11.   Simple bacteria have no cell nuclei.

12.   Some bacteria have two similar quorum sensing systems, like a fail-safe system in which the bacterial bomb cannot be activated unless two keys are put in the lock.

13.   Surface bacteria had less food, their population shrank and they consumed less oxygen.

14.   That way, bacteria have less chance to build up immunity to antibiotics.

15.   The bacterium presumably has receptor proteins on its surface that recognize and pull in any pieces of DNA from dead and dying cousins that have this unique sequence.

16.   The bacterium long has frustrated researchers trying to understand how it works because it cannot be grown in laboratory dishes for easy study.

17.   The difference was that most bacteria have trouble growing outside their natural environment, Relman said.

18.   The trouble is that even seemingly clean air contains billions of germs, and dangerous bacteria often have close, harmless relatives.

19.   Usually the bacteria have little effect on fish unless their resistance is lowered by other factors.

20.   Herzberg said the bacteria have structures on their surface that look just like collagen, a protein.