Heat shock gene expression in continuous cultures of Escherichia coli

Heitzer, A.; Mason, Colin; Hamer, G.

doi:10.1016/0168-1656(92)90139-z

Cited by 23 publications

(19 citation statements)

References 52 publications

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“…23 min following reaeration of the culture. This response time is remarkably similar to those encountered for the induction of heat shock proteins encountered in continuous E. coli cultures [6,7], suggesting that perhaps oxygen stress proteins are responsible for the observations made in the current study and that they react at similar rates to those of heat stress proteins. This concept is further supported by the studies of Smith and Neidhardt [10,11] who found similar reaction times for the production of speci®c enzymes following abrupt shifts up and down in oxygen supplied to E. coli cultures.…”

Section: Response Times To Step Changes To and From Oxygen Starvationsupporting

confidence: 72%

“…at cycle time below 2 h. In all circumstances investigated, E. coli ML30 stopped growing in response to a shift-down markedly faster than it started growing in response to a shift-up. The lags observed were similar in duration to the times required for heat stress gene expression in E. coli [6,7].…”

Section: Introductionmentioning

confidence: 51%

“…They suggested that as these changes occurred within the ®rst 15 min it could be speculated that these responses were probably as a result of rapid feedback regulation of metabolism not requiring protein synthesis. This is not necessarily true when one considers the similarly rapid response of E. coli in inducing heat stress [6,7]. This was followed by more gradual changes in speci®c oxygen consumption and the disappearance of fermentative products over the next 8 h. The time taken to reach a new steady state was found to be between 8 and 9 h after reaeration.…”

Section: Response Times To Step Changes To and From Oxygen Starvationmentioning

confidence: 79%

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Oxygen availability and growth of Escherichia coli W3110: Dynamic responses to limitation and starvation

O’Beirne

Hamer

2000

Bioprocess Engineering

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It is well known that oxygen availability can have a profound effect upon the growth of an Escherichia coli culture with respect to acetate excretion or lower product yield. The current investigation seeks to determine the dynamic responses of steady state continuous cultures to abrupt changes in the oxygen supply. This should yield information regarding the behaviour of such cells as they circulate through areas of low and high oxygen availability in an industrial-scale bioreactor. It was found that a decoupling of catabolism and anabolism occurred following sudden switches both from and to oxygen limitation. It also appeared that the imposed growth rate had an effect on the speed of recovery of the system following any such changes. List of symbolsVolume of bioreactor (l) xBiomass concentration (g/l) x i Biomass concentration¯owing into bioreactor (g/l) x 0 Initial biomass concentration at commencement of new growth phase (g/l) l Substrate based biomass speci®c growth rate (h )1 ) l Ã Maximum speci®c biomass growth rate during non-steady state transition periods (h )1 ) l max Maximum speci®c biomass growth rate (h )1 ) IntroductionThe question of the effects of varying oxygen availabilities on the growth of Escherichia coli W3110 in batch culture was examined previously by O'Beirne and Hamer [1]. The objective of these experiments was to establish base-case data concerning the response of E. coli W3110 to constant preset operating parameters in an intensely agitated laboratory-scale bioreactor where perfect mixing could be assumed to be approached. Two series of experiments were conducted. The ®rst involved batch cultures growing on glucose which were subjected to a series of different ®xed sparged air¯ow rates; the second involved similar cultures which were subjected to constant sparged gas¯ow rates, each containing different volumetric oxygen concentrations. However, such results only represent a series of snapshots, rather than an overall picture of the dynamic responses that result from continuously changing oxygen availabilities, as occurs in large industrial-scale bioreactors.Transient responses of faculatively anaerobic bacteria to certain changes in their aeration status in well mixed laboratory-scale bioreactors have been investigated by Harrison and Loveless [2,3] with glucose grown cultures of both E. coli and Klebsiella aerogenes. They demonstrated reduced biomass yield coef®cients and corresponding increases in oxygen uptake rates, without extra cellular product (acetate) formation at low, but not limiting, dissolved oxygen concentrations [2] and that during transition from anaerobic to aerobic growth conditions, both the oxygen and the glucose based biomass yield coef®cients were depressed relative to those for steady state aerobic growth. However, such experiments neither sought to examine nor examined the types of changes and the dynamic responses thereto that occur in aerated cultures of faculative anaerobes subjected to either nutrient (oxygen) or substrate (glucose)¯uctuations. In fact one o...

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Section: Response Times To Step Changes To and From Oxygen Starvationsupporting

confidence: 72%

Section: Introductionmentioning

confidence: 51%

Section: Response Times To Step Changes To and From Oxygen Starvationmentioning

confidence: 79%

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Oxygen availability and growth of Escherichia coli W3110: Dynamic responses to limitation and starvation

O’Beirne

Hamer

2000

Bioprocess Engineering

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“…The current lack of systematic data on the influence of temperature on the kinetics of growth makes the prediction of this effect difficult. Temperature modulation of growth kinetics is to be expected, because both metabolism and cellular composition are affected by cultivation temperature, as was demonstrated by the cellular fatty acid composition (16, 26, 41), the synthesis or degradation of certain proteins (14,15,17,20,25), changes in protein activity (15, 35), changes in maintenance requirements of cells (19,27,39,42,47), changes in end products of metabolism (17), and increases in pigment formation (27).Bacterial metabolism represents a network of reactions. Although these individual biochemical reactions are temperature dependent, the fundamental question of whether the parameters used in growth kinetic models are temperature dependent must be asked.…”

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confidence: 99%

Temperature-dependent growth kinetics of Escherichia coli ML 30 in glucose-limited continuous culture

1996

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Knowledge concerning the influence of environmental factors such as temperature, pH, salinity, etc., on microbial growth is of crucial practical importance in the control of bioprocesses, for the safe handling of food (1, 2, 12, 50, 51), in wastewater treatment (7), and in bioremediation (2). In addition, in taxonomy, cardinal temperatures for growth are key characteristics of microbial strains (37).In recent years, several models for predicting the growth rate of microorganisms as a function of either temperature alone (11,13,22,31,32,52,53) or of temperature in combination with other factors have been proposed (1, 5, 20-22, 36, 50). Surprisingly, few attempts at a better basic understanding have been made to relate the rate of growth and actual substrate concentration. This relationship is traditionally termed growth kinetics (23,30). (However, note that the same expression has also been used for the description of the time courses of population densities [5].) The current lack of systematic data on the influence of temperature on the kinetics of growth makes the prediction of this effect difficult. Temperature modulation of growth kinetics is to be expected, because both metabolism and cellular composition are affected by cultivation temperature, as was demonstrated by the cellular fatty acid composition (16, 26, 41), the synthesis or degradation of certain proteins (14,15,17,20,25), changes in protein activity (15, 35), changes in maintenance requirements of cells (19,27,39,42,47), changes in end products of metabolism (17), and increases in pigment formation (27).Bacterial metabolism represents a network of reactions. Although these individual biochemical reactions are temperature dependent, the fundamental question of whether the parameters used in growth kinetic models are temperature dependent must be asked. To determine this, a detailed comparison of growth kinetics at temperatures below and above the optimal temperature was carried out for Escherichia coli ML 30 cultivated in continuous culture with glucose and/or galactose. Such investigations are possible only by using an extremely sensitive method for measuring low concentrations of sugars (in micrograms per liter) in culture media (40). The objective of the present study was to compare the experimentally established relationships between growth rate and steady-state substrate concentrations at different constant temperatures and to find out whether the whole set of relationships can be described by a simple mathematical model (Table 1 summarizes the nomenclature used throughout). Additionally, the effect of temperature on steady-state substrate concentrations at constant growth rates (dilution rates in continuous culture) was studied.Compendium of the models proposed in the literature. (i) Conventional growth kinetics and models containing an s min term. Various mathematical models have been proposed to quantitatively describe microbial growth kinetics. The Monod model (equation 1) is considered the basic equation (23), which has since been improve...

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“…Monitoring of the stress signal ppGpp is described elsewhere [5]. Stress response on protein level is described due to heat shock [6][7][8][9], cold shock [9,10], oxidative stress [11], and nutrient deprivation [4]. Up to 50 proteins are de novo synthesized in a temporal order upon carbon starvation and more than 20 upon heat shock [4,8].…”

Section: Introductionmentioning

confidence: 99%

Monitoring of protein profiles for the optimization of recombinant fermentation processes using public domain databases

Dürrschmid¹,

Marzban²,

Dürrschmid³

et al. 2003

Electrophoresis

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The expression of human superoxide dismutase in fed-batch fermentation of E. coli HMS174(DE3)(pET3ahSOD) was studied as model system. Due to the frequently used strong T7 promoter system a high metabolic load is exerted, which triggers stress response mechanisms and finally leads to the differentiation of the host cell. As a consequence, host cell metabolism is partly shifted from growth to survival accompanied by significant alterations of the protein pattern. In terms of process optimization two-dimensional electrophoresis deserves as a powerful tool to monitor these changes on protein level. For the analysis of samples derived from different states of recombinant protein production wide-range Immobiline Dry Strips pH 3-10 were used. In order to establish an efficient procedure for accelerated process optimization and to avoid costly and time-consuming analysis like mass spectrometry (MS), a database approach for the identification of significant changes of the protein pattern was evaluated. On average, 935 spots per gel were detected, whereby 50 are presumably stress-relevant. Out of these, 24 proteins could be identified by using the SWISS-2DPAGE database (www.expasy.ch/ch2d/). The identified proteins are involved in regulatory networks, energy metabolism, purine and pyrimidine nucleotide synthesis and translation. By this database approach, significant fluctuations of individual proteins in relation to recombinant protein production could be identified. Seven proteins show strong alterations (>100%) directly after induction and can therefore be stated as reliable marker proteins for the assessment of stress response. For distinctive interpretation of this highly specific information, a bioinformatic and statistic tool would be essential in order to perceive the role and contribution of individual proteins in stress response.

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Heat shock gene expression in continuous cultures of Escherichia coli

Cited by 23 publications

References 52 publications

Oxygen availability and growth of Escherichia coli W3110: Dynamic responses to limitation and starvation

Oxygen availability and growth of Escherichia coli W3110: Dynamic responses to limitation and starvation

Temperature-dependent growth kinetics of Escherichia coli ML 30 in glucose-limited continuous culture

Monitoring of protein profiles for the optimization of recombinant fermentation processes using public domain databases

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