May 11, 2016 at 03:02AM

Yesterday I Learned: 1) Commercial PCR buffers use dNTP (nucleotide) concentrations about an order of magnitude lower than what is generally found in vivo. 2) RNAs have a typical half-life of a few minutes in cell-free extract. Compare with proteins, which tend to not really degrade at all over a 1-day period, unless they're specifically tagged for degradation and special proteases are added to the mix. 3) Bacillis subtilis (B. sub) is a social bacteria with an interesting strategy for forming colonies. It has two modes of life -- a free-swimming mode in which it will move around and try to find good places to live sloughing off daughter cells as it does so, and a chained mode where it will stick to surfaces and grow long chains. By probabilistically switching between the two states, B. sub can plant lots of little colonies all over the place, giving it good odds of laying down a successful colony *somewhere*. Specifically, B. sub spends most of its time in the swimming mode, and will stochastically (and memorilessnessly) switch to chained mode. The transition from swimming to chained is totally random, but the switch *back* is actually pretty well-defined at around 7-8 cell generations after onset of chaining. That's important to keep the size of the colony relatively stable -- because the colonies grow exponentially, linear changes in *time* spent in chained mode result in exponential changes in colony *size*. Really tiny colonies of one or two cells are a waste of switching, and massive colonies of millions of bacteria aren't efficient either (some of them should be off exploring new potential colony sites). The well-defined chained-mode time keeps colonies at just about the right level, which is apparently a few hundred bacteria. Thanks to Andy Halleran for teaching me about this fascinating little slice of B. sub behavior! If you're interested in learning more and have access to Nature, check out http://ift.tt/1TEayx1.