Related Experiment Video
Updated: May 14, 2026
12:03
Expression, Isolation, and Purification of Soluble and Insoluble Biotinylated Proteins for Nerve Tissue Regeneration
Published on: January 22, 2014
Profligate biotin synthesis in α-proteobacteria - a developing or degenerating regulatory system?
Youjun Feng1, Huimin Zhang, John E Cronan
1Department of Microbiology, University of Illinois, Urbana, IL 61801, USA.
Molecular Microbiology
|February 8, 2013
Summary
Bacteria regulate biotin synthesis differently than previously thought. In Agrobacterium tumefaciens, a protein called BioR controls biotin production, unlike the BirA protein in E. coli, leading to excessive biotin synthesis.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Biotin (vitamin H) is an essential enzyme cofactor across all life domains.
- Bacterial biotin demand sensing mechanisms are not fully understood.
- The BirA protein in E. coli ligates biotin and represses its own synthesis.
Purpose of the Study:
- Investigate the mechanism of biotin synthesis regulation in Agrobacterium tumefaciens.
- Test the predicted role of the BioR protein in regulating the biotin operon.
- Characterize the differences in biotin synthesis regulation compared to E. coli and Bacillus subtilis.
Main Methods:
- Bioinformatic analysis to identify potential regulatory proteins.
- Genetic manipulation of Agrobacterium tumefaciens (deletion and overproduction of BioR).
- Electrophoretic mobility shift assays (EMSA) to study protein-DNA binding.
- Quantitative PCR (qPCR) to measure gene expression levels.
- Reporter gene assays (bioB-lacZ) to assess transcriptional repression.
Main Results:
- Agrobacterium tumefaciens biotin protein ligase lacks DNA-binding and regulatory functions.
- The BioR protein was confirmed to repress transcription of biotin synthesis genes.
- BioR binds to a specific operator site upstream of the biotin operon.
- Deletion of BioR led to a 15-fold increase in biotin operon transcription.
- Agrobacterium tumefaciens synthesizes significantly more biotin than required, with most excreted.
Conclusions:
- BioR is the primary regulator of biotin synthesis in Agrobacterium tumefaciens.
- This represents a novel mechanism of biotin regulation distinct from the E. coli paradigm.
- Agrobacterium tumefaciens exhibits unusually high and excreted biotin synthesis, a phenomenon not previously observed in wild-type bacteria.
Related Concept Videos
01:24Biosynthesis in Bacteria
Biosynthesis in bacteria is a fundamental anabolic process that generates essential macromolecules, including proteins, nucleic acids, lipids, and polysaccharides. These macromolecules are critical for cellular growth, replication, and function. The process is tightly regulated and energetically linked to catabolic pathways to ensure optimal resource utilization.Biosynthetic pathways begin with precursor metabolites such as pyruvate, acetyl-CoA, and glucose-6-phosphate derived from glycolysis,...
01:58Prokaryotic Transcriptional Activators and Repressors
The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
Transcription of prokaryotic...
Transcription of prokaryotic...
01:29Coordination of Gene Expression Processes in Bacteria
The DNA replication, transcription, and translation processes are intricately coupled in bacteria, allowing efficient gene expression and rapid protein synthesis. While this physical and functional coordination is advantageous, it introduces challenges that bacteria overcome through specific regulatory mechanisms.Coupling of Replication, Transcription, and TranslationThe coupling of replication, transcription, and translation is a hallmark of bacterial gene expression. As the replisome unwinds...
01:23Stringent Response in E. coli
Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...
02:42Transcription Attenuation in Prokaryotes
Transcriptional attenuation occurs when RNA transcription is prematurely terminated due to the formation of a terminator mRNA hairpin structure. Bacteria use these hairpins to regulate the transcription process and control the synthesis of several amino acids including histidine, lysine, threonine, and phenylalanine. Transcription attenuation takes place in the non-coding regions of mRNA.
There are several different mechanisms used to attenuate transcription. In ribosome mediated...
There are several different mechanisms used to attenuate transcription. In ribosome mediated...
01:30Production of Pharmaceuticals
Industrial insulin production uses genetically engineered E. coli expressing a proinsulin gene controlled by a tryptophan promoter and containing a methionine linker for later cleavage. The cells also carry ampicillin resistance for selective growth. Seed cultures are stored at −80 °C and production begins by thawing a small amount to inoculate starter cultures, which are progressively scaled to a 50,000-L bioreactor. In the bioreactor, E. coli grow in nutrient-rich media under sterile, tightly...