Uptake of methylamine and methanol by Pseudomonas sp. strain AM1.

The uptake of methylamine and of methanol by the facultative methylotroph Pseudomonas sp. strain AM1 was investigated. It was found that this organism possesses two uptake systems for methylamine. One of these operates when methylamine is the sole source of carbon, nitrogen, and energy. It has a Km of 1.33 X 10(-4) M and a Vmax of 67 nmol/min per mg of cells (dry weight). The other system, found when methylamine is the sole nitrogen source only, has a Km of 1.2 X 10(-5) M and a Vmax of 8.9 nmol/min per mg of cells (dry weight). Both uptake systems were severely inhibited by azide, cyanide, carbonyl cyanide-m-chlorophenyl hydrazone, and N-ethylmaleimide, but only the high-affinity system was inhibited by ammonium ions with a Ki of 7.7 mM. Both systems were susceptible to osmotic shock treatment, competitively inhibited by ethylamine, and unaffected by most amino acids. Methanol uptake showed a Km of 4.8 microM and a Vmax of 60.6 nmol/min per mg of cells (dry weight) and was not inhibited by osmotic shock treatment. Azide, cyanide, and N-ethylmaleimide curtailed uptake, but carbonyl cyanide-m-chlorophenyl hydrazone merely reduced the rate of uptake. A methanol dehydrogenase mutant, M15A, was unable to take up methanol. It is proposed that methanol diffuses into the cell where it is rapidly oxidized by methanol dehydrogenase.     

假单胞菌菌株CTN-3对百菌清污染土壤的生物修复

百菌清被美国环境保护署列为优先控制污染物,利用微生物的降解作用修复被污染的土壤、清除环境中的污染物等具有重要的现实意义.假单胞菌(Pseudomonas sp.)菌株CTN-3是一株从污染土壤中分离得到的百菌清降解菌,考察了其在实验室条件下对百菌清污染土壤的生物修复能力及其影响因素.结果表明:降解菌株在灭菌土壤中的降解效果略好于未灭菌土壤;在外源添加降解菌106 CFU·g-1、温度15 ～ 30℃和pH5.8～8.3条件下,该菌株能有效降解土壤中10 ～200 mg·kg-1的百菌清.菌株CTN-3在百菌清污染土壤的生物修复中具有良好的应用前景.     

Growth of Pseudomonas C on C1 compounds: enzyme activites in extracts of Pseudomonas C cells grown on methanol, formaldehyde, and formate as sole carbon sources.

Pseudomonas C can grow on methanol, formaldehyde, or formate as sole carbon source. It is proposed that the assimilation of carbon by Pseudomonas C grown on different C1 growth substrates proceeds via one of two metabolic pathways, the serine pathway or the allulose pathway (the ribose phosphate cycle of formaldehyde fixation). This contention is based on the distribution of two key enzymes, each of which appears to be specifically involved in one of the assimilation pathways, glycerate dehydrogenase (serine pathway) and hexose phosphate synthetase (allulose pathway). The assimilation of methanol in Pseudomonas C cells appears to occur via the allulose pathway, whereas the utilization of formaldehyde or formate in cells grown on formaldehyde or formate as sole carbon sources appears by the serine pathway. When methanol is present together with formaldehyde or formate in the growth medium, the formaldehyde or formate is utilized by the allulose pathway.     

Production of L-serine by the methanol utilizing bacterium,Pseudomonas 3ab

Summary A bacterium capable of growth on methanol and some organic acids as sole source of carbon and energy has been isolated and designated Pseudomonas 3ab. This facultative methylotrophic organism apparently utilizes the serine pathway of formaldehyde fixation.When methanol was used as the sole carbon source for growth, L-serine production by Pseudomonas 3ab occurred upon the addition of glycine and methanol at the end of the exponential growth phase. The maximum yield of L-serine (4.7 g/l) was obtained when 20 g/l glycine and 8 g/l methanol were added and the pH of the culture medium was changed to 8.5.Although Pseudomonas 3ab is unable to grow on L-serine or glycine, it is very active in decomposing these amino acids. The degradation of L-serine and glycine has been shown to be pH-dependent with a minimum at pH 8.5–9.0.     

Assimilation of methanol by Yeasts

Candida lipolytica was cultured on a methanol containing medium as the only C source. The influence of different concentrations of methanol and ammonium sulphate and the effect of addition of some biological active materials to the methanol containing medium were studied. Dry cell yield of C. lipolytica and protein content were determined to be 23.1 g of cells/100 g of methanol added and 40.2%, respectively. Total lipids, phospholipids, keto acid and amino acid composition were estimated. The amino acid composition of the protein was comparable to the composition of the other reported single cell proteins (SCP). These results indicate that C. lipolytica is potentially important for fodder use.     

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.     

Eubacterium acidaminophilum sp. nov., a versatile amino acid-degrading anaerobe producing or utilizing H2 or formate

An obligately anaerobic, rod-shaped bacterium was isolated on alanine in co-culture with H₂-scavenging Desulfovibrio and obtained in pure culture with glycine as sole fermentation substrate. The isolated strain, al-2, was motile by a polar to subpolar flagellum and stained Gram-positive. The guanine plus cytosine content of the DNA was 44.0 mol%. Strain al-2 grew in defined, reduced glycine media supplemented with biotin. The pure culture fermented 4 mol glycine to 3 mol acetate, 4 mol ammonia and 2 mol CO₂. Under optimum conditions (34°C, pH 7.3), the doubling time on glycine was 60 min and the molar growth yield 7.6 g cell dry mass. Serine was fermented to acetate, ethanol, CO₂, H₂ and ammonia. In addition, betaine, sarcosine or creatine served as substrates for growth and acetate production if H₂, formate or e.g. valine were added as H-donors. In pure culture on alanine under N₂, strain al-2 grew very poorly and produced H₂ up to a partial pressure of 3.6 kPa (0.035 atm). Desulfovibrio species, Methanospirillum hungatei and Acetobacterium woodii served as H₂-scavengers that allowed good syntrophic growth on alanine. The co-cultures also grew on aspartate, leucine, valine or malate. Alanine and aspartate were stoichiometrically degraded to acetate and ammonia, whereas the reducing equivalents were recovered as H₂S, CH₄ or newly synthetized acetate, respectively. Growth of strain al-2 in co-culture with the hydrogenase-negative, formate-utilizing Desulfovibrio baarsii indicated that a syntrophy was also possible by interspecies formate transfer. Growth on glycine, or on betaine, sarcosine or creatine (plus H-donors) depended strictly on the addition of selenite (0.1 M); selenite was not required for fermentation of serine, or for degradation of alanine, aspartate or valine by the co-cultures. Cell-free extracts of glycine-grown cells contained active glycine reductase, glycine decarboxylase and reversible methyl viologen-dependent formate dehydrogenase in addition to the other enzymes necessary for an oxidation to CO₂. In all reactions NADP was the preferred H-carrier. Both formate and glycine could be synthesized from bicarbonate. Serine-grown cells did not contain serine hydroxymethyl transferase but serine dehydratase and other enzymes commonly involved in pyruvate metabolism to acetate, CO₂ and H₂. The enzymes involved in glycine metabolism were repressed during growth on serine. By its morphology and physiology, strain al-2 did not resemble described amino acid-degrading species. Therefore, the new isolate is proposed as type strain of a new species, Eubacterium acidaminophilum.     

Degradation of 2-chloroallylalcohol by a Pseudomonas sp.

Three Pseudomonas strains capable of utilizing 2-chloroallylalcohol (2-chloropropenol) as the sole carbon source for growth were isolated from soil. The fastest growth was observed with strain JD2, with a generation time of 3.6 h. Degradation of 2-chloroallylalcohol was accompanied by complete dehalogenation. Chloroallylalcohols that did not support growth were dechlorinated by resting cells; the dechlorination level was highest if an alpha-chlorine substituent was present. Crude extracts of strain JD2 contained inducible alcohol dehydrogenase activity that oxidized mono- and dichloroallylalcohols but not trichloroallylalcohol. The enzyme used phenazine methosulfate as an artificial electron acceptor. Further oxidation yielded 2-chloroacrylic acid. The organism also produced hydrolytic dehalogenases converting 2-chloroacetic acid and 2-chloropropionic acid.     

Isolation and characterization of a Pseudomonas sp. strain PH1 utilizing meta-aminophenol

Pseudomonas sp. strain PH1 was isolated from soil contaminated with pharmaceutical and dye industry waste. The isolate PH1 could use m-aminophenol as a sole source of carbon, nitrogen, and energy to support the growth. PH1 could degrade up to 0.32 mM m-aminophenol in 120 h, when provided as nitrogen source at 0.4 mM concentration with citrate (0.5 mM) as a carbon source in the growth medium. The presence of ammonium chloride as an additional nitrogen source repressed the degradation of m-aminophenol by PH1. To identify strain PH1, the 16S rDNA sequence was amplified by PCR using conserved eubacterial primers. The FASTA program was used to analyze the 16S rDNA sequence and the resulting homology patterns suggested that PH1 is a Pseudomonas.