[Anchorage of cyclodextrin glycosyltransferase on outer membrane of Saccharomyces cerevisiae to produce 2-O-α-D-glucopyranosyl-L-ascorbic acid].

OBJECTIVE: Displaying cyclodextrin glycosyltransferase ( CGTase) from Bacillus circulans 251 on the cell surface of Saccharomyces cerevisiae to improve 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) production. METHODS: CGTase encoding gene cgt was inserted into the 3' terminal of Aga2p of vector pYD1 and the obtained recombinant plasmid pYD1-cgt was then transformed into S. cerevisiae EBY100 to produce surface displayed CGTase and culture conditions (culture medium, inductive temperature and concentration of inducer galactose) were optimized. Moreover, resulted CGTase displayed on the yeast cell surface was used for the AA-2G biosynthesis under the optimized condition. RESULTS: CGTase activity on the cell surface of recombinant yeast, S. cerevisiae EBY100-pYD1-cgt, reached 0.5 U/ml in 48 h fermentation using Yeast Peptone Galactose culture medium with 20% galactose as sole carbon source and inducer at 25 degrees C. The displayed CGTase exhibited better thermostability and pH stability than that of free CGTase. The concentration of AA-2G produced by the surface displayed CGTase was 37% higher than that produced by free CGTase at its optimal transformation conditions of 30 degrees C and pH4. 5. CONCLUSION: The cell surface display system based on α-agglutinin is an effective system for displaying CGTase. During AA-2G production by surface displayed CGTase, the by-product glucose might be consumed by yeast cell and thus facilitated AA-2G production. The whole cell EBY100-pYD1-cgt will have better prospects for applications.

Toxins from bacteria.

Bacterial toxins damage the host at the site of bacterial infection or distant from the site. Bacterial toxins can be single proteins or oligomeric protein complexes that are organized with distinct AB structure-function properties. The A domain encodes a catalytic activity. ADP ribosylation of host proteins is the earliest post-translational modification determined to be performed by bacterial toxins; other modifications include glucosylation and proteolysis. Bacterial toxins also catalyze the non-covalent modification of host protein function or can modify host cell properties through direct protein-protein interactions. The B domain includes two functional domains: a receptor-binding domain, which defines the tropism of a toxin for a cell and a translocation domain that delivers the A domain across a lipid bilayer, either on the plasma membrane or the endosome. Bacterial toxins are often characterized based upon the secretion mechanism that delivers the toxin out of the bacterium, termed types I-VII. This review summarizes the major families of bacterial toxins and also describes the specific structure-function properties of the botulinum neurotoxins.

Identification and characterization of proteins from Bacillus thuringiensis with high toxic activity against the sheep blowfly, Lucilia cuprina.

Current control of the sheep blowfly (Lucilia cuprina) relies on chemical insecticides, however, with the development of resistance and increasing concerns about human health and environmental residues, alternative strategies to control this economically important pest are required. In this study, we have identified several isolates of Bacillus thuringiensis (Bt), collected from various Australian soil samples, that produce crystals containing 130 and 28 kDa proteins. These isolates were highly toxic to feeding larvae in both in vitro bioassays and in vivo on sheep. By N-terminal amino acid sequencing, we identified the smaller crystal band (28 kDa) as a cytological (Cyt) protein. Upon solubilization and proteolytic processing by trypsin, the 130 kDa crystal protein yielded among others, a truncated 55-60 kDa toxin moiety which exhibited larvicidal activity against sheep blowfly. The amino-terminal sequence of the trypsin-resistant protein band revealed that this Bt endotoxin was encoded by a new cry gene. The novel cry protein was present in all the strains that were highly toxic in the larval assay. We have also identified from one of the isolates, a novel secretory toxin with larvicidal activity.

Active and passive immunization with the Pseudomonas V antigen protects against type III intoxication and lung injury.

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that can cause fatal acute lung infections in critically ill individuals. Damage to the lung epithelium is associated with the expression of toxins that are directly injected into eukaryotic cells through a type Ill-mediated secretion and translocation mechanism. Here we show that the P. aeruginosa homolog of the Yersinia V antigen, PcrV, is involved in the translocation of type III toxins. Vaccination against PcrV ensured the survival of challenged mice and decreased lung inflammation and injury. Antibodies to PcrV inhibited the translocation of type III toxins.

[Pharmacology and toxicology of Spirulina alga]. / Farmacología y toxicología del alga spirulina.

Spirulina, a unicellular filamentous blue-green alga has been consumed by man since ancient times in Mexico and central Africa. It is currently grown in many countries by synthetic methods. Initially the interest in Spirulina was on its nutritive value: it was found almost equal to other plant proteins. More recently, some preclinical testing suggests it has several therapeutic properties such as hypocholesterolemic, immunological, antiviral and antimutagenic. This has led to more detailed evaluations such as nucleic acid content and presence of toxic metals, biogenic toxins and organic chemicals: they have shown absence or presence at tolerable levels according to the recommendations of international regulatory agencies. In animal experiments for acute, subchronic and chronic toxicity, reproduction, mutagenicity, and teratogenicity the algae did not cause body or organ toxicity. In all instances, the Spirulina administered to the animals were at much higher amounts than those expected for human consumption. On the other hand there is scant information of the effects of the algae in humans. This area needs more research.