Section outline

  • General

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  • 细菌生殖

    Close-up of Escherichia coli bacteria, showing cells in the process of division.

    How do bacteria reproduce?
    ::细菌如何繁殖?

    Essentially, they grow and divide. Shown here is an example of Escherichia coli . Notice how one bacterium is dividing into two.
    ::基本上,它们生长和分化。在这里显示的是Esherichia大肠杆菌的一个例子。注意一个细菌是如何被分为两个的。

    Reproduction in Prokaryotes
    ::Prokaryotes的复制

    Unlike , increases in the size of ( growth) and their by are tightly linked. Prokaryotes grow to a fixed size and then reproduce through binary fission .  
    ::普罗卡约特斯(Prokaryotes)长成固定大小,然后通过二进制裂变繁殖。

    Binary Fission
    ::二进制纤维

    Binary fission is a type of . It occurs when a parent cell splits into two identical daughter cells . This can result in very rapid . For example, under ideal conditions, bacterial can double every 20 minutes. Such rapid population growth is an adaptation to an unstable environment. Can you explain why?
    ::二进制裂变是一种类型 。 当父细胞分裂成两个完全相同的女儿细胞时, 就会发生这种情况。 这可能导致非常快速 。 例如, 在理想条件下, 细菌每20分钟可以翻一番 。 这种快速的人口增长是适应不稳定环境的。 您能解释为什么吗 ?

    Schematic showing bacterial elongation and binary fission process during prokaryotic reproduction.
    Schematic diagram of cellular growth (elongation) and binary fission of bacilli. Blue and red lines indicate old and newly-synthesized bacterial cell wall, respectively. The DNA inside the bacterium is copied and the daughter cells receive an exact copy of the parent DNA. Fission involves a cytoskeletal protein FtsZ that forms a ring at the site of cell division.

       

     

     

     

    Genetic Transfer
    ::转基因转让

    In asexual reproduction, all the offspring are exactly the same. This is the biggest drawback of this type of reproduction. Why? Lack of increases the risk of extinction . Without variety, there may be no organisms that can survive a major change in the environment.
    ::在性生殖中,所有后代都完全相同。这是这种生殖的最大缺陷。为什么?缺乏增加灭绝的风险。没有多样性,环境可能就没有能够幸存重大变化的生物。

    Prokaryotes have a different way to increase genetic variation. It’s called genetic transfer or bacterial conjugation . It can occur in two ways. One way is when cells “grab” stray pieces of from their environment. The other way is when cells directly exchange DNA (usually plasmids) with other cells. For example, as shown in Figure , the donor cell makes a structure called an F pilus , or sex pilus. The F pilus attaches one cell to another cell. The membranes of the two cells merge and genetic material , usually a plasmid , moves into the recipient cell. Genetic transfer makes bacteria very useful in . It can be used to create bacterial cells that carry new genes .
    ::Prokaryotes有不同的方法来增加基因变异。 它被称为基因转移或细菌共生。 它可以以两种方式发生。 一种是细胞“ grab” 偏离环境的碎片。 另一种是细胞直接将DNA( 通常是颗粒体) 与其他细胞交换。 例如, 如图所示, 捐赠细胞制造了一个叫做 F pilus 或 sex pilus 的结构。 F pilus 将一个细胞连接到另一个细胞中。 两个细胞的膜结合和遗传物质( 通常是一个粒子) 移动到接收细胞中。 遗传转移使细菌在其中非常有用。 它可以用来创造带有新基因的细菌细胞。

    Flowchart illustrating bacterial conjugation and DNA transfer between donor and recipient cells.
    A flowchart showing bacterial conjugation. The donor cell makes a structure called an F pilus, or sex pilus. The F pilus attaches one cell to another cell. The membranes of the two cells merge and genetic material, usually a plasmid, moves into the recipient cell.

      

     

     

     

    Summary
    ::摘要

    • Prokaryotic cells grow to a certain size. Then they divide by binary fission. This is a type of asexual reproduction.
      ::蛋白质细胞生长到一定的大小, 然后除以二进制裂变, 这是一种性生殖。
    • Binary fission produces genetically identical offspring.
      ::二进制裂变产生基因相同的后代。
    • Genetic transfer increases genetic variation in prokaryotes.
      ::基因转移增加了原虫的遗传变异。

    Review
    ::回顾

    1. Describe binary fission.
      ::描述二进制裂变
    2. Why might genetic transfer be important for the survival of prokaryote species?
      ::为什么基因转移对原种物种的生存很重要?
    3. Under ideal conditions, in 2 hours how many bacteria can result from just a single bacterium? 5 hours? 
      ::在理想条件下,在2小时之内,仅仅一个细菌就能产生多少细菌?5小时?