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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 and yogurt strains. Bacteriocins are similar to the [[Saccharomyces#Killer_Wine_Yeast|toxins that some wine yeast strains produce]], ; however, bacteriocins are toxins target other bacteria. 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''. These species include ''L. leichmanii'', ''L. bulgaricus'', ''L. delbruekii'', ''L. lactis'', and ''L. helveticus''. Species that are insensitive to the toxin because they are more distantly related genetically are ''L. plantarum'', ''L. casei'', ''L. viridescens'', and ''L. fermentum''. Some strains of sensitive species might be insensitive to the toxin from certain strains of ''L. acidophilus'' but sensitive to others. The toxin does not affect a wide range of bacteria, nor yeast species <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>. Some species of ''[[Pediococcus]]'' can also create bacteriocins (see this [https://www.facebook.com/BootlegBiology/photos/a.148869931970401.1073741829.124634287727299/465185997005458/?type=1&theater Bootleg Biology Facebook post]).

Some strains of ''L. plantarum'' cultured from Tibetan yaks have been found to have varying levels of bacteriocin activity as well. These strains produced a "class II enterocin" that inhibits the growth of ''E. coli'' and ''Staphylococcus aureus''. A strain of ''Pediococcus pentocaseus'' was also found to produce this enteriocin <ref>[https://www.sciencedirect.com/science/article/pii/S0882401017314559 Antibacterial activity of Lactobacillus plantarum isolated from Tibetan yaks. Lei Wang, Hui Zhang, Mujeeb Ur Rehman, Khalid Mehmood, Xiong Jiang, Mujahid Iqbal, Xiaole Tong, Xing Gao, Jiakui Li. 2017.]</ref>. One strain of ''L. plantarum'' isolated from kombucha was found to produce a bacteriocin called ''SLG10'' which has a broad spectrum of killing power, including affecting both Gram-positive and Gram-negative bacteria and preventing biofilm formation in other bacteria. This bacteriocin works by increasing the permeability of the cell walls of competing bacteria, which causes the target cells to excrete potassium and eventually die <ref>[https://www.sciencedirect.com/science/article/pii/S0956713519305122 Isolation, purification, and structural identification of a new bacteriocin made by Lactobacillus plantarum found in conventional kombucha. Jinjin Pei, Wengang Jin, A.M.Abd El-Aty, Denis A. Baranenko, Xiaoying Gou, Hongxia Zhang, Jingzhang Geng, Lei Jiang, Dejing Chen, Tianli Yue. 2019.]</ref>.