It forms small pores across the outer part of the cell wall functioning as a sieve protecting the cell against toxic proteins but allowing the uptake of small nutrients. This number constitutes only a small fraction of all possible protein structures of all living organisms combined. Bacteriophage The Bacteriophage T4 is a virus infecting bacterial cells such as that of E.coli shown in the next figure. Size of organism 200 nanometers. Bacteria Escherichia coli right before cell division into two daughter cells.
Bacteria are single cell microorganism.
E.coli is one of the model organisms that help geneticists and molecular biologists understand the molecular mechanism of inheritance. These discoveries were greatly facilitated by the help of viruses that infect bacteria and showed scientists the ins and outs of exchange of genetic material between organisms and how cells use their genes to control physiological processes. Bacteria are beneficial as well as dangerous for us humans. Worm Caenorhabditis elegans is a soil nematode found in temperate regions and is used a model organism by biologists since the 1960s. It has a primitive nervous system.