Agrobacterium

[dttom]

It is known that agrobacterium is capable of inserting part of its DNA in its own genome to plant cell in form of Ti (tumor-inducing) plasmid. Ti plasmid includes genes for enzymes for production of special enzymes which use plant cell as factory of food for the bacteria, and gene for production of plant hormone such as PGH.

My question is that, as Ti plasmid only includes part of the bacterium's genome, how is such plasmid be produced? and by what sort of mechanism? Also, I would like to know how could a so-called bridge formed between the bacterium and the plant cell for the transfer of, in this case, the Ti plasmid?

[CharonY]

Many bacteria possess extrachromosomal DNA in the form of plasmids. The Ti plasmids is one of such and is not produced per se but as is replicated like the main chromosome.

The DNA is tranferred into the plant cell with the means of a type IV replication system. Bacteria produce pili which in this case are used to "inject" the DNA into the plant.

[ecoli]

The DNA is tranferred into the plant cell with the means of a type IV replication system. Bacteria produce pili which in this case are used to "inject" the DNA into the plant.

 

hmm... is this the same as type IV pili?

[CharonY]

I posted too late yesterday. First a quick correction: I meant type IV secretion system, of course, not replication system (wouldn't make sense).

 

In general type IV pili are known to be involved in twitching motility rather than secretion. However part of the assembly system of type IV pili is closely related to type II secretion systems. So one could say that the apparatus for type IV pilus secretion is essentially a type II secretion system, but the type IV pilus is the substrate, not the means of the secretion.

(Or in short, type IV pili are not involved in type IV secretion mechanisms).

 

Also one have to add that some classifications of secretion systems are not that streamlined, mainly due to the different cell envelopes of Gram-negative and Gram-positive bacteria.

[ecoli]

I posted too late yesterday. First a quick correction: I meant type IV secretion system, of course, not replication system (wouldn't make sense).

 

In general type IV pili are known to be involved in twitching motility rather than secretion. However part of the assembly system of type IV pili is closely related to type II secretion systems. So one could say that the apparatus for type IV pilus secretion is essentially a type II secretion system, but the type IV pilus is the substrate, not the means of the secretion.

(Or in short, type IV pili are not involved in type IV secretion mechanisms).

 

Ah, ok. That makes more sense.

 

My research actually involves both T2SS and T4P systems, so that's why I asked in the first place. Thanks for clarifying.

[CharonY]

Incidentally, one of my phDs is also working on T4P with a heavy focus on regulation, though.

Enjoy it, tis quite an interesting topic.

Any particular focus in your work (attachment, biofilm or motility?)?