Positive effect of Manganese on growth of two strains of Granulicella sp. revealed by proteomic and genomic analyses

Members of Acidobacteria phylum are difficult to isolate and grow. Nevertheless, for some isolated strains, trace elements solution is needed in culture media for Acidobacteria growth but the impact of these metals on their growth and metabolism is not known. Here we evaluated the effect of trace element solution SL-10 in on the growth of two strains (5B5 and WH15) of Acidobacteria belonging to Granulicella sp. and studied the proteomic responses to the metal with the best growth results, complementing with genomic characterization. Granulicella species had highest growth with the addition of Mn, as well as higher tolerance to this metal compared to seven other metal ions. Variations in tolerance to metal ion concentrations suggests that Granulicella sp. strains possess different mechanisms to deal with metal ion homeostasis and stress. The proteomic profiles of both strains indicated that Mn was more important in enhance enzymatic activity than to protein expression regulation. We did not find the most common transcriptional regulation of Mn homeostasis and we found candidate transporters that could be potentially involved in Mn homeostasis for Granulicella species. The presence of such transporters might be involved in tolerance to higher Mn concentrations, improving the adaptability of bacteria to metal enriched environments, such as the decaying wood-rich Mn environment where these two strains were isolated. Furthermore, strain 5B5 is likely more adapted to survive in an environment with higher concentration of several metal ions when compared to strain WH15.酸杆菌门（Acidobacteria）的细菌普遍难以分离培养。尽管如此，对于部分已分离的菌株，其培养基需添加微量元素溶液才能正常生长，但此类金属元素对其生长与代谢的影响仍未明确。本研究评估了微量元素溶液SL-10对两株隶属于颗粒杆菌属（Granulicella）的酸杆菌（5B5与WH15菌株）生长的影响，并针对生长效果最佳的金属离子开展了蛋白质组响应分析，同时辅以基因组特征解析。相较于其余7种金属离子，添加锰（Mn）时颗粒杆菌属菌株的生长水平最高，且对该金属的耐受性更强。金属离子浓度耐受性的差异表明，颗粒杆菌属菌株拥有不同的金属离子稳态调控与胁迫应对机制。两株菌的蛋白质组谱结果显示，锰在提升酶活性方面的作用相较调控蛋白质表达更为关键。本研究未发现锰稳态最常见的转录调控机制，但鉴定出了可能参与颗粒杆菌属锰稳态调控的候选转运蛋白。这类转运蛋白的存在可能有助于菌株耐受更高浓度的锰，提升细菌对富金属环境的适应性——例如两株菌分离自的富锰腐木环境。此外，相较于WH15菌株，5B5菌株或许更适应富含多种高浓度金属离子的生存环境。