Longevity of growth-arrested bacteria requires protein synthesis and a stringent response

Gram-negative bacteria in infections, biofilms and industrial settings often stop growing due to nutrient depletion, immune responses or environmental stresses. Bacteria in this state tend to be tolerant to antibiotics and are often referred to as dormant. Here we describe the physiology of Rhodopseudomonas palustris, a phototrophic alpha-proteobacterium, in its growth arrested state. R. palustris can maintain almost full viability for over four months and we found that ATP synthesis, proteins synthesis and a stringent response were required for this remarkable longevity. R. palustris is an extreme example of a bacterial species that will stay alive for long periods of time as a relatively homogeneous populations of cells. There is evidence that other gram-negative species also continue to synthesis proteins during growth arrest and that a stringent response is required for their longevity as well. Our observations challenge that notion that growth-arrested cells are dormant and expands our mechanistic understanding of a crucial but understudied phase of the bacterial life cycle.