GENOME COMPLEXITY IN RHODOBACTER SPHAEROIDES 241

描述（改编自申请人的摘要）：在不到十年的时间里， 我们已经了解到细菌和原核生物都拥有 线性染色体和质粒，以及多个，但不同的 染色体 在此之前，原核生物含有 一条独特的环状染色体 到目前为止，大约有5-7个不同的属， 已经发现细菌含有两个或多个染色体， 有趣的是，大多数这些属已被证明与 高等生物的细胞。 如本文所述，本研究旨在 提供了第一个实验方法来理解这条线， 微生物发育 一种方法是基于这样的观察， 有几个基因在染色体I和I之间是杂合的， II中的细菌，Rhodobacter sphaeroides 2.4.1. 利用这个经过充分研究的 细菌，我们将确定之间存在的杂合性的程度 染色体I和II，无论是否为一对同源染色体的两个成员 基因在什么样的生长条件下是有功能的， 以及映射到每条染色体上的真正必需的基因类型， 最后，这条发展路线是否为这一群体的所有成员所共有？ 细菌，如果没有，为什么没有？ 已知杂合性增加了这些群体的“适应性”， 在其生命周期中表现出倍性的高等生物。 这是不是 原核生物是真的，如果是真的，又是如何做到的呢？ 因此， R. sphaeroides 2.4.1以及杂合基因被 他的发言应该有助于解决这个问题。 虽然杂合基因 配对基因也可以是必需基因，但不需要这样的先决条件。 因此，所映射的必需基因的种类和分布 染色体I和II可能有助于揭示的起源（S） R. sphaeroides 2.4.1. 最后，由于几个 的基因对被发现是杂合子是非常相似的基因家族 在高等生物中发现，我们也可以了解真核生物的起源。 型细胞及其内含物。

DESCRIPTION (Adapted from the Applicant's Abstract): In less than a decade we have learned that bacteria and perhaps prokaryotes in general, possess linear chromosomes and plasmids, as well as multiple, but different chromosomes. Heretofore it had been accepted that prokaryotes contained but a unique, circular chromosome. To date, some 5-7 different genera of bacteria have been found to contain two or more chromosomes and it is interesting that most of these genera have been shown to interact with the cells of higher organisms. This research, as described here, is designed to provide the first experimental approach to understanding this line of microbial development. One approach is based on the observation that several genes have been shown to be heterozygous between chromosomes I and II in the bacterium, Rhodobacter sphaeroides 2.4.1. Using this well studied bacterium we will determine the extent of heterozygosity existing between chromosomes I and II, whether or not both members of a pair of homologous genes are functional and under what growth conditions; what are the kinds and types of truly essential genes which are mapped to each chromosome and finally; is this line of development shared by all members of this group of bacteria and if not, why not? Heterozygosity is known to increase the "fitness" of those populations of higher organisms which show ploidy within their life cycle. Can this be true of prokaryotes, and if so, how? Thus, the extent of heterozygosity in R. sphaeroides 2.4.1 and the conditions under which heterozygous genes are expressed should help to address this question. Although heterozygous gene pairs can also be essential genes, no such prerequisite is necessary. Therefore, the kinds and distribution of essential genes which map to chromosomes I and II may help to reveal the origin(s) of the multi-chromosomal state in R. sphaeroides 2.4.1. Finally, because several of the gene pairs found to be heterozygous are very similar to gene families found in higher organisms, we may also learn the origins of the eukaryotic type cell and its inclusions.