Detection of a cephalosporin C acetyl esterase in the carbamate cephalosporin antibiotic-producing culture, Streptomyces clavuligerus

The possible role of a cephalosporin C acetyl esterase in the formation of the beta-lactam antibiotic A16886A, 7-(5-amino-5-carboxyvaleramido)-3-carbamoyloxy-methyl-3-cephem-4-carboxylic acid, by Streptomyces clavuligerus was studied. Addition of dl-valine-(14)C-1 to a fermentation of Cephalosporium acremonium gave cephalosporin C-(14)C-9 (I). The formation of deacetylcephalosporin C-(14)C-9 from I occurred at a greater rate in broths of S. clavuligerus than in the broths of C. acremonium, or in the autoclaved broths of S. clavuligerus. Diisopropylfluorophosphate partially inhibited the deacetylation of I in S. clavuligerus broth. An intracellular cephalosporin C esterase in S. clavuligerus could not be demonstrated. Although A16886A has been chemically synthesized from deacetylcephalosporin C, this reaction could not be demonstrated with S. clavuligerus.     

Biosynthetic origin of hygromycin A

Hygromycin A, an antibiotic produced by Streptomyces hygroscopicus, is an inhibitor of bacterial ribosomal peptidyl transferase. The antibiotic binds to the ribosome in a distinct but overlapping manner with other antibiotics and offers a different template for generation of new agents effective against multidrug-resistant pathogens. Reported herein are the results from a series of stable-isotope-incorporation studies demonstrating the biosynthetic origins of the three distinct structural moieties which comprise hygromycin A. Incorporation of [1-(13)C]mannose and intact incorporation of D-[1,2-(13)C(2)]glucose into the 6-deoxy-5-keto-D-arabino-hexofuranose moiety are consistent with a pathway in which mannose is converted to an activated L-fucose, via a 4-keto-6-deoxy-D-mannose intermediate, with a subsequent unusual mutation of the pyranose to the corresponding furanose. The aminocyclitol moiety was labeled by D-[1,2-(13)C(2)]glucose in a manner consistent with formation of myo-inositol and a subsequent unprecedented oxidation and transamination of the C-2 hydroxyl group to generate neo-inosamine-2. Incorporation of [carboxy-(13)C]-4-hydroxybenzoic acid and intact incorporation of [2,3-(13)C(2)]propionate are consistent with a polyketide synthase-type decarboxylation condensation to generate the 3,4-dihydroxy-alpha-methylcinnamic acid moiety of hygromycin A. No labeling of hygromycin A was observed when [3-(13)C]tyrosine, [3-(13)C]phenylalanine, or [carboxy-(13)C]benzoic acid was used, suggesting that the 4-hydroxybenzoic acid is derived directly from chorismic acid. Consistent with this hypothesis was the observation that hygromycin A titers could be reduced by addition of N-(phosphonomethyl)-glycine (an inhibitor of chorismic acid biosynthesis) and restored by coaddition of 4-hydroxybenzoic acid. The convergent biosynthetic pathway established for hygromycin A offers significant versatility for applying the techniques of combinatorial and directed biosynthesis to production of new antibiotics which target the ribosomal peptidyl transferase activity.     

Some chemical and physical characteristics of pantomycin, and antiobiotic isolated from Streptomyces hygroscopicus.

The production, isolation, and some structural studies of an antifungal, antibacterial, and antiviral substance from cultures of Streptomyces hygroscopicus are described. This material, designated pantomycin, appears to be a polypeptide antibiotic with inclusion of fatty acids and carbohydrate residues. Amino acid analysis of pantomycin acid hydrolysates indicates that it contains threonine, serine, proline, glycine, alanine, valine, alloisoleucine, and an as-yet-unidentified amino acid which appears to be different from types encountered in proteinaceous materials. In addition to the aforementioned compounds, the antibiotic was shown to contain alpha-aminobutyric acid after hydrogenation. Analysis of ether extracts of the hydrolysate mixture indicated the presence of several fatty aicds; myristic, isotridecanoic, lauric, and undecylic acids. The amino and fatty acid composition of pantomycin is similar to the known antibiotic stendomycin. Pantomycin appears to also have at least one carbohydrate-like residue incorporated into its structure. The presence of carbohydrate was indicated by periodic acid-Schiff base staining of electrophoretic patterns as well as positive color formation in the phenol-sulfuric and Molisch tests, but the carbohydrate did not appear to be either a hexose or a pentose. The antibiotic, which appears to be dissociated in alcoholic solution, forms stable aggregates under aqueous conditons.     

Inhibition of antibacterial activity of himastatin, a new antitumor antibiotic from Streptomyces hygroscopicus, by fatty acid sodium salts.

Himastatin, a cyclohexadepsipeptide antibiotic, had in vivo antitumor activity against localized P388 leukemia and B16 melanoma but had no distal site antitumor activity. An in vitro Bacillus subtilis well-agar diffusion assay was employed to test the hypothesis that himastatin was enzymatically inactivated. The activity of himastatin against B. subtilis was inhibited when himastatin was mixed with mouse liver S9 fraction and microsomes. However, subsequent investigations demonstrated that the markedly decreased antibacterial activity was not enzymatic in nature but was related to the presence of certain fatty acid salts. Saturated fatty acid sodium salts with a carbon chain number of 8 or more reduced the antimicrobial activity of himastatin 50 to 100 times. If antibiotics such as ampicillin, bacitracin, chloramphenicol, and tunicamycin were used in place of himastatin, no meaningful reduction in antibacterial activity occurred. However, the antibacterial activity of the membrane-active peptide antibiotic polymyxin B, but not that of polymyxin E (colistin), was reduced in a manner similar to that of himastatin. Importantly, the activity of himastatin against HCT-116 colon adenocarcinoma cells in soft agar was markedly reduced in the presence of sodium palmitate as the reference fatty acid salt. The data indicate that himastatin may be trapped in micelles in vitro. It may be speculated that the lack of distal site antitumor activity resulted from similar complex formation between himastatin and lipids in vivo. The results also suggest that the cancer cytotoxic and antimicrobial effects of himastatin may result from interactions with the cell membrane.     

Genetic and enzymatic basis of hygromycin B resistance in Escherichia coli

A plasmid conferring resistance to the aminocyclitol antibiotic hygromycin B was isolated from Escherichia coli. The gene conferring resistance to this drug was cloned in pBR322, and the gene was localized to a fragment of ca. 1,510 base pairs. Resistance to hygromycin B is determined by an aminocyclitol phosphotransferase that modifies hygromycin B and structurally related antibiotics. The specific modification of hygromycin B is a phosphorylation of the hydroxyl on the 4 position of the cyclitol ring (hyosamine). The presence of the phosphotransferase in E. coli correlates with reduced accumulation of [14C]hygromycin B.     

In vitro antibacterial activity of CE-156811, a novel analog derived from hygromycin A

We evaluated a novel truncated hygromycin A analog in which the furanose ring was replaced with a 2-fluoro-2-cyclopropylethyl substituent for its activity against multidrug resistant gram-positive bacteria and compared its activity to the activities of linezolid, quinupristin-dalfopristin, and vancomycin. CE-156811 demonstrated robust in vitro activity against gram-positive bacteria that was comparable to that of linezolid.     

A nanoscopic icosahedral {Mo72Fe30} cluster catalyzes the aerobic synthesis of benzimidazoles

In this study, the catalytic efficiency of amorphous {Mo₇₂Fe₃₀} nanocapsules as a safe Keplerate polyoxometalate in organic synthesis was exploited. The easy-made solid catalyst exhibited high efficiency using a very low dosage (0.02–0.05 mol%) in the catalyzed condensation of various aromatic 1,2-diamines and aldehydes for the aerobic synthesis of benzimidazoles with very small E-factor values (0.11–0.33). The superior catalytic activity of amorphous nanoclusters compared to that of its crystalline counterpart was demonstrated. The high activity and recyclability of heterogeneous catalysts in a green reaction media under oxygen atmosphere, make this environmentally benign organic process appropriate for our applied goals.

Catalytic activity of amorphous {Mo₇₂Fe₃₀} nanoclusters as a safe Keplerate polyoxometalate in aerobic synthesis of benzimidazoles was described.     

血标本细菌培养菌株的分布

目的:分析菌血症、败血症的菌种分布,为菌血症、败血症的临床抗感染治疗经验用药提供帮助。方法 全自动血培养仪检测有细菌生长后,转种相应平板,36℃孵育18～24小时,用全自动微生物鉴定仪进行菌种鉴定。结果 血液标本中分离出的细菌菌种分布较广,以金黄葡萄球菌和大肠埃希氏菌为主,占40％以上,微球菌及凝固酶阴性葡萄球菌的分离率占20％,伤寒沙门氏菌及副伤寒沙门氏菌的分离率占10％。结论;对菌血症、败血症的患者应尽快作出微生物学诊断,争取尽早在药敏试验结果指导下进行临床抗感染治疗。     

Sucrose formation in the human and animal organism

Using paper chromatography as well as chemical and enzymatic methods it has been found that sucrose is a usual component of human and animal urine. Its concentration in the urine varies from 10 to 100 mg % and does not change significantly on diet which does not contain sucrose. After prolonged total starvation the daily amount of sucrose in the urine of the patients reached 200–300 mg. These data suggest that sucrose is endogenous by origin. Sucrose was isolated also from human foetal kidneys, from foetal cows kidneys and from kidneys of adult rabbits after 3–6 days of total starvation. Its quantity varied from 9.6 to 82.0 mg %. The kidneys are supposed to be the most probable site of sucrose synthesis in the human and animal organism.