Limits...
Regulation of Indole Signalling during the Transition of E. coli from Exponential to Stationary Phase.

Gaimster H, Summers D - PLoS ONE (2015)

Bottom Line: It has recently been shown that cell-associated indole transiently reaches a very high concentration (approx. 60 mM) during stationary phase entry, presumably because indole is being produced more rapidly than it can leave the cell.The magnitude and duration of the resulting indole pulse are dependent upon the availability of exogenous tryptophan.Indole production stops when all the available tryptophan is depleted and the cell-associated indole equilibrates with the supernatant.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, United Kingdom.

ABSTRACT
During the transition from exponential to stationary phase E. coli produces a substantial quantity of the small, aromatic signalling molecule indole. In LB medium the supernatant indole concentration reaches a maximum of 0.5-1 mM. At this concentration indole has been implicated in many processes inducing acid resistance and the modulation of virulence. It has recently been shown that cell-associated indole transiently reaches a very high concentration (approx. 60 mM) during stationary phase entry, presumably because indole is being produced more rapidly than it can leave the cell. It is proposed that this indole pulse inhibits growth and cell division, causing the culture to enter stationary phase before nutrients are completely exhausted, with benefits for survival in long-term stationary phase. This study asks how E. coli cells rapidly upregulate indole production during stationary phase entry and why the indole pulse has a duration of only 10-15 min. We find that at the start of the pulse tryptophanase synthesis is triggered by glucose depletion and that this is correlates with the up-regulation of indole synthesis. The magnitude and duration of the resulting indole pulse are dependent upon the availability of exogenous tryptophan. Indole production stops when all the available tryptophan is depleted and the cell-associated indole equilibrates with the supernatant.

No MeSH data available.


Related in: MedlinePlus

Tryptophanase expression increases rapidly at the same time as indole production.A culture of growing BW25113 TnaA-GFP cells in LB medium were sampled regularly. Panel A shows the increase in external indole as cell approach stationary phase (measured by Kovacs assay) and the raw fluorescence data (excitation 480 nm, emission 510 nm). Panel B shows the measured cell associated indole and calculated fluorescence production rate (Fluorescence production rate = (Δfluorescence/ ΔOD 600)/Δtime). Data shown are the mean values ± standard deviation for three independent repeats.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4557909&req=5

pone.0136691.g001: Tryptophanase expression increases rapidly at the same time as indole production.A culture of growing BW25113 TnaA-GFP cells in LB medium were sampled regularly. Panel A shows the increase in external indole as cell approach stationary phase (measured by Kovacs assay) and the raw fluorescence data (excitation 480 nm, emission 510 nm). Panel B shows the measured cell associated indole and calculated fluorescence production rate (Fluorescence production rate = (Δfluorescence/ ΔOD 600)/Δtime). Data shown are the mean values ± standard deviation for three independent repeats.

Mentions: We investigated whether increased tryptophanase expression during the approach to stationary phase might be responsible for the initiation of the indole pulse. An overnight culture of BW25113 TnaA-GFP (complete list of strains used can be found in Table 1)was diluted into fresh LB medium to an OD 600 of 0.05 (this was defined as t = 0; Fig 1) and grown at 37°C, with shaking. From t = 120 minutes, as the culture approached stationary phase, samples were removed at 5 minute intervals to measure external indole, cell-associated indole and tryptophanase expression (GFP fluorescence).


Regulation of Indole Signalling during the Transition of E. coli from Exponential to Stationary Phase.

Gaimster H, Summers D - PLoS ONE (2015)

Tryptophanase expression increases rapidly at the same time as indole production.A culture of growing BW25113 TnaA-GFP cells in LB medium were sampled regularly. Panel A shows the increase in external indole as cell approach stationary phase (measured by Kovacs assay) and the raw fluorescence data (excitation 480 nm, emission 510 nm). Panel B shows the measured cell associated indole and calculated fluorescence production rate (Fluorescence production rate = (Δfluorescence/ ΔOD 600)/Δtime). Data shown are the mean values ± standard deviation for three independent repeats.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557909&req=5

pone.0136691.g001: Tryptophanase expression increases rapidly at the same time as indole production.A culture of growing BW25113 TnaA-GFP cells in LB medium were sampled regularly. Panel A shows the increase in external indole as cell approach stationary phase (measured by Kovacs assay) and the raw fluorescence data (excitation 480 nm, emission 510 nm). Panel B shows the measured cell associated indole and calculated fluorescence production rate (Fluorescence production rate = (Δfluorescence/ ΔOD 600)/Δtime). Data shown are the mean values ± standard deviation for three independent repeats.
Mentions: We investigated whether increased tryptophanase expression during the approach to stationary phase might be responsible for the initiation of the indole pulse. An overnight culture of BW25113 TnaA-GFP (complete list of strains used can be found in Table 1)was diluted into fresh LB medium to an OD 600 of 0.05 (this was defined as t = 0; Fig 1) and grown at 37°C, with shaking. From t = 120 minutes, as the culture approached stationary phase, samples were removed at 5 minute intervals to measure external indole, cell-associated indole and tryptophanase expression (GFP fluorescence).

Bottom Line: It has recently been shown that cell-associated indole transiently reaches a very high concentration (approx. 60 mM) during stationary phase entry, presumably because indole is being produced more rapidly than it can leave the cell.The magnitude and duration of the resulting indole pulse are dependent upon the availability of exogenous tryptophan.Indole production stops when all the available tryptophan is depleted and the cell-associated indole equilibrates with the supernatant.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, United Kingdom.

ABSTRACT
During the transition from exponential to stationary phase E. coli produces a substantial quantity of the small, aromatic signalling molecule indole. In LB medium the supernatant indole concentration reaches a maximum of 0.5-1 mM. At this concentration indole has been implicated in many processes inducing acid resistance and the modulation of virulence. It has recently been shown that cell-associated indole transiently reaches a very high concentration (approx. 60 mM) during stationary phase entry, presumably because indole is being produced more rapidly than it can leave the cell. It is proposed that this indole pulse inhibits growth and cell division, causing the culture to enter stationary phase before nutrients are completely exhausted, with benefits for survival in long-term stationary phase. This study asks how E. coli cells rapidly upregulate indole production during stationary phase entry and why the indole pulse has a duration of only 10-15 min. We find that at the start of the pulse tryptophanase synthesis is triggered by glucose depletion and that this is correlates with the up-regulation of indole synthesis. The magnitude and duration of the resulting indole pulse are dependent upon the availability of exogenous tryptophan. Indole production stops when all the available tryptophan is depleted and the cell-associated indole equilibrates with the supernatant.

No MeSH data available.


Related in: MedlinePlus