Nelms L F, Odelson D A, Whitehead T R, Hespell R B
Department of Biology, Central Michigan University, Mt. Pleasant 48859, USA.
Curr Microbiol. 1995 Nov;31(5):294-300. doi: 10.1007/BF00314583.
Streptococcus bovis is commonly present in the rumen, but strains of S. bovis have also occasionally been isolated from human blood or fecal samples. Studies were undertaken with 16s rRNA gene sequences and DNA hybridizations to define the genetic relationships between these two groups of strains. Ruminal strains were found to yield genomic DNA restriction endonuclease digest patterns different from human strains when either the 16s rRNA gene amplified from ruminal S. bovis strain JB1 or a conserved universal 23s rRNA fragment was used as probes. A DNA probe based on the V1 region of the 16s rRNA of S. bovis JB1 was found to hybridize to DNAs of other ruminal S. bovis strains (K27FF4, 21-09-6C, five new ruminal isolates, and weak hybridization was found with DNAs from S. bovis 33317 (type strain), S. equinus 9812, and six other ruminal isolates. No hybridization occurred with strains representing different major human biotypes/homology groups (43143, 43144, 27960, V1387). All ruminal S. bovis strains had a guanosine plus cytosine DNA content of 37.4-38.8 mol% and, based on DNA-DNA genomic hybridizations, could be separated into two homology groups, one of which included S. equinus 9812 and S. bovis 33317. Both ruminal groups had less than 38% DNA homology to the human strains, indicating ruminal strains are clearly two separate species distinct from the human strains.
牛链球菌通常存在于瘤胃中，但偶尔也能从人类血液或粪便样本中分离出牛链球菌菌株。研究人员利用16s rRNA基因序列和DNA杂交技术来确定这两组菌株之间的遗传关系。当从瘤胃牛链球菌菌株JB1扩增的16s rRNA基因或保守的通用23s rRNA片段用作探针时，发现瘤胃菌株产生的基因组DNA限制性内切酶消化模式与人类菌株不同。基于牛链球菌JB1的16s rRNA V1区域的DNA探针被发现可与其他瘤胃牛链球菌菌株（K27FF4、21-09-6C、五个新的瘤胃分离株）的DNA杂交，并且与牛链球菌33317（模式菌株）、马肠链球菌9812和其他六个瘤胃分离株的DNA有弱杂交。与代表不同主要人类生物型/同源性组的菌株（43143、43144、27960、V1387）没有杂交。所有瘤胃牛链球菌菌株的鸟嘌呤加胞嘧啶DNA含量为37.4 - 38.8 mol%，基于DNA - DNA基因组杂交，可分为两个同源性组，其中一组包括马肠链球菌9812和牛链球菌33317。两个瘤胃组与人类菌株的DNA同源性均低于38%，表明瘤胃菌株显然是与人类菌株不同的两个独立物种。
