SummaryNatural genetic transformation in Streptococcus pneumoniae is controlled in part by a quorum-sensing system mediated by a peptide pheromone called competence-stimulating peptide (CSP), which acts to coordinate transient activation of genes required for competence. To characterize the transcriptional response and regulatory events occurring when cells are exposed to competence pheromone, we constructed DNA microarrays and analysed the temporal expression profiles of 1817 among the 2129 unique predicted open reading frames present in the S. pneumoniae TIGR4 genome (84%). After CSP stimulation, responsive genes exhibited four temporally distinct expression profiles: early, late and delayed gene induction, and gene repression. At least eight early genes participate in competence regulation including comX , which encodes an alternative sigma factor. Late genes were dependent on ComX for CSPinduced expression, many playing important roles in transformation. Genes in the delayed class (third temporal wave) appear to be stress related. Genes repressed during the CSP response include ribosomal protein loci and other genes involved in protein synthesis. This study increased the number of identified CSP-responsive genes from approximately 40 to 188. Given the relatively large number of induced genes (6% of the genome), it was of interest to determine which genes provide functions essential to transformation. Many of the induced loci were subjected to gene disruption mutagenesis, allowing us to establish that among 124 CSP-inducible genes, 67 were individually dispensable for transformation, whereas 23 were required for transformation.

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THIS paper may be considered as a continuation of one read in the Chemical Section, at the meeting of the American Association for the Advancement of Science held at Montreal, in August, 1882, entitled-" Determinations of Nitrogen in the Soils of some of the Experimental Fields at Rothamsted, and the Bearing of the Results on the Question of the Sources of the Nitrogen of our Crops,"-and in order adequately to bring out the bearings of the new results, embodied in the present communication, it is desirable, first to summarise the main results and conclusions of the previous one. The question of the sources of the nitrogen of our crops is one respecting which very conflicting views are still entertained ; and it may a t once be admitted that so long as the facts of agricultural production alone are studied, without knowledge of, or referewe to, the shanges in the stock of nitrogen in the soil, it would seem not unreasonable to assume that a large proportion of the nitrogen, at any rate of some crops, must be derived, in some way or other, from the atmosphere. Yield of Nitrogen p e y Acre in Diferent Crops. Obviously, it is a point of first importance to determine what really is the annual yield of nitrogen in different crops over a given area, excluding, as far as possible, the amounts due to unknown supplies by manure; thus, as far as practicable, limiting the source t o the stores of the soil itself, and to the atmosphere. The Rothamsted field experiments, in which different crops have been grown for very many years in succession on the same land, both without nitrogenous manure, and wit,h known quantities of such manure, afford valuable data of the kind required ; and, in our former paper, the results were discussed in some detail. It must suffice here to summarise them very briefly. The average yield of nit.rogen per acre per annum was, in wheat, 32 years without manure 20.7 lbs., and 24 years with a complex f Read before the Chemical Section, at the Montreal Meeting of the British Aasociation for the Advancement of Science, September 2, 1884.

The Experiments on the Mixed Herbage of Grass-land were commenced in 1856, and are still in progress, so that the present is the 44th year of their continuance. About seven acres are devoted to the purpose ; and since the first few years there have been 20 main plots, some of which have temporarily been subdivided. There are two continuously unmanured plots, and the remainder have respectively received different descriptions or quantities of manures of known composition. During the first 19 years, first crops only were removed from the land ; the second crops being fed by sheep, or if there were not sufficient for this, they were cut and spread. In the twentieth and subsequent years the second crops were cut, removed, and weighed, excepting in a few seasons when the produce was extremely small; in which cases it was cut and spread on the respective plots. In all cases of both first and second crops, the dry matter and the ash, and in most the nitrogen, have been determined. In selected cases, determinations have been made of the amount of nitrogen existing as albuminoids, and in some, of the amount of “ crude woody-fibre,” and of crude fatty matter. More than 200 complete analyses of the ashes of the produce have also been executed ; besides nearly 40 of the ashes of other crops, the results of which are given and considered. All the ashes have been prepared at Rothamsted, and the analyses made by Mr. R . Richter; in the earlier years in the Rothamsted Laboratory, but subsequently in his own laboratory at Charlottenburg, Berlin. Lastly, samples of the soil of every plot, in some cases at different periods, and generally representing the first, second, third, fourth, fifth, and sixth, depths of nine inches each, or to a total depth of 54 inches, have been collected ; and they have been chemically examined in various ways.