Complete Genome Sequence of Dickeya dadantii subsp. dieffenbachiae Strain S3-1, Isolated from a White-Flowered Calla Lily in Taiwan

Erwinia chrysanthemi S3-1 is a bacterial soft rot pathogen of the white-flowered calla lily. The complete genome sequence of the strain was determined and used to reclassify the strain as Dickeya dadantii subsp. dieffenbachiae . The sequence will be useful to study plant host-driven speciation in strains of D. dadantii .

Improved pharmacokinetic and pharmacodynamic profile of a novel PEGylated native Erwinia chrysanthemi L-Asparaginase

SummaryIntroduction. Erwinase® (native Erwinia chrysanthemi L-Asparaginase (nErA)) is an approved second-line treatment for acute lymphoblastic leukaemia (ALL) in children and adolescents, who develop hypersensitivity or neutralising antibodies to E.coli derived L-Asparaginases (ASNases). However, nErA has a short in vivo half-life requiring frequent dosing schedules in patients. In this study, nErA was covalently conjugated to PEG molecules with the aim of extending its half-life in vivo. Methods. Firstly, efficacy of this novel product PEG-nErA was investigated on human ALL cell lines (Jurkat, CCRF-CEM and CCRF-HSB2), in vitro. Secondly, its pharmacokinetic (PK) and pharmacodynamic (PD) characteristics were determined, in vivo (12 rats in each group). Results. It was found that the specific activity (U/mg of enzyme) and the kinetic constant (KM) of nErA remained unaltered post PEGylation. PEG-nErA was shown to have similar cytotoxicity to nErA (IC50: 0.06–0.17 U/mL) on human ALL cell lines, in vitro. Further, when compared to nErA, PEG-nErA showed a significantly improved half-life in vivo, which meant that L-Asparagine (Asn) levels in plasma remained depleted for up to 25 days with a four-fold lower dose (100 U/kg) compared with 72 h for nErA at 400 U/kg dose. Conclusion. Overall, this next generation product PEG-nErA (with improved PK and PD characteristics compared to nErA) would bring a significant advantage to the therapeutic needs of ALL patients and should be further explored in clinical trials.

L-asparaginase: New about Well-Known Drug

The history of asparaginase clinical use is inextricably linked to the improvement of treatment programs for acute lymphoblastic leukaemia (ALL). Asparaginase, obtained from E. coli, has become the crucial part in the protocols for the treatment of ALL in children and adults since the 1960s-1970s due to its antitumor effect on lymphoid leukemia cells. Despite the evolution of therapeutic approaches in ALL management, changes in used chemotherapeutic agents, their administration regimens and doses, the asparaginase remains one of the leading therapeutic agents in ALL patients. With time ideas about the asparaginase mechanisms have expanded, new data have been accumulated on adverse effects (allergic reactions, thrombotic complications, pancreatitis, hepatic dysfunction, etc.). The asparaginase obtained from Erwinia chrysanthemi and PEGylated forms of the drug were used to reduce the frequency of any of such adverse effects. This literature review provides current concepts on the mechanism of L-asparaginase dosage forms action, describes side effects associated with the use of this medication. We also present our own clinical case of L-asparaginase (obtained from Erwinia chrysanthemi) administration in ALL patient with allergic reaction to PEG-L-asparaginase.

The Right-Handed Parallel β-Helix Topology of Erwinia chrysanthemi Pectin Methylesterase Is Intimately Associated with Both Sequential Folding and Resistance to High Pressure

The complex topologies of large multi-domain globular proteins make the study of their folding and assembly particularly demanding. It is often characterized by complex kinetics and undesired side reactions, such as aggregation. The structural simplicity of tandem-repeat proteins, which are characterized by the repetition of a basic structural motif and are stabilized exclusively by sequentially localized contacts, has provided opportunities for dissecting their folding landscapes. In this study, we focus on the Erwinia chrysanthemi pectin methylesterase (342 residues), an all-β pectinolytic enzyme with a right-handed parallel β-helix structure. Chemicals and pressure were chosen as denaturants and a variety of optical techniques were used in conjunction with stopped-flow equipment to investigate the folding mechanism of the enzyme at 25 °C. Under equilibrium conditions, both chemical- and pressure-induced unfolding show two-state transitions, with average conformational stability (ΔG° = 35 ± 5 kJ·mol−1) but exceptionally high resistance to pressure (Pm = 800 ± 7 MPa). Stopped-flow kinetic experiments revealed a very rapid (τ < 1 ms) hydrophobic collapse accompanied by the formation of an extended secondary structure but did not reveal stable tertiary contacts. This is followed by three distinct cooperative phases and the significant population of two intermediate species. The kinetics followed by intrinsic fluorescence shows a lag phase, strongly indicating that these intermediates are productive species on a sequential folding pathway, for which we propose a plausible model. These combined data demonstrate that even a large repeat protein can fold in a highly cooperative manner.

Early Emergence of Dickeya solani Revealed by Analysis of Dickeya Diversity of Potato Blackleg and Soft Rot Causing Pathogens in Switzerland

Blackleg and soft rot in potato caused by Pectobacterium and Dickeya enterobacteral genera are among the most destructive bacterial diseases in this crop worldwide. In Europe, over the last century, Pectobacterium spp. were the predominant causal agents of these diseases. As for Dickeya, before the large outbreak caused by D. solani in the 2000s, only D. dianthicola was isolated in Europe. The population dynamics of potato blackleg causing soft rot Pectobacteriaceae was, however, different in Switzerland as compared to that in other European countries with a high incidence (60 up to 90%) of Dickeya species (at the time called Erwinia chrysanthemi) already in the 1980s. To pinpoint what may underlie this Swiss peculiarity, we analysed the diversity present in the E. chrysanthemi Agroscope collection gathering potato isolates from 1985 to 2000s. Like elsewhere in Europe during this period, the majority of Swiss isolates belonged to D. dianthicola. However, we also identified a few isolates, such as D. chrysanthemi and D. oryzeae, two species that have not yet been reported in potatoes in Europe. Interestingly, this study allowed the characterisation of two “early” D. solani isolated in the 1990s. Genomic comparison between these early D. solani strains and strains isolated later during the large outbreak in the 2000s in Europe revealed only a few SNP and gene content differences, none of them affecting genes known to be important for virulence.