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In our continued search for the production of j3-lactam-containing molecules from bacteria, we report the isolation and structure determination of a simple carbapenem SQ 27,860, produced by species of Serratia and Erwinia. The antibiotic is highly unstable and isolation was achieved through the p-nitrobenzyl ester.

Two new acetylenic antibiotics, cepacins A and B, have been isolated from the fermentation broth of Pseudomonas cepacia SC 11,783 and assigned structures 1 and 2. Cepacin A has good activity against staphylococci (MIC 0.2 / 50 µg/ml). Cepacin B has excellent activity against staphylococci (MIC <0.05 Erg/ml) and some Gramnegative organisms (MIC values 0

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Aerocyanidin, a new antibiotic containing an isonitrile group, has been isolated from fermentations of Chromobacterium violaceum ATCC53434. Structure 1 was assigned on the basis of spectroscopic characterization of the antibiotic and of a degradation product that results from treatment with base. The antibiotic is primarily active against Gram-positive bacteria.In the course of screening for new antibiotics with activity against Gram-positive bacteria, it was found that Chromobacterium violaceum ATCC53434 produces two novel antibiotics. One of these, aerocavin, is the subject of the preceding paper1} in which the producing organism is described. The other antibiotic, aerocyanidin, is the subject of this paper. FermentationSeed culture was prepared by transferring loopfuls of surface growth from an agar slant into 500-ml Erlenmeyer flasks containing 100-ml portions of Nutrient medium composed of Tryptone 0.5 %, malt extract 0.3 %, glucose 1.0% and yeast extract 0.3 % in distilled water. The flasks were incubated for 24 hours at 25°C on a rotary shaker (300 rpm, 5.1-cm stroke) and the contents used to inoculate additional 100-ml portions of the same mediumthat were incubated under the same conditions. This growth was used as inoculum (1.5 %) for 250 liters of medium consisting of Tryptone 0.5 %, malt extract 0.3%, cerelose hydrate 1.1 %, yeast extract 0.3% and Ucon-LB 625 0.05% in distilled water. The fermentation was carried out in a 380-liter stainless steel vessel for 24 hours at 25°C with an agitation rate of 130 rpm and an air flow of 285 liters/minute. IsolationThe isolation of aerocyanidin was monitored by conventional paper-disc agar diffusion assay using Staphylococcus aureus FDA209P as the test organism and also colorimetrically with a modified Sievert-Hermsdorf method2). The lability of this antibiotic caused considerable difficulty in devising an efficient isolation procedure. Silica gel chromatography was particularly unsuitable because of extensive decomposition on this adsorbent.However, a combination of countercurrent chromatography using a high-speed countercurrent chromatograph followed by reversed-phase chromatography on a macroreticular polystyrene resin proved highly effective in giving essentially pure aerocyanidin. The procedure outlined in Fig. 1 gave an overall recovery of activity from the crude ethyl acetate extract to the final crystalline antibiotic of 33 % based on the colorimetric Sievert-Hermsdorf assay.

Xylocandins Ai, A2, Bl5 B2, Q, C2, Dx and D2 are new antifungal peptides isolated from Pseudomonascepacia ATCC 39277. The molecular weights of the xylocandins were determined by fast atom bombardment mass spectrometry (Ai m/z 1,215; A2 1,199; Bx 1,229; B2 1,213; Ci 1,097; C2 1,081; T>x 1,083; D2 1,067). Each xylocandin is a cyclic peptide containing glycine (1), serine (2), asparagine (1~3 residues), /J-hydroxytyrosine (1), and an unusual amino acid with the formula Ci8H37NO5 (1). Additionally Al9 A2, D: and D2 contain 2,4-diaminobutyric acid (1) ; Au B1? Q and Dx contain erythro-P-hydroxyaspamgim(1); and A1? A2, Bx and B2 contain xylose (1). For each xylocandin pair, an erjtf/zr0-/3-hydroxyasparagine residue in the first component of the pair is thus replaced by an asparagine in the second component, accounting for the 16 dalton mass difference for each pair. Chemical modification of Ai and A2 at the diaminobutyric acid and^S-hydroxytyrosine residues was used to probe structural requirements for activity.Xylocandin is a complex of novel peptide antibiotics produced by Pseudomonas cepacia exhibiting potent activity in vitro against dermatophytes and yeasts, including Candida albicans. Details of the discovery, isolation and biological activity of four pairs of xylocandin components (Ax and A2, B2 and B2, Q and C2, and Dx and D2) are described in the preceding paper13. In this paper we describe the characterization of these eight componentsas well as chemical modifications of the AJA2pair designed to probe structural requirements for activity.Efficient preparative-scale procedures for the separation of the two components of each xylocandin pair were not found, although small quantities of A1 and A2 could be isolated by preparative TLC as described below. Therefore, with the exception of some separate analyses for Ax and A2, all chemical and spectral analyses were carried out on the xylocandins as two-component mixtures, i.e. AJA29 BJB2, Q/Qj and T>JT>2' Someanalyses were not carried out on the T>JD2 pair due to insufficient quantities of this material.Lowresolution fast atom bombardmentmass spectrometry (FAB-MS)of each xylocandin pair provided clean parent ion data for each component, indicating the following molecular weights: A± XHNMRspectra for the AJA2, BJB2 and CJC2 pair are shown in Figs. 1 and 2, respectively. UV absorbance data is shown in Table 1. The total acid hydrolysate (6 n HC1, 18 hours, 105°C) of each xylocandin pair was analyzed and the results are summarized in Table 2. For each xylocandin pair, integral ratios of glycine, serine, and, where present, 2,4-diaminobutyric acid were found. Non-integral values were recorded for aspartic acid, however. These values fell between one and two residues (relative to glycine) for AJA2 and Di/D2, and between two and three residues (relative to glycine) for BJB2 and CJC2. Erythro-

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