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207 records · Page 12Linked to original sources
PubMed1998

The role of microbial biofilms in deterioration of space station candidate materials.

Formation of microbial biofilms on surfaces of a wide range of materials being considered as candidates for use on the International Space Station was investigated. The materials included a fibre-reinforced polymeric composite, an adhesive sealant, a polyimide insulation foam, teflon cable insulation, titanium, and an aliphatic polyurethane coating. They were exposed to a natural mixed population of bacteria under controlled conditions of temperature and relative humidity (RH). Biofilms formed on the surfaces of the materials at a wide range of temperatures and RHs. The biofilm population was dominated by Pseudomonas aeruginosa, Ochrobactrum anthropi, Alcaligenes denitrificans, Xanthomonas maltophila, and Vibrio harveyi. The biocide, diiodomethyl-p-tolyl sulfone, impregnated in the polyurethane coating, was ineffective against microbial colonization and growth. Degradation of the polyurethane coatings was monitored with electrochemical impedance spectroscopy (EIS). The impedance spectra indicated that microbial degradation of the coating occurred in several stages. The initial decreases in impedance were due to the transport of water and solutes into the polymeric matrices. Further decreases were a result of polymer degradation by microorganisms. Our data showed that these candidate materials for space application are susceptible to biofilm formation and subsequent degradation. Our study suggests that candidate materials for use in space missions need to be carefully evaluated for their susceptibility to microbial biofilm formation and biodegradation.

Bacterial Physiological Phenomena↗
PubMedDate not supplied

['In vitro' activity of different antimicrobial agents on Gram-negative nonfermentative bacilli, excluding Pseudomonas aeruginosa and Acinetobacter spp].

Gram-negative nonfermentative bacilli (NFB) are widely spread in the environment. Besides of difficulties for identification, they often have a marked multiresistance to antimicrobial agents, including those active against Pseudomonas aeruginosa. The objective of this study was to evaluate the 'in vitro' activity of different antimicrobial agents on 177 gram-negative nonfermentative bacilli isolates (excluding Pseudomonas aeruginosa and Acinetobacter spp.) isolated from clinical specimens. Minimum inhibitory concentrations (MIC) were determined according to the Mueller Hinton agar dilution method against the following antibacterial agents: ampicillin, piperacillin, piperacillin-tazobactam, sulbactam, cefoperazone, cefoperazone-sulbactam, ceftazidime, cefepime, aztreonam, imipenem, meropenem, colistin, gentamicin, amikacin, trimethoprim-sulfamethoxazole, chloramphenicol, erythromycin, rifampin, norfloxacin, ciprofloxacin and minocycline. Seven isolates: Sphingobacterium multivorum (2), Sphingobacteriumspiritivorum (1), Empedobacterbrevis (1), Weeksella virosa (1), Bergeyella zoohelcum (1) and Oligella urethralis (1), were tested for amoxicillin-clavulanic acid and ampicillin-sulbactam susceptibility, and susceptibility to cefoperazone or sulbactam was not determined. Multiresistance was generally found in Stenotrophomonas maltophilia, Burkholderia cepacia, Chryseobacterium spp., Myroides spp., Achromobacter xylosoxidans, and Ochrobactrum anthropi isolates. On the other hand, Pseudomonas stutzeri, Shewanella putrefaciens-algae, Sphingomonas paucimobilis, and Pseudomonas oryzihabitans, Bergeyella zoohelcum, Weeksella virosa and Oligella urethralis were widely susceptible to the antibacterial agents tested. As a result of the wide variation in antimicrobial susceptibility shown by different species, a test on susceptibility to different antibacterial agents is essential in order to select an adequate therapy. The marked multiresistance evidenced by some species, prompts the need to develop new antimicrobial agents active against this group of bacteria and to search for synergistic combinations.

Anti-Bacterial Agents↗
PubMed2000

The use of silica gel prepared by sol-gel method and polyurethane foam as microbial carriers in the continuous degradation of phenol.

A mixed microbial culture was immobilized by entrapment into silica gel (SG) and entrapment/ adsorption on polyurethane foam (PU) and ceramic foam. The phenol degradation performance of the SG biocatalyst was studied in a packed-bed reactor (PBR), packed-bed reactor with ceramic foam (PBRC) and fluidized-bed reactor (FBR). In continuous experiments the maximum degradation rate of phenol (q(s)max) decreased in the order: PBRC (598 mg l(-1) h(-1)) > PBR (PU, 471 mg l(-1)h(-1)) > PBR(SG, 394 mg l(-1) h(-1)) > FBR (PU, 161 mg l(-1) h(-1)) > FBR (SG, 91 mg l(-1) h(-1)). The long-term use of the SG biocatalyst in continuous phenol degradation resulted in the formation of a 100-200 microm thick layer with a high cell density on the surface of the gel particles. The abrasion of the surface layer in the FBR contributed to the poor degradation performance of this reactor configuration. Coating the ceramic foam with a layer of cells immobilized in colloidal SiO2 enhanced the phenol degradation efficiency during the first 3 days of the PBRC operation, in comparison with untreated ceramic packing.

Biodegradation, Environmental↗
PubMed2007

Characterization of a simple bacterial consortium for effective treatment of wastewaters with reactive dyes and Cr(VI).

A microbial consortia consisting of three bacteria isolated from tanning and textile wastewaters revealed high capacity to simultaneously bioaccumulate dye and Cr(VI). The identity of the bacteria were determined by 16S rRNA gene analysis to be closely related to Ochrobactrium sp., Salmonella enterica and Pseudomonas aeruginosa. Dependence of initial pH values and range of concentrations of the dye Reactive Black B (33.2-103.1 mg l(-1)) and Cr(VI) (19.9-127.6 mg l(-1)) were examined to find the effect of pH on the dye and Cr(VI) bioaccumulation. Optimal pH for growth of the consortia in media containing 35 mg l(-1) dye and 50 mg l(-1) Cr(VI) was determined to be around 8. The Cr(VI) bioaccumulation by the consortia was rapid in media containing molasses with or without reactive dye with a maximum Cr(VI) bioaccumulation yield ranging from 90% to 99% within a 2-4d period. A slightly lower yield for the dye bioaccumulation was measured with a maximum dye bioaccumulation of 80% at 59.3 mg l(-1) dye and 69.8 mg l(-1) Cr(VI). The highest specific Cr uptake value was obtained as 76.7 mg g(-1) at 117.1 mg l(-1) Cr(VI) and 50.8 mg l(-1) dye concentration. This ability to bioaccumulate dye and Cr(VI) was more efficient than the enriched sludge from which they were isolated.

Biodegradation, Environmental↗
PubMed2002

Toxicity and biodegradation of diamines.

Phytotoxicity and cytotoxicity of 2,4-diaminotoluene (2,4-D), 4,4'-methylenedianiline (4,4-D), and 1,6-hexanediamine (1,6-D) were investigated by observing the germination of young radish seeds and the viability of HeLa cells, respectively. 2,4-D showed the highest, 4,4-D intermediate, and 1,6-D lowest cytotoxicity. However, the phytotoxicity decreased in the order of 4,4-D > 2,4-D > 1,6-D. Contrary to the results previously reported, in the modified Sturm test the activated sludge degraded 2,4-D and 4,4-D as well as 1,6-D without any pre-acclimation. Ochrobacterium antropi was isolated for degradation of 2,4-D and 4,4-D and Pseudomonas citronellolis for 1,6-D degradation. Thielevia sp. was isolated as 2,4-D degrading fungus and Aspergillus sp. as 4,4-D and 1,6-D degrading fungus. The fungi degraded the diamines faster than the bacteria.

Aniline Compounds↗
PubMed2005

DOM-fold: a structure with crossing loops found in DmpA, ornithine acetyltransferase, and molybdenum cofactor-binding domain.

Understanding relationships between sequence, structure, and evolution is important for functional characterization of proteins. Here, we define a novel DOM-fold as a consensus structure of the domains in DmpA (L-aminopeptidase D-Ala-esterase/amidase), OAT (ornithine acetyltransferase), and MocoBD (molybdenum cofactor-binding domain), and discuss possible evolutionary scenarios of its origin. As shown by a comprehensive structure similarity search, DOM-fold distinguished by a two-layered beta/alpha architecture of a particular topology with unusual crossing loops is unique to those three protein families. DmpA and OAT are evolutionarily related as indicated by their sequence, structural, and functional similarities. Structural similarity between the DmpA/OAT superfamily and the MocoBD domains has not been reported before. Contrary to previous reports, we conclude that functional similarities between DmpA/OAT proteins and N-terminal nucleophile (Ntn) hydrolases are convergent and are unlikely to be inherited from a common ancestor.

Acetyltransferases↗
PubMed2004

S-stereoselective piperazine-2-tert-butylcarboxamide hydrolase from Pseudomonas azotoformans IAM 1603 is a novel L-amino acid amidase.

An amidase acting on (R,S)-piperazine-2-tert-butylcarboxamide was purified from Pseudomonas azotoformans IAM 1603 and characterized. The enzyme acted S-stereoselectively on (R,S)-piperazine-2-tert-butylcarboxamide to yield (S)-piperazine-2-carboxylic acid. N-terminal and internal amino acid sequences of the enzyme were determined. The gene encoding the S-stereoselective piperazine-2-tert-butylcarboxamide amidase was cloned from the chromosomal DNA of the strain and sequenced. Analysis of 2.1 kb of genomic DNA revealed the presence of two ORFs, one of which (laaA) encodes the amidase. This enzyme, LaaA is composed of 310 amino acid residues (molecular mass 34 514 Da), and the deduced amino acid sequence exhibits significant similarity to hypothetical and functionally characterized proline iminopeptidases from several bacteria. The laaA gene modified in the nucleotide sequence upstream from its start codon was overexpressed in Escherichia coli. The activity of the recombinant LaaA enzyme in cell-free extracts of E. coli was 13.1 units.mg(-1) with l-prolinamide as substrate. This enzyme was purified to electrophoretic homogeneity by ammonium sulfate fractionation and two column chromatography steps. On gel-filtration chromatography, the enzyme appeared to be a monomer with a molecular mass of 32 kDa. It had maximal activity at 45 degrees C and pH 9.0, and was completely inactivated in the presence of phenylhydrazine, Zn2+, Ag+, Cd2+ or Hg2+. LaaA had hydrolyzing activity toward L-amino acid amides such as L-prolinamide, L-proline-p-nitroanilide, L-alaninamide and L-methioninamide, but did not act on the peptide substrates for the proline iminopeptidases despite their sequence similarity to LaaA. The enzyme also acted S-stereoselectively on (R,S)-piperidine-2-carboxamide, (R,S)-piperazine-2-carboxamide and (R,S)-piperazine-2-tert-butylcarboxamide. Based on its specificity towards L-amino acid amides, the enzyme was named L-amino acid amidase. E. coli transformants overexpressing the laaA gene could be used for the S-stereoselective hydrolysis of (R,S)-piperazine-2-tert-butylcarboxamide.

Amides↗
PubMed2006

Percutaneous balloon pericardiotomy for the treatment of infected pericardial effusion with tamponade.

Percutaneous balloon pericardiotomy has been used as an alternative for surgically created pericardial window mainly for the management of malignant pericardial effusions in critically ill patients. We describe a patient with purulent pericardial effusion and cardiac tamponade who was treated successfully and without complications with percutaneous balloon pericardiotomy.

Anti-Bacterial Agents↗