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Plasmid addiction systems: from bacterial toxins to molecular biology tools

Posted by Jennifer Tsang on Nov 1, 2018 8:35:58 AM

Members of the bacterial world produce an assortment toxins to claim territory or kill competing microorganisms, but did you know bacteria also produce substances toxic to themselves?

These toxic substances are part of toxin-antitoxin systems that are widely present in bacteria. They consist of a toxin which can affect a variety of cellular processes and an antitoxin that suppresses the toxin’s activity. The key to these systems is that the toxin is stable while the antitoxin is unstable, meaning that the cells must continually produce antitoxin to avoid cell death.

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Topics: Plasmid Cloning, Plasmid Technology, Plasmid Elements

Stabilized Bacterial Promoters: Constant Gene Expression at any Copy Number

Posted by Jennifer Tsang on Sep 4, 2018 8:53:28 AM

Researchers express genes of interest from plasmids in order to study gene function or to engineer cells for specific purposes. Unfortunately, plasmid copy numbers vary within cell populations and over time resulting in variable gene expression that can impact observed phenotypes. Factors such as the growth medium, growth temperature, and growth rate can all impact plasmid copy number in a cell.

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Topics: Plasmid Technology, Synthetic Biology, Plasmid Elements

Plasmids 101: Terminators and PolyA signals

Posted by Julian Taylor-Parker on Mar 31, 2016 10:30:00 AM

Plasmids designed to express genes in a given host cell type are generally broken down into two broad categories, prokaryotic or eukaryotic, based on the functional elements they contain. Plasmid DNA in both prokaryotic and eukaryotic systems must be transcribed into RNA, which occurs in three phases: initiation, elongation, and termination. In a previous post we discussed the promoter's role in the initiation step of gene transcription; today we'll provide an overview on how transcription stops, or termination. Read on to learn more!

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Topics: Plasmid Elements, Plasmids 101

Anatomy of a Plasmid Page at Addgene

Posted by Jessica Welch on Feb 4, 2016 10:30:00 AM

Have you ever found yourself bamboozled by all of the different kinds of information on our plasmid pages? Well, to help make the most of these pages, we've written this post to guide you through them and make the best use of all the information provided by your colleagues.

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Topics: Plasmid Elements, Inside Addgene

Plasmids 101: Stringent Regulation of Replication

Posted by Jason Niehaus on Dec 3, 2015 10:30:00 AM

Plasmids utilize their host cell's replication machinery in order to replicate. As described in our previous Origin of Replication post, DNA replication is initiated at the ORI and may be synchronized with the replication of the host cell's chromosomal DNA or may be independent of the host's cell cycle. 

Plasmids are said to be under stringent control of replication when they are dependent on the presence of initiation proteins synthesized by the host cell in order to start their own replication. In general, these types of plasmids tend to be low copy number. Conversely, plasmids that can initiate DNA replication independently of the host's initiation proteins are said to be under relaxed control, as they only require the host's replication machinery for elongation and termination. These types of plasmids tend to be high copy number.

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Topics: Plasmid Elements, Plasmids 101

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