[In vivo replacement of phosphatidylethanolamine by phosphatidylcholine affects biological function of E. coli].
OBJECTIVE
We investigated differences in morphology, physiology, periplasmic proteins and phagocytosis by macrophage among E. coli strains AD93 (PE- PC-), AD93/ptac67 (PE- PC+), Top10/ptac66(PE+ PC+) and the wild types in order to understand if phosphatidylcholine (PC) can substitute phosphatidylethanolamine (PE) in vivo.


METHODS
Bacterial cells were observed under microscope after staining with Gram-staining kit or by electron microscope. Bacterial growth under different conditions was monitored by measuring the absorbance at the wavelength of 600 nm. Periplasmic proteins were analyzed using SDS-PAGE and 2-D electrophoresis. Bacterial adherence and phagocytosis by macrophage were also examined by using murine RAW264.7 macrophage.


RESULTS
100% bacterial cells in AD93/pDD72 were bar-shaped but 25% AD93/ptac67 cells came out as long filaments. Different from AD93/ pDD72, AD93/ptac67 and AD93 required Mg2+ or Ca2+ for growth. Moreover, AD93/ptac67 displayed a different pattern of periplasmic proteins on a 2-D gel and a low relatively phagocytic efficiency in the phagocytosis test when compared to AD93/pDD72 and AD93. Both Top10/ptac66 and the wild-type Top10/ptac85 cells were bar-shaped under microscope, but the former showed noticeably difference in the outer-layer structure of cell wall, and its stress resistance and periplasmic protein composition were also different from those of the latter.


CONCLUSIONS
Substitution of phosphatidylethanolamine with phosphatidylcholine in E. coli cells is unable to restore the phonotype of PE- mutant to the wild type. Biological functions of PE and PC are different, and phosphatidylcholine cannot substitute phosphatidylethanolamine in vivo.
Faculty of Life Sciences, Hubei University, Wuhan 430062, China.
Bin
B
Wu
Qing
Q
Ye
Yang
Y
Li
Changyu
C
Li
Xuejing
X
Yu
Shu
S
Zhou
Xingguo
X
Wang
D000818:Animals; D001422:Bacterial Adhesion; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D010713:Phosphatidylcholines / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism*
D029968:Escherichia coli Proteins; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; C483858:phosphatidylethanolamine