Noting an interesting tidbit in John Gribbin's new book, "In 
the Beginning" (Little, Brown & Co.; 1993), which is about 
evolution, life, and the universe as a whole...

Scanned in, page 114---> (Reference Lynn Margulis' theory that 
bacteria became symbiotic with eukaryptic cells)

"This would all still seem a little far-fetched, though, were 
it not for an extraordinary discovery made by Kwang Jeon, of 
the University of Tennessee, who spotted this kind of evolution 
at work in his laboratory, and gave it a helping hand. Jeon was 
working with microscopic, single-celled creatures called 
amoebas, when they were struck by a disease that spread through 
all the amoeba colonies in his laboratory. Almost all of them 
stopped feeding, ceased dividing into two to reproduce, and 
eventually died. Just a few of the amoebas seemed to be 
struggling along in spite of the disease. dividing about once 
every month instead of once every day, as they had done when 
they were healthy.

The obvious thing for Jeon to have done would have been to 
discard all the diseased amoebas and start again with a fresh, 
uninfected batch, but he was curious about the nature of the 
disease that had infected them. Studying the diseased amoebas 
through a microscope, he found that they contained tens of 
thousands of tiny, rod-shaped bacteria which had invaded the 
cells of the amoebas, disrupting their biological processes and 
killing them. And yet, a few of the 'bacteriarized' amoebas 
were struggling along, albeit with difficulty. Jeon decided to 
keep a colony of the survivors, and watch what happened to them.

For five years Jeon tended the colony, regularly picking out 
the ones that fed and reproduced best and letting the others 
die. This is a classic example of the kind of artificial 
selection used by pigeon breeders or dog fanciers. But because 
of the rapid life cycle of the amoebas, the effects of 
selection became apparent much more quickly than they do when 
breeding mammals or birds, which take much longer to 
reproduce. At the end of five years, Jeon had a colony of 
bacteriarized amoebas that seemed healthy in all respects, and 
were dividing every day, just like their non-infected cousins. 
Each of these amoebas, though, still contained as many as 
40,000 bacteria.

This is still not the end of the story. Usually, with amoebas 
of the same species, it is possible to tweak out the nuclei 
from two different cells and swap them over. The amoebas with 
the swapped nuclei happily carry on growing and dividing, since 
each nucleus carries essentially the same DNA 'message', and 
each cell contains essentially the same chemical 'factories'. 
But when Jeon removed the nuclei from the new strain of 
bacteriarized amoebas and put them into non- bacteriarized 
amoebas from the original species whose nuclei had been 
removed, the cells without the bacteria died. And yet if, just 
before it died, the 'clean' cell containing the new nucleus was 
deliberately infected with a few of the bacteria, they 
reproduced and increased up to a population of about 40,000, 
while the cell recovered its health. The nuclei from the 
bacteriarized cells could no longer function properly without 
the bacteria. Partly as a result of an accidental infection, 
and partly thanks to Jeon's artificial selection, a new 
symbiotic species of amoeba had been created.

This particular new species would probably not have survived 
without his aid. Even the few original infected cells that did 
reproduce were very sensitive to heat and cold, and much more 
easily killed by antibiotics than normal, 'non-bacteriarized' 
amoebas. But imagine the situation, something over 1.5 billion 
years ago, when different kinds of cell existed side by side in 
the waters of the Earth. Large cells, containing a relative 
wealth of biological material, would have been the prey of 
smaller bacteria, which would invade them (like the bacteria 
that invaded Jeon's amoebas) and feast upon thc resources they 
containcd. But when the host died, many of the invaders would 
die as well."