摘要以镇江市蚕研所桑园土壤为研究对象，开展重金属镉离子对桑园土壤磺胺类 抗生素抗性的抗性菌的影响及其抗性菌的特性研究，这对于充分的了解抗镉和耐 磺胺类药物的菌株有重大的现实意义。由于自然环境下，土壤中的微生物会受到 很多因素的干扰，因此本实验的土壤培养在恒温下（25℃）进行，同时定时的加 去离子水保持土壤中的含水率基本不变来做下一步的研究。

在 25℃恒温培养箱中进行培养时，土壤中抗性菌的数目与镉离子的浓度和培 养时间有着密切的关系。随着镉离子浓度的增大，抗性菌的数目会越来越少，当 Cd≥50mmol/g 时，抗性菌的数量非常的少。另一方面，随着时间的延长，抗性 菌的数目呈现出一开始平缓（0-5h），随后数目增长较快（5-10h），最后数目 下降的趋势（10-30h），这完全符合微生物的生长定律。

另外，对培养出的两种菌株进行了分子鉴定、生理生化特性的测定，及药敏 实验。分子鉴定的结果：一种菌株是淡紫色拟青霉素，另一种是铜绿甲单孢菌。 生理生化的测试结果表明拟青霉素是阳性菌而铜绿甲单孢菌是阴性菌。药敏实验 发现拟青霉素对磺胺噻唑，新霉素，庆大霉素能产生抗性但是却对其他抗生素没 有抗性，铜绿甲孢菌对磺胺噻唑，庆大霉素，头孢霉素均有抗性但是对链霉素， 新霉素和青霉素没有抗性。83155

随着镉离子浓度的增加，两种菌液的吸光度值都在不断的下降。随着溶解氧 含量的下降，两种菌液的吸光度值也会不断地下降。拟青霉素的最佳培养体系是 温度 30℃-35℃，pH 值 6-8。铜绿甲单孢菌的最佳培养体系是温度 25℃-30℃， pH 值 6-8。

毕业论文关键词：重金属镉；抗性菌；分子鉴定；最佳培养体系

Abstract This experiment takes the soil of the Mulberry in Zhenjiang city as the object of the research to carry out the research on the impact which the heavy mental cadmium ion of mulberry field soil has on resistance of bacteria。This research has great realistic significance because people can know the bacteria which have resistance on both the heavy mental cadmium ion and the the sulfamido。The microorganism in the soil will

be influenced by many kinds of factors，So the soil in this experiment fostered  under

the fixed temperature of 25℃，the distilled water without ion should be added into the soil to keep the moisture content constant。

When the resistance bacteria are fostered in the constant temperature incubator,the number of them has a close relationship with the concentration of the  the heavy mental cadmium ion and the time。When the concentration of the heavy mental cadmium ion increases,the number of resistant bacteria decreases。Especially when the the concentration of the heavy mental cadmium ion scales out 50 mmol/L,the number of  resistant  bacteria  is  very  low。Also,When  the  time  extends,the  number  of    the

resistant bacteria keeps mild in the beginning(0-5h),Then the number of the resistant bacteria keeps increasing quickly（5-10h)。Finally,the number of it decreases(10-30h)。It completely conforms to the laws of microbial growth。

In addition,I make the molecular identification of two strains which grow up in the laboratory。At the same time,I measure the characteristics of pHysics and biochemical and measure the ability of the resistance which these two bacteria have on other antibiotics。the result of the molecular identification:A strain is mauve to penicillin, and the other one is green a single spore fungus。 pHysiological and biochemical test results show that the proposed penicillin is positive and verdigris a single spore bacteria was negative。Penicillin of sulfathiazole, neomycin, gentamicin can generate resistance but other antibiotics have no resistance, verdigris spore fungus of sulfathiazole, gentamycin, cepHalosporins drug were resistant to streptomycin, however, neomycin and penicillin have no resistance。