Acetogenesis from Dichloromethane by a Two-Component Mixed Culture Comprising a Novel Bacterium

A strictly anaerobic two-component culture able to grow exponentially with a doubling time of 20 h on a medium containing dichloromethane as the carbon and energy source was characterized. On a medium without sulfate, we observed (per mol of dichloromethane) a mass balance of 2 mol of chloride, 0.26 mol of acetate, 0.05 mol of formate, and 0.25 mol of carbon in biomass. One component of the culture, strain DMB, was identified by a 16S ribosomal DNA analysis as a Desulfovibrio sp. The other component, the gram-positive organism strain DMC, could not be isolated. It was possible, however, to associate strain DMC on a medium containing dichloromethane in a coculture with Acetobacterium woodii or Methanospirillum hungatei. Coculture of strain DMC with the Archaeon M. hungatei allowed us to specifically amplify by PCR the 16S rRNA gene of strain DMC. A phylogenetic analysis of the 16S ribosomal DNA sequence revealed that this organism groups within the radiation of the Clostridium-Bacillus subphylum and exhibits the highest levels of sequence similarity (89%) with Desulfotomaculum orientis and Desulfitobacterium dehalogenans. Since the novel organism strain DMC was able to grow acetogenically with dichloromethane when it was associated with one of three metabolically different partners and since, in contrast to strain DMB, strain DMC contained carbon monoxide dehydrogenase activity, this bacterium is responsible for both the dehalogenation of dichloromethane and the acetogenesis observed in the original two-component culture. The obligatory dependence of strain DMC on a partner during growth with dichloromethane is thought to stem from the need for a growth factor produced by the associated organism.     

一株新型同型产乙酸菌Clostridium sp.的自养和异养生长特性

【背景】同型产乙酸菌是一类利用乙酰辅酶A途径固定CO_2合成自身细胞物质并生成乙酸、乙醇等代谢产物的厌氧菌群,其分布广泛、种类繁多且代谢多样。深入研究同型产乙酸菌菌株的代谢能力及特性,对探索该种群的生理生化特性及其环境作用至关重要。【目的】研究一株同型产乙酸菌Clostridium sp. BXX的最适培养条件及其自养与异养生长特性。【方法】设置BXX菌株培养温度10-55°C、初始pH 6.0-9.0、NaCl浓度0-2.0%、不同氮源,测定菌体细胞含量和产物生成浓度,确定菌株最适培养条件。研究BXX菌株分别以H_2/CO_2、合成气、CO、葡萄糖、1,2-丙二醇、甲酸钠、乙二醇甲醚、甘油、丙酮酸和乳酸为底物时的底物消耗、产物生成、菌体细胞含量和pH等,探究其自养和异养生长特性。【结果】BXX菌株的最适培养温度为30°C,初始pH为7.0,NaCl浓度为1.0%,氮源为酵母粉。BXX菌株能以H2/CO2、合成气、葡萄糖、1,2-丙二醇、甲酸钠、乙二醇甲醚和甘油为底物生长,不能以CO、丙酮酸或乳酸为底物生长。【结论】BXX菌株既能自养生长产乙酸,又能异养生长产乙醇。BXX菌株是乙酸发酵的优良菌种资源,有较好的工业应用潜力。     

Hydrogen-using bacteria in a methanogenic acetate enrichment culture

A rcher , D.B. 1984. Hydrogen-using bacteria in a methanogenic acetate enrichment culture. Journal of Applied Bacteriology 56 , 125–129.
In a study of the anaerobic utilization of acetate, an enrichment culture of sewage sludge organisms was initiated with calcium acetate as the sole carbon and energy source. A mixed bacterial population became established from which 14 anaerobic species were isolated. Two of the isolates were methanogenic bacteria but only one of these, Methanosarcina barkeri , utilised acetate as an energy source in axenic culture. The other methanogenic isolate, a Methanobacterium sp., utilised H₂/CO₂ but not acetate. A third methanogen, which was morphologically identical to Methanothrix soehngenii , was detected in the enrichment but was not obtained in monoculture. 2-Bromoethanesulphonate, a specific inhibitor of methanogenesis. completely inhibited the enrichment at a concentration of 10 μmol/1. Addition of H₂ formate or methanol to the enrichment did not affect the rate of methanogenesis. An H₂-utilizing Desulfovibrio sp. was also isolated from the enrichment.     

Eubacterium aggreganssp. nov., a new homoacetogenic bacterium from olive mill wastewater treatment digestor

A strictly anaerobic, homoacetogenic, gram-positive, non spore-forming bacterium, designated strain SR12(T) (T = type strain), was isolated from an anaerobic methanogenic digestor fed with olive mill wastewater. Yeast extract was required for growth but could also be used as sole carbon and energy source. Strain SR12(T) utilized a few carbohydrates (glucose, fructose and sucrose), organic compounds (lactate, crotonate, formate and betaine), alcohols (methanol), the methoxyl group of some methoxylated aromatic compounds, and H2 + CO2. The end-products of carbohydrate fermentation were acetate, formate, butyrate, H2 and CO2. End-products from lactate and methoxylated aromatic compounds were acetate and butyrate. Strain SR12(T) was non-motile, formed aggregates, had a G+C content of 55 mol % and grew optimally at 35 degrees C and pH 7.2 on a medium containing glucose. Phylogenetically, strain SR12(T) was related to Eubacterium barkeri, E. callanderi, and E. limosum with E. barkeri as the closest relative (similarity of 98%) with which it bears little phenotypic similarity or DNA homology (60%). On the basis of its phenotypic, genotypic, and phylogenetic characteristics, we propose to designate strain SR12(T) as Eubacterium aggregans sp. nov. The type strain is SR12(T) (= DSM 12183).     

Complete genome sequence of a carbon monoxide-utilizing acetogen, Eubacterium limosum KIST612

Eubacterium limosum KIST612 is an anaerobic acetogenic bacterium that uses CO as the sole carbon/energy source and produces acetate, butyrate, and ethanol. To evaluate its potential as a syngas microbial catalyst, we have sequenced the complete 4.3-Mb genome of E. limosum KIST612.     

Carbon dioxide fixation and mixotrophic metabolism by strain DCB-1, a dehalogenating anaerobic bacterium.

Fixation by strain DCB-1 of CO2 carbon into cell material and organic acids occurred during growth on pyruvate both with and without thiosulfate. By using sodium [14C]bicarbonate and sodium [2-14C]pyruvate, the isotopic composition of products and cells was investigated. Up to 70% of cell carbon was derived from CO2. CO2 carbon was also incorporated into succinate, formate, and acetate. Both carbons of acetate underwent exchange reactions with CO2, although the carboxyl-group exchange was twice as fast. Because strain DCB-1 uses CO2 as its major but not sole carbon source while deriving energy from pyruvate metabolism, we describe its metabolism as mixotrophic. Other mixotrophic conditions also supported growth. Lactate or butyrate, which could not support growth in mineral medium, could replace pyruvate as the oxidizable substrate only when acetate was added to the medium.     

Carbon dioxide fixation and mixotrophic metabolism by strain DCB-1, a dehalogenating anaerobic bacterium

Fixation by strain DCB-1 of CO2 carbon into cell material and organic acids occurred during growth on pyruvate both with and without thiosulfate. By using sodium [14C]bicarbonate and sodium [2-14C]pyruvate, the isotopic composition of products and cells was investigated. Up to 70% of cell carbon was derived from CO2. CO2 carbon was also incorporated into succinate, formate, and acetate. Both carbons of acetate underwent exchange reactions with CO2, although the carboxyl-group exchange was twice as fast. Because strain DCB-1 uses CO2 as its major but not sole carbon source while deriving energy from pyruvate metabolism, we describe its metabolism as mixotrophic. Other mixotrophic conditions also supported growth. Lactate or butyrate, which could not support growth in mineral medium, could replace pyruvate as the oxidizable substrate only when acetate was added to the medium.     

Microaerophilic growth of Wolinella recta ATCC 33238

Abstract The influence of oxygen on growth and fumarate-dependent respiration of Wolinella recta ATCC 33238 was studied in continuous culture. Steady states were obtained with formate-limited cultures grown at a specific growth rate of 0.1 h⁻¹ with different levels of oxygenation. The extent of aeration was regulated by means of a redox control system permitting reproducible cultivation at oxygen levels below the detection limit of conventional lead-silver probes. The ratio of succinate produced to that of formate consumed (Suc/For) decreased from 0.99 in strictly anaerobic cultures to 0.06–0.10 in aerated cultures. The growth yield did not change significantly with increasing redox readings: 4.9–5.2 g cell carbon/mol formate. The ability to use O₂ as the sole electron acceptor was demonstrated in a chemostat culture with formate as electron donor and succinate as carbon source. Washed cells from all chemostat cultures comsumed O₂ with formate as electron donor at a high rate (2.1–3.7 μmol/min per mg protein) and possessed b - and c -type cytochromes and CO-binding pigments. These results clearly indicated the microaerophilic nature of W. recta .     

Carbon assimilation pathways in sulfate reducing bacteria. Formate,carbon dioxide,carbon monoxide,and acetate assimilation by Desulfovibrio baarsii

Desulfovibrio baarsii is a sulfate reducing bacterium, which can grown on formate plus sulfate as sole energy source and formate and CO₂ as sole carbon sources. It is shown by ¹⁴C labelling studies that more than 60% of the cell carbon is derived from CO₂ and the rest from formate. The cells thus grow autotrophically. Labelling studies with [¹⁴C]acetate, ¹⁴CO and [¹⁴C]formate indicate that CO₂ fixation does not proceed via the Calvin cycle. The labelling patterns of alanine, aspartate, glutamate, and glucosamine indicate that acetate (or activated acetic acid) is an early intermediate in formate and CO₂ assimilation; the methyl group of acetate is derived from formate, and the carboxyl group from CO₂ via CO; pyruvate is formed from acetyl-CoA by reductive carboxylation. The capacity to synthesize an acetate unit from two C₁-compounds obviously distinguishes D. baarsii from those Desulfovibrio species, which require acetate as a carbon source in addition to CO₂.     

Identification and isolation of anaerobic, syntrophic phthalate isomer-degrading microbes from methanogenic sludges treating wastewater from terephthalate manufacturing

The microbial populations responsible for anaerobic degradation of phthalate isomers were investigated by enrichment and isolation of those microbes from anaerobic sludge treating wastewater from the manufacturing of terephthalic acid. Primary enrichments were made with each of three phthalate isomers (ortho-, iso-, and terephthalate) as the sole energy source at 37 degrees C with two sources of anaerobic sludge (both had been used to treat wastewater containing high concentrations of phthalate isomers) as the inoculum. Six methanogenic enrichment cultures were obtained which not only degraded the isomer used for the enrichment but also had the potential to degrade part of other phthalate isomers as well as benzoate with concomitant production of methane, presumably involving strictly syntrophic substrate degradation. Our 16S rRNA gene-cloning analysis combined with fluorescence in situ hybridization revealed that the predominant bacteria in the enrichment cultures were affiliated with a recently recognized non-sulfate-reducing subcluster (subcluster Ih) in the group 'Desulfotomaculum lineage I' or a clone cluster (group TA) in the class delta-PROTEOBACTERIA: Several attempts were made to isolate these microbes, resulting in the isolation of a terephthalate-degrading bacterium, designated strain JT, in pure culture. A coculture of the strain with the hydrogenotrophic methanogen Methanospirillum hungatei converted terephthalate to acetate and methane within 3 months of incubation, whereas strain JT could not degrade terephthalate in pure culture. During the degradation of terephthalate, a small amount of benzoate was transiently accumulated as an intermediate, indicative of decarboxylation of terephthalate to benzoate as the initial step of the degradation. 16S rRNA gene sequence analysis revealed that the strain was a member of subcluster Ih of the group 'Desulfotomaculum lineage I', but it was only distantly related to other known species.     

Biodegradation of dichloromethane and its utilization as a growth substrate under methanogenic conditions.

Biodegradation of dichloromethane (DCM) to environmentally acceptable products was demonstrated under methanogenic conditions (35 degrees C). When DCM was supplied to enrichment cultures as the sole organic compound at a low enough concentration to avoid inhibition of methanogenesis, the molar ratio of CH4 formed to DCM consumed (0.473) was very close to the amount predicted by stoichiometric conservation of electrons. DCM degradation was also demonstrated when methanogenesis was partially inhibited (with 0.5 to 1.5 mM 2-bromoethanesulfonate or approximately 2 mM DCM) or completely stopped (with 50 to 55.5 mM 2-bromoethanesulfonate). Addition of a eubacterial inhibitor (vancomycin, 100 mg/liter) greatly reduced the rate of DCM degradation. 14CO2 was the principal product of [14C]DCM degradation, followed by 14CH4 (when methanogenesis was uninhibited) or 14CH3COOH (when methanogenesis was partially or completely inhibited). Hydrogen accumulated during DCM degradation and then returned to background levels when DCM was consumed. These results suggested that nonmethanogenic organisms mediated DCM degradation, oxidizing a portion to CO2 and fermenting the remainder to acetate; acetate formation suggested involvement of an acetogen. Methanogens in the enrichment culture then converted the products of DCM degradation to CH4. Aceticlastic methanogens were more easily inhibited by 2-bromoethanesulfonate and DCM than were CO2-reducing methanogens. When DCM was the sole organic-carbon and electron donor source supplied, its use as a growth substrate was demonstrated. The highest observed yield was 0.085 g of suspended organic carbon formed per g of DCM carbon consumed. Approximately 85% of the biomass formed was attributable to the growth of nonmethanogens, and 15% was attributable to methanogens.     

Biodegradation of dichloromethane and its utilization as a growth substrate under methanogenic conditions.

Biodegradation of dichloromethane (DCM) to environmentally acceptable products was demonstrated under methanogenic conditions (35 degrees C). When DCM was supplied to enrichment cultures as the sole organic compound at a low enough concentration to avoid inhibition of methanogenesis, the molar ratio of CH4 formed to DCM consumed (0.473) was very close to the amount predicted by stoichiometric conservation of electrons. DCM degradation was also demonstrated when methanogenesis was partially inhibited (with 0.5 to 1.5 mM 2-bromoethanesulfonate or approximately 2 mM DCM) or completely stopped (with 50 to 55.5 mM 2-bromoethanesulfonate). Addition of a eubacterial inhibitor (vancomycin, 100 mg/liter) greatly reduced the rate of DCM degradation. 14CO2 was the principal product of [14C]DCM degradation, followed by 14CH4 (when methanogenesis was uninhibited) or 14CH3COOH (when methanogenesis was partially or completely inhibited). Hydrogen accumulated during DCM degradation and then returned to background levels when DCM was consumed. These results suggested that nonmethanogenic organisms mediated DCM degradation, oxidizing a portion to CO2 and fermenting the remainder to acetate; acetate formation suggested involvement of an acetogen. Methanogens in the enrichment culture then converted the products of DCM degradation to CH4. Aceticlastic methanogens were more easily inhibited by 2-bromoethanesulfonate and DCM than were CO2-reducing methanogens. When DCM was the sole organic-carbon and electron donor source supplied, its use as a growth substrate was demonstrated. The highest observed yield was 0.085 g of suspended organic carbon formed per g of DCM carbon consumed. Approximately 85% of the biomass formed was attributable to the growth of nonmethanogens, and 15% was attributable to methanogens.     

Fermentation of 2-methoxyethanol by Acetobacterium malicum sp. nov. and Pelobacter venetianus

Anaerobic bacteria degrading 2-methoxyethanol were enriched from freshwater sediments, and three strains were isolated in pure culture. Two of them were Grampositive non-spore-forming rods and grew strictly anaerobically by acetogenic fermentation. Optimal growth occurred at 30°C, initial pH 7.5–8.0. 2-Methoxyethanol and 2-ethoxyethanol were fermented to acetate and corresponding alcohols. Hydrogen plus carbon dioxide, formate, acetoin, l-malate, lactate, pyruvate, fructose, and methoxyl groups of 3,4,5-trimethoxybenzoate and 3,4,5-trimethoxycinnamate were fermented to acetate. 1,2-Propanediol was fermented to acetate, propionate, and propanol. Strain MuME1 was described as a new species, Actetobacterium malicum. It had a DNA base composition of 44.1 mol% guanine plus cytosine. The third strain, which was identified as Pelobacter venetianus, fermented 2-methoxyethanol to methanol, ethanol, and acetate.     

Complete oxidation of catechol by the strictly anaerobic sulfate-reducing Desulfobacterium catecholicum sp. nov.

From an anaerobic enrichment culture with vanillate as substrate, a catechol-degrading lemon-shaped nonsporing sulfate-reducing bacterium, strain NZva20, was isolated in pure culture. Growth occurred in defined, bicarbonate-buffered, sulfide-reduced freshwater medium with catechol as sole electron donor and carbon source. Catechol was completely oxidized to CO₂ with an average growth yield of 31 g cell dry mass per mol of catechol, corresponding to 9.5 g cell dry mass per mol of sulfate reduced. Further substrates utilized as electron donors and carbon sources were resorcinol, hydroquinone, benzoate and several other aromatic compounds, hydrogen plus carbon dioxide, formate, lactate, pyruvate, alcohols including methanol, dicarboxylic acids, acetate, propionate and higher fatty acids up to 18 carbon atoms. Instead of sulfate, sulfite, thiosulfate, dithionite or nitrate served as electron acceptors. Nitrate was reduced to ammonium. Strain NZva20 is the first bacterium in which the complete oxidation of organic substrates is linked to the ammonification of nitrate. Elemental sulfur was not utilized as electron acceptor. In the absence of an electron acceptor slow growth occurred on pyruvate or fumarate. The G+C content of the DNA of strain NZva20 was 52.4 mol%. Cytochromes were present. Desulfoviridin could not be detected. Strain NZva20 is described as type strain of a new species, Desulfobacterium catecholicum sp. nov.Affectionately dedicated to Professor Ralph S. Wolfe on the occassion of his 65th birthday     

Eubacterium aggreganssp. nov., a New Homoacetogenic Bacterium from Olive Mill Wastewater Treatment Digestor

A strictly anaerobic, homoacetogenic, Gram-positive, non spore-forming bacterium, designated strain SR12^T(T=type strain), was isolated from an anaerobic methanogenic digestor fed with olive mill wastewater. Yeast extract was required for growth but could also be used as sole carbon and energy source. Strain SR12^Tutilized a few carbohydrates (glucose, fructose and sucrose), organic compounds (lactate, crotonate, formate and betaine), alcohols (methanol), the methoxyl group of some methoxylated aromatic compounds, and H₂+CO₂. The end-products of carbohydrate fermentation were acetate, formate, butyrate, H₂and CO₂. End-products from lactate and methoxylated aromatic compounds were acetate and butyrate. Strain SR12^Twas non-motile, formed aggregates, had a G+C content of 55 mol % and grew optimally at 35°C and pH 7.2 on a medium containing glucose. Phylogenetically, strain SR12^Twas related toEubacterium barkeri, E. callanderi, andE. limosumwithE. barkerias the closest relative (similarity of 98%) with which it bears little phenotypic similarity or DNA homology (60%). On the basis of its phenotypic, genotypic, and phylogenetic characteristics, we propose to designate strain SR12^TasEubacterium aggreganssp. nov. The type strain is SR12^T(=DSM 12183).     

Reciprocal Isomerization of Butyrate and Isobutyrate by the Strictly Anaerobic Bacterium Strain WoG13 and Methanogenic Isobutyrate Degradation by a Defined Triculture

Isomerization of butyrate and isobutyrate was investigated with the recently isolated strictly anaerobic bacterium strain WoG13 which ferments glutarate to butyrate, isobutyrate, CO₂, and small amounts of acetate. Dense cell suspensions converted butyrate to isobutyrate and isobutyrate to butyrate. ¹³C-nuclear magnetic resonance experiments proved that this isomerization was accomplished by migration of the carboxyl group to the adjacent carbon atom. In cell extracts, both butyrate and isobutyrate were activated to their coenzyme A (CoA) esters by acyl-CoA:acetate CoA-transferases. The reciprocal rearrangement of butyryl-CoA and isobutyryl-CoA was catalyzed by a butyryl-CoA:isobutyryl-CoA mutase which depended strictly on the presence of coenzyme B₁₂. Isobutyrate was completely degraded via butyrate to acetate and methane by a defined triculture of strain WoG13, Syntrophomonas wolfei, and Methanospirillum hungatei.     

Fermentative degradation of polyethylene glycol by a strictly anaerobic, gram-negative, nonsporeforming bacterium, Pelobacter venetianus sp. nov.

The synthetic polyether polyethylene glycol (PEG) with a molecular weight of 20,000 was anaerobically degraded in enrichment cultures inoculated with mud of limnic and marine origins. Three strains (Gra PEG 1, Gra PEG 2, and Ko PEG 2) of rod-shaped, gram-negative, nonsporeforming, strictly anaerobic bacteria were isolated in mineral medium with PEG as the sole source of carbon and energy. All strains degraded dimers, oligomers, and polymers of PEG up to a molecular weight of 20,000 completely by fermentation to nearly equal amounts of acetate and ethanol. The monomer ethylene glycol was not degraded. An ethylene glycol-fermenting anaerobe (strain Gra EG 12) isolated from the same enrichments was identified as Acetobacterium woodii. The PEG-fermenting strains did not excrete extracellular depolymerizing enzymes and were inhibited by ethylene glycol, probably owing to a blocking of the cellular uptake system. PEG, some PEG-containing nonionic detergents, 1,2-propanediol, 1,2-butanediol, glycerol, and acetoin were the only growth substrates utilized of a broad variety of sugars, organic acids, and alcohols. The isolates did not reduce sulfate, sulfur, thiosulfate, or nitrate and were independent of growth factors. In coculture with A. woodii or Methanospirillum hungatei, PEGs and ethanol were completely fermented to acetate (and methane). A marine isolate is described as the type strain of a new species, Pelobacter venetianus sp. nov. Its physiology and ecological significance, as well as the importance and possible mechanism of anaerobic polyether degradation, are discussed.     

Benzoate fermentation by the anaerobic bacterium Syntrophus aciditrophicus in the absence of hydrogen-using microorganisms.

The anaerobic bacterium Syntrophus aciditrophicus metabolized benzoate in pure culture in the absence of hydrogen-utilizing partners or terminal electron acceptors. The pure culture of S. aciditrophicus produced approximately 0.5 mol of cyclohexane carboxylate and 1.5 mol of acetate per mol of benzoate, while a coculture of S. aciditrophicus with the hydrogen-using methanogen Methanospirillum hungatei produced 3 mol of acetate and 0.75 mol of methane per mol of benzoate. The growth yield of the S. aciditrophicus pure culture was 6.9 g (dry weight) per mol of benzoate metabolized, whereas the growth yield of the S. aciditrophicus-M. hungatei coculture was 11.8 g (dry weight) per mol of benzoate. Cyclohexane carboxylate was metabolized by S. aciditrophicus only in a coculture with a hydrogen user and was not metabolized by S. aciditrophicus pure cultures. Cyclohex-1-ene carboxylate was incompletely degraded by S. aciditrophicus pure cultures until a free energy change (DeltaG') of -9.2 kJ/mol was reached (-4.7 kJ/mol for the hydrogen-producing reaction). Cyclohex-1-ene carboxylate, pimelate, and glutarate transiently accumulated at micromolar levels during growth of an S. aciditrophicus pure culture with benzoate. High hydrogen (10.1 kPa) and acetate (60 mM) levels inhibited benzoate metabolism by S. aciditrophicus pure cultures. These results suggest that benzoate fermentation by S. aciditrophicus in the absence of hydrogen users proceeds via a dismutation reaction in which the reducing equivalents produced during oxidation of one benzoate molecule to acetate and carbon dioxide are used to reduce another benzoate molecule to cyclohexane carboxylate, which is not metabolized further. Benzoate fermentation to acetate, CO(2), and cyclohexane carboxylate is thermodynamically favorable and can proceed at free energy values more positive than -20 kJ/mol, the postulated minimum free energy value for substrate metabolism.     

Metabolism of homoacetogens

Homoacetogenic bacteria are strictly anaerobic microorganisms that catalyze the formation of acetate from C₁ units in their energy metabolism. Most of these organisms are able to grow at the expense of hydrogen plus CO₂ as the sole energy source. Hydrogen then serves as the electron donor for CO₂ reduction to acetate. The methyl group of acetate is formed from CO₂ via formate and reduced C₁ intermediates bound to tetrahydrofolate. The carboxyl group is derived from carbon monoxide, which is synthesized from CO₂ by carbon monoxide dehydrogenase. The latter enzyme also catalyzes the formation of acetyl-CoA from the methyl group plus CO. Acetyl-CoA is then converted either to acetate in the catabolism or to cell carbon in the anabolism of the bacteria. The homoacetogens are very versatile anaerobes, which convert a variety of different substrates to acetate as the major end product.     

A Gram-Negative Anaerobic Bacterium That Utilizes O-Methyl Substituents of Aromatic Acids

A novel strain of gram-negative anaerobic rods which utilized O-methyl substituents of monoaromatic acids as a sole organic source of carbon was isolated from municipal sewage sludge. Energy for growth seemed to be generated by an acetate formation pathway. The growth yield in defined medium was 7.9 g (dry weight) of cells per mol of ferulate utilized. This isolate and other O-demethylating anaerobes may play a role in the turnover of acetate and the metabolism of highly methoxylated lignaceous materials in anaerobic environments.