一株食源性单增李斯特菌镉、砷耐受基因的测序分析

Sequencing Analysis of Cadmium and Arsenic Resistance Genes in a Listeria monocytogenes Strain Isolated from Meat

摘要:

为了探究食源性单核细胞增生李斯特菌对重金属的耐受性及耐受基因，本研究在一株食源性单增李斯特菌LM3中发现一段携带重金属镉耐受基因盒cadAC4及砷耐受基因盒arsD1A1R1D2R2A2B1B2的插入序列。通过琼脂稀释法测定菌株对重金属镉和砷的耐受性，PCR及DNA测序、生物信息学分析，对插入序列的结构进行分析鉴定及与不同种属携带相似基因岛进行了分析。该菌株表现出低水平的镉耐受性，对砷表现为敏感。菌株携带cadA4，及arsA1和arsA2基因，不携带cadA1，cadA2及cadA3基因。镉耐受基因cadAC4能介导低水平的镉耐受性，相反地，砷耐受基因盒arsD1A1R1D2R2A2B1B2并未表达或表达受到抑制。测得序列长36629 bp，具有高度保守性，是亚洲国家首次在食源性单增李斯特菌中发现该插入序列。砷耐受基因盒存在位置具多样性，且可以由不同基因组合。

Abstract:

In order to study the heavy metal resistance of food-borne Listeria monocytogenes and its resistance genes, an insertion sequence harboring a cadmium (Cd) resistance gene cassette, cadAC4, and an arsenic (As) resistance gene cassette, arsD1A1R1D2R2A2B1B2, from a single Listeria monocytogenes LM3 strain was identified in this experiment. The cadmium and arsenic resistance of the strain were measured by agar dilution method, and polymerase chain reaction (PCR), DNA analysis, and bioinformatics analysis were used to identify the structure of the insertion sequence and analyze the genetic islands harboring similar genes from different species. This strain exhibited a low level of cadmium resistance and was sensitive to arsenic. The strain harbored genes cadA4, arsA1, and arsA2, and did not harbor genes cadA1, cadA2, or cadA3. The cadmium resistance gene cadAC4 could mediate the low level of cadmium resistance, while the arsenic resistance gene cassette arsD1A1R1D2R2A2B1B2 was not expressed, or its expression was suppressed. The length of the sequence was 36629 bp, and it was highly conserved. This insertion sequence was identified for the first time in food-borne Listeria monocytogenes in an Asian country. The arsenic resistance gene cassette had a variety of locations and could be composed of different genes.