Cited research: Mol. Microbiol. doi:10.1111/j.1365-2958.2010.07241.x (2010)

A group of bacteria that can multiply only in a host cell is less needy than scientists thought.

Members of the phylum Chlamydiae, which include human pathogens and symbionts of amoebae, were thought to be metabolically dependent on the cells they infect. Michael Wagner at the University of Vienna and his colleagues used Raman microspectroscopy to distinguish between the active and resting stages of the bacterium Protochlamydia amoebophila (pictured in green) on the basis of their chemical composition.

They expected resting bacteria to be metabolically inactive, but found that the cells took up the amino acid phenylalanine to produce proteins, even when outside their host cells. This uptake continued for up to three weeks, and the bacteria remained infective throughout. And the species was not alone: the human pathogen Chlamydia trachomatis also synthesized proteins independently of its hosts. H.L.

Credit: B. SIXT/UNIV. VIENNA