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While most species of ''Lactobacillus'' do not produce bacteriocins, many strains of ''L. acidophilus'' are well known for being able to produce bacteriocins, including probiotics strains. Bacteriocins are similar to the [[Saccharomyces#Killer_Wine_Yeast|toxins that some wine yeast strains produce]], however bacteriocins tend to target other species that are closely related to the toxin-producing species (although there are some exceptions to this in the literature). The bacteriocin that ''L. acidophilus'' produces is a narrow spectrum class II bacteriocin, lactacin B (narrow spectrum means that this toxin kills a very narrow range of closely related Gram-positive bacteria). Species that are susceptible to the lactacin B toxin include species that are genetically closely related to ''L. acidophilus'': ''L. leichmanii'', ''L. bulgaricus'', ''L. delbruekii'', ''L. lactis'', and ''L. helveticus''. Species that are insensitive to the toxin are ''L. plantarum'', ''L. casei'', ''L. viridescens'', and ''L. fermentum''. Some strains of sensitive species may still be insensitive to the toxin from certain strains of ''L. acidophilus'' <ref>[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC242543/ Detection and activity of lactacin B, a bacteriocin produced by Lactobacillus acidophilus. S F Barefoot and T R Klaenhammer. 1983.]</ref><ref>[https://link.springer.com/article/10.1007/s12602-017-9326-2 Lack of Heterogeneity in Bacteriocin Production Across a Selection of Commercial Probiotic Products. J. W. Hegarty, C. M. Guinane, R. P. RossC. Hill, P. D. Cotter. 2017.]</ref>.