In his classic comedy routine, “A Place for your Stuff,” George Carlin argues that the whole point of life is to find an appropriately sized space for the things you own. What holds for people is also true for bacteria.
Just as people endlessly calculate how to upsize or downsize, bacteria continually adjust their volume (their stuff) to fit inside their membrane (their space). How they do this is not obvious: Petra Levin‘s lab at Washington University in St. Louis has spent years trying to figure it out.
The lab had made considerable headway but still couldn’t entirely explain why some cells grew to two or three times the size of others. So they tried a new approach, looking at biosynthesis rather cell-cycle control (the coordination of division and growth), which had long been the focus of the cell-size field.
What fell out of this work was a stunningly simple revelation published online June 19 in Current Biology. Fat (lipids) limits how big bacterial cells can be. “If you prevent cells from making fat, they’re smaller, and if you give them extra fat or allow them to make more fat, they get bigger,” said Levin, professor of biology in Arts & Sciences. “Fat makes cells fat.”
“It makes sense when you think about what lipids do,” said Stephen Vadia, a postdoctoral research associate in the Levin lab and the lead author on the paper. “The membrane that defines the boundary between the inside and outside of the cell is made almost entirely of fat. So it’s not really surprising that fat synthesis would limit cell size.
“I thought, ‘Well, this seems pretty obvious, now that I see the data in front of me,'” he added, punctuating with a laugh.