scholarly journals Bacteriophages Limit the Existence Conditions for Conjugative Plasmids

mBio ◽  
2015 ◽  
Vol 6 (3) ◽  
Author(s):  
Ellie Harrison ◽  
A. Jamie Wood ◽  
Calvin Dytham ◽  
Jonathan W. Pitchford ◽  
Julie Truman ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Experimental Evolution ◽  
Phage Resistance ◽  
Bacterial Cells ◽  
Resistance Mutations ◽  
Weak Selection ◽  
Bacterial Populations ◽  
Conjugative Plasmids ◽  
Existence Conditions ◽  
Selection For

ABSTRACTBacteriophages are a major cause of bacterial mortality and impose strong selection on natural bacterial populations, yet their effects on the dynamics of conjugative plasmids have rarely been tested. We combined experimental evolution, mathematical modeling, and individual-based simulations to explain how the ecological and population genetics effects of bacteriophages upon bacteria interact to determine the dynamics of conjugative plasmids and their persistence. The ecological effects of bacteriophages on bacteria are predicted to limit the existence conditions for conjugative plasmids, preventing persistence under weak selection for plasmid accessory traits. Experiments showed that phages drove faster extinction of plasmids in environments where the plasmid conferred no benefit, but they also revealed more complex effects of phages on plasmid dynamics under these conditions, specifically, the temporary maintenance of plasmids at fixation followed by rapid loss. We hypothesized that the population genetic effects of bacteriophages, specifically, selection for phage resistance mutations, may have caused this. Further mathematical modeling and individual-based simulations supported our hypothesis, showing that conjugative plasmids may hitchhike with phage resistance mutations in the bacterial chromosome.IMPORTANCEConjugative plasmids are infectious loops of DNA capable of transmitting DNA between bacterial cells and between species. Because plasmids often carry extra genes that allow bacteria to live in otherwise-inhospitable environments, their dynamics are central to understanding bacterial adaptive evolution. The plasmid-bacterium interaction has typically been studied in isolation, but in natural bacterial communities, bacteriophages, viruses that infect bacteria, are ubiquitous. Using experiments, mathematical models, and computer simulations we show that bacteriophages drive plasmid dynamics through their ecological and evolutionary effects on bacteria and ultimately limit the conditions allowing plasmid existence. These results advance our understanding of bacterial adaptation and show that bacteriophages could be used to select against plasmids carrying undesirable traits, such as antibiotic resistance.

scholarly journals Plasmid carriage can limit bacteria–phage coevolution

2015 ◽  
Vol 11 (8) ◽  
pp. 20150361 ◽  
Author(s):  
Ellie Harrison ◽  
Julie Truman ◽  
Rosanna Wright ◽  
Andrew J. Spiers ◽  
Steve Paterson ◽  
...  
Keyword(s):  
Conjugative Plasmid ◽  
Phage Resistance ◽  
Resistance Mutations ◽  
Accessory Gene ◽  
Bacterial Populations ◽  
High Frequencies ◽  
Qualitative Resistance ◽  
Selection For ◽  
Evolutionary Consequences ◽  
Plasmid Carriage

Coevolution with bacteriophages is a major selective force shaping bacterial populations and communities. A variety of both environmental and genetic factors has been shown to influence the mode and tempo of bacteria–phage coevolution. Here, we test the effects that carriage of a large conjugative plasmid, pQBR103, had on antagonistic coevolution between the bacterium Pseudomonas fluorescens and its phage, SBW25 ϕ 2. Plasmid carriage limited bacteria–phage coevolution; bacteria evolved lower phage-resistance and phages evolved lower infectivity in plasmid-carrying compared with plasmid-free populations. These differences were not explained by effects of plasmid carriage on the costs of phage resistance mutations. Surprisingly, in the presence of phages, plasmid carriage resulted in the evolution of high frequencies of mucoid bacterial colonies. Mucoidy can provide weak partial resistance against SBW25 ϕ 2, which may have limited selection for qualitative resistance mutations in our experiments. Taken together, our results suggest that plasmids can have evolutionary consequences for bacteria that go beyond the direct phenotypic effects of their accessory gene cargo.

scholarly journals Division of labor, bet hedging, and the evolution of mixed biofilm investment strategies

2017 ◽  
Author(s):  
Nick Vallespir Lowery ◽  
Luke McNally ◽  
William C. Ratcliff ◽  
Sam P. Brown
Keyword(s):  
Division Of Labor ◽  
Experimental Evolution ◽  
Cost Effective ◽  
Investment Strategies ◽  
Bacterial Cells ◽  
Bet Hedging ◽  
Planktonic Cells ◽  
Selection For ◽  
Experimental Findings ◽  
Slow Growing

ABSTRACTBacterial cells, like many other organisms, face a tradeoff between longevity and fecundity. Planktonic cells are fast growing and fragile, while biofilm cells are often slower growing but stress resistant. Here we ask: why do bacterial lineages invest simultaneously in both fast and slow growing types? We develop a population dynamical model of lineage expansion across a patchy environment, and find that mixed investment is favored across a broad range of environmental conditions, even when transmission is entirely via biofilm cells. This mixed strategy is favored because of a division of labor, where exponentially dividing planktonic cells can act as an engine for the production of future biofilm cells, which grow more slowly. We use experimental evolution to test our predictions, and show that phenotypic heterogeneity is persistent even under selection for purely planktonic or purely biofilm transmission. Furthermore, simulations suggest that maintenance of a biofilm subpopulation serves as a cost-effective hedge against environmental uncertainty, which is also consistent with our experimental findings.

scholarly journals Stochasticity in Colonial Growth Dynamics of Individual Bacterial Cells

2013 ◽  
Vol 79 (7) ◽  
pp. 2294-2301 ◽  
Author(s):  
Konstantinos P. Koutsoumanis ◽  
Alexandra Lianou
Keyword(s):  
Kinetic Parameters ◽  
Single Cells ◽  
Growth Curves ◽  
Growth Dynamics ◽  
Time Lapse ◽  
Initial Population ◽  
Bacterial Cells ◽  
Stochastic Growth ◽  
Bacterial Populations ◽  
Content Type

ABSTRACTConventional bacterial growth studies rely on large bacterial populations without considering the individual cells. Individual cells, however, can exhibit marked behavioral heterogeneity. Here, we present experimental observations on the colonial growth of 220 individual cells ofSalmonella entericaserotype Typhimurium using time-lapse microscopy videos. We found a highly heterogeneous behavior. Some cells did not grow, showing filamentation or lysis before division. Cells that were able to grow and form microcolonies showed highly diverse growth dynamics. The quality of the videos allowed for counting the cells over time and estimating the kinetic parameters lag time (λ) and maximum specific growth rate (μmax) for each microcolony originating from a single cell. To interpret the observations, the variability of the kinetic parameters was characterized using appropriate probability distributions and introduced to a stochastic model that allows for taking into account heterogeneity using Monte Carlo simulation. The model provides stochastic growth curves demonstrating that growth of single cells or small microbial populations is a pool of events each one of which has its own probability to occur. Simulations of the model illustrated how the apparent variability in population growth gradually decreases with increasing initial population size (N0). For bacterial populations withN0of >100 cells, the variability is almost eliminated and the system seems to behave deterministically, even though the underlying law is stochastic. We also used the model to demonstrate the effect of the presence and extent of a nongrowing population fraction on the stochastic growth of bacterial populations.

scholarly journals Prokaryotic Single-Cell RNA Sequencing by In Situ Combinatorial Indexing

2019 ◽  
Author(s):  
Sydney B. Blattman ◽  
Wenyan Jiang ◽  
Panos Oikonomou ◽  
Saeed Tavazoie
Keyword(s):  
Single Cell ◽  
Rna Sequencing ◽  
Low Cost ◽  
Bacterial Cells ◽  
Single Experiment ◽  
Bacterial Populations ◽  
Single Cell Rna Sequencing ◽  
Gene Expression Heterogeneity ◽  
Mrna Polyadenylation

AbstractDespite longstanding appreciation of gene expression heterogeneity in isogenic bacterial populations, affordable and scalable technologies for studying single bacterial cells have been limited. While single-cell RNA sequencing (scRNA-seq) has revolutionized studies of transcriptional heterogeneity in diverse eukaryotic systems, application of scRNA-seq to prokaryotes has been hindered by their extremely low mRNA abundance, lack of mRNA polyadenylation, and thick cell walls. Here, we present Prokaryotic Expression-profiling by Tagging RNA In Situ and sequencing (PETRI-seq), a low-cost, high-throughput, prokaryotic scRNA-seq pipeline that overcomes these technical obstacles. PETRI-seq uses in situ combinatorial indexing to barcode transcripts from tens of thousands of cells in a single experiment. PETRI-seq captures single cell transcriptomes of Gram-negative and Gram-positive bacteria with high purity and low bias, with median capture rates >200 mRNAs/cell for exponentially growing E. coli. These characteristics enable robust discrimination of cell-states corresponding to different phases of growth. When applied to wild-type S. aureus, PETRI-seq revealed a rare sub-population of cells undergoing prophage induction. We anticipate broad utility of PETRI-seq in defining single-cell states and their dynamics in complex microbial communities.

scholarly journals Genotyping of evolving prokaryotic populations

2016 ◽  
Author(s):  
Markus Zojer ◽  
Lisa N Schuster ◽  
Frederik Schulz ◽  
Alexander Pfundner ◽  
Matthias Horn ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Bacterial Species ◽  
Clinical Diagnostics ◽  
Structural Variations ◽  
Natural Habitats ◽  
Reliable Prediction ◽  
Low Frequencies ◽  
Bacterial Populations ◽  
Sequencing Errors ◽  
Genomic Environment

Genomic heterogeneity of bacterial species is observed and studied in experimental evolution experiments, clinical diagnostics and occurs as micro-diversity of natural habitats. The challenge for genome research is to accurately capture this heterogeneity with the currently used short sequencing reads. Recent advances in NGS technologies improved the speed and coverage and thus allowed for deep sequencing of bacterial populations. This facilitates the quantitative assessment of genomic heterogeneity, including low frequent alleles or haplotypes. However, false positive variant predictions due to sequencing errors and mapping artifacts of short reads need to be prevented. We therefore created VarCap, a workflow for the reliable prediction of different types of variants even at low frequencies. In order to predict SNPs, indels and structural variations, we evaluated the sensitivity and accuracy of different software tools using synthetic read data. The results suggested that the best sensitivity could be reached by a combination of different tools. We identified possible reasons for false predictions and used this knowledge to improve the accuracy by post-filtering the predicted variants according to properties such as frequency, coverage, genomic environment/localization and co-localization with other variants. This resulted in the reliable prediction of variants above a minimum relative abundance of 2%. VarCap is designed for being routinely used within experimental evolution experiments or for clinical diagnostics. The detected variants are reported as frequencies within a vcf file and as a graphical overview of the distribution of the different variant/allele/haplotype frequencies. The source code of VarCap is available at https://github.com/ma2o/VarCap. In order to provide this workflow to a broad community, we implemeted VarCap on a Galaxy webserver (Afgan et al. 2016) , which is accessible at http://galaxy.csb.univie.ac.at.

scholarly journals Death and population dynamics affect mutation rate estimates and evolvability under stress in bacteria

2017 ◽  
Author(s):  
Antoine Frénoy ◽  
Sebastian Bonhoeffer
Keyword(s):  
Population Dynamics ◽  
Mutation Rate ◽  
Death Rate ◽  
Mutation Rates ◽  
Resistance Mutations ◽  
Bacterial Populations ◽  
Plasmid Segregation ◽  
Genome Wide ◽  
Response To Stress ◽  
Induced Mutagenesis

AbstractThe stress-induced mutagenesis paradigm postulates that in response to stress, bacteria increase their genome-wide mutation rate, in turn increasing the chances that a descendant is able to withstand the stress. This has implications for antibiotic treatment: exposure to sub-inhibitory doses of antibiotics has been reported to increase bacterial mutation rates, and thus probably the rate at which resistance mutations appear and lead to treatment failure.Measuring mutation rates under stress, however, is problematic, because existing methods assume there is no death. Yet sub-inhibitory stress levels may induce a substantial death rate. Death events need to be compensated by extra replication to reach a given population size, thus giving more opportunities to acquire mutations. We show that ignoring death leads to a systematic overestimation of mutation rates under stress.We developed a system using plasmid segregation to measure death and growth rates simultaneously in bacterial populations. We use it to replicate classical experiments reporting antibiotic-induced mutagenesis. We found that a substantial death rate occurs at the tested sub-inhibitory concentrations, and taking this death into account lowers and sometimes removes the signal for stress-induced mutagenesis. Moreover even when antibiotics increase mutation rate, sub-inhibitory treatments do not increase genetic diversity and evolvability, again because of effects of the antibiotics on population dynamics.Beside showing that population dynamic is a crucial but neglected parameter affecting evolvability, we provide better experimental and computational tools to study evolvability under stress, leading to a re-assessment of the magnitude and significance of the stress-induced mutagenesis paradigm.

scholarly journals Broadscale phage therapy is unlikely to select for widespread evolution of bacterial resistance to virus infection

2020 ◽  
Vol 6 (2) ◽  
Author(s):  
Frederick M Cohan ◽  
Matthew Zandi ◽  
Paul E Turner
Keyword(s):  
Bacterial Resistance ◽  
Phage Therapy ◽  
Patient Treatment ◽  
Resistant Bacteria ◽  
Bacterial Populations ◽  
Recent Success ◽  
Adaptive Value ◽  
Global Spread ◽  
Classic Approach ◽  
Selection For

Abstract Multi-drug resistant bacterial pathogens are alarmingly on the rise, signaling that the golden age of antibiotics may be over. Phage therapy is a classic approach that often employs strictly lytic bacteriophages (bacteria-specific viruses that kill cells) to combat infections. Recent success in using phages in patient treatment stimulates greater interest in phage therapy among Western physicians. But there is concern that widespread use of phage therapy would eventually lead to global spread of phage-resistant bacteria and widespread failure of the approach. Here, we argue that various mechanisms of horizontal genetic transfer (HGT) have largely contributed to broad acquisition of antibiotic resistance in bacterial populations and species, whereas similar evolution of broad resistance to therapeutic phages is unlikely. The tendency for phages to infect only particular bacterial genotypes limits their broad use in therapy, in turn reducing the likelihood that bacteria could acquire beneficial resistance genes from distant relatives via HGT. We additionally consider whether HGT of clustered regularly interspaced short palindromic repeats (CRISPR) immunity would thwart generalized use of phages in therapy, and argue that phage-specific CRISPR spacer regions from one taxon are unlikely to provide adaptive value if horizontally-transferred to other taxa. For these reasons, we conclude that broadscale phage therapy efforts are unlikely to produce widespread selection for evolution of bacterial resistance.

scholarly journals Impact of Fluoroquinolone Resistance Mutations on Gonococcal Fitness and In Vivo Selection for Compensatory Mutations

2012 ◽  
Vol 205 (12) ◽  
pp. 1821-1829 ◽  
Author(s):  
A. N. Kunz ◽  
A. A. Begum ◽  
H. Wu ◽  
J. A. D'Ambrozio ◽  
J. M. Robinson ◽  
...  
Keyword(s):  
Fluoroquinolone Resistance ◽  
Resistance Mutations ◽  
In Vivo Selection ◽  
Compensatory Mutations ◽  
Selection For

scholarly journals Off Earth Identification of Bacterial Populations Using 16S rDNA Nanopore Sequencing

Genes ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 76 ◽  
Author(s):  
Aaron S. Burton ◽  
Sarah E. Stahl ◽  
Kristen K. John ◽  
Miten Jain ◽  
Sissel Juul ◽  
...  
Keyword(s):  
High Performance ◽  
Space Station ◽  
Bacterial Cells ◽  
Sequencing Data ◽  
Mock Community ◽  
Bacterial Populations ◽  
Microbial Identification ◽  
Staphylococcus Capitis ◽  
Staphylococcus Hominis ◽  
Community Standard

The MinION sequencer has made in situ sequencing feasible in remote locations. Following our initial demonstration of its high performance off planet with Earth-prepared samples, we developed and tested an end-to-end, sample-to-sequencer process that could be conducted entirely aboard the International Space Station (ISS). Initial experiments demonstrated the process with a microbial mock community standard. The DNA was successfully amplified, primers were degraded, and libraries prepared and sequenced. The median percent identities for both datasets were 84%, as assessed from alignment of the mock community. The ability to correctly identify the organisms in the mock community standard was comparable for the sequencing data obtained in flight and on the ground. To validate the process on microbes collected from and cultured aboard the ISS, bacterial cells were selected from a NASA Environmental Health Systems Surface Sample Kit contact slide. The locations of bacterial colonies chosen for identification were labeled, and a small number of cells were directly added as input into the sequencing workflow. Prepared DNA was sequenced, and the data were downlinked to Earth. Return of the contact slide to the ground allowed for standard laboratory processing for bacterial identification. The identifications obtained aboard the ISS, Staphylococcus hominis and Staphylococcus capitis, matched those determined on the ground down to the species level. This marks the first ever identification of microbes entirely off Earth, and this validated process could be used for in-flight microbial identification, diagnosis of infectious disease in a crewmember, and as a research platform for investigators around the world.

scholarly journals No selection for change in polyandry under experimental evolution

2019 ◽  
Author(s):  
Andreas Sutter ◽  
Laura M. Travers ◽  
Melanie Weedon ◽  
Keiko Oku ◽  
Thomas A. R. Price ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Selection For
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