Influence of low-coherent speckles on the colonies grows is investigated. It has been demonstrated that effects of light on the inhibition or re-activation of cells are connected with speckle dynamics. The regimes of cell suspension perflJsion with purpose of devitalization of hazard bacteria, caused very dangerous infections, are found. Mathematical model of interaction of low-coherent laser radiation with bacteria suspension has been proposed. Computer simulations of the processes of laser-cells interaction have been carried out.