Micro Journal Club: Mitogenic radiation

Meta Kuehn kuehn at MENDEL.BERKELEY.EDU
Mon Sep 26 20:07:32 EST 1994


Dear Fellow Netters:

First, let me re-iterate that journal club suggestions are always
welcome!!! Please mail them to me as soon as you think of something good.
Ideas for topics of discussion are welcome too--as you will find from the
choice of the article below:


Lets begin another topic of discussion of a journal article on Sat. Oct. 1st.

An interesting topic and related papers have been brought to our attention
(with thanks to contributor Ronan O'Kennedy) regarding the ressurection of
the topic of mitogenic radiation (emission of UV light upon division)
by Quickenden,Tilbury et al at U.Western Australia .   Ronan pointed out
that they "confirmed that certain yeasts emit weak UV radiation but did not
demostrate any growth stimulation."  Then asks: "IF MR doesn't serve a
purpose as far as growth goes then why do the bugs waste energy emitting
UV? Is it an inherent part of replication?  If so,can MR be demonstrated in
vitro and do other high energy-consuming biosynthetic pathways emit low
level UV (eg Tryptophan biosynthesis)."

Since I found that the references were hard to obtain, I have included two
here, and their abstracts.  So even those without access to these
specialized journals can put in their two-cents worth.


Reference 1:
Tilbury RN; Quickenden TI.
      Luminescence from the yeast Candida utilis and comparisons across three
      genera.
    Journal of Bioluminescence and Chemiluminescence, 1992 Oct, 7(4):245-53.


 Abstract: Weak luminescence was detected from oxygenated liquid cultures of the
yeast Candida utilis during two stages of its growth cycle. The first
period of emission occurred during the exponential phase of growth and
comprised an ultraviolet band (270-390 nm; ca 19 photons s-1 cm-2 of
culture surface) and
a visible band (450-620 nm; ca 68 photons s-1 cm-2). The second period of
emission occurred late in the stationary phase of growth and was comprised
almost entirely of a visible region band (450-620 nm; 6.8 x 10(2) photons
s-1 cm-2). No luminescence was observed when the yeast was grown
anaerobically. These observations are compared with those previously
obtained for two other yeasts, Saccharomyces cerevisiae and
Schizosaccharomyces pombe. The ratios of the intensities of the blue/red
emissions in the stationary phase luminescences correlated with the ratio of
the saturated/unsaturated lipid content for the three yeasts. This result
provided further support for the claim that the stationary phase
luminescence arises from the reactions associated with lipid peroxidation. A
number of previously suggested sources of the exponential phase luminescence
are discussed and rejected. Oxidative side reactions accompanying protein
synthesis remain a possible source of that emission.

 Reference 2:  Quickenden TI; Tilbury RN.
      Luminescence spectra of exponential and stationary phase cultures of
      respiratory deficient Saccharomyces cerevisiae.
    Journal of Photochemistry and Photobiology. B, Biology, 1991 Jan,
    8(2):169-74.
      (UI:  91268971)

 Abstract: The spectral distributions of the luminescences emitted by the
     respiratory-deficient mutant of Saccharomyces cerevisiae and the normal
    yeast have been determined during the exponential phase of growth and during
     the stationary phase. The respiratory-deficient mutant gave a more intense
     emission in the visible region than did the normal yeast, but the UV
     intensities from the two yeasts did not differ greatly. These differences
     were explained in terms of higher O2- concentrations in the
     respiratory-deficient mutant which lead to enhanced visible region
     chemiluminescence from lipid peroxidation reactions.

Some other questions to consider:  Has anyone else seen or heard of this
phenomenon?  What would cause two different phases of luminescence in
dividing yeast? Could it be a useful tool for identifying membrane
fusion/division events?

 JC disclaimer:  If the author(s) of the paper are listening, please forgive
and correct any errors made during the presentation or discussion of the
contents of the article.


Meta Kuehn






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