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CONFERENCE ON VIRUS AND RICKETTSIAL
CLASSIFICATION AND NOMENCLATURE
New York Academy of Sciences, Section of Biology
January 11 and 12, 1952
A Resum6
R . E . Buchanan, Iowa State College, Ames, Iowa
The statement approved by the plenary s e s s i o n of the first International
Congress of Microbiology a t P a r i s i n 1930 h a s historical significance: "It i s c l e a r l y r e c o g n i z e d t h a t t h e l i v i n g f o r m s w i t h
which the microbiologists concern themselves a r e in
part plants, in part animals, and in part primitive."
The need for adequate considerationof t h e p r o b l e m s of a l l phases of m i crobiological nomenclature was there recognized and emphasized. L a t e r
when the International Bacteriological Code of Nomenclature was approved
a t the fourth Congress a t Copenhagen, the following wording was authorized: IlB a c t e r i o 1o g i c a 1 n o m e n c 1a t u r e c o n s i d e r s b a c t e r i a , related o r g a n i sm s, and the viruses".
-
The nomenclature and taxonomy of the v i r u s e s have recently received
i n c r e a s e d attention. The plant pathologists interested i n plant v i r u s e s
have considered s e v e r a l s y s t e m s of nomenclature proposed. The bacterial virologists have made tentative use of quite different s y s t e m s . The
animal virologists in many c a s e s have felt that the time was not opportune
for any definite action looking toward either classification o r nomenclat u r e of the animal viruses. It has become increasinglyapparent that the
t h r e e groups of virologists, those i n t e r e s t e d i n the higher animals, in the
higher plants, and in the bacteriahave much i n common. However, t h e r e
was little opportunity for these groups to m e e t to discuss their common
problems. The f i r s t major effort to coordinate thinking i n the nomenclat u r e was that of Holmes (1) who in1939 in his Handbook of the Phytopathogenic Viruses proposed that a l l the v i r u s e s be placedin a s e p a r a t e group,
the V i r a , and that the Linnaean s y s t e m of binomial nomenclature be
applied. The classification was considerably expanded i n Supplement 2
in Bergey's Manual of Determinative Bacteriology ( e d . 6, 1948 ). All
v i r u s e s w e r e grouped i n a single o r d e r , the V i r a1 e 8 , with t h r e e subo r d e r s for the bacterial v i r u s e s , the plant v i r u s e s and the animal v i r u s e s
respectively. A relatively elaborate classification of each suborder w a s
developed, c a r r i e d through to families, g e n e r a and species. Holmes'
e a r l i e r classification (1939) of the plant v i r u s e s had considerable acceptance among plant pathologists and the binomial s y s t e m was used by many
authors of p a p e r s . However, some of those working i n the field of the
animal v i r u s e s felt that the t r e a t m e n t of these o r g a n i s m s by Holmee in
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1948 was p r e m a t u r e , and that g r e a t c a r e needed to be used in preventing
the straight-jacketing of the nomenclature in this group. It was suggested that s o m e method shouldbe worked out for withholding the final acceptance of all names until there had been an opportunity for the specialists
carefully to review the field and to propose a system of nomenclature
that would f r o m the beginning have a high degree of acceptability and
s tab ility .
This widespread feeling on the p a r t df animal virologists led t o the organization through the International Committee on Bacteriological Nomenclature of a special Subcommittee on Viruses to m e e t with the fifth International Microbiological Congress a t Rio de Janeiro in 1950. Dr. C. H.
Andrewee of London was designatedas chairman, and asked to s e l e c t the
m e m b e r s of such a committee. This he did, and the Committee held
s e v e r a l meetings at Rio de J a n e i r o and made a s e r i e s of recommendations to the International Committee on Bacteriological Nomenclature.
These r e p o r t s and recommendations have been summarized in previous
i s s u e s of this BULLETIN ( 2 , 3, 4). The final outcome of the Rio de Jan e i r o Congress with its attendant conferences was the enlargement of the
work of Dr. Andrewes' Subcommittee on Viruses t o m a k e i t representative
of all of the major fields of virology. The Committee was asked to o r g a nize as a general Committee onNomenclature and Taxonomy of t h e v i r u s
e 8 , with three sub-committees o r Commissions representing each of
the three subdivisions of the subject. Dr. Andrewes remained c h a i r m a n
of the Subcommittee on Virology andof the Commission on Animal V i r o logy. Later Dr. L. M. Black of Brooklyn was designated a s c h a i r m a n
of the Commission on P l a n t Viruses and Dr. J. Craigie of London ar
chairman of the Commission on Bacterial Viruses.
Lack of opportunity in the p a s t f o r the s e v e r a l groups of virologists to
meet to discuss their common p r o b l e m s led the New York Academy of
Sciences through i t s Section of Biology to provide f o r a n International
Conference on Virus and Rickettsia1 Classification andNomenclature, held
in New York January 11 and 12, 1952. The conference was truly international in that many countries w e r e repreeentedandinclusive i n that those
interested in the m o s t v a r i e d groups of viruses w e r e in attendance.
Abstracts of about thirty p a p e r s and a complete copy of the a d d r e s s of
the chairman S i r MacFarlane Burnet were i s s u e d a s a preprint.
Several papers of general significance w e r e followed by discussions of
the problems of classification of various groups, including the r i c k e t t s i a s ,
the v i r u s e s o f the higher plants, of insects, of the bacteria, and of higher
animals, including such subgroups a s the psittacosis, pox, influenza,
arthropod borne , Coxsackie , poliomyelitis and encephalomyocarditis
viru s e s .
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Several of the presentations had to do with general problems of nomenclature of classification and of speciation. D r . E r n s t Mayr of the Museum
of Natural History in New York attemptedto shed some light on the p r o blems of taxonomy and nomenclature in the field of microbiology by consideration of species and taxon concepts developed in recent y e a r s in
zoology, particularly in ornithology. His overemphasis upon the univer sality of sexual reproductionamong living things, with the inference that
r e a l progress in systematic microbiology and virology can be achieved
only when something i s known of sexual recombinations i n lower forms
such a s the bacteria and the viruses, left the listener with the distinct
impression that the application of the standard rules of nomenclature to
microorganisms not showing sexual reproduction was scarcely feasible.
The suggestion was made that i t mightbe well i f the microbiologists and
the virologists left the naming of their organisms to national o r international committees. D r . Burnet emphasized that the valuable developments
i n modern population genetics which have led to a better understanding of
development and differentiation of species in the higher f o r m s a r e quite
without application in the g r e a t groups of agamic microorganisms. He
formulated useful c r i t e r i a to be used in the differentiation and classification of the viruses, and emphasized that the organisms cultivated in the
laboratory often a r e quite different in certain characters f r o m the organisms a s found in the original host. With some proposed modifications
he felt that the outlines of procedure formulated at the Rio de Janeiro
Congress could well serve as guides.
Dr. Holmes' paper on the problems of nomenclature and classification
emphasized some of the special difficulties that a r i s e when virologists
in the several fields of bacterial, plant and animal viruses attempt to
compose their differences. Holmes, of course, believes that with suitable modifications the Linnaean binomial system of nomenclature is 8 8 tisfactorily applicable to the viruses.
In a well-organizedpaper Dr. Andrewes (London) discussed the decisions
reached by the Fifth International Microbiological Congress, and outlined
the organization that had been evolved to insure orderly p r o g r e s s in the
development of a report on nomenclature and taxonomy for presentation
a t the sixth Congress a t Rome. It is apparent that Dr. Andrewes and the
Committee on Virus Nomenclature and Taxonomy which he heads have a
difficult task. Specifically Dr. Andrewes as chairman of a Commission
to study one group of animal viruses has the task of organizing a r e p o r t
relative to its delimitation, subdivisions and nomenclature, further he
has the task af coordinating the work of the s e v e r a l commissions of the
animal virology subcommittee, and in turn attempting to formulate r e solutions and suggestions that will be accepted by the plant virologists,
the bacterial virologists and the animal virologis<s.
Much i n t e r e s t centeredin the rather lively controversy as to whether the
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Linnaean system of binomial nomenclature should either now o r eventually
be used in the naming of the viruses. Dr. Johnson of Wisconsin insisted
that a numbering system for plant viruses of the type proposed by his
committee a t the -9msterdam Botanical Congress was preferable. Dr.
3awden of Rothamsted, England, made what appeared to many a s a futile
gesture to discredit the binomial system of nomenclature of viruses by
ridicule. No poll was taken of the sentiment of the members of the conference a s a whole, but the thinking of certain groups was quite c l e a r .
Those interested in the rickettsias seemed reasonably confident that a
satisfactory binomial nomenclature in this group was largely developed
and increasingly accepted. Similarly there seemed t o be acceptance of
binomial nomenclature by those working with the viruses of insects, even
though stability has not been achievedas yet. The plant virologists were
apparently divided a s to their wishes. Some would develop numbering
systems , some felt the binomial system inapplicable and inappropriate,
out there was much evidence of increasing acceptance of the Linnaean
system in the field of plant pathology. Dr. Andrewes stated that a queetionnaire sent by him to plant virologists in many countries showed opinion to be rather evenly divided for and against the binomial system.
One of the American workers pointedout that in a poll of plant virologist.
in the United States sentiment i n favor of the binomial system was m a r k edly predominant. No very definite expressionwas given by those working with bacteriophages. The problems in this group seem at present to
be largely those of differentiation and classification rather than of nomenclature.
Sentiment among the animal virologists is rather more difficult to a s s e s s .
There seemed to be no deepseated aversion to the use of the binomial
system but it r a s fervently hoped that some method could be devised that
would keep animal virology from being engulfed in a nomenclatural mor a s s such a s once threatened nomenclatural stability in bacteriology. Is
it not possible in some way to fix uponnames by means of an international
agreement? Some were not a v e r s e to Mayr's proposal to have a suitable
international committee fix names of taxa by fiat.
Several speakers emphasizedthat some groups of viruses a r e much better
characterized than a r e others. Some groups maybe readily broken down
into genera and speciea, while others a r e still poorly described. A suggestion developed by Dr. Bitancourt of Sao Paulo met with some support.
He pointed out a parallelism between the situation existing in the fungi
and in the viruses. Scores of genera and thousands of species of fungi
cannot be placed with certainty in the formal classification based largely
upon the characteristics of the so called perfect stages and a r e allocated
to the Fungi Imperfecti, a group created to include those f o r m s whose
perfect stage ie unknown or has been completely l o s t from the growth
cycle. The Fungi Imperfecti a r e divided into families, genera and apecies and the binomial s y a k m of nomenclature i e applied. Whenever the
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perfect stage of one of these l'imperfect fungi" i s discovered i t may be
placed in its appropriate genus and if necessary rechristened. It was
proposed that a somewhat analogous scheme be adopted for the viruses.
Those sufficiently characterizedwouldbe regularly designatedby suitable
binomials and the others placedin a group of viruses imperfectly known,
and given tentative names with the expectation that when m o r e adequate
descriptions a r e available they would be t r a n s f e r r e d to their places in a
logical system. Uncertainties a s to classification in some c a s e s could
be recognized appropriately by the use of the common Latin phrase indicating uncertainty, there could be viral "G e n e r a I n c e r t a e S e d i s I t
as well a s " S p e c i e s I n c e r t a e S e d i s " . This procedure might give
a usable nomenclature while m o r e perfect taxonomic outlines were being
developed.
Several of the papers had special nomenclatural implications. Dr. Black
of the Brooklyn Botanical Gardens called attention to the existence of a
special problem of classification in the more recently identified group of
viruees in which multiplication occurs both in the plant host and in the
insect vector. F o u r virus diseases of plants transmitted by leaf hoppers
a r e known to belong to this group, Dr. Limaeset of Versailles reviewed
i n detail the objections that have been raised to the binomial system of
nomenclature as applied to the viruses and concluded that they a r e not
rerioue and that some temporary difficultiee might be resolved by use
of the grouping "Vira Imperfectar'
Dr. Rake of the Squibb Inetitute for Medical Research concluded that c e r tain viruses and rickettsiae a r e sufficiently well characterized to justify
their being grouped into genera. The s e v e r a l c r i t e r i a useful i n the development of a classification of the bacterial viruses were outlined by
Dr. M a m a of New York University, including serological, morphological
physical and physiological characteristics and the results of mixed infections. There a r e a s yet no adequate c r i t e r i a f o r the definition of bacteriophage genera, and the use of binomials may well be postponed until well
characterized strains have beenagreed upon as types, and a satisfactory
method of maintaining anddistributing such s t r a i n s developed. D r . Coles
f r o m hie South African experience presented anincomplete classification
of the rickettsias inwhich emphasis was laidupon morphology, serology,
culture in eggs, the nature of the m a t r i x etc. He recognized that a satisfactory classification and nomenclature must wait upon m o r e complete
understanding of the organisms. Dr. Philip of the Rocky Mountain Laboratory outlined a tentative classification of the R i c k e t t s i a 1 e s in
which he recognized one family, three genera and three subgenera. Dr.
Bergold of the Canadian Laboratory of Insect Pathology and D r , Steinhaus
of the University of Californiaaccepted in principle the binomial system
of naming the ineect viruses, but pointed out some of the p r e s e n t difficult problems both of classification and of nomenclature. The f o r m e r
ruggested that some international committee might well be given some
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degree of authority relative to the names finally to be accepted, a committee that could be consultedby investigators. Dr. Steinhaus listed two
genera of insect viruses that seemed to be well established, together with
their species , and withdesignationof the type species. Two other genera
were includedinthecategoryof G e n e r a e t S p e c i e s I n c e r t a e S e dis.
The problems to be solved relative to nomenclature of the s e v e r a l groups
of animal viruses vary widely. Dr. Karl Meyer of the University of California posed the difficulties in the psittacosis -ornithosis group of l a r g e
viruses and protested the unsatisfactory nomenclature. Dr. Rake of the
Squibb Institute, New York, suggested that the lymphogranuloma-psittacosis group showed closer relationships to the rickettsiae than to the v i r u s e s . It i s apparent from the reports given by Dr. F r a n c i s of the U n i versity of Michiganandby S i r MacFarlane Burnet of Melbourne, Australia
that substantialprogress i s being made inanunderstanding of the influellza
v i r u s group and i n eventual systematization of the nomenclature. Dr.
Hammon of the University of Pittsburgh believes that there is insufficient
knowledge of the arthropod-borne encephalitis viruses to make possible
at present a rational use of the binomial system of nomenclature, and that
the classificationproposed by Holmes wae premature. Dr. Lepine of the
P a s t e u r Institute, P a r i s a l s o discussed this group and indicated that subrtantial p r o g r e s s is being made. A suggested grouping of the arthropod
viruses was noted, emphasizing that the s e v e r a l v i r u s e s appear to belong
together although causing very distinct diseases and with distinct a r t h r o pod vectors. A suggested generic diagnosis for the Coxsackie viruses
and diagnoses of two groups within the genus was presented by Dr. D a l l dorf of the New York State Department of Health. He was able to differentiate ten types i n the f i r s t group and three i n the second. Dr. Malnick
of Yale University pointed out certaindifficulties in the acceptance of the
two groups of Coxsackie virus a s proposed by Dalldorf. A constructive
c r i t i c i s m of the Holmes's classification of the poliomyelitis viruses was
presented by Dr. Rhodes of the University of Toronto. The poliomyelitis
group and c r i t e r i a f o r diagnosis of a single genus with two o r three species
were discussed by D r . Koprowski of the LederPe Laboratories, emphasis
being laid upon morphology as determined by the use of the electron microscope. A schema for the encephalomyocarditis group wae outlined by
Dr. Warren of the Army Medical Service Graduate School, Washington.
The need of adequate and reliable type culture collections for the viruses
was emphasized by several speakers. Dr. Smadel of the Army Medical
Service Graduate School outlined the service of the Virus and Rickettsial
Registry U. S.A. , and Dr. McKinney the need for an adequate culture collection for the use of those interested in plant virology.
The l a s t session of the Conference was devoted to an open discussion of
the problems of virus nomenclature under the chairmanship of S i r Mac-
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Farlane Burnet. The results of the conference and the papers presented
a r e in process of publication by the New York Academy of Science. They
will constitute a reference book of r e a l value to a l l i n t e r e s t e d in the virus
field and in its systematics.
In summary, it may be noted that Dr. Andrewes and his committee and
commissions on virological nomenclature have the important task of p r e paring nomenclatural and taxonomic recommendations to be submitted to
the next International Congress of Microbiology in September 1953. As
f a r as practicable, virologists should take an active i n t e r e s t in the work
of this committee and render all needed assistance. The task of the committee is complicated and difficult. Among its s e v e r a l assignments is
that of making a definite proposalfor a suitable date of departure for the
nomenclature of the viruses. This fixing of a date is needed, no matter
what form of nomenclature may be finally proposed or approved. There
a r e many possible solutions to the problem. The deliberations of the
conference and a survey of the actions that have been taken by international agreement in botany, zoology and bacteriology suggest the general
nature of some of the possible solutions. To the reviewer, four s e e m
worthy of mention.
1. The Committee might consider recommending that all names validly
published in the literature of virology be regarded as available f r o m the
standpoint of priority (essentially the practice in m o s t branches of biology 1.
2. The Committee might consider recommending that the starting point
in virological nomenclature be some published monograph of the viruses,
and all older names nottherein recognizedbe ignored. Such an arrangement is in effect in botany for some groups of the fungi and of the algae,
In the event of such a proposal, the monographof Holmes would be among
those to be considered.
3. The Committee might consider the advisability of preparing or of supervising the preparation of an authoritative monograph on the viruses,
describing all the genera and higher taxa recognized, listing and naming
the species accepted, and designating type species and type genera. O r
the monograph might be definitive for certain of the better known groups
of the viruses, with those not well known o r indefinitely characterized
placed in some such category a s Vira imperfecta or Viraincertae sedis.
Those organisms indefinitely placed would l a t e r be given recognized s t a tus when better characterized. Such a proposal would essentially be a
recommendation for the conservation of a list of generic names with designation of the types.
4. The Committee may well find that the time available before the 1953
Congrese is too limited to complete fully the task assigned. A recommendation that additional time be granted the Committee would doubtless
be approved. It is to be hoped, however that substantial p r o g r e s s may
have been made before any postponement is requested. There is rapidly
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mounting p r e s s u r e , c e r t a i n l y in America, f o r definitive action on v i r u s
nomenclature. A s u r v e y of r e c e n t l i t e r a t u r e r e v e a l s that binomial n a m e s
f o r the v i r u s e s are increasingly employed and a r e accepted by a l a r g e
proportion of the virologists. Obviously no author of a text which t r e a t s
of the v i r u s e s , e i t h e r of plants or animals, c a n ignore the n a m e s that a r e
comiag into u s e . It s e e m s probable that the flood p r e s s u r e m a y well be
held under control until 1953 but it is to be hoped that the r e g u l a t o r y dev i c e s m a y be p r e t t y well completed by that t i m e .
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