Antibacterial properties of the stem cells and human- and plant- derived microvesicles are attracting increasing attention of the research community. Awareness of publications pointing out to the pronounced anti-bacterial properties of microvesicles isolated from the supernatants of different human origin prompted us to test corresponding properties of supernatant isolated using simplified protocol. Extensive research with more than 100 laboratory strains and hospital isolates of Gram-positive and Gram- negative bacteria point out to a pronounced anti-bacterial activity of the supernatant isolated from the cultures of actively dividing human cells. Simultaneous support of cell proliferation homeostasis and anti-bacterial activity led us to the hypotheses suggesting that there exists some archaic (possibly relict) mechanism with bivalent activity, which is provided by certain entities present in the supernatant. Taking into account that dried supernatant does not lose its potency for relatively long time, we would like to attract activity of wide research community to the opening application possibilities, and to the critical discussions over the formulated hypothesis.