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1.  Complete genome sequence of producer of the glycopeptide antibiotic Aculeximycin Kutzneria albida DSM 43870T, a representative of minor genus of Pseudonocardiaceae 
BMC Genomics  2014;15(1):885.
Background
Kutzneria is a representative of a rarely observed genus of the family Pseudonocardiaceae. Kutzneria species were initially placed in the Streptosporangiaceae genus and later reconsidered to be an independent genus of the Pseudonocardiaceae. Kutzneria albida is one of the eight known members of the genus. This strain is a unique producer of the glycosylated polyole macrolide aculeximycin which is active against both bacteria and fungi. Kutzneria albida genome sequencing and analysis allow a deeper understanding of evolution of this genus of Pseudonocardiaceae, provide new insight in the phylogeny of the genus, as well as decipher the hidden secondary metabolic potential of these rare actinobacteria.
Results
To explore the biosynthetic potential of Kutzneria albida to its full extent, the complete genome was sequenced. With a size of 9,874,926 bp, coding for 8,822 genes, it stands alongside other Pseudonocardiaceae with large circular genomes. Genome analysis revealed 46 gene clusters potentially encoding secondary metabolite biosynthesis pathways. Two large genomic islands were identified, containing regions most enriched with secondary metabolism gene clusters. Large parts of this secondary metabolism “clustome” are dedicated to siderophores production.
Conclusions
Kutzneria albida is the first species of the genus Kutzneria with a completely sequenced genome. Genome sequencing allowed identifying the gene cluster responsible for the biosynthesis of aculeximycin, one of the largest known oligosaccharide-macrolide antibiotics. Moreover, the genome revealed 45 additional putative secondary metabolite gene clusters, suggesting a huge biosynthetic potential, which makes Kutzneria albida a very rich source of natural products. Comparison of the Kutzneria albida genome to genomes of other actinobacteria clearly shows its close relations with Pseudonocardiaceae in line with the taxonomic position of the genus.
Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-885) contains supplementary material, which is available to authorized users.
doi:10.1186/1471-2164-15-885
PMCID: PMC4210621  PMID: 25301375
Kutzneria; Genome; Genomic islands; Secondary metabolism; Aculeximycin
2.  Comprehensive analysis of the Corynebacterium glutamicum transcriptome using an improved RNAseq technique 
BMC Genomics  2013;14:888.
Background
The use of RNAseq to resolve the transcriptional organization of an organism was established in recent years and also showed the complexity and dynamics of bacterial transcriptomes. The aim of this study was to comprehensively investigate the transcriptome of the industrially relevant amino acid producer and model organism Corynebacterium glutamicum by RNAseq in order to improve its genome annotation and to describe important features for transcription and translation.
Results
RNAseq data sets were obtained by two methods, one that focuses on 5′-ends of primary transcripts and another that provides the overall transcriptome with an improved resolution of 3′-ends of transcripts. Subsequent data analysis led to the identification of more than 2,000 transcription start sites (TSSs), the definition of 5′-UTRs (untranslated regions) for annotated protein-coding genes, operon structures and many novel transcripts located between or in antisense orientation to protein-coding regions. Interestingly, a high number of mRNAs (33%) is transcribed as leaderless transcripts. From the data, consensus promoter and ribosome binding site (RBS) motifs were identified and it was shown that the majority of genes in C. glutamicum are transcribed monocistronically, but operons containing up to 16 genes are also present.
Conclusions
The comprehensive transcriptome map of C. glutamicum established in this study represents a major step forward towards a complete definition of genetic elements (e.g. promoter regions, gene starts and stops, 5′-UTRs, RBSs, transcript starts and ends) and provides the ideal basis for further analyses on transcriptional regulatory networks in this organism. The methods developed are easily applicable for other bacteria and have the potential to be used also for quantification of transcriptomes, replacing microarrays in the near future.
doi:10.1186/1471-2164-14-888
PMCID: PMC3890552  PMID: 24341750
Corynebacterium glutamicum; RNA; High-throughput sequencing; Transcriptome
3.  Comprehensive discovery and characterization of small RNAs in Corynebacterium glutamicum ATCC 13032 
BMC Genomics  2013;14(1):714.
Background
Recent discoveries on bacterial transcriptomes gave evidence that small RNAs (sRNAs) have important regulatory roles in prokaryotic cells. Modern high-throughput sequencing approaches (RNA-Seq) enable the most detailed view on transcriptomes offering an unmatched comprehensiveness and single-base resolution. Whole transcriptome data obtained by RNA-Seq can be used to detect and characterize all transcript species, including small RNAs. Here, we describe an RNA-Seq approach for comprehensive detection and characterization of small RNAs from Corynebacterium glutamicum, an actinobacterium of high industrial relevance and model organism for medically important Corynebacterianeae, such as C. diphtheriae and Mycobacterium tuberculosis.
Results
In our RNA-Seq approach, total RNA from C. glutamicum ATCC 13032 was prepared from cultures grown in minimal medium at exponential growth or challenged by physical (heat shock, cold shock) or by chemical stresses (diamide, H2O2, NaCl) at this time point. Total RNA samples were pooled and sequencing libraries were prepared from the isolated small RNA fraction. High throughput short read sequencing and mapping yielded over 800 sRNA genes. By determining their 5′- and 3′-ends and inspection of their locations, these potential sRNA genes were classified into UTRs of mRNAs (316), cis-antisense sRNAs (543), and trans-encoded sRNAs (262). For 77 of trans-encoded sRNAs significant sequence and secondary structure conservation was found by a computational approach using a whole genome alignment with the closely related species C. efficiens YS-314 and C. diphtheriae NCTC 13129. Three selected trans-encoded sRNAs were characterized by Northern blot analysis and stress-specific transcript patterns were found.
Conclusions
The study showed comparable numbers of sRNAs known from genome-wide surveys in other bacteria. In detail, our results give deep insight into the comprehensive equipment of sRNAs in C. glutamicum and provide a sound basis for further studies concerning the functions of these sRNAs.
Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-14-714) contains supplementary material, which is available to authorized users.
doi:10.1186/1471-2164-14-714
PMCID: PMC4046766  PMID: 24138339
Bacteria; Non-coding RNA; High-throughput sequencing; RNA regulation
4.  A novel type of N-acetylglutamate synthase is involved in the first step of arginine biosynthesis in Corynebacterium glutamicum 
BMC Genomics  2013;14:713.
Background
Arginine biosynthesis in Corynebacterium glutamicum consists of eight enzymatic steps, starting with acetylation of glutamate, catalysed by N-acetylglutamate synthase (NAGS). There are different kinds of known NAGSs, for example, “classical” ArgA, bifunctional ArgJ, ArgO, and S-NAGS. However, since C. glutamicum possesses a monofunctional ArgJ, which catalyses only the fifth step of the arginine biosynthesis pathway, glutamate must be acetylated by an as of yet unknown NAGS gene.
Results
Arginine biosynthesis was investigated by metabolome profiling using defined gene deletion mutants that were expected to accumulate corresponding intracellular metabolites. HPLC-ESI-qTOF analyses gave detailed insights into arginine metabolism by detecting six out of seven intermediates of arginine biosynthesis. Accumulation of N-acetylglutamate in all mutants was a further confirmation of the unknown NAGS activity. To elucidate the identity of this gene, a genomic library of C. glutamicum was created and used to complement an Escherichia coli ΔargA mutant. The plasmid identified, which allowed functional complementation, contained part of gene cg3035, which contains an acetyltransferase domain in its amino acid sequence. Deletion of cg3035 in the C. glutamicum genome led to a partial auxotrophy for arginine. Heterologous overexpression of the entire cg3035 gene verified its ability to complement the E. coli ΔargA mutant in vivo and homologous overexpression led to a significantly higher intracellular N-acetylglutamate pool. Enzyme assays confirmed the N-acetylglutamate synthase activity of Cg3035 in vitro. However, the amino acid sequence of Cg3035 revealed no similarities to members of known NAGS gene families.
Conclusions
The N-acetylglutamate synthase Cg3035 is able to catalyse the first step of arginine biosynthesis in C. glutamicum. It represents a novel class of NAGS genes apparently present only in bacteria of the suborder Corynebacterineae, comprising amongst others the genera Corynebacterium, Mycobacterium, and Nocardia. Therefore, the name C-NAGS (Corynebacterineae-type NAGS) is proposed for this new family.
doi:10.1186/1471-2164-14-713
PMCID: PMC3827942  PMID: 24138314
Corynebacterium glutamicum; N-acetylglutamate synthase; NAGS; Arginine biosynthesis; ArgA; HPLC-ESI-qTOF
5.  Complete genome sequence of Saccharothrix espanaensis DSM 44229T and comparison to the other completely sequenced Pseudonocardiaceae 
BMC Genomics  2012;13:465.
Background
The genus Saccharothrix is a representative of the family Pseudonocardiaceae, known to include producer strains of a wide variety of potent antibiotics. Saccharothrix espanaensis produces both saccharomicins A and B of the promising new class of heptadecaglycoside antibiotics, active against both bacteria and yeast.
Results
To better assess its capabilities, the complete genome sequence of S. espanaensis was established. With a size of 9,360,653 bp, coding for 8,501 genes, it stands alongside other Pseudonocardiaceae with large genomes. Besides a predicted core genome of 810 genes shared in the family, S. espanaensis has a large number of accessory genes: 2,967 singletons when compared to the family, of which 1,292 have no clear orthologs in the RefSeq database. The genome analysis revealed the presence of 26 biosynthetic gene clusters potentially encoding secondary metabolites. Among them, the cluster coding for the saccharomicins could be identified.
Conclusion
S. espanaensis is the first completely sequenced species of the genus Saccharothrix. The genome discloses the cluster responsible for the biosynthesis of the saccharomicins, the largest oligosaccharide antibiotic currently identified. Moreover, the genome revealed 25 additional putative secondary metabolite gene clusters further suggesting the strain’s potential for natural product synthesis.
doi:10.1186/1471-2164-13-465
PMCID: PMC3469384  PMID: 22958348
6.  The complete genome sequence of the acarbose producer Actinoplanes sp. SE50/110 
BMC Genomics  2012;13:112.
Background
Actinoplanes sp. SE50/110 is known as the wild type producer of the alpha-glucosidase inhibitor acarbose, a potent drug used worldwide in the treatment of type-2 diabetes mellitus. As the incidence of diabetes is rapidly rising worldwide, an ever increasing demand for diabetes drugs, such as acarbose, needs to be anticipated. Consequently, derived Actinoplanes strains with increased acarbose yields are being used in large scale industrial batch fermentation since 1990 and were continuously optimized by conventional mutagenesis and screening experiments. This strategy reached its limits and is generally superseded by modern genetic engineering approaches. As a prerequisite for targeted genetic modifications, the complete genome sequence of the organism has to be known.
Results
Here, we present the complete genome sequence of Actinoplanes sp. SE50/110 [GenBank:CP003170], the first publicly available genome of the genus Actinoplanes, comprising various producers of pharmaceutically and economically important secondary metabolites. The genome features a high mean G + C content of 71.32% and consists of one circular chromosome with a size of 9,239,851 bp hosting 8,270 predicted protein coding sequences. Phylogenetic analysis of the core genome revealed a rather distant relation to other sequenced species of the family Micromonosporaceae whereas Actinoplanes utahensis was found to be the closest species based on 16S rRNA gene sequence comparison. Besides the already published acarbose biosynthetic gene cluster sequence, several new non-ribosomal peptide synthetase-, polyketide synthase- and hybrid-clusters were identified on the Actinoplanes genome. Another key feature of the genome represents the discovery of a functional actinomycete integrative and conjugative element.
Conclusions
The complete genome sequence of Actinoplanes sp. SE50/110 marks an important step towards the rational genetic optimization of the acarbose production. In this regard, the identified actinomycete integrative and conjugative element could play a central role by providing the basis for the development of a genetic transformation system for Actinoplanes sp. SE50/110 and other Actinoplanes spp. Furthermore, the identified non-ribosomal peptide synthetase- and polyketide synthase-clusters potentially encode new antibiotics and/or other bioactive compounds, which might be of pharmacologic interest.
doi:10.1186/1471-2164-13-112
PMCID: PMC3364876  PMID: 22443545
Genomics; Actinomycetes; Actinoplanes; Complete genome sequence; Acarbose; AICE
7.  Complete genome and comparative analysis of Streptococcus gallolyticus subsp. gallolyticus, an emerging pathogen of infective endocarditis 
BMC Genomics  2011;12:400.
Background
Streptococcus gallolyticus subsp. gallolyticus is an important causative agent of infectious endocarditis, while the pathogenicity of this species is widely unclear. To gain insight into the pathomechanisms and the underlying genetic elements for lateral gene transfer, we sequenced the entire genome of this pathogen.
Results
We sequenced the whole genome of S. gallolyticus subsp. gallolyticus strain ATCC BAA-2069, consisting of a 2,356,444 bp circular DNA molecule with a G+C-content of 37.65% and a novel 20,765 bp plasmid designated as pSGG1. Bioinformatic analysis predicted 2,309 ORFs and the presence of 80 tRNAs and 21 rRNAs in the chromosome. Furthermore, 21 ORFs were detected on the plasmid pSGG1, including tetracycline resistance genes telL and tet(O/W/32/O). Screening of 41 S. gallolyticus subsp. gallolyticus isolates revealed one plasmid (pSGG2) homologous to pSGG1. We further predicted 21 surface proteins containing the cell wall-sorting motif LPxTG, which were shown to play a functional role in the adhesion of bacteria to host cells. In addition, we performed a whole genome comparison to the recently sequenced S. gallolyticus subsp. gallolyticus strain UCN34, revealing significant differences.
Conclusions
The analysis of the whole genome sequence of S. gallolyticus subsp. gallolyticus promotes understanding of genetic factors concerning the pathogenesis and adhesion to ECM of this pathogen. For the first time we detected the presence of the mobilizable pSGG1 plasmid, which may play a functional role in lateral gene transfer and promote a selective advantage due to a tetracycline resistance.
doi:10.1186/1471-2164-12-400
PMCID: PMC3173452  PMID: 21824414
8.  Functional genomics of pH homeostasis in Corynebacterium glutamicum revealed novel links between pH response, oxidative stress, iron homeostasis and methionine synthesis 
BMC Genomics  2009;10:621.
Background
The maintenance of internal pH in bacterial cells is challenged by natural stress conditions, during host infection or in biotechnological production processes. Comprehensive transcriptomic and proteomic analyses has been conducted in several bacterial model systems, yet questions remain as to the mechanisms of pH homeostasis.
Results
Here we present the comprehensive analysis of pH homeostasis in C. glutamicum, a bacterium of industrial importance. At pH values between 6 and 9 effective maintenance of the internal pH at 7.5 ± 0.5 pH units was found. By DNA microarray analyses differential mRNA patterns were identified. The expression profiles were validated and extended by 1D-LC-ESI-MS/MS based quantification of soluble and membrane proteins. Regulators involved were identified and thereby participation of numerous signaling modules in pH response was found. The functional analysis revealed for the first time the occurrence of oxidative stress in C. glutamicum cells at neutral and low pH conditions accompanied by activation of the iron starvation response. Intracellular metabolite pool analysis unraveled inhibition of the TCA and other pathways at low pH. Methionine and cysteine synthesis were found to be activated via the McbR regulator, cysteine accumulation was observed and addition of cysteine was shown to be toxic under acidic conditions.
Conclusions
Novel limitations for C. glutamicum at non-optimal pH values were identified by a comprehensive analysis on the level of the transcriptome, proteome, and metabolome indicating a functional link between pH acclimatization, oxidative stress, iron homeostasis, and metabolic alterations. The results offer new insights into bacterial stress physiology and new starting points for bacterial strain design or pathogen defense.
doi:10.1186/1471-2164-10-621
PMCID: PMC2807442  PMID: 20025733
9.  The dual transcriptional regulator CysR in Corynebacterium glutamicum ATCC 13032 controls a subset of genes of the McbR regulon in response to the availability of sulphide acceptor molecules 
BMC Genomics  2008;9:483.
Background
Regulation of sulphur metabolism in Corynebacterium glutamicum ATCC 13032 has been studied intensively in the last few years, due to its industrial as well as scientific importance. Previously, the gene cg0156 was shown to belong to the regulon of McbR, a global transcriptional repressor of sulphur metabolism in C. glutamicum. This gene encodes a putative ROK-type regulator, a paralogue of the activator of sulphonate utilisation, SsuR. Therefore, it is an interesting candidate for study to further the understanding of the regulation of sulphur metabolism in C. glutamicum.
Results
Deletion of cg0156, now designated cysR, results in the inability of the mutant to utilise sulphate and aliphatic sulphonates. DNA microarray hybridisations revealed 49 genes with significantly increased and 48 with decreased transcript levels in presence of the native CysR compared to a cysR deletion mutant. Among the genes positively controlled by CysR were the gene cluster involved in sulphate reduction, fpr2 cysIXHDNYZ, and ssuR. Gel retardation experiments demonstrated that binding of CysR to DNA depends in vitro on the presence of either O-acetyl-L-serine or O-acetyl-L-homoserine. Mapping of the transcription start points of five transcription units helped to identify a 10 bp inverted repeat as the possible CysR binding site. Subsequent in vivo tests proved this motif to be necessary for CysR-dependent transcriptional regulation.
Conclusion
CysR acts as the functional analogue of the unrelated LysR-type regulator CysB from Escherichia coli, controlling sulphide production in response to acceptor availability. In both bacteria, gene duplication events seem to have taken place which resulted in the evolution of dedicated regulators for the control of sulphonate utilisation. The striking convergent evolution of network topology indicates the strong selective pressure to control the metabolism of the essential but often toxic sulphur-containing (bio-)molecules.
doi:10.1186/1471-2164-9-483
PMCID: PMC2580772  PMID: 18854009
10.  The missing link: Bordetella petrii is endowed with both the metabolic versatility of environmental bacteria and virulence traits of pathogenic Bordetellae 
BMC Genomics  2008;9:449.
Background
Bordetella petrii is the only environmental species hitherto found among the otherwise host-restricted and pathogenic members of the genus Bordetella. Phylogenetically, it connects the pathogenic Bordetellae and environmental bacteria of the genera Achromobacter and Alcaligenes, which are opportunistic pathogens. B. petrii strains have been isolated from very different environmental niches, including river sediment, polluted soil, marine sponges and a grass root. Recently, clinical isolates associated with bone degenerative disease or cystic fibrosis have also been described.
Results
In this manuscript we present the results of the analysis of the completely annotated genome sequence of the B. petrii strain DSMZ12804. B. petrii has a mosaic genome of 5,287,950 bp harboring numerous mobile genetic elements, including seven large genomic islands. Four of them are highly related to the clc element of Pseudomonas knackmussii B13, which encodes genes involved in the degradation of aromatics. Though being an environmental isolate, the sequenced B. petrii strain also encodes proteins related to virulence factors of the pathogenic Bordetellae, including the filamentous hemagglutinin, which is a major colonization factor of B. pertussis, and the master virulence regulator BvgAS. However, it lacks all known toxins of the pathogenic Bordetellae.
Conclusion
The genomic analysis suggests that B. petrii represents an evolutionary link between free-living environmental bacteria and the host-restricted obligate pathogenic Bordetellae. Its remarkable metabolic versatility may enable B. petrii to thrive in very different ecological niches.
doi:10.1186/1471-2164-9-449
PMCID: PMC2572626  PMID: 18826580
11.  Bioinformatic evaluation of L-arginine catabolic pathways in 24 cyanobacteria and transcriptional analysis of genes encoding enzymes of L-arginine catabolism in the cyanobacterium Synechocystis sp. PCC 6803 
BMC Genomics  2007;8:437.
Background
So far very limited knowledge exists on L-arginine catabolism in cyanobacteria, although six major L-arginine-degrading pathways have been described for prokaryotes. Thus, we have performed a bioinformatic analysis of possible L-arginine-degrading pathways in cyanobacteria. Further, we chose Synechocystis sp. PCC 6803 for a more detailed bioinformatic analysis and for validation of the bioinformatic predictions on L-arginine catabolism with a transcript analysis.
Results
We have evaluated 24 cyanobacterial genomes of freshwater or marine strains for the presence of putative L-arginine-degrading enzymes. We identified an L-arginine decarboxylase pathway in all 24 strains. In addition, cyanobacteria have one or two further pathways representing either an arginase pathway or L-arginine deiminase pathway or an L-arginine oxidase/dehydrogenase pathway. An L-arginine amidinotransferase pathway as a major L-arginine-degrading pathway is not likely but can not be entirely excluded. A rather unusual finding was that the cyanobacterial L-arginine deiminases are substantially larger than the enzymes in non-photosynthetic bacteria and that they are membrane-bound. A more detailed bioinformatic analysis of Synechocystis sp. PCC 6803 revealed that three different L-arginine-degrading pathways may in principle be functional in this cyanobacterium. These are (i) an L-arginine decarboxylase pathway, (ii) an L-arginine deiminase pathway, and (iii) an L-arginine oxidase/dehydrogenase pathway. A transcript analysis of cells grown either with nitrate or L-arginine as sole N-source and with an illumination of 50 μmol photons m-2 s-1 showed that the transcripts for the first enzyme(s) of all three pathways were present, but that the transcript levels for the L-arginine deiminase and the L-arginine oxidase/dehydrogenase were substantially higher than that of the three isoenzymes of L-arginine decarboxylase.
Conclusion
The evaluation of 24 cyanobacterial genomes revealed that five different L-arginine-degrading pathways are present in the investigated cyanobacterial species. In Synechocystis sp. PCC 6803 an L-arginine deiminase pathway and an L-arginine oxidase/dehydrogenase pathway represent the major pathways, while the L-arginine decarboxylase pathway most likely only functions in polyamine biosynthesis. The transcripts encoding the enzymes of the two major pathways were constitutively expressed with the exception of the transcript for the carbamate kinase, which was substantially up-regulated in cells grown with L-arginine.
doi:10.1186/1471-2164-8-437
PMCID: PMC2242806  PMID: 18045455
12.  Random mutagenesis in Corynebacterium glutamicum ATCC 13032 using an IS6100-based transposon vector identified the last unknown gene in the histidine biosynthesis pathway 
BMC Genomics  2006;7:205.
Background
Corynebacterium glutamicum, a Gram-positive bacterium of the class Actinobacteria, is an industrially relevant producer of amino acids. Several methods for the targeted genetic manipulation of this organism and rational strain improvement have been developed. An efficient transposon mutagenesis system for the completely sequenced type strain ATCC 13032 would significantly advance functional genome analysis in this bacterium.
Results
A comprehensive transposon mutant library comprising 10,080 independent clones was constructed by electrotransformation of the restriction-deficient derivative of strain ATCC 13032, C. glutamicum RES167, with an IS6100-containing non-replicative plasmid. Transposon mutants had stable cointegrates between the transposon vector and the chromosome. Altogether 172 transposon integration sites have been determined by sequencing of the chromosomal inserts, revealing that each integration occurred at a different locus. Statistical target site analyses revealed an apparent absence of a target site preference. From the library, auxotrophic mutants were obtained with a frequency of 2.9%. By auxanography analyses nearly two thirds of the auxotrophs were further characterized, including mutants with single, double and alternative nutritional requirements. In most cases the nutritional requirement observed could be correlated to the annotation of the mutated gene involved in the biosynthesis of an amino acid, a nucleotide or a vitamin. One notable exception was a clone mutagenized by transposition into the gene cg0910, which exhibited an auxotrophy for histidine. The protein sequence deduced from cg0910 showed high sequence similarities to inositol-1(or 4)-monophosphatases (EC 3.1.3.25). Subsequent genetic deletion of cg0910 delivered the same histidine-auxotrophic phenotype. Genetic complementation of the mutants as well as supplementation by histidinol suggests that cg0910 encodes the hitherto unknown essential L-histidinol-phosphate phosphatase (EC 3.1.3.15) in C. glutamicum. The cg0910 gene, renamed hisN, and its encoded enzyme have putative orthologs in almost all Actinobacteria, including mycobacteria and streptomycetes.
Conclusion
The absence of regional and sequence preferences of IS6100-transposition demonstrate that the established system is suitable for efficient genome-scale random mutagenesis in the sequenced type strain C.glutamicum ATCC 13032. The identification of the hisN gene encoding histidinol-phosphate phosphatase in C. glutamicum closed the last gap in histidine synthesis in the Actinobacteria. The system might be a valuable genetic tool also in other bacteria due to the broad host-spectrum of IS6100.
doi:10.1186/1471-2164-7-205
PMCID: PMC1590026  PMID: 16901339
13.  Functional genomics and expression analysis of the Corynebacterium glutamicum fpr2-cysIXHDNYZ gene cluster involved in assimilatory sulphate reduction 
BMC Genomics  2005;6:121.
Background
Corynebacterium glutamicum is a high-GC Gram-positive soil bacterium of great biotechnological importance for the production of amino acids. To facilitate the rational design of sulphur amino acid-producing strains, the pathway for assimilatory sulphate reduction providing the necessary reduced sulfur moieties has to be known. Although this pathway has been well studied in Gram-negative bacteria like Escherichia coli and low-GC Gram-positives like Bacillus subtilis, little is known for the Actinomycetales and other high-GC Gram-positive bacteria.
Results
The genome sequence of C. glutamicum was searched for genes involved in the assimilatory reduction of inorganic sulphur compounds. A cluster of eight candidate genes could be identified by combining sequence similarity searches with a subsequent synteny analysis between C. glutamicum and the closely related C. efficiens. Using mutational analysis, seven of the eight candidate genes, namely cysZ, cysY, cysN, cysD, cysH, cysX, and cysI, were demonstrated to be involved in the reduction of inorganic sulphur compounds. For three of the up to now unknown genes possible functions could be proposed: CysZ is likely to be the sulphate permease, while CysX and CysY are possibly involved in electron transfer and cofactor biosynthesis, respectively. Finally, the candidate gene designated fpr2 influences sulphur utilisation only weakly and might be involved in electron transport for the reduction of sulphite. Real-time RT-PCR experiments revealed that cysIXHDNYZ form an operon and that transcription of the extended cluster fpr2 cysIXHDNYZ is strongly influenced by the availability of inorganic sulphur, as well as L-cysteine. Mapping of the fpr2 and cysIXHDNYZ promoters using RACE-PCR indicated that both promoters overlap with binding-sites of the transcriptional repressor McbR, suggesting an involvement of McbR in the observed regulation. Comparative genomics revealed that large parts of the extended cluster are conserved in 11 of 17 completely sequenced members of the Actinomycetales.
Conclusion
The set of C. glutamicum genes involved in assimilatory sulphate reduction was identified and four novel genes involved in this pathway were found. The high degree of conservation of this cluster among the Actinomycetales supports the hypothesis that a different metabolic pathway for the reduction of inorganic sulphur compounds than that known from the well-studied model organisms E. coli and B. subtilis is used by members of this order, providing the basis for further biochemical studies.
doi:10.1186/1471-2164-6-121
PMCID: PMC1266029  PMID: 16159395

Results 1-13 (13)