The current invention is directed to oligonucleotide sequences isolated from a sequence designated rbl-1 [SEQ ID NO. 19] that either kill or inhibit growth, or prevent the production of endogenously expressed toxin, of microorganisms. These ssDNA sequences, identified through use of a screening method, appear to act as modulators of essential growth functions which may act at the level of triplex formation, antisense inhibition, or as aptamers that alter gene function. The sequences, referred to as minimum functional regions, or MFRs, are useful inter alia as therapeutic agents for treatment of sepsis and other pathologies caused by microorganisms such as sepsis and/or in which microorganisms are contributory agents.