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PubMed1976

Fluorescent pseudomonads capable of growth at 41 degrees C but distinct from Pseudomonas aeruginosa.

One hundred and twenty-seven apyocyanogenic fluorescent Pseudomonas strains capable of growth at 41 degrees C, but differing from Pseudomonas aeruginosa, were typed serologically and tested for pyocin production, antibiotic susceptibility, selected biochemical reactions, and utilization of selected substrates. Results were compared with those from 40 apyocyanogenic and 14 pyocyanin-producing strains of P. aeruginosa. Unidentified fluorescent Pseudomonas (UFP) strains generally were not agglutinated by P. aeruginosa antisera and showed little or no pyocin activity. In contrast to P. aeruginosa strains, UFP strains usually failed to oxidize D-gluconate or reduce nitrate to nitrogen gas. They could not use D-gluconate or D-mannitol as sole carbon source and were susceptible to kanamycin. The cellular fatty acid compositions of major UFP groups resembled those of the alcaligenes-stutzeri groups.

Anti-Bacterial Agents↗

PubMed1975

Morphology and physiology of Spirochaeta aurantia strains isolated from aquatic habitats.

1. Seven strains of Spirochaeta aurantia were isolated from pond and swamp water by means of a selective technique which utilized the ability of these organisms to move through bacterial filters and to diffuse through agar media. Although most of the isolations were accomplished when enrichment media low in carbohydrates were used, all seven strains were found to be exclusively saccharolytic. 2. The isolates could be divided into two groups on the basis of cell morphology: a loosely coiled group, and a tightly coiled group with markedly smaller wave length and wave apmlitude. Spirochetes of the latter group possessed a slightly lower GC content in their DNA. The isolates were facultative anaerobes, synthesized carotenoid pigments which conferred an orange color to aerobic colonies, and utilized a variety of carbohydrates--but not amino acids--as energy sources. Exogenous thiamine was required by six isolates tested, riboflavin by four, and biotin by one. The major products of glucose fermentation were acetate, ethanol, CO2 and H2. Growth of the isolates was inhibited by a variety of antibiotics. Determinations of GC contents of DNA showed that strains of S. aurantia are phylogenetically distant from spirochetes classified in the genera Treponema and Leptospira. 3. S. aurantia populations inoculated in the center of agar medium plates migrated in the form of growth rings toward the periphery of the plates. The rate of migration of glucose-utilizing rings was greatest at low glucose concentrations (e.g., 0.02 g/100 ml). It was concluded that migration of cells present in these rings was mainly due to a chemotactic response to glucose which served both as the attractant and the substrate. Chemotaxis of S. aurantia toward glucose may be used as a selective factor in isolating this bacterium from natural environments. 4. The subspecific epithet stricta is proposed to recognize, taxonomically, the tightly coiled strains of S. aurantia.

Aerobiosis↗

PubMed1975

High-temperature production of protein-enriched feed from cassava by fungi.

A simple, nonaseptic, low-cast process for the conversion of cassava, a starchy tropical root crop, into microbial protein for use as animal feed was sought. Screening tests culminated in the isolation of a thermotolerant, amylase-producing mold, designated I-21, which was identified as Aspergillus fumigatus. The optimum pH for protein synthesis was 3-5, but the optimum temperature was less than the desired temperature (larger than or equal to 45 C) required for a nonaseptic fermentation. A. fumigatus I-21 and its asporogenous mutant I-21A grew equally well in a medium prepared from whole cassava roots with a mean protein doubling time at 45 C and pH 3.5 of 3.5 h. In batch culture, approximately 4% carbohydrate, supplied as whole cassava, could be feremented in 20 h, giving a final yield of 24 g of dry product, containing 36.9% crude protein, per liter. The conversion of carbohydrate used to crude protein was 22.1%. When determined as amino acids, the protein content of the product, which contained cassava bark and other unfermented residues, was 27.1%. With urea as the nitrogen source, no pH control was necessary. Preliminary data indicated that medium prepared from whole cassava roots was inhibitory to the mold unless the cassava pulp was heated to 70 C immediately after being ground. Heating to 70 C was required to gelatinize the starch and permit its complete utilization.

Animal Feed↗

PubMed2026

Discovery of Glycosylated β-Amino Acid-Containing Macrolactams from Nonomuraea sp. 0L2P via Genome Mining.

β-Amino acid-containing macrolactams (β-AACMs) are a class of bioactive natural products characterized by nitrogen-containing starter units within polyketide-derived macrocycles. Here, we report four previously undescribed macrolactams, gruelactams A-D (1-4), from Nonomuraea sp. 0L2P, discovered through an integrated approach combining genome mining, 15N-labeling, and antibacterial screening. Their planar structures were elucidated by comprehensive spectroscopic analyses, including 1D and 2D NMR and HRESI-MS, and their configurations were partially assigned based on ROESY data and bioinformatic analysis. Genome sequencing and antiSMASH analysis identified a putative type I polyketide synthase (PKS) biosynthetic gene cluster, enabling the proposal of a biosynthetic pathway. Bioactivity assays showed that gruelactam D (4) exhibits antibacterial activity against Bacillus cereus and Staphylococcus aureus, with MIC values of 8 and 16 μg/mL, respectively. These findings expand the chemical diversity of β-AACMs and demonstrate the utility of genome-guided approaches for discovering bioactive natural products from rare actinomycetes.

Anti-Bacterial Agents↗

PubMed1978

The biology of the gonococcus.

Gonorrhea has been known since antiquity. Today, this disease is the most commonly reported infectious disease in the U.S. The natural environment of the etiological agent, Neisseria gonorrhoeae, is man. In this host, the organism usually parasitizes mucosal surfaces populated by columnar epithelial cells. Under certain conditions, the gonococcus may disseminate or spread to adjacent organs. The gonococcus is well adapted to its environment and is a successful parasite. Until recently, gonococci were uniformly sensitive to penicilin. However, a plasmid encoding beta-lactamase has been identified in some isolates. Most strains exhibit specific requirements for various amino acids, vitamins, purines, and pyrimidines. Only glucose, pyruvate, and lactate are utilized as sources of energy. Glucose is dissimilated by a combination of the Entner-Doudoroff and pentose phosphate pathways. A tricarboxylic acid cycle is also present and active under certain conditions. Structurally, the cell envelope of the gonococcus resembles that of a typical Gram-negative bacterium. Gonococci are highly autolytic, especially in older cultures or after depletion of the energy source. Autolysis is not due solely to peptidoglycan hydrolysis, but appears to involve a destabilization of the outer membrane as well. Cell surface components such as pili, lipopolysaccharide, outer membrane proteins, and a capsule are associated with the virulence and pathogenicity of this organism.

Amino Acids↗

PubMed1977

Arginine hydroxamate-resistant mutants of Bacillus subtilis with altered control of arginine metabolism.

Arginine hydroxamate inhibits the growth of Bacillus subtilis. From a large number of mutants isolated as resistant to this arginine analogue, 29 were chosen for further investigation. Most of these shared diminished ability to utilize arginine, citrulline and/or ornithine as sole nitrogen source. All 29 had reduced levels of the catabolic enzymes arginase and ornithine aminotransferase under various conditions in which these enzymes are induced in the parent. In some circumstances, five of the mutants also showed elevated levels of the biosynthetic enzyme ornithine carbamoyltransferase. On the basis of these data, the 29 mutants were divided into six phenotypic classes; in four of these, control of ornithine carbamoyltransferase was the same as in the wild type, while in the other two it was altered. It is suggested that the isolates carry regulatory mutations, and that certain of these may affect simultaneously the formation of arginine catabolic and biosynthetic enzymes. The implication of the latter is that in B. subtilis, as in yeast, controls of the catabolic and biosynthetic pathways are connected. Single representatives of five of the phenotypic classes carry mutations conferring arginine hydroxamate resistance linked to cysA by transduction with phage PBSI; this did not appear to be true for a representative of the sixth class.

Arginase↗

PubMed1992

Influence of outer membrane mutations on susceptibility of Escherichia coli to the dibasic macrolide azithromycin.

Azithromycin differs chemically from erythromycin by having an extra positive charge created by the presence of a methyl-substituted nitrogen in the 15-membered macrolide ring. This results in substantially increased potency against Gram-negative bacteria. Therefore, the possibility was considered that azithromycin was taken across the outer membrane of Escherichia coli by the self-promoted uptake route, which is utilized by other cationic antibiotics including polymyxins and aminoglycosides. Azithromycin, like polymyxin B and gentamicin, demonstrated equal activity against porin-sufficient and porin-deficient E. coli strains but its MIC was increased eight-fold by magnesium supplementation. Nevertheless, an outer membrane-altered mutant DC2 was eight-fold more susceptible than its parent strain UB1005 to azithromycin, indicating that the outer membrane was a permeability barrier to this macrolide. A mutant SC9252 which had an alteration in the self-promoted uptake of polymyxin and gentamicin, was more resistant to azithromycin, polymyxin and gentamicin compared to its parent SC9251. Further azithromycin, like polymyxin B and gentamicin, was capable of weakly permeabilizing cells to the hydrophobic fluorophor 1-N-phenyl-naphthylamine, a process antagonized by Mg2+. The monobasic macrolide erythromycin on the other hand was less affected by the SC9252 mutation, less effectively antagonized by Mg2+, and was a far less effective permeabilizer than dibasic azithromycin. These data are consistent with the hypothesis that the improved efficacy of azithromycin compared to erythromycin against E. coli reflects its better access to the self-promoted uptake pathway due to its additional positive charge.

Azithromycin↗