Abstract：
The genus Natronospira is represented by a single species of extremely salt-tolerant aerobic alkaliphilic proteolytic bacterium, isolated from hypersaline soda lakes. When cells of Gram-positive cocci were used as a substrate instead of proteins at extremely haloalkaline conditions, two new members of this genus were enriched and isolated in pure culture from the same sites. Strains AB-CW1 and AB-CW4 are obligate aerobic heterotrophic proteolytic bacteria able to feed on both live and dead cells of staphylococci and a range of proteins and peptides. Similar to the type species, N. proteinivora, the isolates are extremely salt-tolerant obligate alkaliphiles. However, N. proteinivora was unable to use bacterial cells as a substrate. Electron microscopy showed direct contact between the prey and predator cells. Functional analysis of the AB-CW1 and AB-CW4 genomes identified two sets of genes coding for extracellular enzymes potentially involved in the predation and proteolysis, respectively. The first set includes several copies of lysozyme-like GH23 peptidoglycan-lyase and murein-specific M23 [Zn]-di-peptidase enabling the cell wall degradation. The second set features multiple copies of secreted serine and metallopeptidases apparently allowing for the strong proteolytic phenotype. Phylogenomic analysis placed the isolates into the genus Natronospira as two novel species members, and furthermore indicated that this genus forms a deep-branching lineage of a new family (Natronospiraceae) and order (Natronospirales) within the class Gammaproteobacteria. On the basis of distinct phenotypic and genomic properties, strain AB-CW1T (JCM 335396 = UQM 41579) is proposed to be classified as Natronospira elongata sp. nov., and AB-CW4T (JCM 335397 = UQM 41580) as Natronospira bacteriovora sp. nov.
摘要：
Natronospira属由单一物种的极耐盐好氧碱蛋白水解细菌代表，从高盐苏打湖中分离出来。当革兰氏阳性球菌的细胞被用作底物而不是在极端卤碱性条件下的蛋白质时，该属的两个新成员在同一地点的纯培养中被富集和分离。菌株AB-CW1和AB-CW4是专性需氧异养蛋白水解细菌，能够以葡萄球菌的活细胞和死细胞以及一系列蛋白质和肽为食。与类型物种相似，变形虫，分离株是极度耐盐的专性碱。然而,变形杆菌无法使用细菌细胞作为底物。电子显微镜显示猎物和捕食者细胞之间直接接触。AB-CW1和AB-CW4基因组的功能分析确定了两组编码可能参与捕食和蛋白水解的胞外酶的基因。分别。第一组包括几个拷贝的溶菌酶样GH23肽聚糖裂解酶和能够降解细胞壁的murein特异性M23[Zn]-二肽酶。第二组以分泌的丝氨酸和金属肽酶的多个拷贝为特征,显然允许强蛋白水解表型。系统基因组分析将分离株作为两个新物种成员放入Natronospira属中，并进一步表明，该属在Gammaproteobacteria类中形成了一个新科（Natronospiraceae）和顺序（Natronospirales）的深分支谱系。基于独特的表型和基因组特性，AB-CW1T菌株（JCM335396=UQM41579）被归类为长尾螺旋体。11月。,和AB-CW4T（JCM335397=UQM41580）作为纳氏螺旋藻细菌。11月。
