Induced expression of the Serratia entomophila Sep proteins shows activity towards the larvae of the New Zealand grass grub Costelytra zealandica

Serratia entomophila and Serratia proteamaculans cause amber disease of the grass grub Costelytra zealandica (Coleoptera: Scarabaeidae). Three genes required for virulence, sepABC, are located on a large plasmid, pADAP. The translated products of the sep genes are members of the toxin complex (Tc) family of insecticidal toxins that reside in the genomes of some Enterobacteriaceae. Each of the sep genes was placed either singly or as various combinations under the control of an inducible arabinose promoter, allowing their inductive expression. Western Immunoblot confirmed that each of the Sep proteins migrated at their predicted size on sodium dodecyl sulphate-polyacrylamide gel electrophoresis gel. Bioassays of sonicated filtrates derived from the various arabinose-induced para-SEP constructs showed that only when sepA, sepB and sepC were coexpressed were amber disease symptoms observed in grass grub larvae. Fourteen days after ingestion of the Sep protein filtrate, approximately 64% of the larvae reverted from a diseased to a healthy phenotype. Redosing the revertents with a fresh Sep protein filtrate reinitiated the amber pathotype, indicating that the Sep proteins are needed to be continuously present to exert an effect.     

血清浓度及溶氧对培养rCHO细胞生产尿激酶原的影响

在30L搅拌式反应器中用多孔微载体培养分泌尿激酶原的DNA重组中国仓鼠卵巢细胞(rCHO),研究了血清浓度及溶氧对细胞生长和表达的影响.结果表明,在2×105/ml低密度接种条件下,使用低(无)血清培养基会延长细胞生长延滞期并降低比生长速率,而细胞密度大于106/ml时,血清浓度对细胞生长和产物表达的影响没有显著差别.溶氧(DO)维持在20%～45%时,对细胞表达产物和葡萄糖代谢无明显影响,但溶氧降至7%～9%时,细胞表达水平明显降低,葡萄糖代谢转化为乳酸的比例上升.     

Influence of dilution rate and dissolved oxygen concentration on continuous keto acid production by Gluconobacter oxydans subsp. melanogenum

The influence of dilution rate and dissolved oxygen concentration on continuous production of 2,5-diketogluconic acid (2,5-DKGA) by Gluconobacter oxydans subsp. melanogenum is described. Under suitable dissolved oxygen conditions, the glucose oxidation rate is independent of variations in dilution rates over a wide range (D < 0.33 h⁻¹). The higher dilution rate, however, leads to a partial oxidation of the substrate and therefore accumulation of more gluconic acid. Contrary to this, a longer residence time (lower dilution rate) was more suitable for better ketogenic activity, thereby facilitating accumulation of 2,5-DKGA in higher yields. A high dissolved oxygen concentration is further shown to positively influence the overall oxidation process through an organized induction of membrane-bound NAD(P)⁺-independent dehydrogenases.     

Combined approach of NMR and chemometrics for screening peptones used in the cell culture medium for the production of a recombinant therapeutic protein

Soy peptones or soy hydrolysates are widely used as key medium additives in serum-free cell culture processes for industrial production of therapeutic recombinant proteins. The heterogeneous nature of these vegetable-derived materials can lead to substantial lot- to-lot variability in cell culture processes. In this study, we demonstrated the feasibility of nuclear magnetic resonance (NMR) spectroscopy in combination with chemometrics in rapid screening peptone lots in order to optimize efficiency and consistency of large-scale protein production. This report is the first that shows a correlation between the intrinsic NMR spectral characteristics of complex heterogeneous materials and product titer using chemometrics.     

Effects of dissolved oxygen tension and agitation rate on the production of heat-shock protein glycoprotein 96 by MethA tumor cell suspension culture in stirred-tank bioreactors

Heat-shock protein glycoprotein (gp96) serves as a natural adjuvant for chaperoning antigenic peptide into the immune surveillance pathway. In our laboratory, MethA tumor cell suspension culture process has been recently developed for gp96 production in spinner flask. In this work, effects of dissolved oxygen tension (DOT) and agitation rate on this process were studied in stirred-tank bioreactor. The optimal conditions for gp96 production were different with those for MethA tumor cell growth. MethA tumor cell growth pattern was not much changed by various levels of DOT and agitation rate, while gp96 biosynthesis was more sensitive to DOT and agitation rate. Compared with 50% of DOT, the production and specific productivity of gp96 was increased by 27 and 66% at 10% of DOT, respectively. Compared with the agitation rate of 100 rpm, the production and volumetric productivity of gp96 was increased by 48 and 144% at the agitation rate of 200 rpm, respectively. Low DOT (i.e., 10% of air saturation) and high agitation rate (i.e., 200 rpm) were identified to be favorable for gp96 biosynthesis. The results of this work might be useful to scale-up the bioprocess into the pilot scale.     

Plant/pathogen interactions observed during host range testing of the rust fungus Uromyces pencanus,a classical biological control agent for Chilean needle grass (Nassella neesiana) in Australia and New Zealand

Nassella neesiana (Chilean needle grass) is a South American grass species that is a serious weed in Australia and New Zealand. The rust fungus Uromyces pencanus is a promising biocontrol agent that could be used to control the weed in both countries. Extensive host range testing has been conducted to explore the specificity of the rust. In this paper we discuss the different degrees of invasion by the rust of the tissues of target and non-target species; the plant defences elicited by such invasion at the cellular level; and their relevance to the biological control of Chilean needle grass.