Figure 26 / 27 · Result 2

Phosphate is the switch that turns the broadcaster advantage on and off.

Six Vibrio strains degraded alginate particles across a phosphate gradient. The gap between broadcasters and aggregators opens at intermediate phosphate and closes at both extremes.

2.1×

broadcaster advantage at 0.2 mM phosphate (82.5% vs 39.3%)

n.s.

advantage at 0 mM — phosphate depletion erases it

338

particles tracked over 24.6 days

Broadcasters (12B01, 13B01)

Aggregators (ZF270, 9ZC77, 9ZC13, ZF57)

Enzyme secretion strategy determines degradation rate in a phosphate-dependent manner. Median volume reduction (ΔV%, T0→T2) of alginate particles pooled by secretion strategy — broadcaster (green, n = 92) and aggregator (blue, n = 246) — across a KH₂PO₄ gradient (0, 0.05, 0.2, 0.4 mM) in MMM-0-NC medium, 589.78 h incubation. Bars show the group median; italic values give the broadcaster/aggregator fold difference; significance from two-sided Mann–Whitney U tests (n.s. not significant, ** P < 0.01, *** P < 0.001). The advantage peaks at 0.2 mM and is statistically absent at both 0 and 0.4 mM — phosphate acts as a specific metabolic switch rather than a general nutrient signal.