Biodegradation of propoxur by Pseudomonas species

A bacterium capable of degrading propoxur (2-isopropoxyphenyl-N-methylcarbamate) was isolated from soil by enrichment cultures and was identified as a Pseudomonas species. The organism grew on propoxur at 2 g/l as sole source of carbon and nitrogen, and accumulated 2-isopropoxyphenol as metabolite in the culture medium. The cell free extract of Pseudomonas sp. grown on propoxur contained the activity of propoxur hydrolase. The results suggest that the organism degraded propoxur by hydrolysis to yield 2-isopropoxyphenol and methylamine, which was further utilized as carbon source.     

Utilization of homoserine lactone as a sole source of carbon and energy by soil Arthrobacter and Burkholderia species

Homoserine lactone (HSL) is a ubiquitous product of metabolism. It is generated by all known biota during the editing of certain mischarged aminoacyl-tRNA reactions, and is also released as a product of quorum signal degradation by bacterial species expressing acyl-HSL acylases. Little is known about its environmental fate over long or short periods of time. The mammalian enzyme paraoxonase, which has no known homologs in bacteria, has been reported to degrade HSL via a lactonase mechanism. Certain strains of Variovorax and Arthrobacter utilize HSL as a sole source of nitrogen, but not as a sole source of carbon or energy. In this study, the enrichment and isolation of four strains of soil bacteria capable of utilizing HSL as a carbon and energy source are described. Phylogenetic analysis of these isolates indicates that three are distinct members of the genus Arthrobacter, whereas the fourth clusters within the non-clinical Burkholderia. The optimal pH for growth of the isolates ranged from 6.0 to 6.5, at which their HSL-dependent doubling times ranged from 1.4 to 4 h. The biodegradation of HSL by these 4 isolates far outpaced its chemical decay. HSL degradation by soil bacteria has implications for the consortial mineralization of acyl-homoserine lactones by bacteria associated with quorum sensing populations.     

Toxic effects of toluene on the growth of activated sludge bacteria

Two bacteria were isolated from the activated sludge sample of a wastewater treatment plant in Dublin by enrichment culture technique with toluene as the sole source of carbon and energy. They were identified as Aeromonas caviae (To-4) and Pseudomonas putida (To-5). The growth of these bacteria depended on the manner in which toluene was supplied. In general, growth was better when toluene was supplied in the vapour phase. When toluene was added directly to the growth medium it was found to be toxic to the organisms but the toxic effect could be alleviated in the presence of other carbon sources and by the acclimation of the cells. The growth of To-4 on toluene has never been previously reported.     

Biodegradation of 4-chlorobiphenyl by Micrococcus species

A Micrococcus sp., isolated by enrichment culture, grew on 4-chlorobiphenyl at 2 g/l as sole carbon source and produced 4-chlorobenzoic acid in the culture medium as a dead-end metabolite. The organism degraded 4-chlorobiphenyl by 2,3-dihydroxylation followed by meta-ring cleavage to yield 4-chlorobenzoate and carbon fragments for cell growth.     

Carbon assimilation and extracellular antigens of some yeast-like fungi

Many yeast-like fungi assimilated n-hexadecane, butylamine and putrescine as sole carbon sources. Methanol was not assimilated. This points to a physiological similarity to endomycetous, hydrocarbon-utilizing yeasts. Stephanoascus ciferrii assimilated uric acid, adenine and allantoin as sole source of carbon and nitrogen. All strains of Geotrichum candidum and many other yeast-like fungi assimilated acetoin and butan-2,3-diol. Assimilation tests for adenine, uric acid, allantoin, acetoin and butan-2,3-diol were found to be suitable for taxonomic purposes.Extracellular antigens immunologically related to those produced by Geotrichum candidum were detected in the cell-free culture liquids of several yeast-like fungi. The extracellular antigen excreted by Stephanoascus ciferrii was species-specific.     

Discovery of the heliobacteria

The first photosynthetic bacterium obtained in pure culture wasRhodospirillum rubrum, isolated by Erwin Esmarch in 1887. The organism appeared to be an aerobic heterotroph, and Esmarch was unaware of its photosynthetic capability. The overall general characteristics of a number of major species of photosynthetic bacteria were described by Molisch and van Niel before 1945. Subsequently, our knowledge of the anoxygenic phototrophs increased greatly through the systematic study of numerous new species isolated from enrichment cultures in which capacity for anaerobic (and anoxygenic) growth with light as the energy source was a primary selective factor. A further refinement of the enrichment technique required ability to use N₂ as the sole source of nitrogen for growth under anaerobic photosynthetic conditions, and this led to the isolation of additional new species, including the heliobacteria. The first recognition of the heliobacteria was facilitated by serendipity, which was a significant factor in a number of other researches on photosynthetic bacteria (Gest 1992).     

Degradation of Fumonisin B1 by a Bacterial Strain Isolated from Soil

A mixed microbial culture degrading fumonisin B l was obtained from soil samples using an enrichment culture procedure. A bacterial isolate from the enrichment culture (strain NCB 1492) degraded fumonisin B1 after incubation for 3 h, as indicated by TLC and HPLC analysis. On the basis of the sequence analysis of 16S rDNA, strain NCB 1492 was related to the Delftia/Comamonas group. Thin-layer chromatographic analysis indicated the presence of metabolites in the NCB 1492 culture filtrates after degradation of fumonisin B1 supplied as sole carbon and nitrogen source in phosphate buffer. Four metabolites were identified by mass spectrometry analysis.     

Glyphosate degradation byAgrobacterium radiobacter isolated from activated sludge

Summary Two species of bacteria capable of growth onN-phosphonomethylglycine (glyphosate) were isolated from a bench scale sequencing batch reactor degrading a waste stream containing glyphosate. The enrichment and isolation medium contained defined salts and glyphosate as the sole carbon and energy source. Glyphosate was stoichiometrically degraded to aminomethylphosphonic acid (AMPA). The bacteria have been identified asAgrobacterium radiobacter andAchromobacter Group V D.     

Bacterial degradation of benzalphthalide

APseudomonas sp., isolated by an enrichment culture technique, grew on benzalphthalide at up to 1 g/l as sole carbon source. Cells oxidized both benzalphthalide ando-phthalate at enhanced rates compared with glucose-grown cells, but catechol, gentisate and protocatechuate were oxidized slowly and equally by benzalphthalide-and glucose-grown cells.     

Rhodospirillum centenum,sp. nov., a thermotolerant cyst-forming anoxygenic photosynthetic bacterium

A novel non-sulfur purple photosynthetic bacterium, designated Rhodospirillum centenum, was isolated from an enrichment culture designed to favor growth of anoxygenic photosynthetic N₂-fixing bacteria. R. centenum grows optimally at 40–42° C and has the capacity to produce cytoplasmic R bodies, refractile structures not observed hitherto in photosynthetic prokaryotes. The bacterium is also unusual among photosynthetic bacteria in that it forms desiccation-resistant cysts when grown aerobically in darkness with butyrate as the sole carbon source.     

Fermentative degradation of dipicolinic acid (pyridine-2,6-dicarboxylic acid) by a defined coculture of strictly anaerobic bacteria

Degradation of dipicolinic acid (pyridine-2,6-dicarboxylic acid) under strictly anaerobic conditions was studied in enrichment cultures from marine and freshwater sediments. In all cases, dipicolinic acid was completely degraded. From an enrichment culture from a marine sediment, a defined coculture of two bacteria was isolated. The dipicolinic acid-fermenting bacterium was a Gram-negative, non-sporeforming strictly anaerobic short rod which utilized dipicolinic acid as sole source of carbon, energy, and nitrogen, and fermented it to acetate, propionate, ammonia, and 2CO₂. No other substrate was fermented. This bacterium could be cultivated only in coculture with another Gram-negative, non-sporeforming rod from the same enrichment culture which oxidized acetate to CO₂ with fumarate, malate, or elemental sulfur as electron acceptor, similar to Desulfuromonas acetoxidans. Since this metabolic activity is not important in substrate degradation by the coculture, the basis of the dependence of the dipicolinic acid-degrading bacterium on the sulfur reducer may be sought in the assimilatory metabolism.     

Isolation of dieldrin- and endrin-degrading bacteria using 1,2-epoxycyclohexane as a structural analog of both compounds

This report describes the selective isolation of dieldrin- and endrin-degrading bacteria from soil with high degradation activity toward dieldrin and endrin. Several enrichment cultures from the soil were arranged with several structural analogs of dieldrin and endrin as a growth substrate and examined for their degradation activities toward dieldrin and endrin. An enrichment culture with 1,2-epoxycyclohexane (ECH) was found to aerobically degrade dieldrin and endrin. Denaturing gradient gel electrophoresis (DGGE) indicated that three types of bacteria were predominant in the ECH enrichment culture. Of the three major bacteria, two isolates, Burkholderia sp. strain MED-7 and Cupriavidus sp. strain MED-5, showed high degradation activity toward dieldrin and endrin. The degradation efficiencies of strain MED-7 and MED-5 were 49% and 38% toward dieldrin, respectively, and 51% and 40% toward endrin, respectively, in the presence of ECH for 14 days. These results indicated that ECH was a useful substrate for selective and efficient isolation of dieldrin- and endrin-degrading bacteria from soil containing numerous bacteria. Interestingly, the two isolates could also degrade dieldrin and endrin even in the absence of ECH. These are the first microorganisms demonstrated to grow on dieldrin and endrin as the sole carbon and energy source under aerobic conditions.     

Production of volatile organic compounds (VOCs) by yeasts isolated from the ascocarps of black (<Emphasis Type="Italic">Tuber melanosporum</Emphasis> Vitt.) and white (<Emphasis Type="Italic">Tuber magnatum</Emphasis> Pico) truffles

Twenty-nine yeast strains were isolated from the ascocarps of black and white truffles (Tuber melanosporum Vitt. and Tuber magnatum Pico, respectively), and identified using a polyphasic approach. According to the conventional taxonomic methods, MSP-PCR fingerprinting and sequencing of the D1/D2 domain of 26S rDNA, the strains were identified as Candida saitoana, Debaryomyces hansenii, Cryptococcus sp., Rhodotorula mucilaginosa, and Trichosporon moniliiforme. All isolates assimilated l-methionine as a sole nitrogen source and produced the volatile organic compounds (VOCs), 2-methyl butanol, 3-methyl butanol, methanethiol, S-methyl thioacetate, dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, dihydro-2-methyl-3(2H)-thiophenone and 3-(methylthio)-1-propanol (MTP). ANOVA analysis of data showed significant (P<0.01) differences in VOCs produced by different yeasts, with MTP as the major component (produced at concentrations ranging from 19.8 to 225.6 mg/l). In addition, since some molecules produced by the isolates of this study are also characteristic of truffle complex aroma, it is possible to hypothesize a complementary role of yeasts associated with this ecosystem in contributing to final Tuber spp. aroma through the independent synthesis of yeast-specific volatile constituents.     

A novel medium for the isolation of <Emphasis Type="Italic">N</Emphasis>-acylhomoserine lactone-degrading bacteria

A novel chemically defined medium, named KG medium, supplemented with N-3-oxo-hexanoylhomoserine lactone (3-oxo-C6-HSL), an acylhomoserine lactone (AHL) used as signalling molecules in Gram-negative bacterial cell-to-cell communication, as the sole source of carbon and nitrogen, was designed and successfully used for the enrichment and isolation of AHL-degrading bacteria. A 3-oxo-C6-HSL-degrading bacterium, 13sw7, was isolated from sewage after six enrichment transfers in the 3-oxo-C6-HSL-containing KG medium. On the basis of the almost complete 16S ribosomal DNA sequence, isolate 13sw7 was clustered with unculturable β-proteobacteria. This study indicates that the AHL-containing KG medium is effective in isolating AHL-degrading bacteria, including those previously considered unculturable, from environmental sources. To the best of our knowledge, this is the first documentation of the isolation of an AHL-degrading proteobacterium from sewage.     

Production of (<Emphasis Type="Italic">R</Emphasis>)-ethyl-3,4-epoxybutyrate by newly isolated <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis> containing epoxide hydrolase

Several new microorganisms have been isolated from soil samples with high epoxide hydrolase activity toward ethyl 3,4-epoxybutyrate. Screening was performed by enrichment culture on alkenes as sole carbon source, followed by chiral gas chromatography. Eight strains were discovered with enantioselectivity from moderate to high level and identified as bacterial and yeast species. Cells were cultivated under aerobic condition at 30°C using glucose as carbon source and resting cells were used as biocatalysts for kinetic resolution of ethyl 3,4-epoxybutyrate. Among isolated microorganisms, Acinetobacter baumannii showed highest enantioselectivity for (S)-enantiomer, resulting in (R)-ethyl-3,4-epoxybutyrates (>99%ee, 46% yield). It is the first report on the fact that epoxide hydrolases originating from bacterial species of A. baumannii was applied to kinetic resolution of ethyl 3,4-epoxybutyrate in order to obtain enantiopure high-value-added (R)-ethyl-3,4-epoxybutyrate.     

Biodegradation of crude oil by soil microorganisms in the tropic

Five microorganisms, three bacteria and two yeasts, capable of degrading Tapis light crude oil were isolated from oil-contaminated soil in Bangkok, Thailand. Soil enrichment culture was done by inoculating the soil in mineral salt medium with 0.5% v/v Tapis crude oil as the sole carbon source. Crude oil biodegradation was measured by gas chromatography method. Five strains of pure microorganisms with petroleum degrading ability were isolated: three were bacteria and the other two were yeasts. Candida tropicalis strains 7Y and 15Y were identified as efficient oil degraders. Strain 15Y was more efficient, it was able to reduce 87.3% of the total petroleum or 99.6% of n-alkanes within the 7-day incubation period at room temperature of 25 ± 2 °C.     

Degradation of olestra, a non caloric fat replacer, by microorganisms isolated from activated sludge and other environments

Olestra is a non-caloric fat substitute consisting of fatty acids esterified to sucrose. Previous work has shown that olestra is not metabolized in the gut and is excreted unmodified in human feces. To better understand the fate of olestra in engineered and natural environments, aerobic bacteria and fungi that degrade olestra were enriched from sewage sludges, soils and municipal solid waste compost not previously exposed to olestra. Various mixed and pure cultures were obtained from these sources which were able to utilize olestra as a sole carbon and energy source. The fastest growing enrichment was obtained from activated sludge and later yielded an olestra-degrading pure culture of Pseudomonas aeruginosa. This mixed culture extensively degraded both ¹⁴C-fatty acid labeled olestra and ¹⁴C-sucrose labeled olestra during 8 days of incubation. Longer-term incubation with pure cultures of P. aeruginosa demonstrated that >98% of ¹⁴C-sucrose labeled olestra and >72% of ¹⁴C-fatty acid labeled olestra was mineralized to CO₂ after 69 days. These results indicate that olestra degraders are present in environments not previously exposed to olestra and that olestra can serve as a sole carbon and energy source. Furthermore, a common bacterial species was isolated from activated sludge and shown to have the ability to degrade olestra.     

Cosubstrate independent mineralization of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by a <Emphasis Type="Italic">Desulfovibrio</Emphasis> species under anaerobic conditions

Past handling practices associated with the manufacturing and processing of the high explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has resulted in extensive environmental contamination. In-situ biodegradation is a promising technology for remediating RDX contaminated sites but often relies on the addition of a cosubstrate. A sulfate-reducing bacterium isolated from an RDX-degrading enrichment culture was studied for its ability to grow on RDX as a sole source of carbon and nitrogen and for its ability to mineralize RDX in the absence of a cosubstrate. The results showed the isolate degraded 140 μM RDX in 63 days when grown on RDX as a carbon source. Biomass within the carbon limited culture increased 9-fold compared to the RDX unamended controls. When the isolate was incubated with RDX as sole source of nitrogen it degraded 160 μM RDX in 41 days and exhibited a 4-fold increase in biomass compared to RDX unamended controls. Radiolabeled studies under carbon limiting conditions with ¹⁴C-hexahydro-1,3,5-trinitro-1,3,5-triazine confirmed mineralization of the cyclic nitramine. After 60 days incubation 26% of the radiolabel was recovered as ¹⁴CO₂, while in the control bottles less than 1% of the radiolabel was recovered as ¹⁴CO₂. Additionally, ~2% of the radiolabeled carbon was found to be associated with the biomass. The 16S rDNA gene was sequenced and identified the isolate as a novel species of Desulfovibrio, having a 95.1% sequence similarity to Desulfovibrio desulfuricans. This is the first known anaerobic bacterium capable of mineralizing RDX when using it as a carbon and energy source for growth.     

Isolation and Characterization of a Pseudomonas putida Strain able to Grow with Trimethyl-1,2-dihydroxy-propyl-ammonium as Sole Source of Carbon, Energy and Nitrogen

Trimethyl-1,2-dihydroxypropyl-ammonium (TM) originates from the hydrolysis of the parent esterquat surfactant, which is widely used as softener in fabric care. Based on test procedures mimicking complex biological systems, TM is supposed to degrade completely when reaching the environment. However, no organisms able to degrade TM were isolated nor has the degradation pathway been elucidated so far. We isolated a Gram-negative rod able to grow with TM as sole source of carbon, energy and nitrogen. The strain reached a maximum specific growth rate of 0.4 h^–1 when growing with TM as the sole source of carbon, energy and nitrogen. TM was degraded to completion and surplus nitrogen was excreted as ammonium into the growth medium. A high percentage of the carbon in TM (68% in continuous culture and 60% in batch culture) was combusted to CO₂ resulting in a low yield of 0.54 mg cell dry weight per mg carbon during continuous cultivation and 0.73 mg cell dry weight per mg carbon in batch cultures. Choline, a natural structurally related compound, served as a growth substrate, whereas a couple of similar other quaternary aminoalcohols also used in softeners did not. The isolated bacterium was identified by 16S-rDNA sequencing as a strain of Pseudomonas putida with a difference of only one base pair to P. putida DSM 291^T. Despite their high identity, the reference strain P. putida DSM 291^T was not able to grow with TM and the two strains differed even in shape when growing on the same medium. This is the first microbial isolate able to degrade a quaternary ammonium softener head group to completion. Previously described strains growing on quaternary ammonium surfactants (decyltrimethylammonium, hexadecyltrimethylammonium and didecyldimethylammonium) either excreted metabolites or a consortium of bacteria was required for complete degradation.     

Metabolism of acrylonitrile by Klebsiella pneumoniae

A gram-negative rod-shaped bacterium capable of utilizing acrylonitrile as the sole source of nitrogen was isolated from industrial sewage and identified as Klebsiella pneumoniae. The isolate was capable of utilizing aliphatic nitriles containing 1 to 5 carbon atoms or benzonitrile as the sole source of nitrogen and either acetamide or propionamide as the sole source of both carbon and nitrogen. Gas chromatographic and mass spectral analyses of culture filtrates indicated that K. pneumoniae was capable of hydrolyzing 6.15 mmol of acrylonitrile to 5.15 mmol of acrylamide within 24 h. The acrylamide was hydrolyzed to 1.0 mmol of acrylic acid within 72 h. Another metabolite of acrylonitrile metabolism was ammonia, which reached a maximum concentration of 3.69 mM within 48 h. Nitrile hydratase and amidase, the two hydrolytic enzymes responsible for the sequential metabolism of nitrile compounds, were induced by acrylonitrile. The optimum temperature for nitrile hydratase activity was 55°C and that for amidase was 40°C; both enzymes had pH optima of 8.0.Abbreviations PBM phosphate buffered medium - GC gas chromatography - GC/MS gas chromatography/mass spectrometry