Enhanced expression of a second mosquito larvicidal gene fromB.sphaericus 1593M inE.coli

Response dynamics of 26-, 34-, 39-, 54-, and 80-kDa proteases in induced cultures of recombinant Escherichia coli

Several researchers have demonstrated that the presence of a heterologous protein in recombinant Escherichia coli elicits a response similar to the heat-shock response, which includes enhanced protease expression. The present work detects, quantifies, and characterizes intracellular protease activity in E. coli that are "shocked" by the induction of a recombinant protein, CAT, which is an endogenous protein in some E. coli strains. A novel, sodium dodecyl sulfate gelatin poly-acrylamide gel electrophoresis (SDS-GPAGE) method is used to detect, quantify, and characterize the presence of these proteases. A hypothesis is proposed which links the amplified protease activity to a temporary depletion of specific amino acid pools, and a stringent-like stress response.

Enhancement of recombinant protein synthesis and stability via coordinated amino acid addition

In this work, effective feeding schemes that would minimize stress responses to cloned-protein overexpression are investigated. The cloned-protein (chloramphenicolacetyl-transferase, CAT) contains a high aromatic amino acid content, most notably a high phenylalanine content. Experiments performed on Escherichia coli RR1 [pBR329] (constitutive promoter) and E. coli JM105 [pSH101] (inducible promoter) demonstrated that phenylalanine addition increases the rate of synthesis and yield of CAT. A previous study correlating inducer strength with CAT expression in E. coli JM105 [pSH101] indicated that the highest expression rate was accompanied by the highest apparent rate of protein degradation. In this work, the combined addition of isopropyl-beta-D-thiogalactopyranoside (IPTG) and phenylalanine at intermediate levels resulted in substantial increase of CAT synthesis and partial reduction of protein degradation. Furthermore, transmission electron micrographs verified the absence of inclusion bodies, which, along with proteases, were suspected to reduce protein activity. The research demonstrates that significant enhancement in production and stability of heterologous proteins is possible by designing feeding strategies that incorporate knowledge of the interaction between primary cellular metabolism and foreign protein expression.

Polymerase chain reaction and non-radioactive gene probe based identification of mosquito larvicidal strains of Bacillus sphaericus and monitoring of B. sphaericus 1593M, released in the environment

In attempts towards an accurate monitoring in the environment, the status of the deliberate release of Bacillus sphaericus, a powerful mosquito larvicidal agent, as well as to evolve a rapid method of screening for potent isolates of B. sphaericus, we have developed a polymerase chain reaction (PCR) method of analysis. Using specific primers spanning the 5' and 3' ends of the coding sequences of these two mosquito larvicidal genes, a 1.3 and a 1.1 kb product from gene A and a 2.6 kb product from gene B have been amplified by PCR. The primers and the products amplified from them in PCR are highly specific for B. sphaericus. We used digoxigenin based non-radioactive chemiluminescence method for the detection of PCR products and the sensitivity of the method was high enough to detect the presence of 1 to 5 cells of B. sphaericus. A simple and inexpensive sample processing procedure has also been developed for direct PCR amplification of B. sphaericus DNA from field samples collected from areas where it had been applied. Several highly toxic to non-toxic strains of B. sphaericus were screened with these primers by PCR for the presence of either or both of these toxin genes. The results indicate that there is a good correlation between the presence of both genes with higher toxicity of the strains.