A proposal for a descriptive and convenient system of genetic nomenclature for bacteria was drafted by the staff and a number of visitors at Cold Spring Harbor in the summer of 1958 (Demerec, 1958). The proposal had as its basis a system developed by Demerec (1956), which largely adhered to previous genetic conventions yet avoided the complications that have developed in the genetic descriptions of some organisms. At conferences held during the summers of 1962 and 1963 the proposal was critically reviewed and revised in accordance with the increased number of genetic markers available, with usage in other areas (e.g. protein chemistry), with suitability for computer analysis, and with interim developments in bacterial genetics (Demerec, The current proposal is an outgrowth of its predecessors, developed by the present authors in consultation with colleagues in other laboratories and in other countries. The basic system has proven convenient to use in the laboratory and has greatly facilitated understanding and communication among many laboratories in the intervening years; increasing use of the system also speaks for its practicality. Thus this proposal does not intend to present a rigid, 'official', frozen system of nomenclature. The system is bound to evolve as knowledge advances in the future. The present communication is aimed at making widely available the proposal as developed to date. Comments, suggestions, and additions are welcome. The aims of the present proposal are: uniformity; a unique designation for each strain ; convenience for typing, editing, printing, record-keeping, and information retrieval ; and adaptability, simplicity, clarity, and comprehension by workers in all areas of biology; adaptability to new developments in the foreseeable future. The proposal takes the form of a set of guiding principles for dealing with categories where usage can be clearly defined; application to specific situations is left to each individual worker. The standardized system of genetic symbols is designed to serve the following purposes : (I) To distinguish clearly between symbols representing the genotype of a bacterial strain, and abbreviations of words which describe phenotypic properties. (2) To provide a uniform set of symbols for genetic loci, mutant alleles and mutation 1963).

It is a well-established fact that strains of bacteria resistant to various sulfa drugs, as well as strains resistant to penicillin, may readily be obtained by growing bacteria on media containing increasingly higher concentrations of the respective chemicals. The purpose of this study was to make a quantitative survey of the origin of resistant bacteria, and to clarify the genetic aspect of the mechanism through which resistance is formed. A preliminary report summarizing the results obtained is given below.Material and Method.-A strain of Staphylococcus aureus obtained from the Northern Regional Research Laboratory, Peoria, Illinois, carrying the N.R.R.L. number 313, was used in these experiments. This particular strain is employed by several laboratories for assaying penicillin. Before the experiment was started, a broth culture was prepared with bacteria from a single colony, and from this broth culture three agar slants were inoculated. These three stock cultures were kept in a refrigerator and served daily as the source of inoculum for all experiments. In a long series of experiments conducted over a considerable period of time, this procedure yields material that should be genetically more uniform than if the stock were maintained by consecutive transfers.Penicillin was taken from a lot of sodium salt of penicillin prepared by E. R. Squibb and Sons, New York, which was packed in ampules containing 25,000 Oxford units each. The material of one ampule was dissolved in 10 cc. of phosphate buffer of pH 6, and-kept in the refrigerator as a stock solution containing 2500 Oxford units of penicillin per cc. From this, other stock solutions containing 250 and 25 units per cc. were prepared under sterile conditions. Assays made at intervals indicated that the potency of penicillin in the stock solutions was not affected by storage.The resistance of the bacteria to penicillin was determined by mixing them with an agar-nutrient medium to which the penicillin solution had been added, and plating the mixture in a Petri dish. Precautions were taken not to have the agar warmer than 45 degrees Centigrade.In order to have a check of the potency of the penicillin, an assay was made for every experiment by diluting the solution used in that experiment to one Oxford unit per cc. and making a standard Oxford cup test. In this way any appreciable decrease in the potency of the penicillin solution would have been detected.Reaction of Staphylococcus to PeniciUin.-The strain of bacteria used in 16 PROC. X. A. S.

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