Objections to the Transfer of Francisella Novicida to the Subspecies Rank of Francisella Tularensis – Response to Johansson Et Al
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Letters to the Editor Huber, B. E., Escudero, R., Busse, H. J., systematics. Proc Natl Acad Sci U S A 105, tularensis, a facultative intracellular pathogen. Seibold, E., Scholz, H. C., Anda, P., Ka¨ mpfer, P. 2504–2509. PLoS Pathog 5, e1000472. & Splettstoesser, W. D. (2010). Description of Lapage, S. P., Sneath, P. H. A., Lessel, E. F., Olsufiev, N. G., Emelyanova, O. S. & Dunayeva, Francisella hispaniensis sp. nov., isolated from Skerman, V. B. D., Seeliger, H. P. R. & Clark, T. N. (1959). Comparative study of strains of B. human blood, reclassification of Francisella W. A. (editors) (1992). International Code of tularense in the old and new world and their novicida (Larson et al. 1955) Olsufiev et al. 1959 Nomenclature of Bacteria (1990 Revision). taxonomy. J Hyg Epidemiol Microbiol Immunol as Francisella tularensis subsp. novicida comb. Bacteriological Code. Washington, DC: American 3, 138–149. nov., and emended description of the genus Society for Microbiology. Francisella. 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Objections to the transfer of Francisella novicida to the subspecies rank of Francisella tularensis – response to Johansson et al. The description of novel species requires experiments, F. novicida is genetically close the results from the literature and the the careful selection and use of a wide to F. tularensis (Hollis et al., 1989) and the results from our investigations, but also for variety of methodologies. As pointed out phenotypic differences observed (Huber et sake of consistency, it is obvious that our by Tindall et al. (2010), experience gained al., 2010) are in agreement with the proposal to assign F. novicida to F. over the past six decades has continued to subspecies concept. Another important tularensis as a novel subspecies is well demonstrate the value of comparing point supporting this taxonomic supported. different datasets and also of basing the rearrangement is the acceptance of the new Below are some additional replies to description and delineation of taxa on as combination within the scientific certain arguments proposed by Johansson wide a dataset as possible. A combination community. The use of this not yet validly et al. (2010) to support their stance against of data acquired from DNA-based published new combination may be related the reclassification of F. novicida. methods (DNA–DNA hybridization, gene to the fact that in Bergey’s Manual of sequences, genomic fingerprints) and Systematic Bacteriology (often erroneously It is argued, that: phenotyping (chemotaxonomic, considered as the ‘bible’ of bacterial ‘From a practical standpoint, sep- physiological and morphological traits) systematics by those interested in bacterial arate species names are useful in a provides a sound basis for the taxonomy of taxonomy), the transfer of F. novicida to microbiological laboratory or a the prokaryotes (Tindall et al., 2010). The Francisella tularensis subsp. novicida was clinical setting and also as a basis decision as to whether two bacteria are recommended in the chapter dealing with for regulations governing the hand- members of a single species is still based on the genus Francisella (Sjo¨stedt, 2005). ling of medically important organ- the results from DNA–DNA hybridizations Although this proposal was never formally isms. [...] Importantly, it is fairly (Wayne et al., 1987; Stackebrandt et al., recognized, numerous microbiologists are easy to distinguish F. novicida and 2002). In general, two bacterial strains are already using the name. An online search F. tularensis on the basis of their assigned to the same species if their DNAs survey in ‘Pubmed’ (http://www.ncbi.nlm. different growth and metabolic reassociate at levels greater than 70 % and nih.gov/sites/entrez?db=PubMed) indi- requirements on artificial media’. 5 % or less DTm (Wayne et al., 1987), but cates that in recent years there is no the latter criterion is only rarely applied. In significant difference in the frequencies of In contrast to tularaemia caused by F. addition, Wayne et al. (1987) pointed out the use of the names F. novicida and F. tularensis subsp. tularensis or F. tular- ‘Subspecies designations can be used for tularensis subsp. novicida. ensis subsp. holarctica, human or genetically close organisms that diverge in animal infections with strains of F. phenotype’. From our point of view, it is not consistent tularensis subsp. novicida are extre- to have a species F. tularensis with three mely rare and there are very few Our proposal to transfer Francisella subspecies supported by DNA–DNA publications reporting the isolation novicida as a novel subspecies to F. relatedness data but distinguishable by of this facultative pathogen. Most of tularensis subsp. novicida is in agreement phenotypic traits and a separate species F. these reports have shown that it was with the above-mentioned novicida that also shares high DNA–DNA very difficult to distinguish those recommendations. As demonstrated by the relatedness values (.85 %) but which is isolates from strains of F. tularensis, results from DNA–DNA reassociation phenotypically distinguishable. Based on not only for routine clinical laborat- Downloaded from www.microbiologyresearch.org by 1718 International Journal of Systematic and Evolutionary Microbiology 60 IP: 54.70.40.11 On: Tue, 11 Dec 2018 06:22:18 Letters to the Editor ories, but also for a reference labor- four traits from one or the other be validly published according to the atory (Birdsell et al., 2009). We have subspecies (Huber et al., 2009). requirements of the Bacteriological the impression that the majority of Code. In fact the term ‘valid’ can only It is argued that: routine laboratories will not be able to be applied to the valid publication of distinguish between the two subspe- ‘In 1989, Hollis et al. (1989) showed the name. This does not mean that the cies on the basis of phenotypic char- that F. novicida and F. tularensis scientific conclusions of the paper of acteristics or metabolic requirements. could be considered one species as Hollis et al. (1989) are incorrect. judged from DNA–DNA hybridiza- It is also difficult to understand why It is argued that: tion experiments (Hollis et al., only separate species are useful in a 1989). Their publication was not ‘Notably, earlier publications con- microbiological laboratory or a clinical valid according to the requirements sidered F. novicida and F. tularensis setting but not separate subspecies. outlined in the Bacteriological Code to be separate species based on The same is true for the basis of (Lapage et al., 1992; Tindall et al., differences in phenotype including regulations governing the handling of 2006). As a result, the proposed chemotaxonomic markers, distinct medically important organisms. In fact, elimination of the species F. novicida ecological roles, different clinical there is a clear example showing that and the demotion of it to a biogroup and epidemiological characteris- subspecies differentiation can be of F. tularensis was not included tics, and differing abilities and applied for different classification of among prokaryotic names with modes of invasion and mechan- medically important bacteria. Accord- standing in nomenclature’. isms of tissue damage in mammals ing to EU guideline 2000/54/EC, which In the paper of Hollis et al. (1989), the (Larson et al., 1955; Olsufiev et al., had to be translated into national law authors presented data on which they 1959; Skerman et al., 1980)’. in 27 European countries, F. tularensis proposed the transfer of Yersinia Microbiologists, including bacterial subsp. tularensis [Francisella tularensis philomiragia to the genus Francisella taxonomists, have always made use of (Type A)] is classified as a BSL 3 as Francisella philomiragia comb. nov. the tools that are available to them at pathogen, while F. tularensis subsp. Furthermore, based on results from the time. Unfortunately, the paper of holarctica [Francisella tularensis (Type DNA–DNA hybridizations (.85 % Olsufiev et al. (1959) was not accessible B)] is classified as a BSL 2 pathogen reassociation) they also proposed to to us, but neither Larson et al. (1955) (European Communities, 2000; EU transfer Francisella novicida to the nor Skerman et al. (1980) mention any directive 2000/54/EC). species Francisella tularensis as the chemotaxonomic markers that they had It is argued, that: third biogroup Francisella tularensis examined. To the best of our know- biogroup novicida in addition to the ledge, studies in bacterial taxonomy in ‘Indeed,inTable2ofHuberet al. biogroups tularensis and palaeartica. It the