INTERNATIONAL BULLETIN OF BACTERIOLOGICAL
NOMENCLATURE AND TAXONOMY
VoL. 13, No. 4
October 15, 1963
pp. 181-186
ON THE SPECIES-DEFINITION
F. Kauffmann
In te rnationa 1 Sa lmone 1la Cen te r
Statens Se r u m i n s t i tut
Copenhagen
ABSTRACT. I n m o d e r n c l a s s i f i c a t i o n t h e s p e c i e s a r e d e f i n e d a s g r o u p s of r e l a t e d s e r o fermentative phage-types and a r e the fundamental units, while in orthodox classification,
which is beginning with the higher groups, the
s p e c i e s a r e defined only by b i o c h e m i c a l (mostly f e r m e n t a t i v e ) methods.
-
We have two different classifications which we can c a l l
the orthodox and the modern classification. The orthodox
classification i s r e p r e s e n t e d by B e r g e y ' s Manual and the
modern classification by the 1 s t Report of t h e Salmonella
Subcommittee in 1934.
In the orthodox classification the s p e c i e s a r e defined only
by biochemical methods, w h e r e a s i n the modern classification the s p e c i e s a r e defined biochemically as well a s s e r o Logically and a r e subdivided into serofermentative phage
types. In c o n t r a s t to g e n e r a and subgenerawhich a r e defined
biochemically, the definition of s p e c i e s i s based mostly on
serological methods.
The f i r s t 36 Salmonella s p e c i e s were published by the
Salmonella Subcommittee i n 1934. F u r t h e r s p e c i e s w e r e
published by the Subcommittee i n the R e p o r t s to the I n t e r national C o n g r e s s e s i n New York 1939 and i n Copenhagen
1947. At the end of 1947, 140 Salmonella s p e c i e s w e r e
recognized and vaLidly published i n the Proceedings of t h e s e
Congresses.
In the following y e a r s a change o c c u r r e d , since the Ent e r o b a c t e r i a c e a e Subcommittee used only common n a m e s
Like "group" a n d "type."
I r e g r e t that I have followed t h e s e
suggestions f o r a long time, but finally I r e a l i z e that i t is
wrong f o r m e m b e r s of a Subcommittee of the Nomenclature
Committee to u s e only common n a m e s . We have to propose
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INTERNATIONAL BULLETIN
scientific n a m e s and to u s e the aceepted designations g e n e r a
and species according to the Bacteriological Code.
Therefore, I r e t u r n e d to the 1 s t Report of the Salmonella
Subcommittee and have published i n 1961 a l l known "types"
a s s p e c i e s . I have defined the s p e c i e s a s follows: "A spec i e s i s a group of r e l a t e d serofermentative phage types."
To give a n example, let u s consider the species 5. typhim u r i u m , one of the l a r g e s t apecies consisting of many s e r o fermentative phage types which a r e the s m a l l e s t units. All
c u l t u r e s of 5. typhi-murium belong t o t h e serotype 1 , 4 , 5,
12:i:l, 2 but o c c u r i n 4 different serological subtypes:
1,4,5,12:i:l, 2
4, 5, 12:i:l, 2
1,4,12:i:l, 2
4, 12:i:l, 2.
These 4 subtypes a r e combined in the Kauffmann-WhiteScheme to 1 , 4 , 5, 12:i:l, 2, only f o r simplification.
Each of t h e s e serological subtypes can be divided into
different fermentative types, f o r example, into inositolpositive o r negative types o r into d-tartrate-positive o r
negative types, etc. F u r t h e r , each of these s e r o f e r m e n t a tive types can be divided into s e v e r a l phage types. T h e r e f o r e , the fundamental elements of the s p e c i e s a r e the exactly
defined serofermentative phage types, f o r example: s e r o type 4, 5, 12:i:1,*2 fermentative type 20 phage type 1.
Such a culture i s the s m a l l e s t entity which we a r e d e t e r mining in our routine diagnosis, this being a s e r o f e r m e n t a tive phage type. If we combine 20 o r 40 of s u c h fundamental
elements a l l belonging to t h e serotype 1,4,5, 12:i:l, 2 to one
group a n d call t h i s group a s p e c i e s , we a r e right to do t h i s .
Since the officially accepted type species of the genus Salmonella is 2. cholerae-suis, i t i s c o r r e c t and logical to c a l l
S. typhi-murium a s p e c i e s a s done in the 1st Report of the
Salmonella Subcommittee.
As the s a m e fermentative types can occur a l s o i n other
serotypes, and a s the phage types a r e not always determined,
the diagnosis of the serotype is the most important procedu r e and the b a s i s of the whole classification.
To avoid misunderstandings, it should be s t r e s s e d that
the orthodox definition of the s p e c i e s which is biochemically
defined, is abandoned in the modern classification. The biochemical subdividions of a genus a r e now called subgenera.
In the genus Salmonella I have established 3 biochemically
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BACTERIOLOGICAL NOMENCLATURE
AND TAXONOMY
defined subgenera I, I1 and 111, but I cannot a g r e e to r e g a r d
these 3 subgenera as s p e c i e s since they a r e defined only
biochemically. We have to take those e l e m e n t s a s s p e c i e s
which can be defined both biochemically a n d serologically.
Only in this way is a n exact diagnosis possible ( s e e Table).
Table
Genus
Sa lmon e 1la
Subgenus
I
I1
III
-S. paratyphi-A )
)
S. paratyphi-B
S.
t@hi
-mu
r
i
u
m
)
-
Species
I
etc.
Serofermentative phage type
t yphi -mu r i u m
serotype 4,5,12:i:l, 2 )
fermentative type 20 )
phage type 1
)
s_.
With r e g a r d to biochemical t e s t s , especially f e r m e n t a t i v e
reactions, the value of such a t e s t i s not t h e s a m e i n different g e n e r a o r f a m i l i e s . A l s o inside the s a m e genus thevalue
of different t e s t s is not the s a m e .
The organic a c i d s , like
d - t a r t r a t e , sodium-citrate and malonate, a r e much m o r e
important than other t e s t s like m a l t o s e fermentation. T h e r e f o r e , i t is not possible t o r e g a r d a l l these t e s t s a s equal a n d
to t r e a t the r e s u l t s uniformly.
I have to mention t h i s a s i t is not possible to d i s c u s s the
problem of s p e c i e s definition without a g e n e r a l discussion
on classification. Therefore, I have to touch a l s o t h e probl e m of the so-called n a t u r a l classification.
As known i t i s possible to make transductions o r r e c o m binations i n t h e laboratory, to c r e a t e new s p e c i e s . We suppose that such recombinations etc. occur a l s o i n n a t u r e , but
we don't know the p a r e n t s of these c u l t u r e s and cannot e s tabLish a family t r e e .
Therefore, I am regarding a n a t u r a l
classification as a utopia.
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We have to classify our c u l t u r e s by the determination of
their reactions, i n other words we have to diagnose the
phenotype. In the diagnosis of Enterobacteriaceae we a r e
determining the biochemical, the serological and the phage
reactions.
In t h i s way we have established a solid c l a s s i f i cation f r o m below, just as a house i s built f r o m the b a s e ment and not f r o m t h e roof.
The b a s i c e l e m e n t s a r e the
species which a r e composed of many serofermentative phage
types. T h e r e f o r e , we have to s t a r t our classification with
these species, and not with higher units like genera, f a m i l i e s
etc.
While the orthodox classification s t a r t s with t h e higher
units, the modern classification begins f r o m below. The
higher groups a r e only biochemically defined and t h e r e f o r e
badly defined.
T h e r e a r e not s h a r p f r o n t i e r s between t h e s e
higher groups, they cannot be defined exactly. However, a
species, like 2. typhi-murium, can be defined exactly by
40-50 different r e a c t i o n s . A culture which h a s the antigens
4,5, 125:1, 2 and the typical fermentative behaviour, can be
diagnosed quicklyand p r e c i s e l y . E v e r y day hundreds of such
c u l t u r e s a r e diagnosed in many laboratories a l l over the
world. Such a diagnosis gives a l l the n e c e s s a r y d a t a f o r a n
epidemiological investigation, not only f o r p r a c t i c a l p u r p o s e s , but a l s o f o r scientific studies. If we know that the 0
antigens a r e 4, 5,12, we know simultaneously t h e chemical
constitution of the sugar-components.
We know that t h i s
culture contains glucosamine, heptose, galactose, glucose,
mannose and abequose which constitute the determinative
componentfor the 0 a n t i g e n 4 of the Kauffmann-White Scheme,
In determining serological p r o p e r t i e s , we a r e determining
in reality p a r t of the chemical constitution of the bacterium.
These r e s u l t s in combination with the determination of the
enzymes, o r the fermentative p r o p e r t i e s , give such a complete and reliable picture that i t i s the solid b a s i s f o r our
classification.
I am convinced that we cannot extablish a b e t t e r o r m o r e
expedient c las sification.
In summarizing, I should like to s t r e s s the following
points :
We have to s t a r t our classification f r o m below, beginning
with the species which a r e groups of r e l a t e d serofermentative
phage types. This i s the decisive point in modern c l a s s i f i cation, in c o n t r a s t to orthodox classification in which only
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BACTERIOLOGICAL NOMENCLATURE
A N D TAXONOMY
biochemical methods a r e u s e d f o r the determination of highe r groups.
The modern classification was s t a r t e d by the 1 s t Report
of the Salmonella Subcommittee, and i s c h a r a c t e r i z e d by the
combination of biochemical and serological methods i n the
diagnosis of s p e c i e s . During t h i r t y y e a r s i t h a s been c l e a r l y
demonstrated that this s y s t e m i s effective and useful both
f o r p r a c t i c a l and scientific investigations. This i s valid not
only f o r the genus Salmonella, but a l s o f o r other g e n e r a of
the family Enterobacteriaceae and f o r other f a m i l i e s . It i s
therefore a general principle.
In routine diagnosis the m o s t important investigation i s
the determination of the serofermentative phage types, that
m e a n s the diagnosis of the species, but not the definition of
higher groups, like f a m i l i e s , o r d e r s etc., since only .the
species can be sharply defined.
Therefore, the International Nomenclature Committee i s
requested to d i r e c t the attention to the species level and to
s t a r t classification f r o m below and not f r o m above. We have
to s t a r t with the definition of the species and to analyse the
o r g a n i s m s both by biochemical and serological methods.
In c o n t r a s t to orthodox classification the definition of the
species a s a group of r e l a t e d serofermentative phage types
i s the fundamental point a n d the solid basis of modern c l a s sification.
If we want to classify, we have to know exactly the whole
m a t e r i a l which we want to classify, but in bacteriology this
i s not the c a s e today, with the exception of t h e genus Salmonella and s o m e other g e n e r a .
Therefore, i t h a s not beenpossible to e s t a b l i s h a general,
useful classification. To do t h i s we have to s t a r t with the
serofermentative phage types which a r e the fundamental
elements forming the s p e c i e s . The 1 s t Report of the
monella Subcommittee i s b a s e d on such a n investigation,
but B e r g e y ' s Manual h a s not such a b a s i s . The n e c e s s a r y
knowledge of the whole m a t e r i a l which should be classified
is lacking. This fact explains c l e a r l y the good r e s u l t s of
modern classification and the f a i l u r e of orthodox c l a s s i f i c a tion o r of B e r g e y ' s Manual. T h e r e is "chaos" in c l a s s i f i c a tion because we have not t h e n e c e s s a r y knowledge today. I
can only a d v i s e the abandonment of e v e r y classification of a
new field until i t has been investigated in the s a m e way a s
the genus Salmonella. We c a n talk on this problem 30 y e a r s
w-
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f r o m n o w s i n c e the teamwork of many i n v e s t i g a t o r s f o r a
p e r i o d of about 30 y e a r s i s n e c e s s a r y to anaLyse a l a r g e
group of b a c t e r i a b e f o r e a useful c l a s s i f i c a t i o n c a n be s t a r t ed.
REFERENCES
Kauffmann, F. 1961. Die Bakteriologie d e r Salmone llaS p e c i e s . Munksgaard, Copenhagep.
1961. T h e species-definition i n t h e f a m i l y Ent rob a c t e r i a c e a e . Intern. B u l l . B a c t . Nomen. Taxon. 11:s.
1960. Two b i o c h e m i c a l subdivisions of the genus
Salmonella, Acta path. e t rnicrobiol. scandinav. 493393.
1963. Zur Differential Diagnose d e r . Salmonella
Subgenera I, I1 a n d 111. Acta path. e t rnicrobiol. s c a n d inav. (in p r e s s )
Salmonella Subcommittee. 1934. The genus Salmonella
L i g n i b r e s , 1900. J o u r . Hyg. 34:333.
.
.
.
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