Year-end Sale % OFF 
Abstract
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. Rhodopseudomonas palustris, a phototrophic alphaproteobacterium, can remain fully viable for more than 4 months when its growth is arrested. Here, we show that protein synthesis, specific proteins involved in translation, and a stringent response are required for this remarkable longevity. Because it can generate ATP from light during growth arrest, R. palustris is an extreme example of a bacterial species that will stay alive for long periods of time as a relatively homogeneous population of cells and it is thus an excellent model organism for studies of bacterial longevity. There is evidence that other Gram-negative species also continue to synthesize proteins during growth arrest and that a stringent response is required for their longevity as well. Our observations challenge the notion that growth-arrested cells are necessarily dormant and metabolically inactive and suggest that such bacteria may have a level of metabolic activity that is higher than many would have assumed. Our results also expand our mechanistic understanding of a crucial but understudied phase of the bacterial life cycle.IMPORTANCE We are surrounded by bacteria, but they do not completely dominate our planet despite the ability of many to grow extremely rapidly in the laboratory. This has been interpreted to mean that bacteria in nature are often in a dormant state. We investigated life in growth arrest of Rhodopseudomonas palustris, a proteobacterium that stays alive for months when it is not growing. We found that cells were metabolically active, and they continued to synthesize proteins and mounted a stringent response, both of which were required for their longevity. Our results suggest that long-lived bacteria are not necessarily inactive but have an active metabolism that is well adjusted to life without growth.
Highlights
Bacteria in nature often exist in viable but non-growing states without forming differentiated structures like spores [1, 2], but this crucial phase of the bacterial life cycle is underexplored
We found that illuminated R. palustris responds to growth arrest by reducing ribosome abundance as is typical of most bacteria when they slow their growth rate
The levels of most proteins involved in tRNA charging and translation elongation and were at similar levels in growing and growth-arrested cells (Figure 4d and SI Table 2), which is consistent with the notion from a previous report that elongation rates are maintained as bacteria slow down their growth-rates even towards zero growth [43]
Summary
Bacteria in nature often exist in viable but non-growing states without forming differentiated structures like spores [1, 2], but this crucial phase of the bacterial life cycle is underexplored. Several bacterial pathogens, including Vibrio cholera, Pseudomonas aeruginosa and Burkholderia pseudomallei can survive for months and even years in a growth-arrested state in distilled water, sterilized seawater or basal salts medium in a laboratory setting [6,7,8,9]. Non-growing pathogenic bacteria occur in human infections and in this form present challenges for treatment because antibiotics tend to target processes such as cell-wall biosynthesis or DNA replication that are active in growing, but not non-growing cells. One example of a bacterium that is recalcitrant to antibiotic treatment in vivo is Mycobacterium tuberculosis, which forms latent infections that persist over many years in the absence of overt signs of growth [11]. There are bacterial antibiotic persisters, a small subpopulation of non-growing or slowly-growing cells that develop in some bacterial infections and are tolerant to antibiotic treatment [12,13,14]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
