During bloom events, Escherichia coli cell counts increase to between 10,000 and 100,000 cfu/100 ml of water. The strains responsible for bloom events belong to E. coli phylogenetic groups A and B1, and all have acquired a capsule from Klebsiella. A pan‐genome comparison of phylogroup A E. coli revealed that the ferric citrate uptake system (fecIRABCDE) was overrepresented in phylogroup A bloom strains compared with non‐bloom E. coli. A series of experiments were carried out to investigate if the capsule together with ferric citrate uptake system could confer a growth rate advantage on E. coli. Capsulated strains had a growth rate advantage regardless of the media composition and the presence/absence of the fec operon, and they had a shorter lag phase compared with capsule‐negative strains. The results suggest that the Klebsiella capsule may facilitate nutrient uptake or utilization by a strain. This, together with the protective roles played by the capsule and the shorter lag phase of capsule‐positive strains, may explain why it is only capsule‐positive strains that produce elevated counts in response to nutrient influx.

中文翻译：

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表型特征有助于大肠杆菌布鲁姆菌株的生长增强。

在开花期间，大肠杆菌细胞数增加到10,000至100,000 cfu / 100 ml水。引起水华事件的菌株属于大肠杆菌系统发生组A和B1，并且都已从克雷伯氏菌获得了荚膜。进化组A大肠杆菌的全基因组比较显示，与非开花菌E. coli相比，进化组A布鲁姆菌株中柠檬酸铁吸收系统（fecIRABCDE）的表达过高。进行了一系列实验，以研究该胶囊与柠檬酸铁摄取系统是否可以赋予大肠杆菌以增长速度的优势。无论培养基的组成和fec操纵子的存在与否，被囊化菌株均具有生长速率优势，并且与荚膜阴性菌株相比，它们的滞后期更短。结果表明，克雷伯菌胶囊可以促进菌株吸收或利用养分。这与胶囊发挥的保护作用以及较短的胶囊阳性菌株的滞后期一起，可以解释为什么只有胶囊阳性菌株对养分涌入产生计数升高的原因。