Visualizing genetic loci and molecular machines in living bacteria

An ongoing mission for biologists is to probe the molecular nature of cellular processes within live cells. Although much of what we have discovered during the molecular biology revolution of the last 50 years has been achieved by exploiting bacteria as ‘bags of DNA and proteins’, relatively little has been learnt about how they organize their life processes within cells. The mistaken perception of bacteria cells as unstructured systems arose partly because of the difficulty of performing studies by light microscopy due to their small size (many of them having cell lengths a few times bigger than the wavelength of visible light). With the opportunities provided by a range of new fluorophores and by new microscopic techniques, a revolution in bacterial cell biology is revealing unimagined organization in the bacterial cell. We review the development and exploitation of new visualization methods and reagents and show how they are contributing to the understanding of bacterial structure, chromosome organization, DNA metabolism and their relationship to the cell cycle.