Studies on the energetic metabolism of Shigella flexneri and Escherichia coli hybrids devoid of penetration ability. II. Oxygen uptake and dehydrogenase activity.

Oxygen uptake and dehydrogenase activity are studied with lac+ kcpminus hybrids of Shigella flexneri, being avirulent to the eyes of guinea pigs, because of having lost ability for penetration in epithelial cells. These strains were obtained by hybridization of the virulent strain Shigella flexneri 222 5 a with the Hfr strain Escherichia coli K-12 P4x. It is established that lac+ kcp minus hybrids are characterized by significant decrease of respiratory activity. This decrease is outlined as a tendency studying O2 uptake and is extremely well expressed studying the dehydrogenase activity. The tests being performed with these hybrids show that the loss of virulence and connected with it the loss of the ability for penetration is related to a decrease of the respiratory activity of these bacteria which supply a part of the energy needed for their viability.