“Dapt. of Physics
U. 8. Naval Postgraduate School
Monterey, Calif.

16 Mareh '54

Dr. Joshua Lederberg
Asso. Prof. of Genetics
University of Wisconsin
Madison, Tisconsin

Dear Dr. Lederberg?

As far as TI know, there is nothing in the Literature of
the subject of chemotaxis aside from mere descriptions of
observed chemotactic phenomena. MNolisch (1) describes a
number of these, which seem to support the general idea that
an abrupt decrease in “metabolic rate" is associated with a
tactic response. Working along this hypothesis, in an attempt
to identify this association more specifically, Z am currently
making a fairly exhaustive study of the influences of light and
oxygen on phototactic and aerotactic responses, and on the
rates of photosynthesis and oxidative metabolism. It would -
be interesting to see whether Salmonella exhibits a similar
correlation between tactic behavior and metabolic activity.
This could bechecked with such things as substrate, acid or
alkali, and oxygen. A sensitive method of detecting aerotaxis
is the followings A slide, spacer, and cover glass are joined
with vaseline to form acell in which a moderately turbid
suspension of micro-organisms is contained. Tha spacer, of
glass or aluminum, showld be about 2 mm thick and 1 cm in
diameter. After the suspension has achieved a more or less “
steady-state condition in the cell, a small air bubble is
{ntroduced by prying the cover glass slightly. Accumulation
or withdrawal from the bubble can then be observed.

Contradicting ths above hypothesis are the action spectra
wfxuanxxxrexe for phototaxis of many algse. In these cases,
which I referped to in my third article, light absorbed by
chlorophyll does not appear to be concerned with phototaxis, Sore fen
the carotenoids alone being active. ow

The energy for motility does not appear to be derived
directly from early metakolic pathways, but rather from some... sets
stored source. The evidence for this is scant; it is found
to some extent in Engelmaann's writings (2,3). . The mean speed.
of locomotion of Rhodospirillua reabrul ,was found by Thomas
and Ni jenhuis (4) to increase with tex jerature in the usual:
manner; I have also found this to be tijwe. On the other. had,
Y have noticed that such factors as 1i*ht {ntensity and presmce

or absence of substrate have no observable influence

 

  
 
 

on the Re

   

 
Méd motility of R. rubrum, except after several hours. These

. factors certainly govern the occurence of tactic responser,

at least in the purple bacteria.

T hope that this sketchy account will be of some use to
you. Also, I believe that there is lote of stuff in the
literature, of which T am not aware. A person who agght be
of conséderable help in this matter is

Max Delbrilok_
Division of Biology
Calif. Inst. of Tech.
Pasadena 4, Calif.

Sincerely yours,

. . whe
bedbriek a

Roderick Clayton

1. Molisch, Die Purpurbakterien nach neuen Untersuchun » Jona,
G. Tischer, 1907.

 

2. EngePmann, Pfidg. Arch. f. d. gos. siol. 30, 95(1883)

 

3. * » Botan. 3tg. 46, 661 (1888)

4. Biochim. et Biophys. Acta 6, 317 (1950)

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