Biochemical characteristic of non-streptomycin-producing mutants ofStreptomyces griseus. II. Lipids and fatty acid composition of vegetative mycelia

Comparative and functional genomics of Rhodococcus opacus PD630 for biofuels development

The Actinomycetales bacteria Rhodococcus opacus PD630 and Rhodococcus jostii RHA1 bioconvert a diverse range of organic substrates through lipid biosynthesis into large quantities of energy-rich triacylglycerols (TAGs). To describe the genetic basis of the Rhodococcus oleaginous metabolism, we sequenced and performed comparative analysis of the 9.27 Mb R. opacus PD630 genome. Metabolic-reconstruction assigned 2017 enzymatic reactions to the 8632 R. opacus PD630 genes we identified. Of these, 261 genes were implicated in the R. opacus PD630 TAGs cycle by metabolic reconstruction and gene family analysis. Rhodococcus synthesizes uncommon straight-chain odd-carbon fatty acids in high abundance and stores them as TAGs. We have identified these to be pentadecanoic, heptadecanoic, and cis-heptadecenoic acids. To identify bioconversion pathways, we screened R. opacus PD630, R. jostii RHA1, Ralstonia eutropha H16, and C. glutamicum 13032 for growth on 190 compounds. The results of the catabolic screen, phylogenetic analysis of the TAGs cycle enzymes, and metabolic product characterizations were integrated into a working model of prokaryotic oleaginy.

Relationship between the fatty acid composition and the type of antibiotics produced by Streptomyces lasaliensis

The GC-MS method was used to analyze fatty acids in a parent strain of Streptomyces lasaliensis and its two mutants producing only lasalocid or quinomycin. The biosynthesis of these substances bears relation to differences in the relative proportion of fatty acids. Biosynthetic relationships were revealed between the starter fatty acid units, their precursors, i.e. valine, leucine and isoleucine, and the type of the antibiotic produced.

Fatty acids and production of tylosin-like compounds in Streptomyces fradiae

The composition of fatty acids and the spectrum of macrolide antibiotics produced in 7 mutant strains of Streptomyces fradiae, a tylosin producer, were investigated. The strains under investigation differed in the production level and representation of individual tylosin-like compounds. The composition of fatty acids in the mycelium did not depend on the total production. However, the strains producing relomycin in addition to tylosin produced a significantly higher fraction of fatty acids with a higher melting point, and, on the contrary, the strains producing only tylosin or tylosin and desmycosin synthesized a significantly lower proportion of these acids. The results obtained indicate that in addition to the activity and substrate specificity of secondary metabolism enzymes, the composition of the tylosin-like compounds produced can be influenced by the cell membrane and its function.

Freeze-fracture observations of Corynebacterium glutamicum: the occurrence of an outer membrane-like structure and the influence of temperature on the cytoplasmic membrane

In order to elucidate temperature-dependent morphological changes in the cell envelope of the Gram-positive L-lysine-overproducing Corynebacterium glutamicum 9366 we carried out freeze-fracture investigations of native cells and studied their fatty acid composition. In addition to the cytoplasmic membrane C. glutamicum possesses at the periphery of the cell an additional fracture plane which is unusual in Gram-positive bacteria and is designated here as outer membrane-like structure. The fracture faces of this layer display a distinguishable appearance in several regions of the cell. Bacteria grown at various temperatures showed changes in the relation of the saturated to unsaturated fatty acids. We demonstrated that the cytoplasmic membrane was affected by these changes in the fatty acid composition.

Influence of inorganic phosphate on the lipid synthesis of a phosphate-deregulated mutant of Streptomyces noursei

Phosphate-dependent changes of the mycelial lipid composition were studied in the streptothricin-producing parental strain Streptomyces noursei JA 3890 b/2 and its mutant RG 2. In contrast to its ancestor, the mutant was capable of producing the antibiotic nourseothricin even when large quantities of inorganic phosphate were present in the medium. The apparent insensitivity of the secondary metabolism to phosphate inhibition corresponds to a decreased level of phospholipids in the presence of excessive inorganic phosphate and, during phosphate limitation, to a much higher production of the alkaline phosphatases. A model is discussed which proposed the control by a common genetic element of both the phospholipid and antibiotic production.

Fatty acids of Streptomyces cinnamonensis, producer of monensin

Using the gas chromatography-mass spectrometry (GC-MS) method we found in Streptomyces cinnamonensis saturated fatty acids of iso- and anteiso- types, cyclopropyl acids, and unsaturated fatty acids where the double bond position was determined by MS of their pyrrolidine derivatives.

Substructural study of sporogenesis in Streptomyces griseus

A Streptomyces griseus strain deficient in the formation of aerial mycelium and arthrospore development (Amy-) was studied by electron microscopy and compared with the sporulating parental strain (Amy+). The investigations were performed with colonies grown on solid medium. The substructural characteristics of the essential events of sporogenesis could clearly been demonstrated in the aerial mycelium of the Amy+ colonies. The mycelium of the surface region of the Amy- colonies showed altered features. The most pronounced alteration was the absence of the surface sheath, normally present on the aerial hyphae of the parental strain. The cross wall type II, characteristic of sporogeneous hyphae, was not discernible in the Amy- hyphae. Some substructural features resembling the essential events of normal sporogenesis were evident in the Amy- strain, albeit diminished and interfered with by abnormalities. The resulting propagative cells were of different size and feature.

Effect of the autoregulator from Streptomyces griseus JA 5142 on surface cultures of blocked mutant ZIMET 43682

Zero time addition of the autoregulator (L-factor) from S. griseus (Lkm+Amy+) to surface cultures of its bald mutant ZIMET 43 682 (Amy-Lkm-) restored the capacity to form both anthracycline-type antibiotic leukaemomycin and aerial mycelium. The pertinent mycelia displayed the same growth rate and cellular levels of nucleic acids as the asporogeneous phenotype but the composition of fatty acids and phospholipids as well as the ratio of cytochromes b and c were altered. These differences indicate alterations in the cellular architecture of substrate and aerial hyphae. The results suggest that the autoregulator triggers the onset of a complex programme of differentiation at a very early stage.

Effect of l-valine and l-isoleucine on fatty acid composition of Streptomyces hygroscopicus and S. griseus

The effects of L-valine and L-isoleucine on the composition of mycelial fatty acids were investigated during growth of differentiating parent strains of Streptomyces hygroscopicus and Streptomyces griseus as well as their non-differentiating derivatives (Amy-strains) on a synthetic medium. Both in the Amy+ and Amy- strains, in the presence of L-valine, the portion of the isopalmitic acid (iC16:0) increased, but the addition of L-isoleucine led to an elevated level of the 12-methyltetradecanoic acid (aC15:0). The results suggest that the genetically determined alterations in the ratio of both fatty acids in the non-differentiating derivatives may be due to specific changes in the biosynthetic pathways of both amino acid precursors rather than due to changes of their catabolism.

Genetic segregation in a high-yielding streptomycin-producing strain of Streptomyces griseus

The streptomycin-producing Streptomyces griseus HP spontaneously segregated non-reverting derivatives with altered phenotypes. Clones characterized by increased spore formation and decreased streptomycin production were found. Two other types of derivatives were defective in aerial mycelium and streptomycin formation as well, but differed in the capacity to synthesize a yellow pigment. These derivatives were examined with respect to further properties. The stability of S. griseus HP was investigated in relation to conditions of continuous culture. Both at 26 and 30 degrees C, under glycerol and NH4Cl limitation a rapid segregation and enrichment of streptomycin-non-producing derivatives occurred. At 34 degrees C and glycerol limitation segregation began only after about 35 generations of continuous culture. In NH4Cl-limited chemostats the original strain was stable during 80 generations. In the course of the continuous culture experiments it was shown that the onset of genetic segregation within mycelia can be detected before it becomes obvious in colonies grown from the mycelia. This was achieved by fractionation of the mycelia by protoplast formation and subsequent plating on regeneration medium allowing colony growth and differentiation.