Lazy but smart: The discovery of novel transport proteins reveals how bacteria that live inside unicellular microorganisms exploit their host cells.



Researchers from the Universities of Vienna (M. Horn, M. Wagner) and   Kaiserslautern (I. Haferkamp, E. Neuhaus) have discovered how intracellular bacteria that are closely related with chlamydiae, major pathogens of humans (with more than 60 Million infections per year), exploit their host cells. These symbiotic bacteria thrive within amoebae or human cells and thus can rely on their hosts providing complex and energy-rich nutrients. As a consequence these bacteria have lost the ability to synthesize essential compounds on their own. In the physiological sense, they got "lazy" during evolution. 
This reduction of metabolic capability was only possible by simultaneous development of highly specific transport mechanisms. For the first time the research team was able to identify a transport protein for the universal electron carrier and co-factor NAD+ (nicotinamide adenine-dinucleotide). In concert with similar transport proteins the bacteria are able to in addition import energy (as ATP) and further nucleotides, the basic modules of DNA. These transport proteins thus ensure a constant supply of highly valuable substrates from the host cells nutrient pool, the researchers report in the science magazine Nature (December 2nd 2004). 
As these transporters are only present in the bacteria but not in the host cells, they might represent promising targets for novel antibiotics. The development of novel drugs for anti-bacterial therapy is one of the major challenges of our time.