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Expression of luminescence in Escherichia coli was recently achieved by cloning genes from the marine bacterium Vibrio fischeri. One DNA fragment on a hybrid plasmid encoded regulatory functions and enzymatic activities necessary for light production. We report the results of a genetic analysis to identify the luminescence genes (lux) that reside on this recombinant plasmid. lax gene mutations were generated by hydroxylamine treatment, and these mutations were ordered on a linear map by complementation in trans with a series of polar transposon insertions on other plasmids. lux genes were defined by complementation of lax gene defects on pairs of plasmids in trans in E. coli. Hybrid plasmids were also used to direct the synthesis of polypeptides in the E. coli minicell system. Seven lax genes and the corresponding gene products were identified from the complementation analysis and the minicell programing experiments. These genes, in the order of their position on a linear map, and the apparent molecular weights of the gene products are luxR (27,000), luax (25,000), luxC (53,000), luxD (33,000), luxA (40,000), luxB (38,000), and luxE (42,000). From the luminescence phenotypes of E. coli containing mutant plasmids, functions were assigned to these genes: laxA, luxB, luxC, luxD, and luxE encode enzymes for light production and luxR and lux! encode regulatory functions.Luminescent bacteria are common in the ocean and occupy a variety of ecological niches (1, 2). Vibrio fischeri (strain MJ-1) colonizes the light organ of the fish Monocentris japonicus, and we have initiated studies to determine the genetic and functional components of the luminescence system from this bacterium. The emission of light by marine bacteria is catalyzed by the enzyme luciferase, a mixed function oxidase that has two subunits, a and f3, with molecular weights of -40,000 each (3). In the generation of light, luciferase oxidizes a reduced flavin and a long-chain aldehyde, producing oxidized flavin and the corresponding long chain fatty acid: luciferase RCHO + FMNH2 + 02 -e RCOOH + FMN + H20 + hp.Other components unique to the bioluminescence system include enzymes involved in the synthesis or recycling of the aldehyde substrate. Light production occurs in dense bacterial cultures and is controlled by the synthesis of a sensory molecule termed autoinducer. This molecule is secreted into the extracellular environment where it accumulates and at a critical concentration signals expression of luminescence. This induction can result in a 10,000-fold increase in light emission per cell (4). The autoinducer from V. fischeri has been shown to be N-(/3-ketocaproyl)homoserine lactone (5).We previously isolated a 9-kilobase-pair (kbp) DNA fragment from V. fischeri that encoded all of the functions necessary for light production and that also contained the regulatory elements required for their expression in Escherichia coli. By using transposon mutagenesis, the regions on this DNA fragment that encoded aldehyde, luciferase, and regulatory funct...

The replication of chromosomes in meiosis is an important first step for subsequent chromosomal interactions that promote accurate disjunction in the first of two segregation events to generate haploid gametes. We have developed an assay to monitor DNA replication in vivo in mitotic and meiotic germline nuclei of the nematode Caenorhabditis elegans. Using mutants that affect the mitosis/meiosis switch, we show that meiotic S phase is at least twice as long as mitotic S phase in C. elegans germ cell nuclei. Furthermore, our assay reveals that different regions of the genome replicate at different times, with the heterochromatic-like X chromosomes replicating at a distinct time from the autosomes. Finally, we have exploited S-phase labeling to monitor the timing of progression through meiotic prophase. Meiotic prophase for oocyte production in hermaphrodites lasts 54-60 h. Further, we find that the duration of the pachytene sub-stage is modulated by the presence of sperm. On the other hand, meiotic prophase for sperm production in males is completed by 20-24 h. Possible sources for the sex-specific differences in meiotic prophase kinetics are discussed.

Phospholipid metabolism plays an important role in cellular regulation by