PCP degradation is mediated by closely related strains of the genus Sphingomonas

There have been numerous reports in the literature of diverse bacteria capable of degrading pentachlorophenol (PCP). In order to gain further insight into the phylogenetic relationships of PCP-degrading bacteria, we examined four strains: Arthrobacter sp. strain ATCC 33790, Flavobacterium sp. strain ATCC 39723, Pseudomonas sp. strain SR3, and Sphingomonas sp. strain RA2. These organisms were isolated from different geographical locations and all of them degrade high concentrations (100–200 mg/L) of PCP. Southern blot analyses determined that these bacteria all harbour DNA that encodes similar, if not identical, genes involved in PCP degradation. Comparison of the 16S rRNA nucleotide sequences revealed that these organisms were very closely related and, in fact, represent a monophyletic group. The 16S rRNA analyses together with fatty acid and sphingolipid analyses strongly suggest that the four strains are members of the genus Sphingomonas . The close relationship of the four organisms is supported by nucleotide sequence analysis data of the pcpB locus encoding PCP-4-monooxygenase, the first enzyme in the PCP degradative pathway.     

The role of exopolymers in the attachment of sphingomonas paucimobilis

The importance of exopolymers in the adhesion of Sphingomonas paucimobilis was established by studying the attachment to glass of three mutants with defective gellan production. The attachment assays were performed in either phosphate buffered saline (controls) or in the exopolymeric solutions produced by the mutants. The exopolymer was found to have surface active properties, changing the glass surface from hydrophilic to hydrophobic, making adhesion thermodynamically favourable. Only the cells that had a substantial polymeric layer surrounding their walls were able to significantly colonise glass coated with the exopolymer. It is hypothesised that the exopolymer bound to the glass and the exopolymer present at the surface of the bacteria bound together, overcoming the energy barrier created by the negative charge of both surfaces. It is concluded that the exopolymer from S. paucimobilis has a dual role in the process of adhesion by both coating the surface thereby strengthening adhesion and by enhancing adhesion through the establishment of polymeric bridges.     

鞘氨醇单胞菌TP-3合成新型生物聚合物Ss的发酵条件优化

鞘氨醇单胞菌(Sphingomonas sp.)TP-3能合成一种具有增稠性、假塑性、成凝胶特性和乳化性能的新型生物聚合物Ss。运用单因素实验和均匀设计法对菌株TP-3合成聚合物Ss的发酵条件进行优化, 实验结果表明, 培养基组成为葡萄糖41.2 g/L, 豆饼粉2.0 g/L, NaCl 0.85 g/L, K2HPO4 1.46 g/L, MgSO4 0.12 g/L, MnCl2 0.0075 g/L, FeSO4 0.002 g/L, 初始pH为7.0, 在27°C, 180 r/min的条件下摇床培养60 h, 聚合物Ss的产量达到21.5 g/L。该聚合物生产成本低, 在油田开发中极具应用前景。     

Degradation of 3-O-methylgallate in Sphingomonas paucimobilis SYK-6 by pathways involving protocatechuate 4,5-dioxygenase

Sphingomonas paucimobilis SYK-6 converts vanillate and syringate to protocatechuate and 3-O-methylgallate (3MGA), respectively. 3MGA is metabolized via multiple pathways involving 3MGA 3,4-dioxygenase, protocatechuate 4,5-dioxygenase (LigAB), and gallate dioxygenase whereas protocatechuate is degraded via the protocatechuate 4,5-cleavage pathway. Here the secondary role of LigAB in syringate metabolism is investigated. The reaction product of 3MGA catalyzed by His-tagged LigAB was identified as 4-carboxy-2-hydroxy-6-methoxy-6-oxohexa-2,4-dienoate (CHMOD) and 2-pyrone-4,6-dicarboxylate (PDC), indicating that 3MGA is transformed to CHMOD and PDC by both reactions catalyzed by DesZ and LigAB. Mutant analysis revealed that the 3MGA catabolic pathways involving LigAB are functional in SYK-6.     

Isolation and characterization of genes encoding polycyclic aromatic hydrocarbon dioxygenase from acenaphthene and acenaphthylene degrading Sphingomonas sp. strain A4

Sphingomonas sp. strain A4 is capable of utilizing acenaphthene and acenaphthylene as sole carbon and energy sources, but it is unable to grow on other polycyclic aromatic hydrocarbons (PAHs). The genes encoding terminal oxygenase components of ring-hydroxylating dioxygenase (arhA1 and arhA2) were isolated from this strain by means of the ability to oxidize indole to indigo of the Escherichia coli clone containing electron transport proteins from phenanthrene-degrading Sphingobium sp. strain P2. The translated products of arhA1 and arhA2 exhibited moderate sequence identity (less than 56%) to large and small subunits of dioxygenase of other ring-hydroxylating dioxygenases. Biotransformation with recombinant E. coli clone revealed the broad substrate specificity of this oxygenase toward several PAHs including acenaphthene, acenaphthylene, naphthalene, phenanthrene, anthracene and fluoranthene. Southern hybridization analysis revealed the presence of a putative arhA1 homologue on a locus different from that of the arhA1 gene. Insertion inactivation of the arhA1 gene in strain A4 suggested that the gene but not the putative homologue one was involved in the degradation of acenaphthene and acenaphthylene in this strain.     

Isolation and characterization of a novel sphingomonad capable of growth with chrysene as sole carbon and energy source

A bacterial strain able to grow in pure culture with chrysene as sole added carbon and energy source was isolated from PAH-contaminated soil after successive enrichment cultures in a biphasic growth medium. Initially, growth occurred in the form of a biofilm at the interface between the aqueous and non-aqueous liquid phases. However, after a certain time, a transition occurred in the enrichment cultures, with growth occurring in suspension and a concomitant increase in the rate of chrysene degradation. The strain responsible for chrysene degradation in these cultures, named Sphingomonas sp. CHY-1, was identified by 16S rDNA sequencing as a novel sphingomonad, the closest relative in the databases being Sphingomonas xenophaga BN6T (96% sequence identity). Both these strains clustered with members of the genera Sphingobium and Rhizomonas, but could not be categorically assigned to either genus. Sphingomonas sp. CHY-1 was characterized in terms of its growth on chrysene and other PAH, and the kinetics of chrysene degradation and 14C-chrysene mineralization were measured. At an initial chrysene concentration of 0.5 g l(-1) silicone oil, and an organic/aqueous phase ratio of 1:4, chrysene was 50% degraded after 5 days incubation and 97.5% degraded after 35 days. The protein content of cultures reached a maximum value of 11.5 microg ml(-1) aqueous phase, corresponding to 92 mg g(-1) chrysene. 14C-labelled chrysene was 50% mineralized after 6-8 weeks incubation, 10.7% of the radioactivity was incorporated into cell biomass and 8.4% was found in the aqueous culture supernatant. Sphingomonas sp. CHY-1 also grew on naphthalene, phenanthrene and anthracene, and naphthalene was the preferred substrate, with a doubling time of 6.9 h.     

Occurrence of an alpha-galacturonosyl-ceramide in the dioxin-degrading bacterium Sphingomonas wittichii

The chemical structure of two glycosphingolipids (GSLs) found in the dioxin-degrading bacterium Sphingomonas wittichii strain RW1 was investigated by means of mass spectrometry and (1)H-nuclear magnetic resonance spectroscopy. One of the GSLs was alpha-D-glucuronosyl-ceramide, commonly present in Sphingomonas spp., and the other was proved to be alpha-D-galacturonosyl-ceramide, whose sugar configuration has not been reported before. In both GSLs the ceramide portion was composed of myristic acid or 2-hydroxy-myristic acid as the fatty acid, and 2-amino-1,3-octadecanediol or 2-amino-cis-13,14-methylene-1,3-eicosanediol as the dihydrosphingosine.     

Simultaneous and rapid monitoring of biomass and biopolymer production by Sphingomonas paucimobilis using Fourier transform-near infrared spectroscopy

The application of Fourier Transform near infrared spectroscopy (FT-NIRS) to near real-time monitoring of polysaccharide and biomass concentration was investigated using a gellan-producing strain of Sphingomonas paucimobilis grown in a stirred tank reactor. Successful models for both biomass and gellan were constructed despite the physichochemical complexity of the viscous process fluid. Modelling of biomass proved more challenging than for gellan, partly because of the low range of biomass concentration but a model with a good correlation coefficient (0.94) was formulated based on second derivative spectra. The gellan model was highly satisfactory, with an excellent correlation coefficient (0.98), again based on second derivative spectra. No sample pre-treatment was required and all spectral scanning was carried out on whole broth. Additionally, both models should be robust in practice since both were formulated using low numbers of factors. Thus, the near real time simultaneous monitoring of gellan and biomass in this highly complex matrix using FT-NIRS potentially opens the way to greatly improved process control strategies.     

Ecology, physiology, and phylogeny of deep subsurface Sphingomonas sp

Several new species of the genus Sphingomonas including S. aromaticivorans, S. stygia, and S. subterranea that have the capacity for degrading a broad range of aromatic compounds including toluene, naphthalene, xylenes, p-cresol, fluorene, biphenyl, and dibenzothiophene, were isolated from deeply-buried (>200 m) sediments of the US Atlantic coastal plain (ACP). In S. aromaticivorans F199, many of the genes involved in the catabolism of these aromatic compounds are encoded on a 184-kb conjugative plasmid; some of the genes involved in aromatic catabolism are plasmid-encoded in the other strains as well. Members of the genus Sphingomonas were common among aerobic heterotrophic bacteria cultured from ACP sediments and have been detected in deep subsurface environments elsewhere. The major source of organic carbon for heterotrophic metabolism in ACP deep aquifers is lignite that originated from plant material buried with the sediments. We speculate that the ability of the subsurface Sphingomonas strains to degrade a wide array of aromatic compounds represents an adaptation for utilization of sedimentary lignite. These and related subsurface Sphingomonas spp may play an important role in the transformation of sedimentary organic carbon in the aerobic and microaerobic regions of the deep aquifers of the ACP. Received 12 May 1999/ Accepted in revised form 25 July 1999