Natural Pseudomonas sp. strain N3 in artificial soil microcosms

The lightning-competent Pseudomonas sp. strain N3, recently isolated from soil, has been used to study the extent of natural electrotransformation (NET) or lightning transformation as a horizontal gene transfer mechanism in soil. The variation of electrical fields applied to the soil with a laboratory-scale lightning system provides an estimate of the volume of soil affected by NET. Based on the range of the electric field that induces NET of Pseudomonas strain N3, the volume of soil, where NET could occur, ranges from 2 to 950 m(3) per lightning strike. The influence of DNA parameters (amount, size, and purity) and DNA soil residence time were also investigated. NET frequencies (electrotransformants/recipient cells) ranged from 10(-8) for cell lysate after 1 day of residence in soil to 4 x 10(-7) with a purified plasmid added immediately before the lightning. The electrical field gradient (in kilovolts per cm) also played a role as NET frequencies ranging from 1 x 10(-5) at 2.3 kV/cm to 1.7 x 10(-4) at 6.5 kV/cm.     

Conjugative R-plasmid of facultative methylotrophic bacteria Pseudomonas sp. M

50 Md conjugative plasmid, designated pM3, has been found in the cells from natural isolates of Pseudomonas sp M. The plasmid determines the resistance to tetracycline and streptomycin and is capable of conjugative transfer between the cells of Pseudomonas and Escherichia coli. The conjugative derivatives of pM3 deleted for 14 Md of molecular mass were isolated after acridine dyes treatment of cells harbouring plasmid pM3. The discovered plasmid was not shown to belong to IncP1 incompatibility group.     

Population dynamics of nitrifying bacteria in an aquatic ecosystem.

In a space environment such as Space Shuttle or Space Station, animal experiments with aquatic species in a closed system pose a crucial problem in maintaining their water quality for a long term. In nature, ammonia as an animal wastes is converted by nitrifying bacteria to nitrite or nitrate compounds, which usually become nitrogen sources for plants. Thus an application of the biological reactor with such bacteria attached on some filters has been suggested and experimentally studied for efficient waste managements of ammonia. Although some successful results were reported (Kozu et al. 1995, Nagaoka et al. 1998, Nakamura et al. 1997, 1998) in the space applications, purely empirical approaches have so far been taken to develop a biological filter having a stable nitrifying activity. In this study, we constructed a mathematical model to deal with the dynamics of the ammonia nitrifying processes in a biological reactor. The model describes population dynamics of the ammonia-oxidizing bacteria and the nitrite-oxidizing bacteria cultivated on the same filter. We estimated parameters involved in the model using the experimental data. The result shows that these estimated parameters could be applied to general cases and that the two bacteria are in a symbiotic relationship; they can better perform when both coexist, as has been empirically recognized. Based on the model analysis, we discuss how to prepare a high performance biological filter.     

Survival and detection of bacteria in an aquatic environment.

A genetically engineered plasmid, pPSA131, was used as a DNA probe to detect homologous DNA in Escherichia coli HB101(pPSA131) after it was mixed with aquatic microorganisms from Lake Mead, Nevada, water samples. An isolate from the pLAFR1 chromosomal library of Pseudomonas syringae Cit 7 was used to detect parent P. syringae Cit 7 that had been mixed with Lake Mead water. E. coli(pPSA131) was kept in variously treated samples of lake water or buffer, and its survival was measured by viable cell counting on modified Luria-Bertani (LB) agar. Full-strength LB agar proved better than 0.1 x LB agar at recovering E. coli(pPSA131) after survival in low-nutrient environments. Survival of E. coli(pPSA131) remained high in filtered (0.22-micron pore size) lake water and salts buffer on both selective and nonselective agars but was lower in untreated lake water or lake water filtered with a 0.8-micron-pore-size membrane. Total recoverable colonies grown on LB agar were higher when lake water was filter treated (0.8-micron pore size) than when lake water was untreated. Microorganisms recovered from lake water alone grew rapidly on nonselective media, probably because of the "bottle effect." After being mixed with Lake Mead water, E. coli(pPSA131) and P. syringae were detected by colony blotting with non-radioactively labeled DNA probes. E. coli(pPSA131) were recovered at three times during 48 h from variously treated samples of lake water and from a mixture with Lake Mead water organisms. Colonies were supported on either nonselective or selective agar for comparison.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anthracene biodegradation and surface activity by an iron-stimulated Pseudomonas sp

Iron may enhance polycyclic aromatic hydrocarbons (PAHs) degradation directly by increasing the activity of the enzymes involved in the aerobic biodegradation pathways for hydrocarbons, and indirectly by increasing the PAHs bioavailability due to the stimulation of biosurfactant production. In the present work, the PAH anthracene was used in order to study the effect of different forms and concentrations of iron on its biodegradation and surfactant production by Pseudomonas spp. isolates from a 14-years old petrochemical sludge landfarm site. Among the iron forms, iron nitrate was chosen based on its high solubility and effect on the increase in the growth of the isolate. Iron concentration of 0.1mM was selected as the limit between deficiency and toxicity for isolates growth and anthracene degradation. After 48 days Pseudomonas citronellolis isolate 222A degraded 72% of anthracene related to iron stimulation and surface tension decrease, indicating surfactant production. Pseudomonas aeruginosa isolate 332C was iron-stimulated but did not reduce surface tension while P. aeruginosa isolate 312A exhibited a noniron and surfactant dependence to degrade 72% of anthracene. Isolate 222A showed a direct dependence on iron to stimulate surfactant activity, which probably increased anthracene bioavailability. To our knowledge, this is the first report about the iron effect on anthracene degradation and surfactant production by a Pseudomonas sp. Based on the iron requirement and surfactant activity, the Pseudomonas isolates may be useful for bioremediation of PAHs.     

Interactions between aquatic bacteria and an aquatic hyphomycete on decomposing maple leaves

Processing of leaf litter is an important function in many environments and is influenced strongly by microorganisms. We investigated interactions between an aquatic hyphomycete, Tetrachaetum elegans, and two bacteria from the Cytophaga-Flavobacterium-Bacteroides group, that were isolated from decaying leaves in a stream. Laboratory experiments were used to examine interactions, as indicated by growth, between bacteria and fungi on sugar maple (Acer saccharum) leaves. Responses to amendments with labile dissolved organic carbon (DOC) were also examined. Fungal biomass was not affected by glucose amendment or bacterial presence. Likewise, bacterial biomass did not respond consistently to the glucose amendment, nor did the fungus affect bacterial biomass. In general, we found little evidence of resource competition or facilitation, in contrast to other studies. Our experiments suggest that fungal–bacterial interactions are not always significant and may depend on environmental conditions and the types of microorganisms examined.     

Biopolymer flocculant produced by an Pseudomonas sp.

A biopolymer flocculant produced by Pseudomonas sp. A-99 had flocculating activity both in inorganic suspensions containing Ca2, Mg2 or Fe3 and in organic suspensions containing Fe2, Fe3 or Al3. The flocculant was an acidic protein and contained a small amount of an acidic polysaccharide consisting of galacturonic acid, glucose and galactose. Productivity of the flocculant was about 450 mg/l medium. © Rapid Science Ltd. 1998     

NAD-dependent formate dehydrogenase of methylotrophic bacteria Pseudomonas sp. 101. III. Comparative analysis

The comparative analysis of the primary and tertiary structures of NAD-dependent bacterial formate dehydrogenase (FDH) from methylotrophic bacterium Pseudomonas sp. 101 and a number of structurally characterized NAD-dependent dehydrogenases were performed. FDH has a highly conservative fold of the coenzyme binding domain. Position of the symmetry axis in the FDH molecule relative to the beta-sheets of its coenzyme binding domain with the respective sequences of the other NAD-dependent enzymes was performed on the basis of the spatial homology between these structures. Only one of the three amino acid residues previously thought to be conserved in the coenzyme binding domains of NAD-dependent dehydrogenases is preserved in the FDH molecule (Asp-221). Two glycine residues found in all previously studied dehydrogenases are substituted in FDH by Ala-198 and Pro-256, respectively. Position of the essential thiol of FDH (Cys-255) in the protein structure was established. It is suggested that Cys-255 is situated on or near polypeptide locus taking part in the conformational changes of the protein in the course of the catalysis.     

Influenza A virus-binding activity of glycoglycerolipids of aquatic bacteria

As the aqueous sphere has been proposed to be an important source medium for the virus infection of land animals, the glycolipids of some aquatic organisms were examined for human influenza A virus-binding activity. Active compounds were not found among the eight echinoderm gangliosides, but two active non-sialylated glycoglycerolipids were isolated from an aquatic bacterium, Corynebacterium aquaticum. The structural formula of one of them, H632A, was elucidated to be 1-14-methyl-hexadecanoyl-3-alpha-D-galactopyranosyl-(1-->3)-6-(12-met hyl-tetradecanoyl)-1-alpha-D-mannopyranosyl]-sn-glycerol. The latter together with reported one elsewhere, S365A, 1-14-methyl-hexadecanoyl-3-[alpha-D-mannopyranosyl-(1-->3)-6-(12-meth yl-tetradecanoyl)-1-alpha-D-mannopyranosyl]-sn-glycerol, apparently bound to three human influenza viruses, A/PR/8/34 (H1N1), A/Aichi/2/68 (H3N2), and A/Memphis/1/71 (H3N2), exhibiting 7-12% (H632A) and 10-22% (S365A) of the activities of the control substances (Neu5Acalpha2-3-paragloboside and Neu5Acalpha2-6- paragloboside). Additionally, these glycolipids were assumed to have virus-neutralizing activities for the following two reasons: (i) The hemagglutination and hemolysis activities of the viruses were inhibited by the glycolipid. (ii) The leakage of a cytosolic enzyme (lactate dehydrogenase) from Madin-Darby canine kidney cells on virus infection was prevented by the glycolipids to nearly the same extent as by fetuin. This is the first evidence of the binding- and neutralizing-abilities of native glycoglycerolipids as to influenza viruses.     

Survival and detection of bacteria in an aquatic environment

A genetically engineered plasmid, pPSA131, was used as a DNA probe to detect homologous DNA in Escherichia coli HB101(pPSA131) after it was mixed with aquatic microorganisms from Lake Mead, Nevada, water samples. An isolate from the pLAFR1 chromosomal library of Pseudomonas syringae Cit 7 was used to detect parent P. syringae Cit 7 that had been mixed with Lake Mead water. E. coli(pPSA131) was kept in variously treated samples of lake water or buffer, and its survival was measured by viable cell counting on modified Luria-Bertani (LB) agar. Full-strength LB agar proved better than 0.1 x LB agar at recovering E. coli(pPSA131) after survival in low-nutrient environments. Survival of E. coli(pPSA131) remained high in filtered (0.22-micron pore size) lake water and salts buffer on both selective and nonselective agars but was lower in untreated lake water or lake water filtered with a 0.8-micron-pore-size membrane. Total recoverable colonies grown on LB agar were higher when lake water was filter treated (0.8-micron pore size) than when lake water was untreated. Microorganisms recovered from lake water alone grew rapidly on nonselective media, probably because of the "bottle effect." After being mixed with Lake Mead water, E. coli(pPSA131) and P. syringae were detected by colony blotting with non-radioactively labeled DNA probes. E. coli(pPSA131) were recovered at three times during 48 h from variously treated samples of lake water and from a mixture with Lake Mead water organisms. Colonies were supported on either nonselective or selective agar for comparison.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of the artificial electron acceptor reumycin on the nature of an intermediate accumulated by Pseudomonas aeruginosa bacteria

We investigated the effect of the autooxidizable electron acceptor reumicin on the oversynthesis of intermediates by the bacterium Pseudomonas aeruginosa during its growth limitation by a nitrogen source. Addition of reumicin which accepted the reducing equivalents from NADH(+)-dehydrogenase of the respiratory chain was shown to reduce the rate of alpha-ketoglutarate formation and yield, and to induce the synthesis and excretion of pyruvate into the cultivation medium. The maximal accumulation of pyruvate was observed when reumicin was added at a concentration of 0.4-0.5 mM. It is concluded that the nature of the overproduced intermediate, the rate of its biosynthesis and yield depend on the extent of reducibility of the pyridine nucleotide pool. The oversynthesis of alpha-ketoglutarate is suppressed by chloramphenicol, a protein synthesis inhibitor, which points to a possible involvement of inducible systems including the carriers of the acids via the cytoplasmic membrane.     

Tryptophan of facultative methylotrophic bacteria Pseudomonas sp. M. II. Regulation of tryptophan biosynthesis

Regulation of tryptophan biosynthesis of facultative methylotrophic Pseudomonas sp. M was studied. Repression of the trpE, trpD and trpC genes by tryptophan was demonstrated. It was also shown that the trpE and trpDC genes are derepressed noncoordinately. No regulation of the trpF gene product could be demonstrated, indicating that its synthesis is constitutive. The trpA and trpB genes are inducible by indol-3-glycerophosphate. Anthranilate synthase and tryptophan synthase were sensitive to the feedback inhibition. The tryptophan concentrations giving 50% inhibition were estimated to be 9 microM and 1 microM, respectively. Experimental evidence for activation of the N-5-phosphoribosyl anthranilate isomerase and for inhibition of the indol-3-glycerophosphate synthase by some tryptophan intermediates was obtained.     

Removal of uranium by an exopolysaccharide from Pseudomonas sp.

Summary Accumulation of uranium (U) is reported for isolated exopolysaccharide produced by Pseudomonas sp. EPS-5028. A maximum uptake of 96 g U/mg polymer was observed. In contrast, the maximum accumulation of uranium by deacylated polysaccharide was 46 g/mg. This metal-complexing capacity observed suggests that the anionic reactive sites on the structure could be responsible for this activity. Metal uptake was affected by pH and was not affected by temperature. Expolysaccharide from Pseudomonas sp. EPS-5028 obeyed the Freundlich isotherm indicating single layer adsorption. Offprint requests to: F. Congregado     

Kinetics of p-cresol degradation by an immobilized Pseudomonas sp.

A p-cresol (PCR)-degrading Pseudomonas sp. was isolated from creosote-contaminated soil and shown to degrade PCR by conversion to protocatechuate via p-hydroxybenzaldehyde (PBA) and p-hydroxybenzoate (PHB). Cells of the Pseudomonas sp. were immobilized in calcium alginate beads and in polyurethane foam. The relationship between the PCR concentration and the PCR transformation rate was investigated in batch and continuous culture bioreactors. The biodegradation kinetics of PBA and PHB also were investigated. In batch culture reactors, the maximum PCR degradation rate (Vmax) for the alginate-immobilized Pseudomonas sp. cells was 1.5 mg of PCR g of bead-1 h-1 while the saturation constant (Ks) was 0.22 mM. For PHB degradation, the Vmax was 0.62 mg of PHB g of bead-1 h-1 while the Ks was 0.31 mM. For polyurethane-immobilized Pseudomonas sp. cells, the Vmax of PCR degradation was 0.80 mg of PCR g of foam-1 h-1 while the Ks was 0.28 mM. For PHB degradation, the Vmax was 0.21 mg of PHB g of foam-1 h-1 and the Ks was 0.22 mM. In a continuous column alginate bead reactor, the Vmax for PCR transformation was 2.6 mg g of bead-1 h-1 while the Ks was 0.20 mM. The Vmax and Ks for PBA transformation in the presence of PCR were 0.93 mg g of bead-1 h-1 and 0.063 mM, respectively. When PHB alone was added to a reactor, the Vmax was 1.48 mg g of bead-1 h-1 and the Ks was 0.32 mM.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heterotrophic bacteria in an air-handling system.

Heterotrophic bacteria from structural surfaces, drain pan water, and the airstream of a well-maintained air-handling system with no reported building-related illness were enumerated. Visually the system appeared clean, but large populations of bacteria were found on the fin surface of the supply-side cooling coils (10(5) to 10(6) CFU cm-2), in drain pan water (10(5) to 10(7) CFU ml-1), and in the sump water of the evaporative condenser (10(5) CFU ml-1). Representative bacterial colony types recovered from heterotrophic plate count cultures on R2A medium were identified to the genus level. Budding bacteria belonging to the genus Blastobacter dominated the supply surface of the coil fins, the drain pan water, and the postcoil air. These data and independent scanning electron microscopy indicated that a resident population of predominantly Blastobacter bacteria was present as a biofilm on the supply-side cooling coil fins.     

Heterotrophic bacteria in an air-handling system.

Heterotrophic bacteria from structural surfaces, drain pan water, and the airstream of a well-maintained air-handling system with no reported building-related illness were enumerated. Visually the system appeared clean, but large populations of bacteria were found on the fin surface of the supply-side cooling coils (10(5) to 10(6) CFU cm-2), in drain pan water (10(5) to 10(7) CFU ml-1), and in the sump water of the evaporative condenser (10(5) CFU ml-1). Representative bacterial colony types recovered from heterotrophic plate count cultures on R2A medium were identified to the genus level. Budding bacteria belonging to the genus Blastobacter dominated the supply surface of the coil fins, the drain pan water, and the postcoil air. These data and independent scanning electron microscopy indicated that a resident population of predominantly Blastobacter bacteria was present as a biofilm on the supply-side cooling coil fins.