Bicarbonate-stimulated dark fermentative growth of a phototrophic purple nonsulfur bacterium

Abstract Two strains of soil bacteria, Pseudomonas cepacia and Pseudomonas alcaligenes , which degrade herbicides have been isolated. Both contain plasmids whose presence is correlated with the capacity to metabolise phenylcarbamates. Successive subculturing in the absence of herbicide or curing my mitomycin C leads to the loss of small plasmids from both strains associated with modifications in herbicide degradation. Further, the level of the smallest plasmid of P. cepacia increases when CIPC is the sole carbon source. This plasmid hybridises to several larger molecular species, suggesting a certain degree of structural rearrangement in response to the presence of the herbicide.     

Induction of phenazine biosynthesis in cultures of Pseudomonas aeruginosa by L-N-(3-oxohexanoyl) homoserine lactone

Abstract A range of Pseudomonas spp. and other Gram-negative bacteria were screened for induction of antimicrobial activity in response to the autoregulatory factor l - N -(3-oxohexanoyl)homoserine lactone. In one of these, P. aeruginosa ATCC 10145, the production of phenazine metabolites was shown to be inducible in a dose-dependent manner. The production of phenazine-1-carboxamide increased over 50-fold compared to control cultures when supplemented with 200 μg/ml of the autoregulator. In addition, the production of an unidentified polar antibacterial substance by this strain increased with autoregulator concentration.     

Role of extracellular polymeric substances in Cu(II) adsorption on Bacillus subtilis and Pseudomonas putida

The effect of extracellular polymeric substances (EPS) of Gram-positive Bacillus subtilis and Gram-negative Pseudomonas putida on Cu(II) adsorption was investigated using a combination of batch adsorption, potentiometric titrations, Fourier transform infrared spectroscopy. Both the potentiometric titrations and the Cu(II) adsorption experiments indicated that the presence of EPS in a biomass sample significantly enhance Cu(II) adsorption capacity. Surface complexation modeling showed that the pK_a values for the three functional groups (carboxyl, phosphate and hydroxyl) were very similar for untreated and EPS-free cells, indicating no qualitative difference in composition. However, site concentrations on the untreated cell surface were found to be significantly higher than those on the EPS-free cell surface. Infrared analysis provided supporting evidence and demonstrated that carboxyl and phosphate groups are responsible for Cu(II) adsorption on the native and EPS-free cells.     

In vitro lung delivery of bacteriophages KS4‐M and ΦKZ using dry powder inhalers for treatment of Burkholderia cepacia complex and Pseudomonas aeruginosa infections in cystic fibrosis

Aims: To determine the feasibility of formulating and aerosolizing powders containing bacteriophages KS4‐M and ΦKZ for lung delivery and treatment of pulmonary Burkholderia cepacia complex and Pseudomonas aeruginosa infections. Methods and Results: Endotoxin‐removed bacteriophages KS4‐M and ΦKZ were lyophilized in lactose/lactoferrin 60 : 40 w/w matrix and deagglomerated in a mixer mill (without beads) to formulate respirable powders. The powders were then aerosolized using an Aerolizer^® capsule inhaler. Mass median aerodynamic diameter (MMAD) of this inhalable aerosol was determined using Andersen cascade impactor at 60 l min^?1. Measured MMAD for both types of powders was 3·4 μm, and geometric standard deviation was 1·9–2·0. Viability of bacteriophages delivered distal to an idealized mouth‐throat replica was determined from bioassays of samples collected on filters placed after the idealized replica. As a percentage of inhaler load, amount of powder delivered distal to the mouth‐throat replica, which is a measure of lung delivery, was 33·7 ± 0·3% for KS4‐M and 32·7 ± 0·9% for ΦKZ. Titres collected downstream of the mouth throat were (3·4 ± 2·5) × 10⁶ PFU for KS4‐M with an Aerolizer capsule load of (9·8 ± 4·8) × 10⁶ and (1·9 ± 0·6) × 10⁷ for ΦKZ with an Aerolizer capsule load of (6·5 ± 1·9) × 10⁷. Conclusions: Bacteriophages KS4‐M and ΦKZ can be lyophilized without significant loss of viability in a lactose/lactoferrin 60 : 40 w/w matrix. The resulting powders can be aerosolized to deliver viable bacteriophages to the lungs. Significance and Impact of the Study: Development of lactoferrin‐based bacteriophage aerosol powders solidifies the ground for future research on developing novel formulations as an alternative to inhaled antibiotic therapy in patients with cystic fibrosis.     

Photosynthetic and quasi-photosynthetic bacteria

Abstract Nine different bacterial strains that utilise phenylacetic acid as the only carbon and energy source were isolated from samples of different geographical origin. The isolates were characterised taxonomically and physiologically. Evidence is presented that in all the isolates as well as in four previously isolated control strains with the ability to utilize phenylacetic acid, the enzyme phenylacetate-CoA ligase is specifically induced during growth on phenylacetic acid. The Michaelis constant ( K _m) in one Pseudomonas strain was sufficiently low (-1 mM) to suggest that the enzyme may have a role in phenylacetic acid metabolism.     

Biosoftening of coir fiber using selected microorganisms

Coir fiber belongs to the group of hard structural fibers obtained from coconut husk. As lignin is the main constituent of coir responsible for its stiffness, microbes that selectively remove lignin without loss of appreciable amounts of cellulose are extremely attractive in biosoftening. Five isolated strains were compared with known strains of bacteria and fungi. The raw fiber treated with Pseudomonas putida and Phanerocheate chrysosporium produced better softened fiber at 30±2 °C and neutral pH. FeSO₄ and humic acid were found to be the best inducers for P. chrysosporium and P. putida, respectively, while sucrose and dextrose were the best C-sources for both. Biosoftening of unretted coir fibers was more advantageous than the retted fibers. Unlike the weak chemically softened fiber, microbial treatment produced soft, whiter fibers having better tensile strength and elongation (44.6–44.8%) properties. Scanning electron microscopy photos showed the mycelia penetrating the pores of the fiber, removing the tylose plug and degrading lignin.     

Influence of petroleum contamination and biostimulation treatment on the diversity of Pseudomonas spp. in soil microcosms as evaluated by 16S rRNA based-PCR and DGGE

AIMS: The aim of this study was to apply a group specific PCR system followed by denaturing gradient gel electrophoresis (DGGE) analysis to evaluate the effect of oil contamination and the biostimulation process on the diversity of Pseudomonas populations in soil ecosystems. METHODS AND RESULTS: Direct DNA extraction from biostimulated- and oil-contaminated soil samples was performed. Primers specific for the genus Pseudomonas spp. were used to amplify 16S rRNA genes and then a semi-nested PCR reaction was applied to obtain smaller fragments for comparing the PCR products by DGGE. Whether in bulk, oil-contaminated or biostimulated soils, the DGGE profiles revealed little change in Pseudomonas community throughout the 270 days of experiment. The presence of a few additional bands observed only in treated samples indicated that a bacterial shift occurred with the addition of nutrients and with oil contamination. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of semi-nested PCR and DGGE was found to be a rapid and sensitive technique to study the diversity within the genus Pseudomonas and may be suitable for further studies concerning the role of this bacterial group in large-scale oil-contaminated areas.     

Revised structures for the capsular polysaccharides from Staphylococcus aureus Types 5 and 8, components of novel glycoconjugate vaccines

Glycoconjugate vaccines based on the capsular polysaccharides (CPSs) from Staphylococcus aureus serotypes 5 and 8 conjugated to genetically detoxified recombinant exoprotein A (rEPA) from Pseudomonas aeruginosa have been shown, in Phase 3 clinical trials, to elicit a strong bactericidal immune response in end-stage renal disease patients. Such vaccines have the potential to reduce morbidity and mortality due to methicillin-resistant Staphylococcus aureus (MRSA), a major cause of hospital-acquired infection. The serotype 5 and 8 polysaccharides have been fully characterized by NMR spectroscopy and full structural analyses carried out. Published structures were found incorrect and the revised structures of the repeat units of the two polysaccharides are: [carbohydrate structure: see text]. Resonances indicative of the presence of peptidoglycan were observed in the spectra of both CPSs, consistent with reports that the CPS is covalently linked to peptidoglycan.