Stem peptide composition of select <i>S</i>. <i>pneumoniae</i> strains.^a

a Each peak corresponds to a specific peptide structure as depicted in S4 Fig. Values represent the mean abundance of the indicated species relative to the total amount of peptide material analyzed and numbers within parentheses denote the standard deviation of two independent experiments. b TIGR4 strain c The murMN coding regions and intervening sequence from each strain (TIGR4, R36A, Pen6) were introduced into ΔmurMN, replacing the chloramphenicol resistance marker at the native chromosomal locus d A crossbridge is defined as a crosslink that directly incorporates the branch structure (covalent linkage between alanine from branch and fourth position alanine of adjacent peptide) Stem peptide composition of select S. pneumoniae strains.aa 每个峰对应S4图中展示的特定肽结构。数值为目标物种相对于所分析肽类总质量的平均丰度，括号内的数字为两次独立实验的标准差。 b TIGR4菌株 c 将各菌株（TIGR4、R36A、Pen6）的murMN编码区及其间隔序列导入ΔmurMN缺失突变株，替换其天然染色体位点上的氯霉素抗性标记。 d 跨桥定义为直接包含分支结构的交联键（即分支位点丙氨酸与相邻肽链第4位丙氨酸之间的共价连接）。 选定肺炎链球菌（S. pneumoniae）菌株的茎肽组成。a