What is the function of plasmid DNA?

Plasmids have multiple functions within bacterial cells and beyond, being powerful tools for modifying genetic material and advancing biotechnological applications. Their discovery in the last century was a tremendous achievement in microbiology and molecular biology, not only leading to a better understanding of bacteria. Today, pDNA is a cornerstone of several therapeutic and biotechnological processes.

This article reviews the multifaceted functions of plasmid DNA and highlights its importance as an extrachromosomal DNA element. In addition, we will highlight pDNA production as an essential component in biopharmaceutical manufacturing processes.

Understanding plasmid DNA

The bacterial genome includes the entire genetic material contained within a bacterium, consisting of both chromosomal DNA and, in some cases, bacterial plasmids as circular DNA molecules. The chromosomal DNA, typically organized in a single, circular molecule, encodes the fundamental genetic information necessary for the bacterium's growth, reproduction, and survival. This chromosomal structure within the bacterial genome is distinctive and varies between different bacterial species.

On the other hand, plasmid DNA, recognized by its distinctive circular structure, sets it apart from the linear chromosomal double-stranded DNA within bacterial cells. Situated in the cytoplasm, plasmids exhibit a remarkable ability to exist independently. These genetic components often carry advantageous genes, providing bacteria with the flexibility to adapt to varying environments.

Plasmid DNA's significance extends to genetic engineering, leveraging its circular configuration for autonomous replication. This property makes plasmids invaluable for introducing foreign genetic material into organisms, serving diverse purposes from gene cloning to biotechnology.

Read more: What is a plasmid?

Diverse plasmid types and functions

In bacterial cells, there can be found several types of plasmids. In fields like gene therapy, knowledge of these small, extrachromosomal DNA molecules is crucial.

In general, one can distinguish between five different plasmid types:

• F-Plasmids (fertility plasmids)
• Resistance plasmids
• Virulence plasmids
• Degradative plasmids
• Colicinogenic plasmids (Col plasmids)
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Facilitating gene transfer

F-plasmids, or fertility plasmids, drive gene transfer in bacteria through conjugation. This process involves forming a conjugation pilus to link donor and recipient cells. Genes, including antibiotic resistance genes, are exchanged, fostering bacterial adaptability. Host organisms like Escherichia coli or Salmonella partake, integrating F-plasmid genes via cell division. This mechanism accelerates genetic diversity, enhancing bacterial survival in changing environments.

Influencing the virulence of bacteria

Virulence plasmids often contain thousands of base-pairs and exert a profound impact on the pathogenicity of bacteria. These plasmids carry genes that enhance the virulence, or disease-causing potential, of the bacteria they inhabit. By acting as expression vectors, they enable the bacterium to produce and deliver factors such as toxins and adhesive molecules. These components foster the bacterium's ability to colonize, invade, and evade the host's immune defenses.

At the core of virulence plasmids are promoters and regulatory elements that precisely control the expression of pathogenicity-related genes. These elements ensure that the genes are turned on or off at the right time, optimizing the bacteria's virulence strategies.

Enabling bacterial digestion

Degradative plasmids drive biodegradation by hosting DNA sequences that code for enzymes breaking down complex compounds. These enzymes enable bacteria to transform substances like hydrocarbons and pollutants into usable resources. This adaptability finds application in bioremediation, where bacteria with degradative plasmids aid in environmental cleanup.

Defending against competitors

Col plasmids, armed with potent weaponry known as bacteriocins or colicins, empower bacteria in their struggle for survival within competitive microbial communities. These plasmids carry genes that enable the production of bacteriocins, which are protein toxins capable of targeting and killing closely related bacterial species.

In environments with high microbial competition, col plasmids offer a clear advantage. Bacteria equipped with these plasmids possess the ability to eliminate neighboring competitors, thus securing resources and space for their own growth. This process plays a significant part in shaping microbial communities and preserving ecological equilibrium.

Inspired by bacteria – pDNA in mRNA production

Illuminating the manifold functions of plasmid DNA in bacteria, scientists started to investigate how to make this potential accessible to biotechnology. As a result, pDNA has become a fundamental tool in mRNA production, providing instructions according to which the genetic information of interest can be synthesized to be used all over biotechnology.

Plasmids' crucial role in biopharmaceuticals

In the biopharmaceutical sector, the use of plasmids has become indispensable, revolutionizing the production of vital medicines. These versatile plasmid vectors serve as carriers for therapeutic genes, enabling their expression in host cells. Through gene cloning and recombinant DNA technology, plasmids provide a means to engineer organisms for the production of proteins with therapeutic applications.

The process begins with selecting a plasmid vector suitable for the host cell, often involving both prokaryotes and eukaryotes. This vector includes essential components like an origin of replication to ensure plasmid replication, a promoter for initiating gene transcription, and a multiple cloning site for inserting target genes. The plasmid's copy number influences the production of therapeutic proteins.

In eukaryotic host cells, plasmids offer an advantage by circumventing potential disruption to the chromosomal DNA. Plasmids are self-replicating, ensuring minimal impact on the host's genome. Once inside the host, plasmids undergo transcription to produce messenger RNA, ultimately leading to protein synthesis.

Notably, plasmids can be engineered to produce large quantities of therapeutic proteins. This potential makes them invaluable in biopharmaceuticals, allowing the creation of treatments for various diseases, from diabetes to cancer.

The versatility of plasmids extends to PCR, a powerful technique for gene amplification, and the generation of recombinant plasmids. These tailored plasmids carry genetic information from different sources, enabling the production of hybrid proteins.

As part of biopharmaceuticals, plasmids play a crucial role in translating genetic engineering into life-saving therapies, acting as the architects of modern medicine. Their diverse functions, ranging from gene expression to protein production, highlight their essentiality in advancing healthcare.

pDNA manufacturing – key to medical breakthroughs

The production of plasmid DNA is an essential process for developing several therapies and biologics - despite the laborious nature. The biopharmaceutical sector aims to improve the safety, efficiency, cost-effectiveness, and sustainability of pDNA manufacturing.

Single Use Support assists pDNA manufacturing companies by providing specialized solutions for fluid management, aliquotation and homogenization of plasmid DNA. They also offer solutions for contamination-free freezing, storing and shipping. By facilitating optimization in the manufacturing process of plasmid DNA, Single Use Support plays an active role in making pDNA technology more accessible and driving progress in this exciting field.