Cryptanaerobacter phenolicus gen. nov., sp. nov., an anaerobe that transforms phenol into benzoate via 4-hydroxybenzoate

161

129

The classical perception of members of the gram-positive Desulfotomaculum cluster I as sulfate-reducing bacteria was recently challenged by the isolation of new representatives lacking the ability for anaerobic sulfate respiration. For example, the two described syntrophic propionate-oxidizing species of the genus Pelotomaculum form the novel Desulfotomaculum subcluster Ih. In the present study, we applied a polyphasic approach by using cultivation-independent and culturing techniques in order to further characterize the occurrence, abundance, and physiological properties of subcluster Ih bacteria in low-sulfate, methanogenic environments. 16S rRNA (gene)-based cloning, quantitative fluorescence in situ hybridization, and real-time PCR analyses showed that the subcluster Ih population composed a considerable part of the Desulfotomaculum cluster I community in almost all samples examined. Additionally, five propionate-degrading syntrophic enrichments of subcluster Ih bacteria were successfully established, from one of which the new strain MGP was isolated in coculture with a hydrogenotrophic methanogen. None of the cultures analyzed, including previously described Pelotomaculum species and strain MGP, consumed sulfite, sulfate, or organosulfonates. In accordance with these phenotypic observations, a PCR-based screening for dsrAB (key genes of the sulfate respiration pathway encoding the alpha and beta subunits of the dissimilatory sulfite reductase) of all enrichments/(co)cultures was negative with one exception. Surprisingly, strain MGP contained dsrAB, which were transcribed in the presence and absence of sulfate. Based on these and previous findings, we hypothesize that members of Desulfotomaculum subcluster Ih have recently adopted a syntrophic lifestyle to thrive in low-sulfate, methanogenic environments and thus have lost their ancestral ability for dissimilatory sulfate/sulfite reduction.Members of Desulfotomaculum cluster I have been generally known as gram-positive, spore-forming, sulfate-reducing bacteria (50, 56) and have frequently been found in various anoxic environments, such as sediments, rice paddy soil, human feces, and anaerobic sludges (for examples, see references 21, 42, 56, 57). The genus Desulfotomaculum includes over 20 validly described mesophilic and thermophilic species, all of which share the ability to oxidize various organic substances, like shortchain fatty acids, alcohols, and aromatic compounds with sulfate as a terminal electron acceptor (56). Due to these physiological traits, members of Desulfotomaculum cluster I have been considered important in sulfidogenic, anoxic environments, where they play crucial roles in the degradation of organic compounds, as well as in the biogeochemical cycling of sulfur (56).On the basis of comparative 16S rRNA gene sequence analysis, Desulfotomaculum cluster I was considered to be comprised of seven well-separated subclusters, Ia to Ig (27,50,52,57). Although it has been argued that each subcluster could be treated taxonomically as an individual...

Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Non-Sulfate-Reducing, Syntrophic Bacteria Affiliated with Desulfotomaculum Cluster I Are Widely Distributed in Methanogenic Environments

Imachi

Sekiguchi

Kamagata

et al. 2006

161

129

“…However, despite the tremendous effort to search for phenol degraders in such environments, only a few examples are known. To date, only one species, Cryptanaerobacter phenolicus, has been isolated and characterized as an anaerobe able to metabolize phenol under methanogenic conditions (16). The organism is an anaerobic bacterium that can transform phenol into benzoate in the presence of as-yet-unidentified electron donors.…”

mentioning

confidence: 99%

Syntrophorhabdus aromaticivorans gen. nov., sp. nov., the First Cultured Anaerobe Capable of Degrading Phenol to Acetate in Obligate Syntrophic Associations with a Hydrogenotrophic Methanogen

Qiu

Hanada

Ohashi

et al. 2008

230

136

Phenol degradation under methanogenic conditions has long been studied, but the anaerobes responsible for the degradation reaction are still largely unknown. An anaerobe, designated strain UI T , was isolated in a pure syntrophic culture. This isolate is the first tangible, obligately anaerobic, syntrophic substrate-degrading organism capable of oxidizing phenol in association with an H 2 -scavenging methanogen partner. Besides phenol, it could metabolize p-cresol, 4-hydroxybenzoate, isophthalate, and benzoate. During the degradation of phenol, a small amount of 4-hydroxybenzoate (a maximum of 4 M) and benzoate (a maximum of 11 M) were formed as transient intermediates. When 4-hydroxybenzoate was used as the substrate, phenol (maximum, 20 M) and benzoate (maximum, 92 M) were detected as intermediates, which were then further degraded to acetate and methane by the coculture. No substrates were found to support the fermentative growth of strain UI T in pure culture, although 88 different substrates were tested for growth. 16S rRNA gene sequence analysis indicated that strain UI T belongs to an uncultured clone cluster (group TA) at the family (or order) level in the class Deltaproteobacteria. Syntrophorhabdus aromaticivorans gen. nov., sp. nov., is proposed for strain UI T , and the novel family Syntrophorhabdaceae fam. nov. is described. Peripheral 16S rRNA gene sequences in the databases indicated that the proposed new family Syntrophorhabdaceae is largely represented by abundant bacteria within anaerobic ecosystems mainly decomposing aromatic compounds.Phenols and phthalate isomers are among the most widely used chemicals and are often found in industrial wastewaters in abundance. These chemicals are known to be inhibitors for the growth of microorganisms in biological treatment processes and are regarded as priority pollutants on the U.S. Environmental Protection Agency list (19,38). Phenol has long been known to be degraded anaerobically in the methanogenic environment (20, 43). Methanogenic degradation of phenol is significant considering the wastewater treatment processes of industrial waste chemicals and biogeochemistry of naturally occurring phenolic compounds in deep subsurface environments, such as an oil reservoir. However, despite the tremendous effort to search for phenol degraders in such environments, only a few examples are known. To date, only one species, Cryptanaerobacter phenolicus, has been isolated and characterized as an anaerobe able to metabolize phenol under methanogenic conditions (16). The organism is an anaerobic bacterium that can transform phenol into benzoate in the presence of as-yet-unidentified electron donors. However, no organisms that are genuinely capable of utilizing phenol as the sole energy source under methanogenic conditions have been isolated so far.Recently, the enrichment and identification of mesophilic phthalate isomer-degrading bacteria from methanogenic sludges treating wastewater from the manufacture of terephthalic and isophthalic acids were reported (29). Thro...

“…Although anaerobic degradation of phenol has been known to occur for a long time (11, 12), biochemical and genetic investigations have been limited. To date, anaerobic biodegradation and remediation studies have focused on consortia, but recently anaerobic phenol-degrading bacteria have been isolated under denitrifying (4, 37, 39, 41), iron-reducing (23), sulfidogenic (3, 5, 18), and fermentative-methanogenic conditions (10,15,21,28,42). Biodegradation of phenolic compounds under denitrifying conditions is well documented, and several bacteria have been characterized, including Azoarcus evansii, "Aromatoleum aromaticum" strain EbN1, Azoarcus sp.…”

mentioning

confidence: 99%

Degradation of Phenol via Phenylphosphate and Carboxylation to 4-Hydroxybenzoate by a Newly Isolated Strain of the Sulfate-Reducing BacteriumDesulfobacterium anilini

Ahn

Chae

Zylstra

et al. 2009

A sulfate-reducing phenol-degrading bacterium, strain AK1, was isolated from a 2-bromophenol-utilizing sulfidogenic estuarine sediment enrichment culture. On the basis of phylogenetic analysis of the 16S rRNA gene and DNA homology, strain AK1 is most closely related to Desulfobacterium anilini strain Ani1 ‫؍(‬ DSM 4660 T ). In addition to phenol, this organism degrades a variety of other aromatic compounds, including benzoate, 2-hydroxybenzoate, 4-hydroxybenzoate, 4-hydroxyphenylacetate, 2-aminobenzoate, 2-fluorophenol, and 2-fluorobenzoate, but it does not degrade aniline, 3-hydroxybenzoate, 4-cyanophenol, 2,4-dihydroxybenzoate, monohalogenated phenols, or monohalogenated benzoates. Growth with sulfate as an electron acceptor occurred with acetate and pyruvate but not with citrate, propionate, butyrate, lactate, glucose, or succinate. Strain AK1 is able to use sulfate, sulfite, and thiosulfate as electron acceptors. A putative phenylphosphate synthase gene responsible for anaerobic phenol degradation was identified in strain AK1. In phenol-grown cultures inducible expression of the ppsA gene was verified by reverse transcriptase PCR, and 4-hydroxybenzoate was detected as an intermediate. These results suggest that the pathway for anaerobic degradation of phenol in D. anilini strain AK1 proceeds via phosphorylation of phenol to phenylphosphate, followed by carboxylation to 4-hydroxybenzoate. The details concerning such reaction pathways in sulfidogenic bacteria have not been characterized previously.Phenol is a key aromatic intermediate in the anaerobic degradation of natural and industrial aromatic compounds. Phenol is highly water soluble, which leads to widespread contamination of river, lake, estuarine, and other aquatic environments. Estuarine sediments serve as important sinks for such contaminants irrespective of the point of origin of the pollutants. Phenol and p-cresol were found in 10 and 38%, respectively, of streambed sediments assessed at 536 sites in 20 major river basins across the United States from 1992 to 1995 (22). The p-cresol and phenol concentrations were up to 210 and 4,800 mg/kg, respectively (22).Phenolic compounds are readily degraded by aerobic bacteria, but they are more recalcitrant under anaerobic conditions. Although anaerobic degradation of phenol has been known to occur for a long time (11, 12), biochemical and genetic investigations have been limited. To date, anaerobic biodegradation and remediation studies have focused on consortia, but recently anaerobic phenol-degrading bacteria have been isolated under denitrifying (4, 37, 39, 41), iron-reducing (23), sulfidogenic (3, 5, 18), and fermentative-methanogenic conditions (10,15,21,28,42). Biodegradation of phenolic compounds under denitrifying conditions is well documented, and several bacteria have been characterized, including Azoarcus evansii, "Aromatoleum aromaticum" strain EbN1, Azoarcus sp. strain BH72, and several Thauera aromatica strains (13,29,30,31). In these organisms, anaerobic degradation of phenol is initiated by ...