Houlihan Adam J, Russell James B
Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA.
Curr Microbiol. 2006 Nov;53(5):365-9. doi: 10.1007/s00284-005-0417-z. Epub 2006 Oct 11.
Some Gram-positive bacteria produce small peptides (bacteriocins) that have antimicrobial activity, but many bacteria can become bacteriocin resistant. Bovicin HC5, a lantibiotic produced by Streptococcus bovis HC5, has the ability to inhibit nisin-resistant bacteria. Because nisin resistance has in many cases been correlated with an alteration of lipoteichoic acids or the polar head groups of membrane phospholipids, we decided to examine the effect of divalent cations on nisin and bovicin HC5 activity. Both bacteriocins catalyzed potassium efflux from S. bovis JB1, a non-bacteriocin-producing strain. The addition of large amounts (100 mM) of calcium or magnesium increased the ability of S. bovis JB1 to bind Congo red (an anionic dye) and counteracted bacteriocin-mediated potassium loss. Calcium was more effective than magnesium in decreasing nisin activity, but the reverse was observed with bovicin HC5. Nisin-resistant S. bovis JB1 cells bound three times as much Congo red as nisin-sensitive cells, and this result is consistent with the idea that changes in cell surface charge can be a mechanism of bacteriocin resistance. The nisin-resistant cells were less susceptible to bovicin HC5, but bovicin HC5 still caused a 50% depletion of intracellular potassium. These results indicate that nisin and bovicin HC5 react differently with the cell surfaces of Gram-positive bacteria.
一些革兰氏阳性菌会产生具有抗菌活性的小肽（细菌素），但许多细菌会对细菌素产生抗性。牛链球菌HC5产生的羊毛硫抗生素Bovicin HC5具有抑制耐乳链菌肽细菌的能力。由于在许多情况下，乳链菌肽抗性与脂磷壁酸或膜磷脂极性头部基团的改变相关，我们决定研究二价阳离子对乳链菌肽和Bovicin HC5活性的影响。两种细菌素都催化了非产细菌素菌株牛链球菌JB1的钾外流。添加大量（100 mM）的钙或镁会增加牛链球菌JB1结合刚果红（一种阴离子染料）的能力，并抵消细菌素介导的钾流失。在降低乳链菌肽活性方面，钙比镁更有效，但在Bovicin HC5方面则观察到相反的情况。耐乳链菌肽的牛链球菌JB1细胞结合的刚果红是对乳链菌肽敏感细胞的三倍，这一结果与细胞表面电荷变化可能是细菌素抗性机制的观点一致。耐乳链菌肽的细胞对Bovicin HC5的敏感性较低，但Bovicin HC5仍会导致细胞内钾含量减少50%。这些结果表明，乳链菌肽和Bovicin HC5与革兰氏阳性菌的细胞表面反应不同。
