在乳链球菌中，伴随有降低噬菌体敏感性机制的共配偶体转移，以及乳糖和蔗糖发酵能力。
Concomitant conjugal transfer of reduced-bacteriophage-sensitivity mechanisms with lactose- and sucrose-fermenting ability in lactic streptococci.
机构信息
Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, Minnesota 55108, and Department of Dairy and Food Microbiology, University College, Cork, Ireland.
出版信息
Appl Environ Microbiol. 1988 Aug;54(8):1951-6. doi: 10.1128/aem.54.8.1951-1956.1988.
Ten previously reported lactose-positive (Lac) transconjugants from Streptococcus lactis, S. cremoris, and S. lactis subsp. diacetylactis and one sucrose-positive (Suc) transconjugant from S. lactis were examined for their sensitivity to prolate- and small isometric-headed bacteriophages. Four of the Lac transconjugants showed a 10- to 100-fold reduction in the efficiency of plating (EOP) as well as a reduced plaque size for the prolate phage c2 and were insensitive to the small isometric phage 712. A fifth Lac transconjugant demonstrated a similar reduced sensitivity to phage c2; however, this transconjugant was able to plaque phage 712, but with a reduced plaque size and EOP. The other five Lac transconjugants were sensitive to both c2 and 712 phages. The Suc transconjugant plaqued phage 712 with a reduced plaque size and EOP, but no reduction in plaque size or EOP was observed for phage c2. The Lac and reduced bacteriophage sensitivity (Rbs) phenotypes were correlated with specific plasmids in the Lac transconjugants. As four of the Lac transconjugants exhibited a phenotypically indistinguishable Rbs, one (AB001) was selected for further study. The Rbs in AB001 for both small isometric- and prolate-headed phages was not related to adsorption, and the reduced EOP for phage c2 was not related to the presence of a restriction and modification system. The latent period for phage c2 was unchanged, but the burst size was reduced 80%. The presence of the plasmid coding for Rbs retarded the lysis of a mitomycin C-induced prophage-containing strain. The Rbs mechanism appears to be abortive phage infection. This study supports previous observations that Rbs and conjugal transfer ability are physically linked among some group N streptococci. The results presented have implications in the identification of plasmids coding for Rbs and may also aid in explaining the dissemination of Rbs genes among lactic streptococci.
先前从乳链球菌、乳脂链球菌和乳脂链球菌亚种二乙酰乳酸链球菌中分离出的 10 株乳糖阳性（Lac）转导子和一株来自乳链球菌的蔗糖阳性（Suc）转导子被检测对长头和小头等轴噬菌体的敏感性。4 株 Lac 转导子的平板效率（EOP）降低了 10 到 100 倍，并且对长头噬菌体 c2 的噬菌斑变小，对小等轴噬菌体 712 不敏感。第 5 株 Lac 转导子对噬菌体 c2 的敏感性也降低了；然而，该转导子能够噬菌斑 712，但噬菌斑大小和 EOP 降低。其他 5 株 Lac 转导子对 c2 和 712 噬菌体均敏感。Suc 转导子噬菌斑 712，但噬菌斑大小和 EOP 降低，而 c2 噬菌体则没有观察到噬菌斑大小或 EOP 的降低。Lac 和降低的噬菌体敏感性（Rbs）表型与 Lac 转导子中的特定质粒相关。由于 4 株 Lac 转导子表现出表型上无法区分的 Rbs，因此选择了其中一株（AB001）进行进一步研究。AB001 对小等轴和长头噬菌体的 Rbs 与吸附无关，而 c2 噬菌体的 EOP 降低与限制修饰系统的存在无关。c2 噬菌体的潜伏期没有改变，但爆发大小降低了 80%。编码 Rbs 的质粒的存在延迟了丝裂霉素 C 诱导的含原噬菌体菌株的裂解。Rbs 机制似乎是噬菌体的无效感染。本研究支持先前的观察结果，即 Rbs 和接合转移能力在某些 N 群链球菌中是物理相关的。所呈现的结果对鉴定编码 Rbs 的质粒具有重要意义，也可能有助于解释 Rbs 基因在乳酸链球菌中的传播。
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