境中生存；这些微生物不断受到营养波动、湿度变化、吸入颗粒物（气味和过敏原）的存在以及与其他微生物的竞争的冲击。事实上，只有一组专门的物种能够在这个生态位上定居并成功地对抗宿主的免疫系统和来自竞争对手的持续威胁。为此，生活在鼻腔中的细菌已经进化出多种方法来在有限的营养和空间上与竞争者竞争；从广义上讲，这些策略可以被视为一种“细菌战”。”对细菌战的更深入的分子理解有可能揭示可以开发为新疗法的新方法或分子。因此，在过去十年中有许多研究试图了解在各种环境中发生的复杂的多种微生物相互作用。在这里，我们回顾了目前已知的关于鼻腔微生物群内年龄依赖性结构和细菌间关系的知识，并总结了预测在这一生态位中决定细菌战争的分子机制。尽管目前描述的相互作用很复杂，但实际上，我们可能只是在真正了解被认为发生在人体内部和表面的细菌间竞争和合作类型方面才触及皮毛。