Department of Chemical Engineering, Indian Institute of Technology Hyderabad, Hyderabad, India.
J Biosci. 2020;45.
Competition for nutrients in a polymicrobial biofilm may lead to susceptible species being subjected to nutritional stress. The influence of bacterial growth rates and interspecies interactions on their susceptibility and response to nutritional stress is not well understood. and are two prevalent causative pathogens that coexist in biofilm-associated infections. Despite being the slower-growing species, dominates in a two-species biofilm by inducing phenotypic switching of S. aureus to a metabolicallychallenged small colony variant (SCV) via the release of 2-heptyl-4-hydroxyquinoline N-oxide (HQNO). We hypothesize that experiences nutritional stress in competition with S. aureus, and that the release of HQNO is an adaptive response to nutritional stress.We present an individual-based two-species biofilm model in which interactions between entities induce emergent properties. As the biofilm matured, the difference in growth rates of the two species caused a non-uniform distribution of nutrients leading to nutritional stress for P. aeruginosa and a concurrent increase in the proportion of subpopulation. The latter resulted in increased release of autoinducer, and subsequently the upregulation of cells via quorum sensing. Upregulated P. aeruginosa cells released HQNO at enhanced rates, thereby inducing phenotypic switching of to SCVs which consume nutrient at a reduced rate. This shifted the nutrient distribution back in favor of , thereby relieving nutritional stress. Increase in nutritional stress potentiated the transformation of into SCVs. HQNO production decreased once nutritional stress was relieved, indicating that phenotypic switching acts as a regulatory stress-adaptive response.
在多微生物生物膜中，营养物质的竞争可能导致易感染的物种受到营养压力。细菌生长率和种间相互作用对其易感性和对营养压力的反应的影响还不太清楚。 和 是两种普遍存在的致病病原体，它们在生物膜相关感染中共存。尽管 生长速度较慢，但通过释放 2-庚基-4-羟基喹啉 N-氧化物（HQNO）诱导金黄色葡萄球菌表型转换为代谢挑战的小菌落变种（SCV），在双物种生物膜中占优势。我们假设 在与金黄色葡萄球菌竞争中经历营养压力，并且 HQNO 的释放是对营养压力的适应性反应。我们提出了一个基于个体的双物种生物膜模型，其中实体之间的相互作用诱导出涌现特性。随着生物膜的成熟，两种物种的生长率差异导致营养物质的不均匀分布，导致铜绿假单胞菌的营养压力增加，同时 亚群的比例增加。后者导致自动诱导物的释放增加，随后通过群体感应上调 细胞。上调的铜绿假单胞菌细胞以更高的速率释放 HQNO，从而诱导 表型转换为 SCV，其以降低的速率消耗营养物质。这将营养物质的分布重新有利于 ，从而缓解营养压力。营养压力的增加促进了 向 SCV 的转化。一旦营养压力得到缓解，HQNO 的产生就会减少，表明表型转换作为一种调节应激适应性反应。
