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From: werner@aecom.UUCP
Newsgroups: sci.bio
Subject: Re: Life Classification ...further comments
Message-ID: <1105@aecom.YU.EDU>
Date: Mon, 1-Jun-87 20:22:56 EDT
Article-I.D.: aecom.1105
Posted: Mon Jun  1 20:22:56 1987
Date-Received: Thu, 4-Jun-87 01:38:13 EDT
References: <9543@duke.cs.duke.edu> <1125@ius2.cs.cmu.edu> <701@edge.UUCP> <1211@sigi.Colorado.EDU>
Organization: Albert Einstein Coll. of Med., NY
Lines: 39

> Dan, is it true that only the Bacillus species can pick up
> and incorporate DNA from the environment? I was under the possibly
> naive impression that pretty much all the bacteria could do this
> trick, called transformation. The principle of bacterial
> transformation is the heart of genetic engineering in E. coli
> (admittedly, coli transformation is artificially enhanced
> in the laboratory),

	Naturally occurring transformation is limited to a small subset
of bacteria.  Streptococcus Pneumonia (formerly Pneumococcus, or also
Diplococcus Pneumoniae) is one of them.  
	It also occurs in Haemophilus influenza, but a certain sequence
is required, so it preferentially picks up its own DNA (or that of
a related strain).
	Bacillus subtilis also undergoes natural transformation.

	No more than a handful of other organisms do.

	Escherichia coli, the darling of molecular biologists does
not undergo natural transformation.  It was known for many years that
DNA could be introduced by spheroplasting cells, but regeneration
of bacteria was inefficient.
	It was only in 1973 that a method (the CaCl2 at 0C technique)
was demonstrated that allows high efficiency DNA transfer into E. coli.
This is far from natural, and less than half of the cells remain
viable after treatment. Still with 10^10 cells/ml of transforming
mixture, factors of 2 aren't really significant.  Douglas Hanahan,
more recently, has described methods using Ca, Mn, Cobalt Hexamine
Chloride, DMSO, and DTT, and other reagants that I can't recall right
off, that boost transformation frequencies several orders of magnitude -
to almost a percent or higher.



-- 
			      Craig Werner (MD/PhD '91)
				!philabs!aecom!werner
              (1935-14E Eastchester Rd., Bronx NY 10461, 212-931-2517)
Everything's different. Nothing's changed. Well, only maybe slightly rearranged.