Anaeropeptidivorans aminofermentans gen. nov., sp. nov., a mesophilic proteolytic salt-tolerant bacterium isolated from a laboratory-scale biogas fermenter, and emended description of Clostridium colinum.

An anaerobic bacterial strain, designated strain M3/9T, was isolated from a laboratory-scale biogas fermenter fed with maize silage supplemented with 5 % wheat straw. Cells were straight, non-motile rods, which stained Gram-negative. Optimal growth occurred between 30 and 40°C, at pH 7.5-8.5, and up to 3.9 % (w/v) NaCl was tolerated. When grown on peptone from casein and soymeal, strain M3/9T produced mainly acetic acid, ethanol, and isobutyric acid. The major cellular fatty acids of the novel strain were C16 : 0 and C16 : 0 DMA. The genome of strain M3/9T is 3757  330 bp in size with a G+C content of 38.45 mol%. Phylogenetic analysis allocated strain M3/9T within the family Lachnospiraceae with Clostridium colinum DSM 6011T and Anaerotignum lactatifermentans DSM 14214T being the most closely related species sharing 57.86 and 56.99% average amino acid identity and 16S rRNA gene sequence similarities of 91.58 and 91.26 %, respectively. Based on physiological, chemotaxonomic and genetic data, we propose the description of a novel species and genus Anaeropeptidivorans aminofermentans gen. nov., sp. nov., represented by the type strain M3/9T (=DSM 100058T=LMG 29527T). In addition, an emended description of Clostridium colinum is provided.

Draft genome sequence of the potato pathogen Rhizoctonia solani AG3-PT isolate Ben3.

The basidiomycetes fungus Rhizoctonia solani AG3 is responsible for black scurf disease on potato and occurs in each potato growing area world-wide. In this study, the draft genome sequence of the black scurf pathogen R. solani AG3-PT isolate Ben3 is presented. The genome sequence of R. solani AG3-PT isolate Ben3 consists of 1385 scaffolds. These scaffolds amount to a size of approx. 51 Mb. Considering coverage analyses of contigs, the size of the diploid genome was estimated to correspond to 116 Mb. Gene prediction by applying AUGUSTUS (3.2.1.) resulted in 12,567 identified genes. Based on automatic annotation using GenDBE, genes potentially encoding cellulases and enzymes involved in secondary metabolite synthesis were identified in the R. solani AG3-PT isolate Ben3 genome. Comparative analyses including the R. solani AG3 isolate Rhs1AP, also originating from potato, revealed first insights into core genes shared by both isolates and unique determinants of each isolate.

Genome analysis of the sugar beet pathogen Rhizoctonia solani AG2-2IIIB revealed high numbers in secreted proteins and cell wall degrading enzymes.

BACKGROUND: Sugar beet (Beta vulgaris) is a crop cultivated for its high content in sugar, but it is vulnerable to many soil-borne pathogens. One of them is the basidiomycete Rhizoctonia solani. This fungal species has a compatibility system regulating hyphal fusions (anastomosis). Consequently, R. solani species are categorized in anastomosis groups (AGs). AG2-2IIIB isolates are most aggressive on sugar beet. In the present study, we report on the draft genome of R. solani AG2-2IIIB using the Illumina technology. Genome analysis, interpretation and comparative genomics of five sequenced R. solani isolates were carried out. RESULTS: The draft genome of R. solani AG2-2IIIB has an estimated size of 56.02 Mb. In addition, two normalized EST libraries were sequenced. In total 20,790 of 21,980 AG2-2IIIB isotigs (transcript isoforms) were mapped on the genome with more than 95 % sequence identity. The genome of R. solani AG2-2IIIB was predicted to harbor 11,897 genes and 4908 were found to be isolate-specific. R. solani AG2-2IIIB was predicted to contain 1142 putatively secreted proteins and 473 of them were found to be unique for this isolate. The R. solani AG2-2IIIB genome encodes a high number of carbohydrate active enzymes. The highest numbers were observed for the polysaccharide lyases family 1 (PL-1), glycoside hydrolase family 43 (GH-43) and carbohydrate estarase family 12 (CE-12). Transcription analysis of selected genes representing different enzyme clades revealed a mixed pattern of up- and down-regulation six days after infection on sugar beets featuring variable levels of resistance compared to mycelia of the fungus grown in vitro. CONCLUSIONS: The established R. solani AG2-2IIIB genome and EST sequences provide important information on the gene content, gene structure and transcriptional activity for this sugar beet pathogen. The enriched genomic platform provides an important platform to enhance our understanding of R. solani biology.

Draft genome sequence of the sugar beet pathogen Rhizoctonia solani AG2-2IIIB strain BBA69670.

Rhizoctonia solani is a widespread plant pathogenic fungus featuring a broad host range including several economically important crops. Accordingly, genome analyses of R. solani isolates are important to uncover their pathogenic potential. Draft genome sequences for four R. solani isolates representing three of the 14 R. solani anastomosis groups (AGs) are available. Here, we present the first draft genome sequence for an R. solani AG2-2IIIB isolate that is pathogenic on sugar beet. The fungal genome was assembled in 2065 scaffolds consisting of 5826 contigs amounting to a size of about 52 Mb which is larger than any other R. solani isolate known today. Genes potentially encoding cellulolytic, lignolytic and pectinolytic enzymes were identified.

Taxonomic analysis of the microbial community in stored sugar beets using high-throughput sequencing of different marker genes.

Post-harvest colonization of sugar beets accompanied by rot development is a serious problem due to sugar losses and negative impact on processing quality. Studies on the microbial community associated with rot development and factors shaping their structure are missing. Therefore, high-throughput sequencing was applied to describe the influence of environment, plant genotype and storage temperature (8°C and 20°C) on three different communities in stored sugar beets, namely fungi (internal transcribed spacers 1 and 2), Fusarium spp. (elongation factor-1α gene fragment) and oomycetes (internal transcribed spacers 1). The composition of the fungal community changed during storage mostly influenced by the storage temperature followed by a weak environmental effect. Botrytis cinerea was the prevalent species at 8°C whereas members of the fungal genera Fusarium and Penicillium became dominant at 20°C. This shift was independent of the plant genotype. Species richness within the genus Fusarium also increased during storage at both temperatures whereas the oomycetes community did not change. Moreover, oomycetes species were absent after storage at 20°C. The results of the present study clearly show that rot development during sugar beet storage is associated with pathogens well known as causal agents of post-harvest diseases in many other crops.

Random mutagenesis in Corynebacterium glutamicum ATCC 13032 using an IS6100-based transposon vector identified the last unknown gene in the histidine biosynthesis pathway.

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.

Different molecular rearrangements in the integron of the IncP-1 beta resistance plasmid pB10 isolated from a wastewater treatment plant result in elevated beta-lactam resistance levels.

The multiresistance IncP-1 beta plasmid pB10 conferring resistance to ampicillin, streptomycin, sulfonamides, tetracycline and mercury ions was previously obtained from activated sludge bacteria by applying the exogenous isolation method with Pseudomonas sp. strain GFP2 as recipient. A pB10 derivative, designated pB10-1, occurred spontaneously and displays an extended NotI restriction fragment. From the pB10 nucleotide sequence, it is known that the corresponding NotI fragment of this plasmid contains a complete class 1 integron with an oxa2 and an orfE-like gene cassette. Sequencing of the integron-specific variable region present on pB10-1 revealed that a second copy of the oxa2 gene cassette has inserted downstream of the orfE-like cassette. Sequences flanking the second oxa2 cassette indicate that this cassette was excised from pB10 and reinserted at a new site in an integrase-catalyzed manner. Duplication of the oxa2 cassette is associated with a higher level of ampicillin resistance. Another pB10 derivative, designated pB10-2, conferring higher resistance to ampicillin, was shown to carry an IS10 insertion upstream of the oxa2 cassette. Since IS10 possesses a promoter-out activity, it can be assumed that the elevated ampicillin resistance level is due to enhanced transcription of the beta-lactamase gene.

The putative transcriptional repressor McbR, member of the TetR-family, is involved in the regulation of the metabolic network directing the synthesis of sulfur containing amino acids in Corynebacterium glutamicum.

In order to isolate transcriptional regulatory proteins involved in L-methionine-dependent repression in Corynebacterium glutamicum, proteins binding to the putative promoter region upstream of the metY gene were isolated by DNA affinity chromatography. One of the isolated proteins was identified as a putative transcriptional repressor of the TetR-family by a mass spectrometry fingerprint technique based on the complete C. glutamicum genome sequence. The respective gene, designated mcbR, was deleted in the mutant strain C. glutamicum DR1. Using 2D-PAGE, the protein contents of the C. glutamicum wild type and the mutant strain DR1 grown in media with or without L-methionine supplementation were compared and a set of six proteins was identified. Their abundance was drastically enhanced in the mutant strain and no longer influenced by L-methionine added to the growth medium. The corresponding genes were identified by mass spectrometry fingerprint analysis. They included metY encoding O-acetyl-L-homoserine sulfhydrylase, metK encoding S-adenosyl-methionine synthethase, hom encoding homoserine dehydrogenase, cysK encoding L-cysteine synthase, cysI encoding an NADPH dependant sulfite reductase, and ssuD encoding an alkanesulfonate monooxygenase. Evidently, the putative transcriptional repressor McbR is involved in the regulation of the metabolic network directing the synthesis of L-methionine in C. glutamicum. The C. glutamicum mcbR mutant can be considered to represent a first step in the construction of an L-methionine production strain.

The exbD2 gene as well as the iron-uptake genes tonB, exbB and exbD1 of Xanthomonas campestris pv. campestris are essential for the induction of a hypersensitive response on pepper (Capsicum annuum).

The tonB, exbB and exbD1 genes of Xanthomonas campestris pv. campestris are essential for ferric iron uptake. In contrast, the exbD2 gene located in the same gene cluster is not essential. Mutational analysis revealed that the ferric-iron-uptake genes tonB, exbB and exbD1 are necessary for the induction of a hypersensitive response (HR) on the nonhost plant pepper (Capsicum annuum) and the induction of typical black rot symptoms on the host plant cauliflower (Brassica oleracea). Again, the exbD2 gene behaved differently. It was found to play a role only in the induction of the HR in pepper but not in the induction of black rot symptoms in cauliflower. Due to the low iron concentration in the plant tissue, the titre of viable bacteria of the ferric-iron-uptake mutants tonB, exbB and exbD1 decreased after leaf infiltration of pepper. The exbD2 mutant, however, which is not impaired in ferric iron uptake, multiplied in the pepper leaf tissue and grew even better than the wild-type strain, probably due to its failure to induce the HR. Nevertheless, the tonB, exbB and exbD1 mutant strains were able to spread systemically in cauliflower.