Page 100 - The Microworld Miracle

On the other hand, some antibiotics, change the levels of vital
substances that enter and leave the bacterium. As we know, a cell
membrane possesses selective permeability that allows beneficial
substances to enter the cell, while harmful substances are recog-
nized and excluded, while wastes are expelled. The antibiotic alters
this special selective permeability in the bacterium's cell membrane.
A bacterium that is unable to absorb nu-

trients, but which harmful sub-
stances can freely enter, soon
dies.
Still other antibiotics target
bacterial proteins. Proteins per-
form cells' vital functions. Therefore,
when proteins are absent these func-
Antibiotic
tions cannot be carried out, and the
death of the bacterium is inevita-
Bacteria una-
ble to resist ble. The ribosome in the cell pro-
the antibiotic duces proteins. The antibiotics
Bacterium that are
not sensitive to the
antibiotic
Bacterium that es-
caped
THE MICROWORLD MIRACLE Dead bacterium

ance

98 Bacterium with improved resist-