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PubMed2004

Studies on the interaction of NADPH with Rhodobacter sphaeroides biotin sulfoxide reductase.

Rhodobacter sphaeroides biotin sulfoxide reductase (BSOR) contains the bis(molybdopterin guanine dinucleotide)molybdenum cofactor and catalyzes the reduction of D-biotin-D-sulfoxide to biotin. This protein is the only member of the dimethyl sulfoxide reductase family of molybdopterin enzymes that utilizes NADPH as the direct electron donor to the catalytic Mo center. Kinetic studies using stopped-flow spectrophotometry indicate that BSOR reduction by NADPH (>1000 s(-1)) is faster than steady-state turnover (440 s(-1)) and has shown that BSOR reduction occurs in concert with NADPH oxidation with no indication of a Mo(V) intermediate species. Because no crystallographic structure is currently available for BSOR, a protein structure was modeled using the structures for R. sphaeroides dimethyl sulfoxide reductase, Rhodobacter capsulatus dimethyl sulfoxide reductase, and Shewanella massilia trimethylamine N-oxide reductase as the templates. A potential NADPH-binding site was identified and tested by site-directed mutagenesis of residues within the area. Mutation of Arg137 or Asp136 reduced the ability of NADPH to serve as the electron donor to BSOR, indicating that the NADPH-binding site in BSOR is located in the active-site funnel of the putative structure where it can directly reduce the Mo center. Along with kinetic and spectroscopic data, the location of this binding site supports a direct hydride transfer mechanism for NADPH reduction of BSOR.

Amino Acid Sequence↗
PubMed1996

Sequential 1H and 15N NMR resonance assignment and secondary structure of ferrocytochrome c2 from Rhodobacter sphaeroides.

Sequence-specific 1H and 15N assignments have been made for the amino acids of the ferrocytochrome c2 from Rhodobacter sphaeroides. Initial assignments were made by analysis of a series of homonuclear 2D COSY, TOCSY, and NOESY spectra obtained with the unlabeled protein. 2D and 3D 1H-15N correlated spectra obtained for a uniformly 15N-labeled ferrocytochrome c2 were used to confirm and extend the assignments. Partial 13C assignments have also been made by means of HSQC experiments on 13C at natural abundance, in particular for about two-thirds of the 13C alpha. Medium-range NOE connectivities, together with 3J(HC alpha NH) coupling constants, indicated the presence of five helices at positions 6-16, 60-68, 74-82, 84-91, and 109-120. No other regular secondary structure was observed. This folding is similar to that previously observed for the ferrocytochrome c2 of Rhodobacter capsulatus in solution, which exhibits approximately 50% sequence identity. Moreover, the rotation rates of the aromatic rings of phenylalanine or tyrosine, when conserved, were similar to those observed for R. capsulatus. Furthermore, C alpha H chemical shifts, which are sensitive to the secondary structure and ring current effects of the heme, appear to be very similar for the two proteins. Consequently, the solution structure of R. sphaeroides ferrocytochrome c2 appears to be very similar to that of R. capsulatus ferrocytochrome c2. These results are compared with the X-ray crystal structure of the R. sphaeroides ferrocytochrome c2.

Amino Acid Sequence↗
PubMed1997

Nucleotide sequence and transcriptional analysis of the flanking region of the gene (spb) for the trans-acting factor that controls light-mediated expression of the puf operon in Rhodobacter sphaeroides.

We recently reported the existence of a trans-acting factor (SPB) in Rhodobacter sphaeroides that repressed the expression of the puf operon during illumination. SPB was somewhat homologous to HvrA of Rhodobacter capsulatus, but these proteins appear to have functionally different properties. We now report an analysis of the flanking region of spb in the genome of R.sphaeroides, and we show that spb is a positional counterpart of hvrA of R. capsulatus. The region directly downstream of spb was found to contain three genes, two of which were highly homologous to orf5 and ahcY in R. capsulatus. However, a gene corresponding to hvrB, which controls the expression of orf5 and ahcY in R. capsulatus, was absent in R. sphaeroides. The level of the transcript of ahcY did not change in cells grown under photosynthetic and by respiratory conditions. By contrast, orf5 was transcribed at a higher rate in photosynthetically grown cells under high-intensity light than under low-intensity light, indicating features of transcription different from those in R. capsulatus. A third gene, orf318, which was absent in the corresponding region of R. capsulatus, encoded an amino acid sequence that was significantly homologous to the consensus sequence of RfaI and RfaJ of E.coli, which are glycosyl transferases involved in the synthesis of lipopolysaccharide. orf318 was transcribed in the opposite direction to ahcY, and at only a low level, under all conditions tested.

Amino Acid Sequence↗
PubMed1998

Rhodobacter capsulatus genes encoding form I ribulose-1,5-bisphosphate carboxylase/oxygenase (cbbLS) and neighbouring genes were acquired by a horizontal gene transfer.

Analysis of the nucleotide sequence of the form I ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) genes (cbbL and cbbS) of the non-sulfur purple bacterium Rhodobacter capsulatus indicated that the deduced amino acid sequence of the large subunit was not closely homologous to the large subunit from related organisms. Indeed, phylogenetic analysis suggested that the large subunit protein (CbbL) more closely resembled the enzyme from alpha/beta/gamma purple bacteria and cyanobacteria and is within a 'green-like' radiation of the RubisCO phylogenetic tree, well separated from CbbL of the related organism Rhodobacter sphaeroides. A cbbQ gene was discovered downstream of cbbS in Rh. capsulatus, a gene arrangement which also appears to be limited to certain organisms containing a 'green-like' RubisCO. Upstream, and divergently transcribed from cbbLSQ, is a gene (cbbRI) that encodes a LysR-type transcriptional activator. Phylogenetic analysis of the deduced amino acid sequence of CbbRI also suggests that this protein is quite distinct from the Rh. sphaeroides CbbR protein, and is even distinct from the previously described CbbRII protein, the gene of which is upstream and divergently transcribed from the cbbII operon of Rh. capsulatus. Interestingly, Rh. capsulatus CbbRI is more closely related to CbbR from bacteria whose RubisCO falls within the 'green-like' radiation of the CbbL tree. These studies suggest that the cbbRI-cbbL-cbbS-cbbQ genes were acquired by Rh. capsulatus via horizontal gene transfer from a bacterial species containing a 'green-like' RubisCO.

Amino Acid Sequence↗
PubMed2007

The AppA and PpsR proteins from Rhodobacter sphaeroides can establish a redox-dependent signal chain but fail to transmit blue-light signals in other bacteria.

The AppA protein of Rhodobacter sphaeroides has the unique ability to sense and transmit redox and light signals. In response to decreasing oxygen tension, AppA antagonizes the transcriptional regulator PpsR, which represses the expression of photosynthesis genes, including the puc operon. This mechanism, which is based on direct protein-protein interaction, is prevented by blue-light absorption of the BLUF domain located in the N-terminal part of AppA. In order to test whether AppA and PpsR are sufficient to transmit redox and light signals, we expressed these proteins in three different bacterial species and monitored oxygen- and blue-light-dependent puc expression either directly or by using a luciferase-based reporter construct. The AppA/PpsR system could mediate redox-dependent gene expression in the alphaproteobacteria Rhodobacter capsulatus and Paracoccus denitrificans but not in the gammaproteobacterium Escherichia coli. Analysis of a prrA mutant strain of R. sphaeroides strongly suggests that light-dependent gene expression requires a balanced interplay of the AppA/PpsR system with the PrrA response regulator. Therefore, the AppA/PpsR system was unable to establish light signaling in other bacteria. Based on our data, we present a model for the interdependence of AppA/PpsR signaling and the PrrA transcriptional activator.

Bacterial Proteins↗
PubMed1997

Analysis of the fnrL gene and its function in Rhodobacter capsulatus.

The fnr gene encodes a regulatory protein involved in the response to oxygen in a variety of bacterial genera. For example, it was previously shown that the anoxygenic, photosynthetic bacterium Rhodobacter sphaeroides requires the fnrL gene for growth under anaerobic, photosynthetic conditions. Additionally, the FnrL protein in R. sphaeroides is required for anaerobic growth in the dark with an alternative electron acceptor, but it is not essential for aerobic growth. In this study, the fnrL locus from Rhodobacter capsulatus was cloned and sequenced. Surprisingly, an R. capsulatus strain with the fnrL gene deleted grows like the wild type under either photosynthetic or aerobic conditions but does not grow anaerobically with alternative electron acceptors such as dimethyl sulfoxide (DMSO) or trimethylamine oxide. It is demonstrated that the c-type cytochrome induced upon anaerobic growth on DMSO is not synthesized in the R. capsulatus fnrL mutant. In contrast to wild-type strains, R. sphaeroides and R. capsulatus fnrL mutants do not synthesize the anaerobically, DMSO-induced reductase. Mechanisms that explain the basis for FnrL function in both organisms are discussed.

Amino Acid Sequence↗
PubMed2005

L-malyl-coenzyme A/beta-methylmalyl-coenzyme A lyase is involved in acetate assimilation of the isocitrate lyase-negative bacterium Rhodobacter capsulatus.

Cell extracts of Rhodobacter capsulatus grown on acetate contained an apparent malate synthase activity but lacked isocitrate lyase activity. Therefore, R. capsulatus cannot use the glyoxylate cycle for acetate assimilation, and a different pathway must exist. It is shown that the apparent malate synthase activity is due to the combination of a malyl-coenzyme A (CoA) lyase and a malyl-CoA-hydrolyzing enzyme. Malyl-CoA lyase activity was 20-fold up-regulated in acetate-grown cells versus glucose-grown cells. Malyl-CoA lyase was purified 250-fold with a recovery of 6%. The enzyme catalyzed not only the reversible condensation of glyoxylate and acetyl-CoA to L-malyl-CoA but also the reversible condensation of glyoxylate and propionyl-CoA to beta-methylmalyl-CoA. Enzyme activity was stimulated by divalent ions with preference for Mn(2+) and was inhibited by EDTA. The N-terminal amino acid sequence was determined, and a corresponding gene coding for a 34.2-kDa protein was identified and designated mcl1. The native molecular mass of the purified protein was 195 +/- 20 kDa, indicating a homohexameric composition. A homologous mcl1 gene was found in the genomes of the isocitrate lyase-negative bacteria Rhodobacter sphaeroides and Rhodospirillum rubrum in similar genomic environments. For Streptomyces coelicolor and Methylobacterium extorquens, mcl1 homologs are located within gene clusters implicated in acetate metabolism. We therefore propose that L-malyl-CoA/beta-methylmalyl-CoA lyase encoded by mcl1 is involved in acetate assimilation by R. capsulatus and possibly other glyoxylate cycle-negative bacteria.

Acetic Acid↗
PubMed2006

Controlling light-use by Rhodobacter capsulatus continuous cultures in a flat-panel photobioreactor.

The main bottleneck in scale-up of phototrophic fermentation is the low efficiency of light energy conversion to the desired product, which is caused by an excessive dissipation of light energy to heat. The photoheterotrophic formation of hydrogen from acetate and light energy by the microorganism Rhodobacter capsulatus NCIMB 11773 was chosen as a case study in this work. A light energy balance was set up, in which the total bacterial light energy absorption is split up and attributed to its destinations. These are biomass growth and maintenance, generation of hydrogen and photosynthetic heat dissipation. The constants defined in the light energy balance were determined experimentally using a flat-panel photobioreactor with a 3-cm optical path. An experimental method called D-stat was applied. Continuous cultures were kept in a so-called pseudo steady state, while the dilution rate was reduced slowly and smoothly. The biomass yield and maintenance coefficients of Rhodobacter capsulatus biomass on light energy were determined at 12.4 W/m(2) (400-950 nm) and amounted to 2.58 x 10(-8) +/- 0.04 x 10(-8) kg/J and 102 +/- 3.5 W/kg, respectively. The fraction of the absorbed light energy that was dissipated to heat at 473 W/m(2) depended on the biomass concentration in the reactor and varied between 0.80 and 0.88, as the biomass concentration was increased from 2.0 to 8.0 kg/m(3). The process conditions were estimated at which a 3.7% conversion efficiency of absorbed light energy to produced hydrogen energy should be attainable at 473 W/m(2).

Biomass↗
PubMed1998

Genome encyclopedias and their use for comparative analysis of Rhodobacter capsulatus strains.

This paper consists of two components: the use of gene encyclopedias in genomic studies and Rhodobacter capsulatus genome project. A survey of vectors used for encyclopedia construction includes a brief discussion of their relative advantages and limitations. Projects employing various methods of encyclopedia assembly including the comparison of restriction patterns, restriction maps, linking by hybridization, oligonucleotide fingerprinting, sequence tagged site (STS) fingerprinting and encyclopedias derived from genetic maps are listed and briefly described. The R. capsulatus SB 1003 genome project started with the construction of its cosmid encyclopedia, which comprises 192 cosmids covering the chromosome and the 134 kbp plasmid in strain SB 1003, with the exact map coordinates of each cosmid. In a pilot sequencing study, several cosmids were individually subcloned using the vector M13mp18 and merged into one 189 kbp contig. About 160 open reading frames (ORFs) identified by the CodonUse program were subjected to similarity searches. The biological functions of eighty ORFs could be assigned reliably using the WIT (what is there) genome investigation environment. Eighty percent of these recognizable ORFs were organized in functional clusters, which simplified assignment decisions and increased the strength of the predictions. A set of 26 genes for cobalamin biosynthesis, genes for polyhydroxyalkanoic acid metabolism, DNA replication and recombination, and DNA gyrase were among those identified. Recently, another 1.2 Mbp genome fragment of the Rhodobacter genome was sequenced using a slightly modified approach. These results together with some genome investigation tools, have been placed at our web site (http://capsulapedia.uchicago.edu). The sequence of R. capsulatus is expected to be completed by summer 1998. A project to construct a systematic set of deletion strains of R. capsulatus in order to assign functions to unknown ORFs has been started. Preliminary data demonstrate the extreme convenience of the unique gene transfer agent (GTA) system to perform such work.

Animals↗
PubMed1995

Expression of rat liver AdoHcy hydrolase in a Rhodobacter capsulatus ahcY mutant restores pigment formation and photosynthetic growth.

An amino acid alignment of fourteen S-adenosylhomocysteine hydrolases shows that sequences from six photosynthetic species and one species possibly derived from algae have an internal 36 to 41 amino acid sequence that is not present in hydrolase sequences from seven non-photosynthetic species. In the photosynthetic eubacterium Rhodobacter capsulatus, the StLB1 strain has a disrupted hydrolase gene, and hydrolase activity is not detectable. Photopigment synthesis and photosynthetic growth are significantly reduced in the StLB1 strain. Introduction of rat hydrolase cDNA into the StLB1 strain restored hydrolase activity, photopigment synthesis and photosynthetic growth. The results show that the 36 amino acid sequence of Rhodobacter capsulatus S-adenosylhomocysteine hydrolase does not have a photosynthesis specific function.

Adenosylhomocysteinase↗
PubMed2001

The RegB/RegA two-component regulatory system controls synthesis of photosynthesis and respiratory electron transfer components in Rhodobacter capsulatus.

Recently, we demonstrated that the RegB/RegA two-component regulatory system from Rhodobacter capsulatus functions as a global regulator of metabolic processes that either generate or consume reducing equivalents. For example, the RegB/RegA system controls expression of such energy generating processes as photosynthesis and hydrogen utilization. In addition, RegB/RegA also control nitrogen and carbon fixation pathways that utilize reducing equivalents. Here, we use a combination of DNase I protection and plasmid-based reporter expression studies to demonstrate that RegA directly controls synthesis of cytochrome cbb3 and ubiquinol oxidases that function as terminal electron acceptors in a branched respiratory chain. We also demonstrate that RegA controls expression of cytochromes c2, c(y) and the cytochrome bc1 complex that are involved in both photosynthetic and respiratory electron transfer events. These data provide evidence that the RegB/RegA two-component system has a major role in controlling the synthesis of numerous processes that affect reducing equivalents in Rhodobacter capsulatus.

Bacterial Proteins↗
PubMed1993

Identification of a new class of nitrogen fixation genes in Rhodobacter capsulatus: a putative membrane complex involved in electron transport to nitrogenase.

DNA sequence analysis of a 12236 bp fragment, which is located upstream of nifE in Rhodobacter capsulatus nif region A, revealed the presence of ten open reading frames. With the exception of fdxC and fdxN, which encode a plant-type and a bacterial-type ferredoxin, the deduced products of these coding regions exhibited no significant homology to known proteins. Analysis of defined insertion and deletion mutants demonstrated that six of these genes were required for nitrogen fixation. Therefore, we propose to call these genes rnfA, rnfB, rnfC, rnfD, rnfE and rnfF (for Rhodobacter nitrogen fixation). Secondary structure predictions suggested that the rnf genes encode four potential membrane proteins and two putative iron-sulphur proteins, which contain cysteine motifs (C-X2-C-X2-C-X3-C-P) typical for [4Fe--4S] proteins. Comparison of the in vivo and in vitro nitrogenase activities of fdxN and rnf mutants suggested that the products encoded by these genes are involved in electron transport to nitrogenase. In addition, these mutants were shown to contain significantly reduced amounts of nitrogenase. The hypothesis that this new class of nitrogen fixation genes encodes components of an electron transfer system to nitrogenase was corroborated by analysing the effect of metronidazole. Both the fdxN and rnf mutants had higher growth yields in the presence of metronidazole than the wild type, suggesting that these mutants contained lower amounts of reduced ferredoxins.

Amino Acid Sequence↗
PubMed1998

Microbial photodegradation of aminoarenes. Metabolism of 2-amino-4-nitrophenol by Rhodobacter capsulatus.

The phototrophic bacterium Rhodobacter capsulatus photoreduces 2,4-dinitrophenol to 2-amino-4-nitrophenol, which is further metabolized by an aerobic pathway that is also light-dependent. The catabolism of 2-amino-4-nitrophenol requires O2 and the presence of alternative carbon (C) and nitrogen (N) sources, preferably acetate and ammonium. Rhodobacter capsulatus B10, a bacterium unable to assimilate nitrate, releases negligible amounts of nitrite when growing with 2-amino-4-nitrophenol, thus suggesting that an oxygenase, nitrite-producing activity is not involved in the metabolization of the compound. The diazotrophic growth of R. capsulatus increases in the presence of 2-amino-4-nitrophenol, but growth with ammonium is clearly inhibited by the compound. Mutant strains of R. capsulatus B10, which are affected in nifHDK, nifR1, or nifR4 genes, unable to fix dinitrogen, do not grow with 2-amino-4-nitrophenol as the sole N source. This indicates that the compound cannot be used as a N source. The nif mutants degrade 2-amino-4-nitrophenol to the same extent as the wild-type in the presence of ammonium. The compound is not used as a C source by the bacterium, either. Aromatic stable intermediates, such as 2,4-diaminophenol or 4-nitrocatechol, are not detectable in microaerobic cultures of R. capsulatus growing with 2,4-dinitrophenol or 2-amino-4-nitrophenol.

Aerobiosis↗
PubMed2003

Rhodobacter sphaeroides has a family II pyrophosphatase: comparison with other species of photosynthetic bacteria.

The cytoplasmic pyrophosphatase from Rhodobacter sphaeroides was purified and characterized. The enzyme is a homodimer of 64 kDa. The N-terminus was sequenced and used to obtain the complete pyrophosphatase sequence from the preliminary genome sequence of Rba. sphaeroides, showing extensive sequence similarity to family II or class C pyrophosphatases. The enzyme hydrolyzes only Mg-PP(i) and Mn-PP(i) with a K(m) of 0.35 mM for both substrates. It is not activated by free Mg (2+), in contrast to the cytoplasmic pyrophosphatase from Rhodospirillum rubrum, and it is not inhibited by NaF, methylendiphosphate, or imidodiphosphate. This work shows that Rba. sphaeroides and Rhodobacter capsulatus cytoplasmic pyrophosphatases belong to family II, in contrast to Rsp. rubrum, Rhodopseudomonas palustris, Rhodopseudomonas gelatinosa, and Rhodomicrobium vannielii cytoplasmic pyrophosphatases which should be classified as members of family I. This is the first report of family II cytoplasmic pyrophosphatases in photosynthetic bacteria and in a gram-negative organism.

Alphaproteobacteria↗
PubMed2000

Maintenance and control of redox poise in Rhodobacter capsulatus strains deficient in the Calvin-Benson-Bassham pathway.

Carbon dioxide serves as the preferred electron acceptor during photoheterotrophic growth of nonsulfur purple photosynthetic bacteria such as Rhodobacter capsulatus and Rhodobacter sphaeroides. This CO2, produced as a result of the oxidation of preferred organic carbon sources, is reduced through reactions of the Calvin-Benson-Bassham reductive pentose phosphate pathway. This pathway is thus crucial to maintain a balanced intracellular oxidation-reduction potential (or redox poise) under photoheterotrophic growth conditions. In the absence of a functional Calvin-Benson-Bassham pathway, either an exogenous electron acceptor, such as dimethylsulfoxide, must be supplied or the organism must somehow develop alternative electron acceptor pathways to preserve the intracellular redox state of the cell. Spontaneous variants of Rba. capsulatus strains deficient in the Calvin-Benson-Bassham pathway that have become photoheterotrophically competent (in the absence of an exogenous electron acceptor) were isolated. These strains (SBP-PHC and RCNd1, RCNd3, and RCNd4) were shown to obviate normal ammonia control and derepress synthesis of the dinitrogenase enzyme complex for the dissipation of excess reducing equivalents and generation of H2 gas via proton reduction. In contrast to previous studies with other organisms, the dinitrogenase reductase polypeptides were maintained in an active and unmodified form in strain SBP-PHC and the respective RCNd strains. Unlike the situation in Rba. sphaeroides, the Rba. capsulatus strains did not regain full ammonia control when complemented with plasmids that reconstituted a functional Calvin-Benson-Bassham pathway. Moreover, dinitrogenase derepression in Rba. capsulatas was responsive to the addition of the auxiliary electron acceptor dimethylsulfoxide. These results indicated a hierarchical control over the removal of reducing equivalents during photoheterotrophic growth that differs from strains of Rba. sphaeroides and Rhodospirillum rubrum deficient in the Calvin-Benson-Bassham pathway.

Carbon Dioxide↗
PubMed2001

Growth of the purple bacterium Rhodobacter capsulatus on the aromatic compound hippurate.

The purple nonsulfur bacterium Rhodobacter capsulatus strain B10 grew phototrophically on the aromatic compound hippurate (N-benzoyl-L-glycine) and related benzoyl amino acids. Absorption spectra, extraction, and GC/MS analysis of culture supernatants showed that hippurate was stoichiometrically converted to benzoate and glycine, with the latter used as a carbon or nitrogen source for growth. This conclusion was supported by detection of the enzyme hippuricase in permeabilized intact cells. Chemotrophic growth on hippurate by Rba. capsulatus, either at full or reduced oxygen tensions, was not observed. The type strain of Rhodobacter sphaeroides as well as four strains of Rhodopseudomonas palustris also grew phototrophically on hippurate, while several other aromatic-degrading species of purple bacteria did not.

Benzoates↗
PubMed2002

Evolutionary implications of phylogenetic analyses of the gene transfer agent (GTA) of Rhodobacter capsulatus.

The gene transfer agent (GTA) of the a-proteobacterium Rhodobacter capsulatus is a cell-controlled genetic exchange vector. Genes that encode the GTA structure are clustered in a 15-kb region of the R. capsulatus chromosome, and some of these genes show sequence similarity to known bacteriophage head and tail genes. However, the production of GTA is controlled at the level of transcription by a cellular two-component signal transduction system. This paper describes homologues of both the GTA structural gene cluster and the GTA regulatory genes in the a-proteobacteria Rhodopseudomonas palustris, Rhodobacter sphaeroides, Caulobacter crescentus, Agrobacterium tumefaciens and Brucella melitensis. These sequences were used in a phylogenetic tree approach to examine the evolutionary relationships of selected GTA proteins to these homologues and (pro)phage proteins, which was compared to a 16S rRNA tree. The data indicate that a GTA-like element was present in a single progenitor of the extant species that contain both GTA structural cluster and regulatory gene homologues. The evolutionary relationships of GTA structural proteins to (pro)phage proteins indicated by the phylogenetic tree patterns suggest a predominantly vertical descent of GTA-like sequences in the a-proteobacteria and little past gene exchange with (pro)phages.

Alphaproteobacteria↗
PubMed2006

Light-dependent transformation of aniline to indole esters by the purple bacterium Rhodobacter sphaeroides OU5.

In an attempt to understand the aromatic hydrocarbon metabolism by purple bacteria that do not grow at their expense, we earlier reported 2-aminobenzoate transformation by a purple non-sulfur bacterium, Rhodobacter sphaeroides OU5 (Sunayana et al., 2005, J Ind Microbiol Biotech 32:41-45), which is extended in the present study with aniline, a major environmental pollutant. Aniline did not support photo (light anaerobic) or chemo (dark aerobic) heterotrophic growth of Rhodobacter sphaeroides OU5 either as a sole source of carbon or nitrogen. However, light-dependent aniline transformation was observed in the culture supernatants and the products were identified as indole derivatives. The transformation was dependent on a tricarboxylate intermediate, fumarate. Five intermediates of the aniline biotransformation pathway were isolated and identified as indole esters having a mass of 443, 441, 279, 189, and 167 with unstoichiometric total indole yields of 0.16 mM: from 5 mM: of aniline consumed. The pathway proposed based on these intermediates suggest a novel xenobiotic detoxification process in bacteria.

Aniline Compounds↗