Bacteria possess a range of mechanisms to move in different environments, and these mechanisms have important direct and correlated impacts on the virulence of opportunistic pathogens. Bacteria use two surface organelles to facilitate motility: a single polar flagellum, and type IV pili, enabling swimming in aqueous habitats and twitching along hard surfaces, respectively. Here, we address whether there are trade-offs between these motility mechanisms, and hence whether different environments could select for altered motility. We experimentally evolved initially isogenic Pseudomonas aeruginosa under conditions which favoured the different types of motility, and found evidence for a trade-off mediated by antagonistic pleiotropy between swimming and twitching. Moreover, changes in motility resulted in correlated changes in other behaviours, including biofilm formation and growth within an insect host. This suggests environmental origins of a particular motile opportunistic pathogen could predictably influence motility and virulence.
Cross Inoculation Data
Cross Inoculation Data.csv, Data description: Data used to create Figure 1: Cross inoculation of evolved strains between evolutionary environments. The data gives the area of dispersal of the evolved strains relative to the ancestral strain from which all strains were derived. There are 6 replicate lines, which were averaged to give “Mean Area Relative to Ancestor”. Data was collected in the lab and analysed using ImageJ. Columns correspond to: Strain Replicate: the name allocated to each of the replicate lines, e.g. H1 corresponds to replicate line 1 evolved on hard agar. Agar Type on which Strain was Evolved: Strains were either evolved in hard or liquid agar. Agar Type onto which Strain was Inoculated: Strains were either inoculated onto hard or liquid agar. Area Relative to Ancestor: Area of evolved strain under each treatment group was divided by area of ancestral strain under the same treatment to give a relative measurement of area dispersed. Selection Type: Strains were either under positive or neutral artificial selection for dispersal.
Vmax Data
Vmax Data.csv, Data description: Data used to create Figure 2: Average growth rate of evolved strains in vitro relative to the ancestral strain. The data gives the growth rate of the evolved strains relative to the ancestral strain from which all strains were derived. There are 6 replicate lines, which were averaged to give “Growth Rate Relative to Ancestor”. Data was collected in the laboratory using a spectrophotometer. Columns correspond to: Strain Replicate; the name allocated to each of the replicate lines, e.g. H1 corresponds to replicate line 1 evolved on hard agar. Vmax Replicate: The Vmax was measured independently twice in order to provide replicates. This value was averaged in statistical analysis. Agar Type on which Strain was Evolved: Strains were either evolved in hard or liquid agar. Vmax Relative to Ancestor: Vmax of evolved strain under each treatment group was divided by Vmax of ancestral strain under the same treatment to give a relative measurement of area dispersed. Averaged Vmax Replicates: Replicate relative Vmax measurements were averaged. Selection Type: Strains were either under positive or neutral artificial selection for dispersal.
Biofilm Data
Biofilm Data.csv, Data description: Data used to create Figure 3: Biofilm production of evolved strains. Results show the average biofilm production of 6 isolates evolved in each experimental environment, relative to the ancestral strain from which all evolved strains were derived. Data was collected in the laboratory using a crystal violet staining method. Columns correspond to: Strain Replicate: the name allocated to each of the replicate lines, e.g. H1 corresponds to replicate line 1 evolved on hard agar. Bioflim Replicate: The biofilm production was measured independently eight times in order to provide replicates. This value was averaged in statistical analysis. Agar Type on which Strain was Evolved: Strains were either evolved in hard or liquid agar. Biofilm Relative to Ancestor: Vmax of evolved strain under each treatment group was divided by Vmax of ancestral strain under the same treatment to give a relative measurement of area dispersed. Averaged Biofilm Replicates: Replicate relative biofilm measurements were averaged. Selection Type: Strains were either under positive or neutral artificial selection for dispersal.
In vivo Growth Data
In vivo Growth Data.csv, Data description: Data used to create Figure 4: Average growth rate of evolved strains within a host (G. mellonella) relative to the ancestral strain. Data was collected in the laboratory. Columns correspond to: Strain Replicate: the name allocated to each of the replicate lines, e.g. H1 corresponds to replicate line 1 evolved on hard agar. In vivo Replicate: The in vivo growth rate production was measured independently four times in order to provide replicates. This value was averaged in statistical analysis. Agar Type on which Strain was Evolved: Strains were either evolved in hard or liquid agar. In vivo Relative to Ancestor: In vivo growth rate of evolved strain under each treatment group was divided by In vivo growth rate of ancestral strain under the same treatment to give a relative measurement of area dispersed. Averaged In vivo Replicates: Replicate relative in vivo growth rate measurements were averaged. Selection Type: Strains were either under positive or neutral artificial selection for dispersal. Caterpillar Fresh Weight: The weight of each caterpillar was measured before inoculation to control for the effects of caterpillar size on bacterial growth.
