Growth and biofilm formation of Cupriavidus metallidurans CH34 on different metallic and polymeric materials used in spaceflight applications

Bacteria biofilm formation and its complications are of special concern in isolated structures, such as offshore stations, manned submarines and space habitats, as maintenance and technical support are poorly accessible due to costs and/or logistical challenges. In addition, considering that future exploration missions are planned to adventure farther and longer in space, unlocking biofilm formation mechanisms and developing new antifouling solutions are key goals in order to ensure spacecraft’s efficiency, crew’s safety and mission success. In this work, we explored the interactions between Cupriavidus metallidurans, a prevalently identified contaminant onboard the International Space Station, and aerospace grade materials such as the titanium alloy TiAl6V4, the stainless steel AISI 316 (SS316) and Polytetrafluoroethylene (PTFE) or Teflon. Borosilicate glass was used as a control and all surfaces were investigated at two different pH values (5.0 and 7.0). Biofilms were almost absent on stainless steel and the titanium alloy contrary to Teflon and glass that were covered by an extensive biofilm formed via monolayers of scattered matrix-free cells and complex multilayered clusters or communities. Filamentous extracellular DNA structures were observed specifically in the complex multilayered clusters adherent to Teflon, indicating that the employed attachment machinery might depend on the physicochemical characteristics of the surface.细菌生物被膜（bacterial biofilm）的形成及其引发的并发症，在离岸站、载人潜艇及太空栖息地这类孤立封闭结构中尤其值得关注。由于成本限制与后勤层面的双重挑战，此类场景的维护与技术支持难以获取。此外，鉴于未来太空探索任务将迈向更远距离、更长时长的深空航行，阐明生物被膜形成机制并开发新型防污方案，已成为保障航天器运行效率、航天员安全与任务成功的核心目标。本研究探究了金属嗜铜菌（Cupriavidus metallidurans）——国际空间站（International Space Station, ISS）上检出率最高的污染菌株——与航空航天级材料之间的相互作用，所涉材料包括钛合金TiAl6V4、不锈钢AISI 316（SS316）以及聚四氟乙烯（Polytetrafluoroethylene, PTFE，又称特氟龙（Teflon））。本研究以硼硅酸盐玻璃作为对照样本，并在两种不同pH值（5.0与7.0）下对所有受试表面开展了表征分析。结果显示，不锈钢与钛合金表面几乎未形成生物被膜；而特氟龙与玻璃表面则被大面积生物被膜覆盖，此类生物被膜由分散的无基质单层细胞与复杂的多层簇状群落共同构成。研究人员仅在特氟龙表面附着的复杂多层簇状群落中观察到了丝状细胞外DNA（extracellular DNA, eDNA）结构，这表明该菌株所采用的附着机制，可能取决于材料表面的物理化学特性。