INTERNATIONAL JOURNAL O F
SYSTEMATIC
BACTERIOLOGY
Vol. 16, No. 2
A p r i l 1966
pp. 171-172
INDOL PRODUCTION BY B A C T E R U
E i n a r Leifson
Departmeht of Microbiology, S t r i t c h School of Medicine and
Graduate School, Loyola University, Chicago, Illinois
ABSTRACT. P r o d u c t i o n o f i n d o l b y b a c t e r i a a p p e a r s t o be l i m i t e d t o t h o s e which produce
acid f r o m glucose fermentatively and reduce
nitrate.
F r o m more limited experience,
Gram-positive and pigmented bacteria did not
produce indol.
- - - - - .- . - - - -
F r i e b e r ( I 952) published a list of b a c t e r i a l c h a r a c t e r i s t i c s which he had found t o be a s s o c i a t e d with indol production: All indol positive c u l t u r e s grow aerobically, do not
produce s p o r e s , a r e Gram-negative, produce acid f r o m
glucose and reduce n i t r a t e . Unfavorable t o indol production
a r e capsulation, pigment production and acidfastnes s. Henr i k s e n (1952), however, r e p o r t e d that a number of h i s cult u r e s of anaerobic b a c t e r i a of the g e n e r a F u s o b a c t e r i u m and
Bacteroides produced indol, and a l s o that many capsulated
b a c t e r i a produced indol, such as species of Klebsiella,
E s cherichia, and Haemophilus influenzae.
My own experience i n this r e g a r d h a s been mainly with
f r e s h - w a t e r and m a r i n e b a c t e r i a which grow aerobically.
Most of t h e s e b a c t e r i a w e r e Gram-negative, s t r a i g h t o r
slightly curved motile rods.
F r o m a study of about 300
cultures of f r e s h - w a t e r b a c t e r i a and about 1,000 c u l t u r e s of
m a r i n e b a c t e r i a , indol production was found to be s t r i c t l y
limited t o the fermentative types. Cultures which produced
acid f r o m glucose oxidatively o r produced no detectable acid
(using the 0-F medium) did not produce indol by the usual
tests with paradimethylaminobenzaldehyde i n a m y l alcohol
In other w o r d s , indol production was
(Kovac reagent).
limited to facultative types and the s t r i c t a e r o b e s did not
produce indol. In a g r e e m e n t with F r i e b e r , all indol prod u c e r s i n m y collection reduced nitrate.
In a g r e e m e n t with Henriksen but not with F r i e b e r , many
of the m a r i n e b a c t e r i a which produced indol w e r e a l s o encapsulated. My experience with Gram-positive b a c t e r i a is
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172
INTERNATIONAL JOURNAL
limited: a study of some 70 strains of Listeria did not show
any which produced indol, nor have I any record of aerobic
spore-formers which produce indol. Regarding pigment
production, I have no definitely pigmented cultures which
produce indol. Pigment production by fermentative bacteria
is mainly limited to the genera S e r r a t i a and Chromobacter&, which in my experience, and from reports in the literature, do not produce indol.
The inability of nonfermenters to produce indol would
make any report of indol production by species of the following genera very suspect: Pseudomonas, Xanthomonas,
Achromobacter, Agrobacterium, Alcaligenes and several
other genera l e s s well defined.
REFERENCES
F r i e b e r , W. 1952. Indolbildung bei bakterien. Internatl.
Bull. Bact. Nomen and Taxon. g(3):94-95.
Henriksen, S. D. 1952. Indol production of bacteria.
Internatl. Bull. Bact. Nomen. and Taxon. k(4):141-142.
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