Date:
Wed, 27/05/202610:00-11:30
Repeats every week every Wednesday 52 times
Location:
Seminar room, Danziger B
Lecturer: Yoav Kaplan (PhD final lecture, Balaban Lab)
Abstract:
The stationary phase of bacterial existence is a condition of low metabolic activity, resilience, and survival that can last for days. CASP1 is such a stationary phase in which bacteria were found to produce proteins at a constant rate for several days, despite being growth-arrested. The term “regulated” growth arrest describes bacteria that enter growth arrest by regulating stress response pathways, such as those in the stationary phase. When the starvation conditions in stationary cultures are replaced with fresh medium, they recover quickly, regardless of the duration of starvation. In contrast, abrupt exposure to strong stresses, such as toxic chemicals, that are too strong and sudden for the bacteria to induce a stress response, was shown to lead to a different kind of growth arrest, termed “disrupted” growth arrest2. Cultures in the disrupted state display slower recovery as the duration of the growth-arrest is increased. A model of physical aging of the intracellular networks was suggested to explain these recovery dynamics, and it was hypothesized that the bacteria are in a dysregulated state. The metabolic activity of these two archetypes of growth arrest has not been systematically studied and compared. Here, we show using microcalorimetry that the metabolic activity of stationary bacteria in CASP remains constant for more than a day and is approximately 15 fW/CFU, 50 times lower than that of exponentially growing bacteria. It is also several times lower than in most disrupted growth arrest states, despite the absence of growth. This high metabolic rate may be caused by dysregulation, unless the ATP metabolism was directly inhibited. In addition, we investigated the factors governing heat production in CASP and found that the stringent response is involved. In summary, the calorimetry results shed new light on growth arrest states, leading to a new understanding of the differences between regulated and disrupted growth arrests.
References
1 Gefen, O., Fridman, O., Ronin, I. & Balaban, N. Direct observation of single stationary-phase bacteria reveals a surprisingly long period of constant protein production activity. Proceedings of the National Academy of Sciences of the United States of America 111, 556–561 (2014). https://doi.org/10.1073/pnas.1314114111
2 Kaplan, Y. et al. Observation of universal ageing dynamics in antibiotic persistence. Nature 600, 290–+ (2021). https://doi.org/10.1038/s41586-021-04114-w
Abstract:
The stationary phase of bacterial existence is a condition of low metabolic activity, resilience, and survival that can last for days. CASP1 is such a stationary phase in which bacteria were found to produce proteins at a constant rate for several days, despite being growth-arrested. The term “regulated” growth arrest describes bacteria that enter growth arrest by regulating stress response pathways, such as those in the stationary phase. When the starvation conditions in stationary cultures are replaced with fresh medium, they recover quickly, regardless of the duration of starvation. In contrast, abrupt exposure to strong stresses, such as toxic chemicals, that are too strong and sudden for the bacteria to induce a stress response, was shown to lead to a different kind of growth arrest, termed “disrupted” growth arrest2. Cultures in the disrupted state display slower recovery as the duration of the growth-arrest is increased. A model of physical aging of the intracellular networks was suggested to explain these recovery dynamics, and it was hypothesized that the bacteria are in a dysregulated state. The metabolic activity of these two archetypes of growth arrest has not been systematically studied and compared. Here, we show using microcalorimetry that the metabolic activity of stationary bacteria in CASP remains constant for more than a day and is approximately 15 fW/CFU, 50 times lower than that of exponentially growing bacteria. It is also several times lower than in most disrupted growth arrest states, despite the absence of growth. This high metabolic rate may be caused by dysregulation, unless the ATP metabolism was directly inhibited. In addition, we investigated the factors governing heat production in CASP and found that the stringent response is involved. In summary, the calorimetry results shed new light on growth arrest states, leading to a new understanding of the differences between regulated and disrupted growth arrests.
References
1 Gefen, O., Fridman, O., Ronin, I. & Balaban, N. Direct observation of single stationary-phase bacteria reveals a surprisingly long period of constant protein production activity. Proceedings of the National Academy of Sciences of the United States of America 111, 556–561 (2014). https://doi.org/10.1073/pnas.1314114111
2 Kaplan, Y. et al. Observation of universal ageing dynamics in antibiotic persistence. Nature 600, 290–+ (2021). https://doi.org/10.1038/s41586-021-04114-w