Additionally to the genetic material contained within the nucleoid, many bacteria contain extra chromosomal DNA molecules called plasmids.

除了包含在拟核中遗传物外，许多细菌含有额外DNA分子，称。

However, plasmids often contain genes that confer a selective advantage to the bacterium such as resistance to antibiotics.

不过通常包含赋予细菌择性优势基因，例如抗生素耐药性。

These plasmids are small double-stranded DNA molecules that can exist independently of the chromosome and they can be circular or linear.

它们是双链DNA小分子，可以独立于细菌染色体（拟核）而存在，可以是环状或线状。

Transfer of the ligated plasmid into an E. coli strain (transformation).

7。转化成功细菌。

The cDNAs had to be linked to prokaryotic transcription and translation signals and inserted into multicopy plasmids.

然而，占总蛋白30%过量表达蛋白是沉淀或不溶形式并且缺少翻译后修饰。

Plasmids have relatively few genes and their genetic information is not essential to the bacterium and cells that lack them usually function normally.

所含基因相对较少，并且它们基因对细菌来说并不是必须，缺少细胞往往也可以正常生长。

More specialized vectors have been engineered to use aspects of plasmids and bacteriophages, such as the plasmid-bacteriophage h hybrids known as cosmids

和噬菌体已经在很多种类细菌中被使用来表达基因，并且一些噬菌体也许已经被用来将DNA整合到宿主基因组上。

Phage h can be used to clone fragments larger than plasmid vectors, and phage M13 allows cloned DNA to be isolated in single-stranded form.

更多载体被改造能同时拥有和噬菌体一些特性，像被称粘-噬菌体λ杂交体。