Comparison of maximum specific growth rates and lag times estimated from absorbance and viable count data by different mathematical models

Dalgaard, Paw; Koutsoumanis, K.

doi:10.1016/s0167-7012(00)00219-0

Cited by 217 publications

(171 citation statements)

References 30 publications

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“…This assumes that all wells are inoculated with the same biomass and is done because the BioScreen measurements are imprecise at low optical densities. This is in accordance with the common definition of lag as the time period until exponential growth is detected (Dalgaard and Koutsoumanis 2001). Differences in initial inoculum size could significantly affect estimates of lag time, hence the lag measurements may be inaccurate and are treated accordingly.…”

Section: Discussionsupporting

confidence: 81%

Experimental Evidence for Sympatric Ecological Diversification Due to Frequency-Dependent Competition in Escherichia Coli

et al. 2004

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Abstract. We investigate adaptive diversification in experimental Escherichia coli populations grown in serial batch cultures on a mixture of glucose and acetate. All 12 experimental lines were started from the same genetically uniform ancestral strain but became highly polymorphic for colony size after 1000 generations. Five populations were clearly dimorphic and thus serve as a model for an adaptive lineage split. We analyzed the ecological basis for this dimorphism by studying bacterial growth curves. All strains exhibit diauxie, that is, sequential growth on the two resources. Thus, they exhibit phenotypic plasticity, using mostly glucose when glucose is abundant, then switching to acetate when glucose concentration is low. However, the coexisting strains differ in their diauxie pattern, with one cluster in the dimorphic populations growing better in the glucose phase, and the other cluster having a much shorter lag when switching to the acetate phase. Using invasion experiments, we show that the dimorphism of these two ecological types is maintained by frequency-dependent selection. Using a mathematical model for the adaptive dynamics of diauxie behavior, we show that evolutionary branching in diauxie behavior is a plausible theoretical scenario. Our results support the hypothesis that, in our experiments, adaptive diversification from a genetically uniform ancestor occurred due to frequency-dependent ecological interactions. Our results have implications for understanding the evolution of cross-feeding polymorphism in microorganisms, as well as adaptive speciation due to frequency-dependent selection on phenotypic plasticity.

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Section: Discussionsupporting

confidence: 81%

Experimental Evidence for Sympatric Ecological Diversification Due to Frequency-Dependent Competition in Escherichia Coli

et al. 2004

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“…(A) Duration of the lag phase of wild-type KT2440 cells (blue) and the streamlined strain EM383 (green) in rich LB medium or M9 minimal medium added with 0.2% (w/v) of either succinate (Suc), citrate (Cit), glucose (Glu), or fructose (Fru). The extent of the lag phase was calculated using data from growth curves as described by Dalgaard and Koutsoumanis [67]. (B) Final cell density (estimated as the optical density at 600 nm, OD 600 ) of shaken-flask cultures of wild-type KT2440 (blue) and the streamlined strain EM383 (green) in rich LB medium.…”

Section: Kt2440mentioning

confidence: 99%

Pseudomonas 2.0: genetic upgrading of P. putida KT2440 as an enhanced host for heterologous gene expression

et al. 2014

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Background: Because of its adaptability to sites polluted with toxic chemicals, the model soil bacterium Pseudomonas putida is naturally endowed with a number of metabolic and stress-endurance qualities which have considerable value for hosting energy-demanding and redox reactions thereof. The growing body of knowledge on P. putida strain KT2440 has been exploited for the rational design of a derivative strain in which the genome has been heavily edited in order to construct a robust microbial cell factory. Results: Eleven non-adjacent genomic deletions, which span 300 genes (i.e., 4.3% of the entire P. putida KT2440 genome), were eliminated; thereby enhancing desirable traits and eliminating attributes which are detrimental in an expression host. Since ATP and NAD(P)H availability -as well as genetic instability, are generally considered to be major bottlenecks for the performance of platform strains, a suite of functions that drain high-energy phosphate from the cells and/or consume NAD(P)H were targeted in particular, the whole flagellar machinery. Four prophages, two transposons, and three components of DNA restriction-modification systems were eliminated as well. The resulting strain (P. putida EM383) displayed growth properties (i.e., lag times, biomass yield, and specific growth rates) clearly superior to the precursor wild-type strain KT2440. Furthermore, it tolerated endogenous oxidative stress, acquired and replicated exogenous DNA, and survived better in stationary phase. The performance of a bi-cistronic GFP-LuxCDABE reporter system as a proxy of combined metabolic vitality, revealed that the deletions in P. putida strain EM383 brought about an increase of >50% in the overall physiological vigour.

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“…Approximately 25 viable count data points were produced for each growth curve. Growth rate (m; h 21 ) values of bacteria were estimated from the growth curves by the Richards model (Dalgaard & Koutsoumanis, 2001). The mean growth rate of strains derived from separate colonies was calculated from 24 parallel experiments.…”

Section: Vgmmentioning

confidence: 99%

Fis regulates the competitiveness of Pseudomonas putida on barley roots by inducing biofilm formation

et al. 2012

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An important link between the environment and the physiological state of bacteria is the regulation of the transcription of a large number of genes by global transcription factors. One of the global regulators, Fis (factor for inversion stimulation), is well studied in Escherichia coli, but the role of this protein in pseudomonads has only been examined briefly. According to studies in Enterobacteriaceae, Fis regulates positively the flagellar movement of bacteria. In pseudomonads, flagellar movement is an important trait for the colonization of plant roots. Therefore we were interested in the role of the Fis protein in Pseudomonas putida, especially the possible regulation of the colonization of plant roots. We observed that Fis reduced the migration of P. putida onto the apices of barley roots and thereby the competitiveness of bacteria on the roots. Moreover, we observed that overexpression of Fis drastically reduced swimming motility and facilitated P. putida biofilm formation, which could be the reason for the decreased migration of bacteria onto the root apices. It is possible that the elevated expression of Fis is important in the adaptation of P. putida during colonization of plant roots by promoting biofilm formation when the migration of bacteria is no longer favoured.

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Comparison of maximum specific growth rates and lag times estimated from absorbance and viable count data by different mathematical models

Cited by 217 publications

References 30 publications

Experimental Evidence for Sympatric Ecological Diversification Due to Frequency-Dependent Competition in Escherichia Coli

Experimental Evidence for Sympatric Ecological Diversification Due to Frequency-Dependent Competition in Escherichia Coli

Pseudomonas 2.0: genetic upgrading of P. putida KT2440 as an enhanced host for heterologous gene expression

Fis regulates the competitiveness of Pseudomonas putida on barley roots by inducing biofilm formation

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