Chandrasekaran S, Venkatesh B, Lalithakumari D
Environmental Biotechnology Programme, Centre for Advanced Studies in Botany, University of Madras, Guindy Campus, Madras 600 025, India.
Curr Microbiol. 1998 Nov;37(5):347-51. doi: 10.1007/s002849900390.
Conjugal transfer of a multiresistance plasmid from Pseudomonas fluorescens to halophilic and halotolerant bacteria was studied under in vitro and in situ conditions. Mating conducted in broth as well as on plates yielded a plasmid transfer frequency of as high as 10(-3). Among these two, plate mating facilitated conjugal transfer of plasmid, because the cell-to-cell contact is more in plate mating. When P. fluorescens was incubated in seawater, the organism progressively lost its colony forming activity within 15 days. Microscopic examination revealed the presence of very short rods, indicating that the cells have become viable but nonculturable (VNC). Mating conducted in natural seawater without any added nutrients revealed that the conjugal transfer is influenced by the physical state of the donor and the recipients as well as the availability of nutrients. But a plasmid transfer frequency of 10(-7) was obtained even after the donor cells have become VNC suggesting that the nonculturable state and nutrient deprived condition may not limit plasmid transfer. The results suggest that the terrestrial bacteria entering into the seawaters with antibiotic resistance plasmids may be responsible for the prevalence of resistance genes in the marine environment.
在体外和原位条件下研究了多抗性质粒从荧光假单胞菌向嗜盐菌和耐盐菌的接合转移。在肉汤和平板上进行的交配产生的质粒转移频率高达10⁻³。在这两种方法中，平板交配促进了质粒的接合转移，因为平板交配中的细胞间接触更多。当荧光假单胞菌在海水中培养时，该生物体在15天内逐渐失去其菌落形成活性。显微镜检查显示存在非常短的杆菌，表明细胞已变得活但不可培养（VNC）。在没有添加任何营养物的天然海水中进行的交配表明，接合转移受供体和受体的物理状态以及营养物可用性的影响。但是，即使供体细胞已变为VNC，仍获得了10⁻⁷的质粒转移频率，这表明不可培养状态和营养缺乏条件可能不会限制质粒转移。结果表明，携带抗生素抗性质粒进入海水的陆生细菌可能是海洋环境中抗性基因普遍存在的原因。
