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Malthusian Parameters as Estimators of the Fitness of Microbes: A Cautionary Tale about the Low Side of High Throughput.

Concepción-Acevedo J, Weiss HN, Chaudhry WN, Levin BR - PLoS ONE (2015)

Bottom Line: The maximum exponential growth rate, the Malthusian parameter (MP), is commonly used as a measure of fitness in experimental studies of adaptive evolution and of the effects of antibiotic resistance and other genes on the fitness of planktonic microbes.Thanks to automated, multi-well optical density plate readers and computers, with little hands-on effort investigators can readily obtain hundreds of estimates of MPs in less than a day.This leads us to question the reliability of estimates of MP obtained with these high throughput devices and the utility of these estimates of the maximum growth rates to detect fitness differences.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Emory University, Atlanta, Georgia, United States of America.

ABSTRACT
The maximum exponential growth rate, the Malthusian parameter (MP), is commonly used as a measure of fitness in experimental studies of adaptive evolution and of the effects of antibiotic resistance and other genes on the fitness of planktonic microbes. Thanks to automated, multi-well optical density plate readers and computers, with little hands-on effort investigators can readily obtain hundreds of estimates of MPs in less than a day. Here we compare estimates of the relative fitness of antibiotic susceptible and resistant strains of E. coli, Pseudomonas aeruginosa and Staphylococcus aureus based on MP data obtained with automated multi-well plate readers with the results from pairwise competition experiments. This leads us to question the reliability of estimates of MP obtained with these high throughput devices and the utility of these estimates of the maximum growth rates to detect fitness differences.

No MeSH data available.


Related in: MedlinePlus

Effects of well volume and initial OD on the estimated MP.(A, B) Effects of volume on estimated MP, respectively Bioscreen (n = 10) and BioTek (n = 12). E. coli WT in glucose-limited (blue) and LB (Red). Mean and standard error: Bioscreen LB F(2,27) = 820.5, p< 0.001, minimal, F (2,27) = 66.6, p<0.0001. Bio-Tek LB F(3, 28) = 78.8, p<0.001, Minimal, F(2,27) = 7.17, p~0.005). (C, D and E) effect of starting OD on the estimated MP, (C) Wild type S. aureus in MHII. (D and E), respectively for wild type E. coli and Pseudomonas aeruginosa in LB broth (black bar) and minimal media (red bar).
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pone.0126915.g001: Effects of well volume and initial OD on the estimated MP.(A, B) Effects of volume on estimated MP, respectively Bioscreen (n = 10) and BioTek (n = 12). E. coli WT in glucose-limited (blue) and LB (Red). Mean and standard error: Bioscreen LB F(2,27) = 820.5, p< 0.001, minimal, F (2,27) = 66.6, p<0.0001. Bio-Tek LB F(3, 28) = 78.8, p<0.001, Minimal, F(2,27) = 7.17, p~0.005). (C, D and E) effect of starting OD on the estimated MP, (C) Wild type S. aureus in MHII. (D and E), respectively for wild type E. coli and Pseudomonas aeruginosa in LB broth (black bar) and minimal media (red bar).

Mentions: To explore the effects of the volume of bacterial suspension in the wells of the microtiter plates on the estimated Malthusian Parameter using the Bioscreen and BioTek data and the Growthrates software, we calculated the MP for E. coli in glucose-limited minimal medium and LB with different volumes of the cells suspensions in the wells. As suggested in [23] and can be seen in Fig 1A and 1B and S1 Table for the statistical analysis, the volume of media in the wells can contribute to the variation in the estimates of the Malthusian parameter. Based on these results, in the experiments that follow, we used 300μl in each well for both the BioscreenC and the BioTek.


Malthusian Parameters as Estimators of the Fitness of Microbes: A Cautionary Tale about the Low Side of High Throughput.

Concepción-Acevedo J, Weiss HN, Chaudhry WN, Levin BR - PLoS ONE (2015)

Effects of well volume and initial OD on the estimated MP.(A, B) Effects of volume on estimated MP, respectively Bioscreen (n = 10) and BioTek (n = 12). E. coli WT in glucose-limited (blue) and LB (Red). Mean and standard error: Bioscreen LB F(2,27) = 820.5, p< 0.001, minimal, F (2,27) = 66.6, p<0.0001. Bio-Tek LB F(3, 28) = 78.8, p<0.001, Minimal, F(2,27) = 7.17, p~0.005). (C, D and E) effect of starting OD on the estimated MP, (C) Wild type S. aureus in MHII. (D and E), respectively for wild type E. coli and Pseudomonas aeruginosa in LB broth (black bar) and minimal media (red bar).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4482697&req=5

pone.0126915.g001: Effects of well volume and initial OD on the estimated MP.(A, B) Effects of volume on estimated MP, respectively Bioscreen (n = 10) and BioTek (n = 12). E. coli WT in glucose-limited (blue) and LB (Red). Mean and standard error: Bioscreen LB F(2,27) = 820.5, p< 0.001, minimal, F (2,27) = 66.6, p<0.0001. Bio-Tek LB F(3, 28) = 78.8, p<0.001, Minimal, F(2,27) = 7.17, p~0.005). (C, D and E) effect of starting OD on the estimated MP, (C) Wild type S. aureus in MHII. (D and E), respectively for wild type E. coli and Pseudomonas aeruginosa in LB broth (black bar) and minimal media (red bar).
Mentions: To explore the effects of the volume of bacterial suspension in the wells of the microtiter plates on the estimated Malthusian Parameter using the Bioscreen and BioTek data and the Growthrates software, we calculated the MP for E. coli in glucose-limited minimal medium and LB with different volumes of the cells suspensions in the wells. As suggested in [23] and can be seen in Fig 1A and 1B and S1 Table for the statistical analysis, the volume of media in the wells can contribute to the variation in the estimates of the Malthusian parameter. Based on these results, in the experiments that follow, we used 300μl in each well for both the BioscreenC and the BioTek.

Bottom Line: The maximum exponential growth rate, the Malthusian parameter (MP), is commonly used as a measure of fitness in experimental studies of adaptive evolution and of the effects of antibiotic resistance and other genes on the fitness of planktonic microbes.Thanks to automated, multi-well optical density plate readers and computers, with little hands-on effort investigators can readily obtain hundreds of estimates of MPs in less than a day.This leads us to question the reliability of estimates of MP obtained with these high throughput devices and the utility of these estimates of the maximum growth rates to detect fitness differences.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Emory University, Atlanta, Georgia, United States of America.

ABSTRACT
The maximum exponential growth rate, the Malthusian parameter (MP), is commonly used as a measure of fitness in experimental studies of adaptive evolution and of the effects of antibiotic resistance and other genes on the fitness of planktonic microbes. Thanks to automated, multi-well optical density plate readers and computers, with little hands-on effort investigators can readily obtain hundreds of estimates of MPs in less than a day. Here we compare estimates of the relative fitness of antibiotic susceptible and resistant strains of E. coli, Pseudomonas aeruginosa and Staphylococcus aureus based on MP data obtained with automated multi-well plate readers with the results from pairwise competition experiments. This leads us to question the reliability of estimates of MP obtained with these high throughput devices and the utility of these estimates of the maximum growth rates to detect fitness differences.

No MeSH data available.


Related in: MedlinePlus