Complete genome sequencing of Agrobacterium sp. H13-3, the former Rhizobium lupini H13-3, reveals a tripartite genome consisting of a circular and a linear chromosome and an accessory plasmid but lacking a tumor-inducing Ti-plasmid

Genome Sequence of the Urethral Isolate Pseudomonas aeruginosa RN21

Pseudomonas aeruginosa is known to cause complicated urinary tract infections (UTI). The improved 7.0-Mb draft genome sequence of P. aeruginosa RN21, isolated from a patient with an acute UTI, was determined. It carries three (pro)phage genomes, genes for two restriction/modification systems, and a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) system.

Draft Genome Sequence of Pseudomonas aeruginosa Strain WS136, a Highly Cytotoxic ExoS-Positive Wound Isolate Recovered from Pyoderma Gangrenosum

Pseudomonas aeruginosa is an opportunistic pathogen that typically infects patients with a compromised immune defense. Here, we present the improved 6.5-Mb draft genome of strain WS136, an ExoS-positive and ExoU-negative highly cytotoxic chronic wound isolate recovered from pyoderma gangrenosum of a patient who received bone marrow transplantation.

Genome Sequence of the Urethral Catheter Isolate Pseudomonas aeruginosa MH19

Pseudomonas aeruginosa is a frequent agent of complicated catheter-associated urinary tract infections (CAUTIs). Here, we present the improved 7.1-Mb draft genome sequence of P. aeruginosa MH19, which was isolated from a patient with an acute hospital-acquired CAUTI. It includes unique genes not represented in other P. aeruginosa genomes.

Comparative metagenomics of biogas-producing microbial communities from production-scale biogas plants operating under wet or dry fermentation conditions

BACKGROUND

Decomposition of biomass for biogas production can be practiced under wet and dry fermentation conditions. In contrast to the dry fermentation technology, wet fermentation is characterized by a high liquid content and a relatively low total solid content. In this study, the composition and functional potential of a biogas-producing microbial community in an agricultural biogas reactor operating under wet fermentation conditions was analyzed by a metagenomic approach applying 454-pyrosequencing. The obtained metagenomic dataset and corresponding 16S rRNA gene amplicon sequences were compared to the previously sequenced comparable metagenome from a dry fermentation process, meeting explicitly identical boundary conditions regarding sample and community DNA preparation, sequencing technology, processing of sequence reads and data analyses by bioinformatics tools.

RESULTS

High-throughput metagenome sequencing of community DNA from the wet fermentation process applying the pyrosequencing approach resulted in 1,532,780 reads, with an average read length of 397 bp, accounting for approximately 594 million bases of sequence information in total. Taxonomic comparison of the communities from wet and dry fermentation revealed similar microbial profiles with Bacteria being the predominant superkingdom, while the superkingdom Archaea was less abundant. In both biogas plants, the bacterial phyla Firmicutes, Bacteroidetes, Spirochaetes and Proteobacteria were identified with descending frequencies. Within the archaeal superkingdom, the phylum Euryarchaeota was most abundant with the dominant class Methanomicrobia. Functional profiles of the communities revealed that environmental gene tags representing methanogenesis enzymes were present in both biogas plants in comparable frequencies. 16S rRNA gene amplicon high-throughput sequencing disclosed differences in the sub-communities comprising methanogenic Archaea between both processes. Fragment recruitments of metagenomic reads to the reference genome of the archaeon Methanoculleus bourgensis MS2(T) revealed that dominant methanogens within the dry fermentation process were highly related to the reference.

CONCLUSIONS

Although process parameters, substrates and technology differ between the wet and dry biogas fermentations analyzed in this study, community profiles are very similar at least at higher taxonomic ranks, illustrating that core community taxa perform key functions in biomass decomposition and methane synthesis. Regarding methanogenesis, Archaea highly related to the type strain M. bourgensis MS2(T) dominate the dry fermentation process, suggesting the adaptation of members belonging to this species to specific fermentation process parameters.

Insights into the annotated genome sequence of Methanoculleus bourgensis MS2(T), related to dominant methanogens in biogas-producing plants

The final step of the biogas production process, the methanogenesis, is frequently dominated by members of the genus Methanoculleus. In particular, the species Methanoculleus bourgensis was identified to play a role in different biogas reactor systems. The genome of the type strain M. bourgensis MS2(T), originally isolated from a sewage sludge digestor, was completely sequenced to analyze putative adaptive genome features conferring competitiveness within biogas reactor environments to the strain. Sequencing and assembly of the M. bourgensis MS2(T) genome yielded a chromosome with a size of 2,789,773 bp. Comparative analysis of M. bourgensis MS2(T) and Methanoculleus marisnigri JR1 revealed significant similarities. The absence of genes for a putative ammonium uptake system may indicate that M. bourgensis MS2(T) is adapted to environments rich in ammonium/ammonia. Specific genes featuring predicted functions in the context of osmolyte production were detected in the genome of M. bourgensis MS2(T). Mapping of metagenome sequences derived from a production-scale biogas plant revealed that M. bourgensis MS2(T) almost completely comprises the genetic information of dominant methanogens present in the biogas reactor analyzed. Hence, availability of the M. bourgensis MS2(T) genome sequence may be valuable regarding further research addressing the performance of Methanoculleus species in agricultural biogas plants.

Complete genome sequence of the methanogenic neotype strain Methanobacterium formicicum MF(T.)

The neotype strain Methanobacterium formicicum MF(T) (DSM1535), a hydrogenotrophic methanogenic Archaeon, was isolated from a domestic sewage sludge digestor in Urbana (IL, USA). Here, the complete genome sequence of the methanogen is reported. The genome is 2,478,074bp in size, featuring a GC content of 41.23%. M. formicicum MF(T) encodes several genes predicted to be involved in adaptation to abiotic stress such as high osmolarity. The strain MF(T) is of biotechnological importance since M. formicicum strains are often found in production-scale biogas plants and it is suggested as a starter culture for the anaerobic biomethanation process.

Complete genome sequence of Peptoniphilus sp. strain ING2-D1G isolated from a mesophilic lab-scale completely stirred tank reactor utilizing maize silage in co-digestion with pig and cattle manure for biomethanation

The bacterium Peptoniphilus sp. strain ING2-D1G (DSM 28672), a mesophilic and obligate anaerobic bacterium belonging to the order Clostridiales was isolated from a biogas-producing lab-scale completely stirred tank reactor (CSTR) optimized for anaerobic digestion of maize silage in co-fermentation with pig and cattle manure. In this study, the whole genome sequence of Peptoniphilus sp. strain ING2-D1G, a new isolate potentially involved in protein breakdown and acidogenesis during biomass degradation, is reported. The chromosome of this strain is 1.6Mb in size and encodes genes predicted to be involved in the production of acetate, lactate and butyrate specifying the acidogenic metabolism of the isolate.

Enhancement of cell ingrowth, proliferation, and early differentiation in a three-dimensional silicon carbide scaffold using low-intensity pulsed ultrasound

Concerns over the use of autografts or allografts have necessitated the development of biomaterials for bone regeneration. Various studies have been performed to optimize the cultivation of osteogenic cells using osteoconductive porous scaffolds. The aim of this study was to evaluate the osteogenic efficiency of bone cell ingrowth, proliferation, and early differentiation in a silicon carbide (SiC) porous ceramic scaffold promoted with low-intensity pulsed ultrasound. MC3T3-E1 mouse preosteoblasts were seeded onto scaffolds and cultured for 4 and 7 days with daily of 20-min ultrasound treatment. The cells were evaluated for cell attachment, morphology, viability, ingrowth depth, volumetric proliferation, and early differentiation. After 4 and 7 days of culture and ultrasound exposure, the cell density was higher in the ultrasound-treated group compared with the sham-treated group on SiC scaffolds. The cell ingrowth depths inside the SiC scaffolds were 149.2±27.3 μm at 1 day, 310.1±12.6 μm for the ultrasound-treated group and 248.0±19.7 μm for the sham control at 4 days, and 359.6±18.5 μm for the ultrasound-treated group and 280.0±17.7 μm for the sham control at 7 days. They were significantly increased, that is, 25% (p=0.0029) and 28% (p=0.0008) increase, respectively, with ultrasound radiation force as compared with those in sham control at 4 and 7 days postseeding. The dsDNA contents were 583.5±19.1 ng/scaffold at 1 day, 2749.9±99.9 ng/scaffold for the ultrasound-treated group and 2514.9±114.7 ng/scaffold for the sham control at 4 days, and 3582.3±325.3 ng/scaffold for the ultrasound-treated group and 2825.7±134.3 ng/scaffold for the sham control at 7 days. There was a significant difference in the dsDNA content between the ultrasound- and sham-treated groups at 4 and 7 days. The ultrasound-treated group with the SiC construct showed a 9% (p=0.00029) and 27% (p=0.00017) increase in the average dsDNA content at 4 and 7 days over the sham control group, respectively. Alkaline phosphatase activity was significantly increased by the treatment of ultrasound at 4 (p=0.012) and 7 days (p=0.035). These results suggested that ultrasound treatment with low-intensity acoustic energy facilitated the cellular ingrowth and enhanced the proliferation and early differentiation of osteoblasts in SiC scaffolds.

IncH-type plasmid harboring bla CTX-M-15, bla DHA-1, and qnrB4 genes recovered from animal isolates

The whole sequence of plasmid pENVA carrying the extended-spectrum β-lactamase gene blaCTX-M-15 was determined. It was identified from a series of clonally related Klebsiella pneumoniae sequence type 274 strains recovered from companion animals. This plasmid was 253,984 bp in size and harbored, in addition to blaCTX-M-15, a large array of genes encoding resistance to many antibiotic molecules, including β-lactams (blaTEM-1, blaDHA-1), aminoglycosides (aacA2, aadA1), tetracycline (tetA), quinolones (qnrB4), trimethoprim (dfrA15), and sulfonamides (two copies of sul1). In addition, genes encoding resistance to mercury, tellurium, nickel, and quaternary compounds were identified. It also carried genes encoding DNA damage protection and mutagenesis repair and a locus for a CRISPR system, which corresponds to an immune system involved in protection against bacteriophages and plasmids. Comparative analysis of the plasmid scaffold showed that it possessed a structure similar to that of only a single plasmid, which was pNDM-MAR encoding the carbapenemase NDM-1 and identified from human K. pneumoniae isolates. Both plasmids possessed two replicons, namely, those of IncFIB-like and IncHIB-like plasmids, which were significantly different from those previously characterized. The blaCTX-M-15 gene, together with the other antibiotic resistance genes, was part of a large module likely acquired through a transposition process. We characterized here a new plasmid type carrying the blaCTX-M-15 gene identified in a K. pneumoniae isolate of animal origin. The extent to which this plasmid type may spread efficiently and possibly further enhance the dissemination of blaCTX-M-15 among animal and human isolates remains to be determined.

Genome Sequence of the Octopine-Type Agrobacterium tumefaciens Strain Ach5

We have sequenced the complete genome of the plant pathogen Agrobacterium tumefaciens strain LBA4213, a derivative of the wild-type strain A. tumefaciens Ach5 and the ancestor of A. tumefaciens strain LBA4404 used in genetic engineering. The genome consists of a circular chromosome and a linear chromosome, as well as a megaplasmid and a tumor-inducing plasmid.

Utilization of glyphosate as phosphate source: biochemistry and genetics of bacterial carbon-phosphorus lyase

After several decades of use of glyphosate, the active ingredient in weed killers such as Roundup, in fields, forests, and gardens, the biochemical pathway of transformation of glyphosate phosphorus to a useful phosphorus source for microorganisms has been disclosed. Glyphosate is a member of a large group of chemicals, phosphonic acids or phosphonates, which are characterized by a carbon-phosphorus bond. This is in contrast to the general phosphorus compounds utilized and metabolized by microorganisms. Here phosphorus is found as phosphoric acid or phosphate ion, phosphoric acid esters, or phosphoric acid anhydrides. The latter compounds contain phosphorus that is bound only to oxygen. Hydrolytic, oxidative, and radical-based mechanisms for carbon-phosphorus bond cleavage have been described. This review deals with the radical-based mechanism employed by the carbon-phosphorus lyase of the carbon-phosphorus lyase pathway, which involves reactions for activation of phosphonate, carbon-phosphorus bond cleavage, and further chemical transformation before a useful phosphate ion is generated in a series of seven or eight enzyme-catalyzed reactions. The phn genes, encoding the enzymes for this pathway, are widespread among bacterial species. The processes are described with emphasis on glyphosate as a substrate. Additionally, the catabolism of glyphosate is intimately connected with that of aminomethylphosphonate, which is also treated in this review. Results of physiological and genetic analyses are combined with those of bioinformatics analyses.

Genes conferring copper resistance in Sinorhizobium meliloti CCNWSX0020 also promote the growth of Medicago lupulina in copper-contaminated soil

Sinorhizobium meliloti CCNWSX0020, isolated from root nodules of Medicago lupulina growing in gold mine tailings in the northwest of China, displayed both copper resistance and growth promotion of leguminous plants in copper-contaminated soil. Nevertheless, the genetic and biochemical mechanisms responsible for copper resistance in S. meliloti CCNWSX0020 remained uncharacterized. To investigate genes involved in copper resistance, an S. meliloti CCNWSX0020 Tn5 insertion library of 14,000 mutants was created. Five copper-sensitive mutants, named SXa-1, SXa-2, SXc-1, SXc-2, and SXn, were isolated, and the disrupted regions involved were identified by inverse PCR and subsequent sequencing. Both SXa-1 and SXa-2 carried a transposon insertion in lpxXL (SM0020_18047), encoding the LpxXL C-28 acyltransferase; SXc-1 and SXc-2 carried a transposon insertion in merR (SM0020_29390), encoding the regulatory activator; SXn contained a transposon insertion in omp (SM0020_18792), encoding a hypothetical outer membrane protein. The results of reverse transcriptase PCR (RT-PCR) combined with transposon gene disruptions revealed that SM0020_05862, encoding an unusual P-type ATPase, was regulated by the MerR protein. Analysis of the genome sequence showed that this P-type ATPase did not contain an N-terminal metal-binding domain or a CPC motif but rather TPCP compared with CopA from Escherichia coli. Pot experiments were carried out to determine whether growth and copper accumulation of the host plant M. lupulina were affected in the presence of the wild type or the different mutants. Soil samples were subjected to three levels of copper contamination, namely, the uncontaminated control and 47.36 and 142.08 mg/kg, and three replicates were conducted for each treatment. The results showed that the wild-type S. meliloti CCNWSX0020 enabled the host plant to grow better and accumulate copper ions. The plant dry weight and copper content of M. lupulina inoculated with the 5 copper-sensitive mutants significantly decreased in the presence of CuSO4.

Large deletions in the pAtC58 megaplasmid of Agrobacterium tumefaciens can confer reduced carriage cost and increased expression of virulence genes

The accessory plasmid pAtC58 of the common laboratory strain of Agrobacterium tumefaciens confers numerous catabolic functions and has been proposed to play a role in virulence. Genomic sequencing of evolved laboratory strains of A. tumefaciens revealed the presence of multiple deletion events in the At plasmid, with reductions in plasmid size ranging from 25% to 30% (115–194 kb). Flanking both ends of the sites of these deletions is a short-nucleotide repeat sequence that is in a single copy in the deleted plasmids, characteristic of a phage- or transposon-mediated deletion event. This repeat sequence is widespread throughout the C58 genome, but concentrated on the At plasmid, suggesting its frequency to be nonrandom. In this study, we assess the prevalence of the larger of these deletions in multiple C58 derivatives and characterize its functional significance. We find that in addition to elevating virulence gene expression, this deletion is associated with a significantly reduced carriage cost to the cell. These observations are a clear demonstration of the dynamic nature of the bacterial genome and suggest a mechanism for genetic plasticity of these costly but otherwise stable plasmids. Additionally, this phenomenon could be the basis for some of the dramatic recombination events so ubiquitous within and among megaplasmids.

Draft genome sequence of Sinorhizobium meliloti RU11/001, a model organism for flagellum structure, motility and chemotaxis

Sinorhizobium meliloti of the order Rhizobiales is a symbiotic nitrogen-fixing bacterium nodulating plants of the genera Medicago, Trigonella and Melilotus and hence is of great agricultural importance. In its free-living state it is motile and capable of modulating its movement patterns in response to chemical attractants. Here, the draft genome consisting of a circular chromosome, the megaplasmids pSymA and pSymB and three accessory plasmids of Sinorhizobium meliloti RU11/001, a model organism for flagellum structure, motility and chemotaxis, is reported.

The Sinorhizobium meliloti essential porin RopA1 is a target for numerous bacteriophages

The symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti harbors a gene, SMc02396, which encodes a predicted outer membrane porin that is conserved in many symbiotic and pathogenic bacteria in the order Rhizobiales. Here, this gene (renamed ropA1) is shown to be required for infection by two commonly utilized transducing bacteriophages (ΦM12 and N3). Mapping of S. meliloti mutations conferring resistance to ΦM12, N3, or both phages simultaneously revealed diverse mutations mapping within the ropA1 open reading frame. Subsequent tests determined that RopA1, lipopolysaccharide, or both are required for infection by all of a larger collection of Sinorhizobium-specific phages. Failed attempts to disrupt or delete ropA1 suggest that this gene is essential for viability. Phylogenetic analysis reveals that ropA1 homologs in many Rhizobiales species are often found as two genetically linked copies and that the intraspecies duplicates are always more closely related to each other than to homologs in other species, suggesting multiple independent duplication events.

Rapid and accurate species and genomic species identification and exhaustive population diversity assessment of Agrobacterium spp. using recA-based PCR

Agrobacteria are common soil bacteria that interact with plants as commensals, plant growth promoting rhizobacteria or alternatively as pathogens. Indigenous agrobacterial populations are composites, generally with several species and/or genomic species and several strains per species. We thus developed a recA-based PCR approach to accurately identify and specifically detect agrobacteria at various taxonomic levels. Specific primers were designed for all species and/or genomic species of Agrobacterium presently known, including 11 genomic species of the Agrobacterium tumefaciens complex (G1-G9, G13 and G14, among which only G2, G4, G8 and G14 still received a Latin epithet: pusense, radiobacter, fabrum and nepotum, respectively), A. larrymoorei, A. rubi, R. skierniewicense, A. sp. 1650, and A. vitis, and for the close relative Allorhizobium undicola. Specific primers were also designed for superior taxa, Agrobacterium spp. and Rhizobiaceace. Primer specificities were assessed with target and non-target pure culture DNAs as well as with DNAs extracted from composite agrobacterial communities. In addition, we showed that the amplicon cloning-sequencing approach used with Agrobacterium-specific or Rhizobiaceae-specific primers is a way to assess the agrobacterial diversity of an indigenous agrobacterial population. Hence, the agrobacterium-specific primers designed in the present study enabled the first accurate and rapid identification of all species and/or genomic species of Agrobacterium, as well as their direct detection in environmental samples.

Genome Sequence of Rhizobium lupini HPC(L) Isolated from Saline Desert Soil, Kutch (Gujarat)

The Rhizobium lupini strain HPC(L) was isolated from saline desert soil. It grows on minimal media supplemented with CaCO₃ as a carbon source. It can also grow under both oligotrophic and heteroptrophic conditions. We report the annotated genome sequence of this strain in a 5.27-Mb scaffold.

Genomic basis of broad host range and environmental adaptability of Rhizobium tropici CIAT 899 and Rhizobium sp. PRF 81 which are used in inoculants for common bean (Phaseolus vulgaris L.)

BACKGROUND

Rhizobium tropici CIAT 899 and Rhizobium sp. PRF 81 are α-Proteobacteria that establish nitrogen-fixing symbioses with a range of legume hosts. These strains are broadly used in commercial inoculants for application to common bean (Phaseolus vulgaris) in South America and Africa. Both strains display intrinsic resistance to several abiotic stressful conditions such as low soil pH and high temperatures, which are common in tropical environments, and to several antimicrobials, including pesticides. The genetic determinants of these interesting characteristics remain largely unknown.

RESULTS

Genome sequencing revealed that CIAT 899 and PRF 81 share a highly-conserved symbiotic plasmid (pSym) that is present also in Rhizobium leucaenae CFN 299, a rhizobium displaying a similar host range. This pSym seems to have arisen by a co-integration event between two replicons. Remarkably, three distinct nodA genes were found in the pSym, a characteristic that may contribute to the broad host range of these rhizobia. Genes for biosynthesis and modulation of plant-hormone levels were also identified in the pSym. Analysis of genes involved in stress response showed that CIAT 899 and PRF 81 are well equipped to cope with low pH, high temperatures and also with oxidative and osmotic stresses. Interestingly, the genomes of CIAT 899 and PRF 81 had large numbers of genes encoding drug-efflux systems, which may explain their high resistance to antimicrobials. Genome analysis also revealed a wide array of traits that may allow these strains to be successful rhizosphere colonizers, including surface polysaccharides, uptake transporters and catabolic enzymes for nutrients, diverse iron-acquisition systems, cell wall-degrading enzymes, type I and IV pili, and novel T1SS and T5SS secreted adhesins.

CONCLUSIONS

Availability of the complete genome sequences of CIAT 899 and PRF 81 may be exploited in further efforts to understand the interaction of tropical rhizobia with common bean and other legume hosts.

Reconciliation of sequence data and updated annotation of the genome of Agrobacterium tumefaciens C58, and distribution of a linear chromosome in the genus Agrobacterium

Two groups independently sequenced the Agrobacterium tumefaciens C58 genome in 2001. We report here consolidation of these sequences, updated annotation, and additional analysis of the evolutionary history of the linear chromosome, which is apparently limited to the biovar I group of Agrobacterium.

The IncF plasmid pRSB225 isolated from a municipal wastewater treatment plant's on-site preflooder combining antibiotic resistance and putative virulence functions is highly related to virulence plasmids identified in pathogenic E. coli isolates

The IncF antibiotic resistance and virulence plasmid pRSB225, isolated from an unknown bacterium released with the purified wastewater from a municipal sewage treatment plant into the environment has been analysed at the genomic level by pyrosequencing. The 164,550bp plasmid comprises 210 coding sequences (cds). It is composed of three replicons (RepFIA, RepFIB, and RepFII) and encodes further plasmid-specific functions for stable maintenance and inheritance and conjugative plasmid transfer. The plasmid is self-transmissible and shows a narrow host range limited to the family Enterobacteriaceae. The accessory modules of the plasmid mainly comprise genes conferring resistance to ampicillin (bla(TEM-1b)), chloramphenicol (catA1), erythromycin (mphA), kanamycin and neomycin (aphA1), streptomycin (strAB), sulphonamides (sul2), tetracycline (tetA(B)) and trimethoprim (dfrA14), as well as mercuric ions (mer genes). In addition, putative virulence-associated genes coding for iron uptake (iutA/iucABCD, sitABCD, and a putative high-affinity Fe²⁺ uptake system) and for a toxin/antitoxin system (vagCD) were identified on the plasmid. All antibiotic and heavy metal resistance genes are located either on class 1 (Tn10-remnant, Tn4352B) and class 2 transposons (Tn2-remnant, Tn21, Tn402-remnant) or a class 1 integron, whereas almost all putative virulence genes are associated with IS elements (IS1, IS26), indicating that transposition and/or recombination events were responsible for acquisition of the accessory pRSB225 modules. Particular modules of plasmid pRSB225 are related to corresponding segments of different virulence plasmids harboured by pathogenic Escherichia coli strains. Moreover, pRSB225 modules were also detected in entero-aggregative-haemorrhagic E. coli (EAHEC) draft genome sequences suggesting that IncF plasmids related to pRSB225 mediated gene transfer into pathogenic E. coli derivatives.

Complete genome sequence of the hydrogenotrophic, methanogenic archaeon Methanoculleus bourgensis strain MS2(T), Isolated from a sewage sludge digester

Methanoculleus bourgensis, of the order Methanomicrobiales, is a dominant methanogenic archaeon in many biogas-producing reactor systems fed with renewable primary products. It is capable of synthesizing methane via the hydrogenotrophic pathway utilizing hydrogen and carbon dioxide or formate as the substrates. Here we report the complete and finished genome sequence of M. bourgensis strain MS2(T), isolated from a sewage sludge digester.

Draft whole genome sequence of the cyanide-degrading bacterium Pseudomonas pseudoalcaligenes CECT5344

Pseudomonas pseudoalcaligenes CECT5344 is a Gram-negative bacterium able to tolerate cyanide and to use it as the sole nitrogen source. We report here the first draft of the whole genome sequence of a P. pseudoalcaligenes strain that assimilates cyanide. Three aspects are specially emphasized in this manuscript. First, some generalities of the genome are shown and discussed in the context of other Pseudomonadaceae genomes, including genome size, G + C content, core genome and singletons among other features. Second, the genome is analysed in the context of cyanide metabolism, describing genes probably involved in cyanide assimilation, like those encoding nitrilases, and genes related to cyanide resistance, like the cio genes encoding the cyanide insensitive oxidases. Finally, the presence of genes probably involved in other processes with a great biotechnological potential like production of bioplastics and biodegradation of pollutants also is discussed.

Minimum requirements of flagellation and motility for infection of Agrobacterium sp. strain H13-3 by flagellotropic bacteriophage 7-7-1

The flagellotropic phage 7-7-1 specifically adsorbs to Agrobacterium sp. strain H13-3 (formerly Rhizobium lupini H13-3) flagella for efficient host infection. The Agrobacterium sp. H13-3 flagellum is complex and consists of three flagellin proteins: the primary flagellin FlaA, which is essential for motility, and the secondary flagellins FlaB and FlaD, which have minor functions in motility. Using quantitative infectivity assays, we showed that absence of FlaD had no effect on phage infection, while absence of FlaB resulted in a 2.5-fold increase in infectivity. A flaA deletion strain, which produces straight and severely truncated flagella, experienced a significantly reduced infectivity, similar to that of a flaB flaD strain, which produces a low number of straight flagella. A strain lacking all three flagellin genes is phage resistant. In addition to flagellation, flagellar rotation is required for infection. A strain that is nonmotile due to an in-frame deletion in the gene encoding the motor component MotA is resistant to phage infection. We also generated two strains with point mutations in the motA gene resulting in replacement of the conserved charged residue Glu98, which is important for modulation of rotary speed. A change to the neutral Gln caused the flagellar motor to rotate at a constant high speed, allowing a 2.2-fold-enhanced infectivity. A change to the positively charged Lys caused a jiggly motility phenotype with very slow flagellar rotation, which significantly reduced the efficiency of infection. In conclusion, flagellar number and length, as well as speed of flagellar rotation, are important determinants for infection by phage 7-7-1.

Genome and proteome analysis of 7-7-1, a flagellotropic phage infecting Agrobacterium sp H13-3

Background

The flagellotropic phage 7-7-1 infects motile cells of Agrobacterium sp H13-3 by attaching to and traveling along the rotating flagellar filament to the secondary receptor at the base, where it injects its DNA into the host cell. Here we describe the complete genomic sequence of 69,391 base pairs of this unusual bacteriophage.

Methods

The sequence of the 7-7-1 genome was determined by pyro(454)sequencing to a coverage of 378-fold. It was annotated using MyRAST and a variety of internet resources. The structural proteome was analyzed by SDS-PAGE coupled electrospray ionization-tandem mass spectrometry (MS/MS).

Results

Sequence annotation and a structural proteome analysis revealed 127 open reading frames, 84 of which are unique. In six cases 7-7-1 proteins showed sequence similarity to proteins from the virulent Burkholderia myovirus BcepB1A. Unique features of the 7-7-1 genome are the physical separation of the genes encoding the small (orf100) and large (orf112) subunits of the DNA packaging complex and the apparent lack of a holin-lysin cassette. Proteomic analysis revealed the presence of 24 structural proteins, five of which were identified as baseplate (orf7), putative tail fibre (orf102), portal (orf113), major capsid (orf115) and tail sheath (orf126) proteins. In the latter case, the N-terminus was removed during capsid maturation, probably by a putative prohead protease (orf114).

Linear chromosome-generating system of Agrobacterium tumefaciens C58: protelomerase generates and protects hairpin ends

Agrobacterium tumefaciens C58, the pathogenic bacteria that causes crown gall disease in plants, harbors one circular and one linear chromosome and two circular plasmids. The telomeres of its unusual linear chromosome are covalently closed hairpins. The circular and linear chromosomes co-segregate and are stably maintained in the organism. We have determined the sequence of the two ends of the linear chromosome thus completing the previously published genome sequence of A. tumefaciens C58. We found that the telomeres carry nearly identical 25-bp sequences at the hairpin ends that are related by dyad symmetry. We further showed that its Atu2523 gene encodes a protelomerase (resolvase) and that the purified enzyme can generate the linear chromosomal closed hairpin ends in a sequence-specific manner. Agrobacterium protelomerase, whose presence is apparently limited to biovar 1 strains, acts via a cleavage-and-religation mechanism by making a pair of transient staggered nicks invariably at 6-bp spacing as the reaction intermediate. The enzyme can be significantly shortened at both the N and C termini and still maintain its enzymatic activity. Although the full-length enzyme can uniquely bind to its product telomeres, the N-terminal truncations cannot. The target site can also be shortened from the native 50-bp inverted repeat to 26 bp; thus, the Agrobacterium hairpin-generating system represents the most compact activity of all hairpin linear chromosome- and plasmid-generating systems to date. The biochemical analyses of the protelomerase reactions further revealed that the tip of the hairpin telomere may be unusually polymorphically capable of accommodating any nucleotide.

Insights into the completely annotated genome of Lactobacillus buchneri CD034, a strain isolated from stable grass silage

Lactobacillus buchneri belongs to the group of heterofermentative lactic acid bacteria and is a common member of the silage microbiome. Here we report the completely annotated genomic sequence of L. buchneri CD034, a strain isolated from stable grass silage. The whole genome of L. buchneri CD034 was sequenced on the Roche Genome Sequencer FLX platform. It was found to consist of four replicons, a circular chromosome, and three plasmids. The circular chromosome was predicted to encode 2319 proteins and contains a genomic island and two prophages which significantly differ in G+C-content from the remaining chromosome. It possesses all genes for enzymes of a complete phosphoketolase pathway, whereas two enzymes necessary for glycolysis are lacking. This confirms the classification of L. buchneri CD034 as an obligate heterofermentative lactic acid bacterium. A set of genes considered to be involved in the lactate degradation pathway and genes putatively involved in the breakdown of plant cell wall polymers were identified. Moreover, several genes encoding putative S-layer proteins and two CRISPR systems, belonging to the subclasses I-E and II-A, are located on the chromosome. The largest plasmid pCD034-3 was predicted to encode 57 genes, including a putative polysaccharide synthesis gene cluster, whereas the functions of the two smaller plasmids, pCD034-1 and pCD034-2, remain cryptic. Phylogenetic analysis based on sequence comparison of the conserved marker gene rpoA reveals that L. buchneri CD034 is more closely related to Lactobacillus hilgardii strains than to Lactobacillus brevis and Lactobacillus plantarum strains. Comparison of the L. buchneri CD034 core genome to other fully sequenced and closely related members of the genus Lactobacillus disclosed a high degree of conservation between L. buchneri CD034 and the recently sequenced L. buchneri strain NRRL B-30929 and a more distant relationship to L. buchneri ATCC 11577 and L. brevis ssp. gravesensis ATCC 27305, which cluster together with L. hilgardii type strain ATCC 8290. L. buchneri CD034 genome information will certainly provide the basis for further postgenome studies with the objective to optimize application of the strain in silage production.

A cost-effective and universal strategy for complete prokaryotic genomic sequencing proposed by computer simulation

BACKGROUND

Pyrosequencing techniques allow scientists to perform prokaryotic genome sequencing to achieve the draft genomic sequences within a few days. However, the assemblies with shotgun sequencing are usually composed of hundreds of contigs. A further multiplex PCR procedure is needed to fill all the gaps and link contigs into complete chromosomal sequence, which is the basis for prokaryotic comparative genomic studies. In this article, we study various pyrosequencing strategies by simulated assembling from 100 prokaryotic genomes.

FINDINGS

Simulation study shows that a single end 454 Jr. run combined with a paired end 454 Jr. run (8 kb library) can produce: 1) ~90% of 100 assemblies with < 10 scaffolds and ~95% of 100 assemblies with < 150 contigs; 2) average contig N50 size is over 331 kb; 3) average single base accuracy is > 99.99%; 4) average false gene duplication rate is < 0.7%; 5) average false gene loss rate is < 0.4%.

CONCLUSIONS

A single end 454 Jr. run combined with a paired end 454 Jr. run (8 kb library) is a cost-effective way for prokaryotic whole genome sequencing. This strategy provides solution to produce high quality draft assemblies for most of prokaryotic organisms within days. Due to the small number of assembled scaffolds, the following multiplex PCR procedure (for gap filling) would be easy. As a result, large scale prokaryotic whole genome sequencing projects may be finished within weeks.

Genomic species are ecological species as revealed by comparative genomics in Agrobacterium tumefaciens

The definition of bacterial species is based on genomic similarities, giving rise to the operational concept of genomic species, but the reasons of the occurrence of differentiated genomic species remain largely unknown. We used the Agrobacterium tumefaciens species complex and particularly the genomic species presently called genomovar G8, which includes the sequenced strain C58, to test the hypothesis of genomic species having specific ecological adaptations possibly involved in the speciation process. We analyzed the gene repertoire specific to G8 to identify potential adaptive genes. By hybridizing 25 strains of A. tumefaciens on DNA microarrays spanning the C58 genome, we highlighted the presence and absence of genes homologous to C58 in the taxon. We found 196 genes specific to genomovar G8 that were mostly clustered into seven genomic islands on the C58 genome—one on the circular chromosome and six on the linear chromosome—suggesting higher plasticity and a major adaptive role of the latter. Clusters encoded putative functional units, four of which had been verified experimentally. The combination of G8-specific functions defines a hypothetical species primary niche for G8 related to commensal interaction with a host plant. This supports that the G8 ancestor was able to exploit a new ecological niche, maybe initiating ecological isolation and thus speciation. Searching genomic data for synapomorphic traits is a powerful way to describe bacterial species. This procedure allowed us to find such phenotypic traits specific to genomovar G8 and thus propose a Latin binomial, Agrobacterium fabrum, for this bona fide genomic species.

De novo sequencing and assembly of the whole genome of Novosphingobium sp. strain PP1Y

Novosphingobium sp. strain PP1Y is a marine bacterium specifically adapted to use fuels as an energy source. We sequenced and assembled its entire genome using the Roche 454 genome sequencer system, which led to the identification of two plasmids and one megaplasmid, besides a 3.9-Mb circular chromosome.