scholarly journals Experimental evolution of a microbial predator's ability to find prey

2008 ◽  
Vol 276 (1656) ◽  
pp. 459-467 ◽  
Author(s):  
Kristina L Hillesland ◽  
Gregory J Velicer ◽  
Richard E Lenski
Keyword(s):  
Escherichia Coli ◽  
Experimental Evolution ◽  
Prey Density ◽  
Myxococcus Xanthus ◽  
Foraging Theory ◽  
High Density ◽  
Fruiting Bodies ◽  
Predatory Behaviour ◽  
Handling Performance

Foraging theory seeks to explain how the distribution and abundance of prey influence the evolution of predatory behaviour, including the allocation of effort to searching for prey and handling them after they are found. While experiments have shown that many predators alter their behaviour phenotypically within individual lifetimes, few have examined the actual evolution of predatory behaviour in light of this theory. Here, we test the effects of prey density on the evolution of a predator's searching and handling behaviours using a bacterial predator, Myxococcus xanthus . Sixteen predator populations evolved for almost a year on agar surfaces containing patches of Escherichia coli prey at low or high density. Improvements in searching rate were significantly greater in those predators that evolved at low prey density. Handling performance also improved in some predator populations, but prey density did not significantly affect the magnitude of these gains. As the predators evolved greater foraging proficiency, their capacity diminished to produce fruiting bodies that enable them to survive prolonged periods of starvation. More generally, these results demonstrate that predators evolve behaviours that reflect at least some of the opportunities and limitations imposed by the distribution and abundance of their prey.

scholarly journals Regulation of dev, an Operon That Includes Genes Essential for Myxococcus xanthus Development and CRISPR-Associated Genes and Repeats

2007 ◽  
Vol 189 (10) ◽  
pp. 3738-3750 ◽  
Author(s):  
Poorna Viswanathan ◽  
Kimberly Murphy ◽  
Bryan Julien ◽  
Anthony G. Garza ◽  
Lee Kroos
Keyword(s):  
Escherichia Coli ◽  
Promoter Activity ◽  
Myxococcus Xanthus ◽  
Regulatory Elements ◽  
Fruiting Bodies ◽  
Wild Type ◽  
Coding Region ◽  
Upstream Gene ◽  
Negative Element ◽  
Growth Induction

ABSTRACT Expression of dev genes is important for triggering spore differentiation inside Myxococcus xanthus fruiting bodies. DNA sequence analysis suggested that dev and cas (CRISPR-associated) genes are cotranscribed at the dev locus, which is adjacent to CRISPR (clustered regularly interspaced short palindromic repeats). Analysis of RNA from developing M. xanthus confirmed that dev and cas genes are cotranscribed with a short upstream gene and at least two repeats of the downstream CRISPR, forming the dev operon. The operon is subject to strong, negative autoregulation during development by DevS. The dev promoter was identified. Its −35 and −10 regions resemble those recognized by M. xanthus σA RNA polymerase, the homolog of Escherichia coli σ70, but the spacer may be too long (20 bp); there is very little expression during growth. Induction during development relies on at least two positive regulatory elements located in the coding region of the next gene upstream. At least two positive regulatory elements and one negative element lie downstream of the dev promoter, such that the region controlling dev expression spans more than 1 kb. The results of testing different fragments for dev promoter activity in wild-type and devS mutant backgrounds strongly suggest that upstream and downstream regulatory elements interact functionally. Strikingly, the 37-bp sequence between the two CRISPR repeats that, minimally, are cotranscribed with dev and cas genes exactly matches a sequence in the bacteriophage Mx8 intP gene, which encodes a form of the integrase needed for lysogenization of M. xanthus.

scholarly journals Long-Term Experimental Evolution in Escherichia coli. VI. Environmental Constraints on Adaptation and Divergence

Genetics ◽  
1997 ◽  
Vol 146 (2) ◽  
pp. 471-479 ◽  
Author(s):  
Michael Travisano
Keyword(s):  
Escherichia Coli ◽  
Genetic Variation ◽  
Experimental Evolution ◽  
Population Genetic ◽  
Environmental Constraints ◽  
Asymmetric Pattern ◽  
Nutrient Environment ◽  
Mean Fitness ◽  
Population Genetic Variation

The effect of environment on adaptation and divergence was examined in two sets of populations of Escherichia coli selected for 1000 generations in either maltose- or glucose-limited media. Twelve replicate populations selected in maltose-limited medium improved in fitness in the selected environment, by an average of 22.5%. Statistically significant among-population genetic variation for fitness was observed during the course of the propagation, but this variation was small relative to the fitness improvement. Mean fitness in a novel nutrient environment, glucose-limited medium, improved to the same extent as in the selected environment, with no statistically significant among-population genetic variation. In contrast, 12 replicate populations previously selected for 1000 generations in glucose-limited medium showed no improvement, as a group, in fitness in maltose-limited medium and substantial genetic variation. This asymmetric pattern of correlated responses suggests that small changes in the environment can have profound effects on adaptation and divergence.

scholarly journals Long-Term Experimental Evolution in Escherichia coli. IV. Targets of Selection and the Specificity of Adaptation

Genetics ◽  
1996 ◽  
Vol 143 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Michael Travisano ◽  
Richard E Lenski
Keyword(s):  
Escherichia Coli ◽  
Experimental Evolution ◽  
Common Ancestor ◽  
The Novel ◽  
Physiological Mechanisms ◽  
Outer Membranes ◽  
Limiting Nutrient ◽  
Novel Environments ◽  
Uptake Mechanisms

Abstract This study investigates the physiological manifestation of adaptive evolutionary change in 12 replicate populations of Escherichia coli that were propagated for 2000 generations in a glucose-limited environment. Representative genotypes from each population were assayed for fitness relative to their common ancestor in the experimental glucose environment and in 11 novel single-nutrient environments. After 2000 generations, the 12 derived genotypes had diverged into at least six distinct phenotypic classes. The nutrients were classified into four groups based upon their uptake physiology. All 12 derived genotypes improved in fitness by similar amounts in the glucose environment, and this pattern of parallel fitness gains was also seen in those novel environments where the limiting nutrient shared uptake mechanisms with glucose. Fitness showed little or no consistent improvement, but much greater genetic variation, in novel environments where the limiting nutrient differed from glucose in its uptake mechanisms. This pattern of fitness variation in the novel nutrient environments suggests that the independently derived genotypes adapted to the glucose environment by similar, but not identical, changes in the physiological mechanisms for moving glucose across both the inner and outer membranes.

scholarly journals Experimental evolution of gallium resistance in Escherichia coli

2019 ◽  
Vol 2019 (1) ◽  
pp. 169-180
Author(s):  
Joseph L Graves ◽  
Akamu J Ewunkem ◽  
Jason Ward ◽  
Constance Staley ◽  
Misty D Thomas ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
Experimental Evolution ◽  
Molecular Mechanisms ◽  
Gallium Nitrate ◽  
Whole Genome ◽  
Mechanisms Of Resistance ◽  
Genomic Changes ◽  
K 12

Abstract Background and Objectives Metallic antimicrobial materials are of growing interest due to their potential to control pathogenic and multidrug-resistant bacteria. Yet we do not know if utilizing these materials can lead to genetic adaptations that produce even more dangerous bacterial varieties. Methodology Here we utilize experimental evolution to produce strains of Escherichia coli K-12 MG1655 resistant to, the iron analog, gallium nitrate (Ga(NO3)3). Whole genome sequencing was utilized to determine genomic changes associated with gallium resistance. Computational modeling was utilized to propose potential molecular mechanisms of resistance. Results By day 10 of evolution, increased gallium resistance was evident in populations cultured in medium containing a sublethal concentration of gallium. Furthermore, these populations showed increased resistance to ionic silver and iron (III), but not iron (II) and no increase in traditional antibiotic resistance compared with controls and the ancestral strain. In contrast, the control populations showed increased resistance to rifampicin relative to the gallium-resistant and ancestral population. Genomic analysis identified hard selective sweeps of mutations in several genes in the gallium (III)-resistant lines including: fecA (iron citrate outer membrane transporter), insl1 (IS30 tranposase) one intergenic mutations arsC →/→ yhiS; (arsenate reductase/pseudogene) and in one pseudogene yedN ←; (iapH/yopM family). Two additional significant intergenic polymorphisms were found at frequencies > 0.500 in fepD ←/→ entS (iron-enterobactin transporter subunit/enterobactin exporter, iron-regulated) and yfgF ←/→ yfgG (cyclic-di-GMP phosphodiesterase, anaerobic/uncharacterized protein). The control populations displayed mutations in the rpoB gene, a gene associated with rifampicin resistance. Conclusions This study corroborates recent results observed in experiments utilizing pathogenic Pseudomonas strains that also showed that Gram-negative bacteria can rapidly evolve resistance to an atom that mimics an essential micronutrient and shows the pleiotropic consequences associated with this adaptation. Lay summary We utilize experimental evolution to produce strains of Escherichia coli K-12 MG1655 resistant to, the iron analog, gallium nitrate (Ga(NO3)3). Whole genome sequencing was utilized to determine genomic changes associated with gallium resistance. Computational modeling was utilized to propose potential molecular mechanisms of resistance.

scholarly journals Local adaptation mediated niche expansion in correlation with genetic richness

2021 ◽  
Author(s):  
Masaomi Kurokawa ◽  
Issei Nishimura ◽  
Bei-Wen YING
Keyword(s):  
Escherichia Coli ◽  
Local Adaptation ◽  
High Throughput ◽  
Experimental Evolution ◽  
Environmental Gradient ◽  
Growth Curves ◽  
Quantitative Relationship ◽  
Central Issue ◽  
Wild Type ◽  
Niche Expansion

As a central issue in evolution and ecology, the quantitative relationship among the genome, adaptation and the niche was investigated. Local adaptation of five Escherichia coli strains carrying either the wild-type genome or reduced genomes was achieved by experimental evolution. A high-throughput fitness assay of the ancestor and evolved populations across an environmental gradient of eight niches resulted in a total of 80 fitness curves generated from 2,220 growth curves. Further analyses showed that the increases in both local adaptiveness and niche broadness were negatively correlated with genetic richness. Local adaptation caused common niche expansion, whereas niche expansion for generality or speciality was decided by genetic richness. The order of the mutations accumulated stepwise was correlated with the magnitude of the fitness increase attributed to mutation accumulation. Pre-adaptation probably participated in coordination among genetic richness, local adaptation and niche expansion.

scholarly journals Sex overrides mutation in Escherichia coli colonizing the gut

2018 ◽  
Author(s):  
N. Frazão ◽  
A. Sousa ◽  
M. Lässig ◽  
I. Gordo
Keyword(s):  
Escherichia Coli ◽  
Experimental Evolution ◽  
Temporal Pattern ◽  
Driving Force ◽  
Laboratory Experiments ◽  
Rapid Evolution ◽  
Point Mutations ◽  
Natural Environments ◽  
E Coli ◽  
Accelerate Evolution

AbstractBacteria evolve by mutation accumulation in laboratory experiments, but the tempo and mode of evolution in natural environments are largely unknown. Here we show, by experimental evolution of E. coli in the mouse gut, that the ecology of the gut controls bacterial evolution. If a resident E. coli strain is present in the gut, an invading strain evolves by rapid horizontal gene transfer; this mode precedes and outweighs evolution by point mutations. An epidemic infection by two phages drives gene uptake and produces multiple co-existing lineages of phage-carrying (lysogenic) bacteria. A minimal dynamical model explains the temporal pattern of phage epidemics and their complex evolutionary outcome as generic effects of phage-mediated selection. We conclude that phages are an important eco-evolutionary driving force – they accelerate evolution and promote genetic diversity of bacteria.One Sentence SummaryBacteriophages drive rapid evolution in the gut.

Sign in / Sign up

Export Citation Format

Share Document