  We investigate dense suspensions of swimming bacteria prepared in a
nutrient-exchange chamber. Near the pellet concentration, nonthermal
fluctuations showed notable agreement between self and collective behaviors, a
phenomenon not previously observed at equilibrium. The viscosity of active
suspensions dramatically decreased compared to their inactive counterparts,
where glassy features, such as non-Newtonian viscosity and dynamic
heterogeneity, disappeared. Instead, the complex shear modulus showed a
power-law rheology,$G^*(\omega)\propto\left(-i\omega\right)^\frac{1}{2}$,
indicating the role of bacterial activity in driving the system towards a
critical jamming state.
