Identification of a Gene Cluster Enabling Lactobacillus casei BL23 To Utilize myo-Inositol
Identification of a Gene Cluster Enabling Lactobacillus casei BL23 To Utilize myo-Inositol
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DOI：
10.1128/aem.00243-07
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发表时间：
2007-04
影响因子：
4.4
通讯作者：
M. J. Yebra;M. Zúñiga;Sophie Beaufils;G. Pérez-Martínez;J. Deutscher;V. Monedero
中科院分区：
文献类型：
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作者：
M. J. Yebra;M. Zúñiga;Sophie Beaufils;G. Pérez-Martínez;J. Deutscher;V. Monedero
摘要 干酪乳杆菌 BL23 的基因组分析表明，与干酪乳杆菌 ATCC 334 相比，它携带 12.8 kb DNA 插入，其中包含参与环状多元醇肌醇 (MI) 分解代谢的基因。事实上，干酪乳杆菌 ATCC 334 不发酵 MI，而菌株 BL23 能够利用这种碳源。插入的DNA由编码DeoR家族转录抑制子的iolR基因和发散转录的iolTABCDG1G2EJK操纵子组成，编码完整的MI分解代谢途径，其中iolK基因可能编码丙二酸半醛脱羧酶。 iolK的存在表明干酪乳杆菌有两条替代的丙二酸半醛代谢途径：（i）经典的MI分解代谢途径，其中IolA（丙二酸半醛脱氢酶）催化丙二酸半醛形成乙酰辅酶A；（ii）iolK产物催化丙二酸半醛转化为乙醛。 iol 基因的功能通过 iolA、iolT 和 iolD 的破坏得到验证，这提供了 MI 阴性菌株。相比之下，iolK 的破坏导致菌株在 MI 利用方面没有明显的缺陷。对不同突变株进行的转录分析表明，iolTABCDG1G2EJK 簇受到转录阻遏物 IolR 失活介导的底物特异性诱导和分解代谢物控制蛋白 A (CcpA) 介导的碳分解代谢物抑制的调节。这是乳酸菌中利用 MI 的操纵子的第一个例子，并说明了干酪乳杆菌 BL23 中碳水化合物利用的多功能性。
ABSTRACT Genome analysis of Lactobacillus casei BL23 revealed that, compared to L. casei ATCC 334, it carries a 12.8-kb DNA insertion containing genes involved in the catabolism of the cyclic polyol myo-inositol (MI). Indeed, L. casei ATCC 334 does not ferment MI, whereas strain BL23 is able to utilize this carbon source. The inserted DNA consists of an iolR gene encoding a DeoR family transcriptional repressor and a divergently transcribed iolTABCDG1G2EJK operon, encoding a complete MI catabolic pathway, in which the iolK gene probably codes for a malonate semialdehyde decarboxylase. The presence of iolK suggests that L. casei has two alternative pathways for the metabolism of malonic semialdehyde: (i) the classical MI catabolic pathway in which IolA (malonate semialdehyde dehydrogenase) catalyzes the formation of acetyl-coenzyme A from malonic semialdehyde and (ii) the conversion of malonic semialdehyde to acetaldehyde catalyzed by the product of iolK. The function of the iol genes was verified by the disruption of iolA, iolT, and iolD, which provided MI-negative strains. By contrast, the disruption of iolK resulted in a strain with no obvious defect in MI utilization. Transcriptional analyses conducted with different mutant strains showed that the iolTABCDG1G2EJK cluster is regulated by substrate-specific induction mediated by the inactivation of the transcriptional repressor IolR and by carbon catabolite repression mediated by the catabolite control protein A (CcpA). This is the first example of an operon for MI utilization in lactic acid bacteria and illustrates the versatility of carbohydrate utilization in L. casei BL23.