Chemistry: molecular biology and microbiology – Micro-organism – per se ; compositions thereof; proces of... – Bacteria or actinomycetales; media therefor
Reexamination Certificate
2001-06-26
2003-09-09
Ketter, James (Department: 1636)
Chemistry: molecular biology and microbiology
Micro-organism, per se ; compositions thereof; proces of...
Bacteria or actinomycetales; media therefor
C435S069100, C435S243000, C435S252300, C435S320100, C435S252500, C435S832000, C435S833000, C536S023200
Reexamination Certificate
active
06617148
ABSTRACT:
FIELD OF THE INVENTION
This application claims the benefit of U.S. Provisional Application No. 60/214,967, filed Jun. 29, 2000 and of U.S. Provisional Application No. 60/268,320, filed Feb. 13, 2001.
This invention is in the field of bacterial gene expression and fermentation monitoring. More specifically, the invention relates to the use of promoter regions isolated from a Bacillus sp. for regulated gene expression and process control monitoring of fermentation cultures.
BACKGROUND INFORMATION
The Bacillus bacteria are useful production hosts for a variety of biological materials including enzymes, antibiotics and other pharmaceutically active products. The use of Bacillus species for production of biomaterials is particularly advantageous as compared with other microbial production hosts, particularly gram negative organisms. For example, the most common gram negative organism used in industrial microbiology,
E. coli
, suffers from the presence of endotoxins which, being pathogenic in man, are undesirable products. Additionally, gram negative hosts often produce proteins in inactive or insoluble forms which necessitate expensive reactivation and purification schemes. In contrast, Bacillus has a highly develop secretory system for the expression and transport of active proteins to the growth medium, thereby facilitating purification and eliminating costly reactivation procedures. Thus Bacillus is a production host of choice for many industrial applications. Methods to enhance gene expression or monitor culture health and biomass production for these organisms are desirable.
The Bacillus sp. and particularly
Bacillus subtilis
is well-known for its stationary metabolism (Stragier, P. and Losick, R. 1996.
Annu. Rev. Genet.
30:297-341, Lazazzera, B. A. 2000.
Curr. Opin. Microbiol.
3:177-182, Msadek, T. 1999.
Trends Microbiol.
7:201-207). A wide variety of genes, such as those involved in catabolism, amino acid biosynthesis, antibiotic production, cell to cell communication, competence, and sporulation, are induced at stationary phase.
Bacillus subtilis
is also a facultative bacterium capable of growing in the presence or absence of oxygen. In the absence of oxygen,
Bacillus subtilis
uses nitrate or nitrite as the alternative electron acceptor or grows in the presence of pyruvate (Nakano et al., 1998.
Annu. Rev. Microbiol.
52:165-190). It has been shown that promoters that control the expression of genes involved in nitrate and nitrite respiration are under the control of the two-component signal transduction system ResDE (Sun et al., 1996.
J. Bacteriol.
178:1374-1385).
In general, prokaryotic promoters can play an important role in biotechnology particularly in expressing those genes whose products can be made in their active forms and in large quantities in prokaryotic hosts. Identification of the promoters regulated during stationary phase growth when the cells reach a certain density is valuable when
Bacillus subtilis
is used as a production host. Similarly, promoters induced by oxygen-limiting conditions are very applicable in industrial settings since oxygen level can adjusted easily.
Investigation of promoter activity in
Bacillus subtilis
or any other bacterium often employs Northern or Southern blots, enzymatic assays, or reporting genes. These methods permit monitoring of the effect of environmental changes on gene expression by comparing expression levels of a limited number of genes. Furthermore, they often enable investigation of one or a subset of the physiological events and fail to monitor the comprehensive responses of a preponderance of individual genes in the genome of an organism in reliable and useful manner.
With the advances in genomic research, a powerful way to identify promoters is the use of DNA microarray. DNA microarray is a technology used to explore gene expression profiles in a genome-wide scale (DeRisi, J. L., V. R. Iyer, and P. O. Brown. 1997.
Science.
278:680-686). It allows for the identification of genes that are expressed in different growth stages or environmental conditions. This is especially valuable for industrial environments where the conditions for promoter induction have to be convenient, cost effective and compatible with a specific bio-manufacturing process. A significant advance in the art would be a process which would allow for analysis of the timing and extent of induction of most of the genes involved in production and provide inclusive information on the state of the biomass and cell response to growth conditions.
The problem to be solved therefore is to identify genes within the Bacillus genome that are regulated by metabolic conditions or growth cycle changes, and to apply these genes for gene expression and bioreactor monitoring in Bacillus sp. cultures. Applicants have solved the stated problem by using microarray technology to identify genes which are responsive to oxygen depletion, the presence of nitrite, or are sensitive to various stages of the stationary growth phase.
SUMMARY OF THE INVENTION
The present invention provides a method for the expression of a coding region of interest in a Bacillus sp comprising: a) providing a transformed Bacillus sp cell containing a chimeric gene comprising a nucleic acid fragment consisting of the promoter region of a Bacillus gene operably linked to a coding region of interest expressible in a Bacillus sp, wherein the nucleic acid fragment comprising the promoter region of a Bacillus gene is selected from the group consisting of narGHJI, csn, yncM, yvyD, yvaWXY, ydjL, sunA, and yolIJK and homologues thereof; and b) growing the transformed Bacillus sp cell of step (a) in the absence of oxygen wherein the chimeric gene of step (a) is expressed.
Optionally cells may be grown in the presence of oxygen to increase the cell biomass and the oxygen level then decreased to allow for induction and expression for the chimeric gene. Subsequently oxygen levels may be restored to permit bioconversion utilizing the product of the expressed coding region.
Similarly the invention provides a method for the expression of a coding region of interest in a Bacillus sp comprising: a) providing a transformed Bacillus sp cell containing a chimeric gene comprising a nucleic acid fragment consisting of the promoter region of a Bacillus gene operably linked to a coding region of interest expressible in a Bacillus sp, wherein the nucleic acid fragment comprising the promoter region of a Bacillus gene is selected from the group consisting of feuABC, ykuNOP, and dhbABC, and homologues thereof; and b) growing the transformed Bacillus sp cell of step (a) in the absence of oxygen and in the presence of nitrite wherein the chimeric gene of step (a) is expressed.
In another embodiment the invention provides a method for the expression of a coding region of interest in a Bacillus sp comprising: a) providing a transformed Bacillus sp cell containing a chimeric gene comprising a nucleic acid fragment consisting of the promoter region of a Bacillus gene operably linked to a coding region of interest expressible in a Bacillus sp, wherein the nucleic acid fragment comprising the promoter region of a Bacillus gene is selected from the group consisting of ycgMN, dhaS rapF, rapG, rapH, rapK, yqhIJ, yveKLMNOPQST, yhfRSTUV, csn, yncM, yvyD, yvaWXY, ydjL, sunA, and yolIJK, and homologues thereof; and b) growing the transformed Bacillus sp cell of step (a) in the presence of oxygen until the cell reaches about T0 of the stationary phase_wherein the chimeric gene of step (a) is expressed.
In an alternate embodiment the invention provides a method for the expression of a coding region of interest in a Bacillus sp comprising: a) providing a transformed Bacillus sp cell containing a chimeric gene comprising a nucleic acid fragment consisting of the promoter region of a Bacillus gene operably linked to a coding region of interest expressible in a Bacillus sp, wherein the nucleic acid fragment comprising the promoter region of a Bacillus gene is selected from the group consisting of acoABCL, and glvAC, and homologu
Bedzyk Laura A.
Wang Tao
Ye Rick
E. I. du Pont de Nemours and Company
Ketter James
Marvich Maria
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