Cyanophycin-degrading bacteria in digestive tracts of mammals, birds and fish and consequences for possible applications of cyanophycin and its dipeptides in nutrition and therapy.

AIMS: To determine the susceptibility of cyanophycin granule polypeptide (CGP) to degradation by several mammalian, avian and fish gut flora. METHODS AND RESULTS: Samples of gut flora were investigated for the occurrence of bacteria capable of CGP degradation. With all samples, a complete anaerobic degradation of CGP was achieved over incubation periods of only 12-48 h at 37 degrees C. CGP-degrading bacteria were detected in all samples, and they occurred in particular high titres in caecum flora from rabbit and sheep and in the digestive tract of carp fish. A total of 62 axenic cultures were isolated. All degraded CGP aerobically, 46 of them degraded CGP also anaerobically over incubation periods ranging from 24 h to 7 days. HPLC analysis revealed that all isolates degraded CGP to its constituting dipeptides. Eight strains were identified by 16S rRNA gene sequencing and were affiliated to the genera Bacillus, Brevibacillus, Pseudomonas, Streptomyces and Micromonospora. CONCLUSIONS: These data demonstrate for the first time the occurrence of a natural niche for CGP in the digestive tracts of animals. SIGNIFICANCE AND IMPACT OF THE STUDY: The biodegradability of CGP by gut flora provides a first confirmation for the potential applications of CGP and its dipeptides in nutrition and therapy as highly bio-available sources for arginine, lysine, aspartate and possibly also other amino acids.

Isolation and characterization of an Achromobacter xylosoxidans strain B3 and other bacteria capable to degrade the synthetic chelating agent iminodisuccinate.

Three bacterial strains were isolated, which used the synthetic chelating agent iminodisuccinate (IDS) as sole carbon source for growth in mineral salts media (MSM). Taxonomic analysis and 16S rDNA sequence analysis identified one of these isolates (B3), which was isolated from sewage sludge, as a strain of Achromobacter xylosoxidans subsp. xylosoxidans. It exhibited a doubling time of approximately 3 h in liquid MSM supplemented with IDS and grew even in the presence of 1.0% (w/v) IDS. Since photometric and high performance liquid chromatography analysis showed that IDS, which came onto the market only recently as an alternative for ethylenediaminetetraacetate, was completely degraded by axenic cultures of bacteria; it will probably be readily degraded in the environment.

Synthesis of medium-chain-length polyhydroxyalkanoates in arabidopsis thaliana using intermediates of peroxisomal fatty acid beta-oxidation.

Polyhydroxyalkanoate (PHA) is a family of polymers composed primarily of R-3-hydroxyalkanoic acids. These polymers have properties of biodegradable thermoplastics and elastomers. Medium-chain-length PHAs (MCL-PHAs) are synthesized in bacteria by using intermediates of the beta-oxidation of alkanoic acids. To assess the feasibility of producing MCL-PHAs in plants, Arabidopsis thaliana was transformed with the PhaC1 synthase from Pseudomonas aeruginosa modified for peroxisome targeting by addition of the carboxyl 34 amino acids from the Brassica napus isocitrate lyase. Immunocytochemistry demonstrated that the modified PHA synthase was appropriately targeted to leaf-type peroxisomes in light-grown plants and glyoxysomes in dark-grown plants. Plants expressing the PHA synthase accumulated electron-lucent inclusions in the glyoxysomes and leaf-type peroxisomes, as well as in the vacuole. These inclusions were similar to bacterial PHA inclusions. Analysis of plant extracts by GC and mass spectrometry demonstrated the presence of MCL-PHA in transgenic plants to approximately 4 mg per g of dry weight. The plant PHA contained saturated and unsaturated 3-hydroxyalkanoic acids ranging from six to 16 carbons with 41% of the monomers being 3-hydroxyoctanoic acid and 3-hydroxyoctenoic acid. These results indicate that the beta-oxidation of plant fatty acids can generate a broad range of R-3-hydroxyacyl-CoA intermediates that can be used to synthesize MCL-PHAs.