E. coli Superdiffusion and Chemotaxis—Search Strategy, Precision, and Motility

Escherichia coli motion is characterized by a sequence of consecutive tumble-and-swim events. In the absence of chemical gradients, the length of individual swims is commonly believed to be distributed exponentially. However, recently there has been experimental indication that the swim-length distribution has the form of a power-law, suggesting that bacteria might perform superdiffusive Lévy-walk motion. In E. coli, the power-law behavior can be induced through stochastic fluctuations in the level of CheR, one of the key enzymes in the chemotaxis signal transmission pathway. We use a mathematical model of the chemotaxis signaling pathway to study the influence of these fluctuations on the E. coli behavior in the absence and presence of chemical gradients. We find that the population with fluctuating CheR performs Lévy-walks in the absence of chemoattractants, and therefore might have an advantage in environments where nutrients are sparse. The more efficient search strategy in sparse environments is accompanied by a generally larger motility, also in the presence of chemoattractants. The tradeoff of this strategy is a reduced precision in sensing and following gradients, as well as a slower adaptation to absolute chemoattractant levels.     

Erratum: Ochnaflavone inhibits TNF‐α‐induced human VSMC proliferation via regulation of cell cycle,ERK1/2, and MMP‐9. S.‐J. Suh,U.‐H. Jin,S.‐H. Kim,H.‐W. Chang,J.‐K. Son,S.H. Lee,K.‐H. Son,C.‐H. Kim

During the corresponding author's transfer from Dongguk University to Sungkyunkwan University in March 2006, data from the previous University was transferred to the corresponding author's new computer. During this data transfer there was a mixing of EMSA data from experiments involving Quercetin (QC), Ochnaflavone (OC), Tanshinone (TS), Crytotanshinone (CT), BMK, and natural extracts. The mixed EMSA data was inadvertently incorporated in more than one publication. Figure 6 has been corrected to new data with re‐confirmation. J. Cell. Biochem. 108: 337, 2009. © 2009 Wiley‐Liss, Inc.

6. Effect of OC on the TNF‐α‐induced DNA binding activities of MMP‐9, NF‐κB, and AP‐1 motif in HASMC. Cells were pretreated with indicated OC for 40 min in serum‐free medium, were incubated with TNF‐α (100 ng/ml) for 24 h. Nuclear extracts were analyzed by EMSA for the activated NF‐κB (A) and AP‐1 (B) using radiolabeled oligonucleotide probes, respectively. Indicated values are means of three triplicate experiments.