Isolation and Characterization of a New Gram-Negative, Acetone-Degrading, Nitrate-Reducing Bacterium from Soil, Paracoccus solventivorans sp. nov.

Abstract

An acetone-degrading, nitrate-reducing, coccoid to rod-shaped bacterium, strain L1, was isolated from soil on the site of a natural gas company. Cells of the logarithmic growth phase reacted gram positive, while those of the stationary growth phase were gram negative. Single organisms were 0.4 to 0.5 by 0.9 to 1.5 pm in size, nonmotile, and non-spore forming and had poly-P-hydroxybutyrate inclusions. The doubling time of strain L1 on acetone-C0,-nitrate at the optimal pH of 7 to 8 and the optimal temperature of 30 to 37°C was 12 h. More than 0.2% NaCl or 10 mM thiosulfate inhibited growth. For oxygen or nitrate respiration, acetone and a few organic chemicals were utilized as carbon sources whereas many others could not be used (for details, see Results). Bicarbonate (or CO,) was essential for growth on acetone but not for growth on acetoacetate. The growth yields for acetone-CO, and acetoacetate were 28.3 and 27.3 g/mol, respectively. With acetone as the carbon source, poly-P-hydroxybutyrate accounted for up to 40% of the cellular dry weight. The DNA of strain L1 had a G+C content of 68.5 mol% (as determined by high-performance liquid chromatography of nucleotides) or 70 mol% (as determined by the T, method). The sequence of the gene coding for the 16s rRNA led to the classification of strain L1 in the paracoccus group of the alpha subclass of the Proteobucteriu. The new isolate is named Paracoccus solventivuruns sp. nov. DSM 6637.Acetone is a fermentation product of fungi (15), clostridia (see, for example, reference 43), and several other bacteria (6, 35,36,51,57,58). It is also excreted into the environment in ripening apples as a bioconversion product derived from p pvate. Commercially, acetone is produced from isopropanol, cumene, or propane to serve as a solvent for resins, fats, oil, plastics, waxes, etc. (30). Acetone may therefore occur in many ecosystems as a naturally produced substance or as an industrial pollutant. It is, however, not accumulating because of its degradability by aerobic (see, e.g., references 25 and 27) and anaerobic (see, e.g., references 28, 36, and 38) bacteria. Because of its biological degradability in the presence or absence of oxygen, it is an especially suitable, nontoxic elutant for extraction of polycyclic aromatic hydrocarbons (PAHs) from contaminated soil for bioremediation. After extraction, the acetone-PAH solution can be easily separated by evaporation or distillation of the solvent. The acetone residue in the soil is harmless because of its rapid biological degradation. In an attempt to study PAH degradation in contaminated soil Samples, PAHs were extracted with acetone. In the first enrichments, nitrate-reducing, acetone-degrading bacteria were obtained. From these enrichments, a new acetone-degrading organism, strain L1, was isolated and subsequently characterized in detail.MATERIALS AND METHODS Sources of organisms. Strain L1 was isolated from a soil sample taken at a depth of 1 m at the site of a defunct natural gas company. (2) and dispensed in an anaerobic c...

Identification of bacterial isolates from biofilters as Paracoccus alkenifer sp. nov. and Paracoccus solventivorans with emended description of Paracoccus solventivorans

“…Paracoccus strains can grow methylotrophically with simple methyl compounds such as methanol or methylamine, or more complex substances such as N,N-dimethylformamide (32) or tetramethylammonium (2 1). Solvents such as acetone can also be utilized (29). The important role of Paracoccus strains in wastewater treatment was high-…”

“…They found Paracoccus strains to be significant in denitrifying sand filters. Most Paracoccus strains have been isolated from wastewater treatment plants ( 1 1, 18, 21, 25) or bioremediation sites of contaminated soils (29) due to their degradative capabilities.…”

Paracoccus chinensis sp. nov., isolated from sediment of a reservoir

“…One species is able to grow methylotrophically with methyl compounds such as methylamine or N,N-dimethylformamide (Urakami et al, 1990). Another species can oxidize reduced sulfur compounds (Rainey et al, 1999), whereas some strains are able to reduce nitrate to N 2 under anaerobic conditions (Siller et al, 1996). Paracoccus koreensis , Paracoccus homiensis (Kim et al, 2006), Paracoccus marinus and Paracoccus halophilus (Liu et al, 2008) were described recently.…”

“…One species is able to grow methylotrophically with methyl compounds such as methylamine or N,N-dimethylformamide (Urakami et al, 1990). Another species can oxidize reduced sulfur compounds (Rainey et al, 1999), whereas some strains are able to reduce nitrate to N 2 under anaerobic conditions (Siller et al, 1996) Strain KS-11 T was isolated from surface sediment of the Guanting reservoir. The samples were suspended and serially diluted in 50 mM phosphate buffer (pH 7.0) and spread on R2A agar plates (containing, l 21 distilled water: 0.5 g glucose, 0.5 g soluble starch, 0.5 g casein hydrolysate, 0.5 g yeast extract, 0.5 g peptone, 0.05 g MgSO 4 .…”

Emended description of Paracoccus kondratievae.

“…At present, the genus Paracoccus includes 13 validated species and has become the focus of many studies on its physiological versatility, and on the ability to degrade unusual and potentially polluting compounds, as extensively reviewed by Kelly et al (2000). Some members of this genus are able to oxidize reduced sulfur compounds such as thiosulfate, thiocyanate, carbonyl sulfide and carbon disulfide to gain energy for autotrophic growth (Katayama et al, 1995 ;Siller et al, 1996 ;Lipski et al, 1998 ;Rainey et al, 1999). Most Paracoccus species are able to grow on carbon dioxide by using hydrogen oxidation as the source of metabolic energy ; some species can also grow methylotrophically with methanol, methylamine (Urakami et al, 1990 ;Ohara et al, 1990 ; Van Verseveld & Stouthamer, 1992), dichloromethane (Doronina et al, 1998), or with more complex substances such as N,N-dimethylformamide (Urakami et al, 1990) or methylated sulfides (Rainey et al, 1999).…”