Article Figures & Data
Figures
- FIG 1
QS requirement for maximal growth of V. harveyi in M9-casein medium. Six strains of V. harveyi were grown for 24 h in M9 medium with different sole carbon sources and were enumerated through viable cell counting (CFU per milliliter). (A) Bar graph showing genotype productivity. Bars, productivity of a given genotype at the culmination of a single growth cycle (24 h) (n = 4 separate biological replicates); error bars, 95% confidence intervals for the mean estimates. WT, wild-type strain; SN, signal-negative strain; D47E, luxO D47E strain. Differences that were statistically significant, compared with the WT strain in the given medium type, are reported. *, P < 0.05; ***, P < 0.001. (B) Images of cooperator and defector genotypes in M9-casein medium after 24 h of growth.
- FIG 2
QS regulation of extracellular protease activity in V. harveyi. (A) Protease levels for cooperator and defector genotypes grown in M9-casein medium, plotted versus growth (measured as CFU per milliliter) (n = 3). Error bars, standard errors of the mean. (B) Effects of supernatant supplementation. Cultures of the ΔluxR strain were supplemented with supernatants from the strains indicated, at the indicated concentrations (n = 4). Error bars, 95% confidence intervals. ***, P < 0.001; N.S., not significant.
- FIG 3
Fitness outcomes from single-growth-cycle competitions between different V. harveyi genotypes. In pairwise competitions between different V. harveyi strains, the starting competitor frequency was altered and competition experiments were completed in M9-casein medium for 24 h. Each point corresponds to a single competition outcome, and fit lines consist of regression fits (solid lines) bounded by 95% confidence intervals (dashed lines) for each competition pairing, according to a linear model. For each pairing, the strain whose relative fitness is reported on the y axis and starting percentage on the x axis is underlined.
- FIG 4
Invasion of the ΔluxOU strain but not the WT strain by the ΔluxR defector. Populations contained one of the two cooperator strains, i.e., the WT strain or the ΔluxOU strain, and the ΔluxR defector at a 99:1 starting mixture, or vice versa. Cultures were grown for 24 h in M9-casein medium, diluted 1,000-fold, and repeated over multiple growth cycles. (A) Defector frequency (determined as nonluminescent colonies) plotted versus generations of growth. (B) Population productivity (measured as CFU per milliliter) plotted versus generations of growth. Error bars, 95% confidence intervals (n = 3 biological replicates per treatment).
- FIG 5
WT strain optimization of growth strategies at low and high cell densities. (A) Bioluminescence induction of the WT strain and the ΔluxOU strain in monoculture over the course of a growth cycle in M9-casein medium. RLU, relative light units. (B) Defector frequency over a single growth cycle for the ΔluxOU strain versus the ΔluxR strain, the ΔluxOU strain versus the WT strain, and the WT strain versus the ΔluxR strain (with the defector strains underlined), started at 1% of the total population and competed in M9-casein medium. (C) Growth of the WT strain, the ΔluxR strain, and the ΔluxOU strain in monoculture over the course of a single growth cycle. Error bars, 95% confidence intervals (n = 4 biological replicates per treatment).
Tables
- TABLE 1
Description of strains used
Strain Genotype Strain description BB120 ATCC BAA-1116 Wild-type strain; has functional QS system KM669 ΔluxR Knockout mutant of gene encoding QS master regulator LuxR; acts as defector JAF78 ΔluxOU Knockout mutant of genes encoding LuxO and LuxU; acts as unconditional cooperator KM83 luxO D47E Point mutant, producing LuxO that constitutively mimics phosphorylated state; acts as defector JMH634 ΔluxM ΔluxS ΔcqsA Triple signal synthase mutant; unable to induce QS but responds to supplemented signal CW2001 ΔluxAB Strain with luciferase genes deleted; has functional QS system but is unable to produce light
Supplemental material
- Supplemental file 1 -
V. harveyi requires QS for maximal signal production in M9-casein (Fig. S1), dependence of the performance of ΔluxR in mixed populations in M9-casein on the competing cooperator strain (Fig. S2), growth performance of mixed populations in competition in M9-casein (Fig. S3), V. harveyi QS providing equivalent fitness against defectors in M9-casein (Fig. S4), growth performance of ΔluxR defector in the presence and absence of competing strains (Fig. S5), and fitness outcomes from single growth cycle competitions between different V. harveyi strains in M9-tryptone media (Fig. S6).
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- Supplemental file 1 -
