[Arabidopsis] brands of agar

Hi Tobias, and Arabidopsis colleagues

Phytagel and Phytagar are definitely different. Phytagar is a genuine
agar (or, I believe, a blend of agars, presumably of algal origin),
while Phytagel is an agar subsitute (other names Gellan gum, Kelcogel,
Gelrite, Gel-Gro) that is produced as a fermentation product by a pure
culture of the bacterium Sphingomonas elodea.

Chemically, agar is a galactose polymer, while Phytagel consists of four
linked monosaccharides, including one molecule of rhamnose, one molecule
of glucuronic acid and two molecules of glucose. The physical properties
of the two gels definitely differ and some people use mixtures of the
two. A different behaviour of root hairs on the two substrates was
reported in this paper from Rich Meagher's lab:
[Only registered users see links. ].

I'm not sure if Invitrogen still supply Phytagel - I just looked and
couldn't find it. There is another product called Phytoblend supplied by
Caisson Laboratories Inc and which they say is similar.

all the best

Brian




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-----Original Message-----
From: Tobias Baskin [mailto:[Only registered users see links. ]]
Sent: 13 February 2008 14:29
To: Grant Cramer; Forde, Brian
Cc: Falbel, Tanya G.; [Only registered users see links. ]
Subject: Re: [Arabidopsis] brands of agar


Greetings,
In replies to this thread, Grant Cramer mentions
"PhytoAgar" and Brian Forde mentions "PhytagelTM" which I think is the
same phytagel we used awhile back too. But is PhytoAgar the same stuff
as Phytagel? or are they different? Do you know?

Thanks,
Tobias

At 4:40 PM -0800 2/12/08, Grant Cramer wrote:

I have found very negative effects on root growth using
BactoAgar both from batches in the United States and Australia. I have
NEVER had a problem with PhytoAgar on root growth in root length assays
up to a week. After that they are in the dish for too long and will
suffer. One can supplement with sucrose in a standard quarter strength
Hoaglands solution without problem. I agree you should not use MS medium
or you will suffer from osmotic stress and perhaps other things that are
out of balance for roots. The roots will grow without the sucrose but
slower. It depends on your experiment, but those shaded cotyledons in a
plastic petri dish can only do so much in the dark or dim light. I
always grow them in the dark, as light inhibits root growth.


Grant R. Cramer

Professor

Department of Biochemistry and Molecular Biology, MS 200

University of Nevada, Reno

Reno, NV 89557

(775) 784-4204

[Only registered users see links. ]

[Only registered users see links. ]




On Feb 11, 2008, at 6:33 AM, Tobias Baskin wrote:


Dear Tanya,

Some years ago, we investigated a
variety of different agars (some of which you mention). We found
reproducible differences in root elongation rate but perhaps on the
order of 10 to 20 %. Clearly the roots liked some agar better than
others. We also found a little bit later when using phytagel that root
elongation rate depended on the temperature the molten mix was held at
before pouring, or might have simply been quite irreproducible. But
again I am talking about differences on the order of 20%. Big enough to
readily measure but not monstrous. On no agar did we see the kind of
developmental change you are mentioning. On some conditions I have seen
(and read) that severely salt stressed or water deficit stressed roots
will swell so I'd guess what you are describing goes way beyond what can
be expected from different brands/formulations of agar.


Hope this helps,

Tobias


At 3:10 PM -0600 2/9/08, Falbel, Tanya G. wrote:


Colleagues:


Over the years, I've used several brands
of agar for growing Arabidopsis seedlings on MS medium,

from Gibco, Sigma, and others. I've
heard that some groups use Noble agar,

others, bacto-agar, others in the past
have washed their own agar, used phytagel or other

gelling agents. I have two questions:


1) What brands of agar are most commonly
in use now by groups? I've found something similar

to Gibco's Phytagar that is now
available through Caisson labs. Other groups seem to like Sigma's

A1296. But besides those, what do most
groups use? I'm especially interested in the opinion of

groups that measure root length or root
branching - growing roots vertically on plates

for more than just a couple of days. (as
opposed to just antibiotic selection)


2) Does anyone know what inhibitors are
washed away? Are micronutrient ions or other toxic

compounds bound to the crude agar? Has
anyone looked into this? This may have been a question

that came up among researchers 10 years
ago, but I couldn't find any record in the archives.


Here's why I'm asking. I made up a batch
of medium with a brand of 'purified agar for microbial use',

and got a very strong inhibition of root
meristems. Seed germination was good, but roots failed to elongate

any further after about 4 days of
growth. The root meristems became a swollen mess, reminiscent of what

happens in weak gnom alleles. I'm trying
to decide if this is something worth looking into.


I know that for regeneration of plants
in tissue culture, folks are very fussy about particular brands of agar.


Please let me know what brands you have
used with success or failure.

I'd be especially interested in other
similar experiences - where a brand

wreaked havoc on root meristems.


Thanks


Tanya Falbel

Department of Biology

105 Garfield Avenue

University of Wisconsin-Eau Claire

Eau Claire, WI 54702-4004, USA


Tel: 715-836-5087

Fax: 715-836-5089




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[sweet2009]

im confused