Biological complexity: magical photosynthesis bacteria (Introduction)

by David Turell , Wednesday, November 07, 2018, 19:28 (1998 days ago) @ David Turell

Cyanobacteria, which are responsible for much of the photosynthesis from 2.5 billion years ago, are designed with tricks to overcome low life conditions:

https://phys.org/news/2018-11-bacteria-strategies-survive-stress.html

"A new study by scientists from the University of Chicago shows how cyanobacteria (bacteria that produce energy through photosynthesis like plants) change the way they grow and divide in response to different levels of light. With typical light conditions, the cells remain relatively short and divide symmetrically. But as light dims, the cells grow longer and divide unevenly, resulting in two daughter cells of different lengths. The researchers believe this may be a survival strategy that evolved to help these bacteria survive in less than ideal conditions.

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"In the new study, a postdoctoral researcher in his lab, used time-lapse imaging to track cell division in Synechococcus elongatus, a rod-shaped cyanobacterium. The researchers saw that under dim light conditions, which cause stress for cells by limiting their energy source, the S. elongatuscells grow longer than usual. When the lights are turned back up, cells shorter than eight micrometers still divide symmetrically, but above this length the divisions become uneven, typically producing one short daughter (about three micrometers) and a longer one.

"In many bacteria, the position where a mother cell splits into two is controlled by something called the Min system, a group of proteins that moves around inside the cell. In a typical short cell, one of the proteins, MinC, pools in one end and then every few minutes moves to the opposite end. As they bounce back and forth, the MinC proteins spend more time at the ends and less at mid-cell, like squeezing a water balloon in the middle and wiggling it back and forth. Since MinC inhibits cell division, this oscillation creates a sort of weak point in the middle where the cell can divide.

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"They found that the Min system exhibits different patterns depending on the cell length. The proteins kept up a characteristic, back-and-forth oscillatory pattern in short cells, but they formed a variety of dynamic patterns in longer cells, including multi-band oscillations, traveling waves, and other more complex patterns. In all of these patterns in long cells, a region without MinC was always seen about three micrometers from the end of the cell, allowing cells to divide off-center and make a short daughter of a specific size.

"'We think the patterns change because it's geometrically sensitive, so it can adapt to a changing cell size," Liao said. "The ability to form these different patterns allows both shorter cells to divide symmetrically and longer cells to produce short daughter cells."

"Rust and Liao said they aren't sure why bacteria divide into different lengths under stressful conditions or whether one length provides an advantage over another. It could be that smaller cells are able to maneuver better to find resources. Elongating themselves could give the cell more surface area to absorb light in dim conditions. There is even evidence that length is a defense mechanism for pathogens, because it's harder for an immune cell to engulf a really long bacterial cell."

Comment: These bacteria, which were so important in creating the Earth's oxygen, were given special ways to handle low light by changing size. A great design.