Data from: The effects of spatial structure, frequency dependence and resistance evolution on the dynamics of toxin-mediated microbial invasions

Recent evidence suggests that interference competition between bacteria shapes the distribution of the opportunistic pathogen Staphylococcus aureus in the lower nasal airway of humans, either by preventing colonization or by driving displacement. This competition within the nasal microbial community would add to known host factors that affect colonization. We tested the role of toxin-mediated interference competition in both structured and unstructured environments, by culturing S. aureus with toxin-producing or nonproducing Staphylococcus epidermidis nasal isolates. Toxin-producing S. epidermidis invaded S. aureus populations more successfully than nonproducers, and invasion was promoted by spatial structure. Complete displacement of S. aureus was prevented by the evolution of toxin resistance. Conversely, toxin-producing S. epidermidis restricted S. aureus invasion. Invasion of toxin-producing S. epidermidis populations by S. aureus resulted from the evolution of toxin resistance, which was favoured by high initial frequency and low spatial structure. Enhanced toxin production also evolved in some invading populations of S. epidermidis. Toxin production therefore promoted invasion by, and constrained invasion into, populations of producers. Spatial structure enhanced both of these invasion effects. Our findings suggest that manipulation of the nasal microbial community could be used to limit colonization by S. aureus, which might limit transmission and infection rates.

现有研究证据表明，细菌间的干扰竞争（interference competition）可通过阻碍定植或推动排挤，塑造机会致病菌金黄色葡萄球菌（Staphylococcus aureus）在人类下鼻腔气道中的分布格局。这种发生于鼻腔微生物群落内的竞争，会叠加于已知的影响定植的宿主因子之上。我们通过将金黄色葡萄球菌与产毒素或不产毒素的表皮葡萄球菌（Staphylococcus epidermidis）鼻腔分离株共培养，在结构化与非结构化环境中检验了毒素介导的干扰竞争所发挥的作用。结果显示，产毒素表皮葡萄球菌相较于不产毒素菌株，更能成功侵入金黄色葡萄球菌种群，且空间结构会促进这一侵入过程。金黄色葡萄球菌的完全排挤会因毒素抗性的演化而被阻断。反之，产毒素表皮葡萄球菌会限制金黄色葡萄球菌的侵入。金黄色葡萄球菌侵入产毒素表皮葡萄球菌种群的过程，源于毒素抗性的演化，而该演化受到高初始频率与低空间结构的青睐。部分侵入性表皮葡萄球菌种群还演化出了增强型毒素产生能力。由此可见，毒素产生既会促进产毒素种群的侵入，也会限制外来种群对其的侵入。空间结构会强化这两种与侵入相关的效应。我们的研究结果提示，可通过调控鼻腔微生物群落来限制金黄色葡萄球菌的定植，这或许能够降低其传播与感染率。