Falsibacillus pallidus to replace the homonym Bacillus pallidus

Correspondence Lihong Xu microbes@yahoo.cn Yu Zhou microbes@yahoo.cn Brian J. Tindall (for matters relating to the Code) bti@dsmz.de Institute of Quality and Standard for Agricultural Products, Zhejiang Academy of Agricultural Sciences (ZAAS), Hangzhou, Zhejiang 310021, PR China Key Laboratory of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, Life Sciences College of Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China DSMZ–Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Inhoffenstraße 7B, D38124 Braunschweig, Germany

There are a number of important principles on which the Bacteriological Code (Lapage et al., 1992) is based.One of them is the fact that the same strain may bear, depending on differing taxonomic opinions, different names.The name to be used according to a particular taxonomic opinion is determined by establishing whether the name is legitimate, is validly published and has priority at a given rank, circumscription and position.There are two important consequences, namely that an organism may have more than one validly published name and such names remain validly published, even if it is generally accepted that an earlier name has become redundant (see Tindall, 1999).Thus on the transfer of the type strain of Bacillus pallidus Scholz et al. 1988(Scholz et al., 1987, 1988) to the genus Geobacillus as Geobacillus pallidus (Scholz et al. 1988) Banat et al. 2004(Banat et al., 2004), the name Bacillus pallidus Scholz et al. 1988 remains validly published, although according to the taxonomic opinion published by Banat et al. (2004) it is currently not the correct name of this taxon.The proposed transfer of this species to the genus Areibacillus Min ˜ana-Galbis et al. 2010 as Aeribacillus pallidus (Scholz et al. 1988) Min ˜ana-Galbis et al. 2010 in a paper in press (Min ˜ana-Galbis et al., 2010) will simply create the situation whereby there are three synonyms, Bacillus pallidus Scholz et al. 1988, Geobacillus pallidus (Scholz et al. 1988) Banat et al. 2004 and Aeribacillus pallidus (Scholz et al. 1988) Min ˜ana-Galbis et al. 2010, all of which are validly published.However, only one name may serve as the correct name according to the taxonomic opinion of whether this species belongs in the genus Bacillus, Geobacillus or Aeribacillus.Zhou et al. (2008) published a description of a new taxon based on strain CW 7 T , for which they also proposed the name Bacillus pallidus.However, Rule 51b states that: 'Among the reasons for which a name may be illegitimate are the following.(4) If it is a later homonym of a name of a taxon of prokaryotes/bacteria, fungi, algae, protozoa, or viruses'.

Rule 51a states:
'A name contrary to a Rule is illegitimate and may not be used'.
Thus the name Bacillus pallidus Zhou et al. 2008 is illegitimate because it is a homonym of the name Bacillus pallidus Scholz et al. 1988 and may not be used.This is also confirmed by Rule 23a, which states: 'Each taxon above species, up to and including order; with a given circumscription, position, and rank can bear only one correct name, that is, the earliest that is in accordance with the Rules of this Code'.
Principle 8 states: 'Each order or taxon of a lower rank with a given circumscription, position, and rank can bear only one correct name, i.e. the earliest that is in accordance with the Rules of this Code'.

Rule 24a also states:
'Valid publication of names (or epithets) which are in accordance with the Rules of this Code dates from the date of publication of the Code'.
These Principles and Rules emphasize the importance of names that are in accordance with the Code, i.e. legitimate names (Rule 23a, note 5), calling into question whether illegitimate names may be validly published (see Tindall, 2008).
The situation is further complicated by the fact that Rule 12b states: 'No specific or subspecific epithets within the same genus may be the same if based on different types'.
Rule 53 states: 'An epithet is illegitimate if it duplicates a specific or subspecific epithet previously validly published for a species or subspecies of the same genus but which is a different bacterium whose name is based upon another type'.
Rule 51a also states: 'However; a name of a taxon which is illegitimate when the taxon is in one taxonomic position is not necessarily illegitimate when the taxon is in another taxonomic position'.

Rule 41a states:
'When a species is transferred to another genus without any change of rank, the specific epithet must be retained, or if it has not been retained (in a previous publication), it must be re-established...' In the present case, it is clear that the Code appears to treat both the combination Bacillus pallidus as a homonym (a result of which is that it is illegitimate) and the epithet pallidus as being illegitimate.It should be noted that the Code is not exact in that it does not require that the name or epithets be specifically linked to the appropriate authority (authors and date), e.g.Bacillus pallidus Zhou et al. 2008 Tindall (2008), with counter arguments published by Young (2009).In the current case, it is clear that the name Bacillus pallidus Zhou et al. 2008 is illegitimate because it is a homonym of Bacillus pallidus Scholz et al. 1988 and that a new name must be proposed for strain CW 7 T .The Code currently also appears to rule that the epithet pallidus in Bacillus pallidus Zhou et al. 2008 is illegitimate and that it may not be used (at that position), but Rule 51a would also determine that the epithet pallidus is legitimate if placed in another genus where there are no such duplications (and attributed to a different authority, i.e. date and authors).However, it would appear that the purpose of Rules 12b and 53 is to avoid homonyms and also the duplication of epithets across the ranks of species and subspecies within the same genus, while homonyms are dealt with by Rule 51a (4) and cross rank duplication by Rule 53.There would appear to be a problem with the wording overlapping and causing unnecessary confusion and over regulation.It is surprising that the name Bacillus pallidus Zhou et al. 2008 could pass the review and editorial process without the fact that it is clearly a homonym being questioned.There is a clear need to refer back to the Code (Lapage et al., 1992) and the interpretation published previously (Tindall, 1999).
In the original article, Zhou et al. (2008) published the description of the new taxon based on the type strain CW 7 T , the major fatty acids of the bacterium were ai-C 15 : 0 , i-C 15 : 0 and ai-C 17 : 0 , the predominant menaquinone was MK-7, the cell-wall peptidoglycan contained mesodiaminopimelic acid and the G+C content of the genomic DNA was 42.3 mol% (Zhou et al., 2008).All of the chemotaxonomic characteristics listed above are fairly common properties of members of the genus Bacillus.Analysis of the 16S rRNA gene sequence also showed that the strain CW 7 T was close to the cluster of the genus Bacillus and showed gene sequence similarity values of about 96 % with its closest neighbours (96.1 % to Bacillus flexus DSM 1320 T , 96.1 % to Bacillus simplex DSM 1321 T , 95.5 % to Bacillus cohnii DSM 6307 T , but 93.9 % to the type species Bacillus subtilis DSM 10 T ).Furthermore, polar lipid profiles have proved to be a most useful tool for the classification and determination of members of the family Bacillaceae in recent years.The polar lipid profile of Bacillus subtilis (the type species of the genus Bacillus) has been shown to be characteristic and should form the basis of part of the description of the genus Bacillus (Ka ¨mpfer et al., 2006).Based on the importance of polar lipids in members of the family Bacillaceae, the phospholipids and glycolipid for strain CW 7 T were reanalysed in this study and stained with different reagents (Minnikin et al., 1984).The polar lipid profile of the type species Bacillus subtilis comprises diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, b-gentiobiosyldiacylglycerol, an unknown aminophospholipid and an unknown glycolipid (Ka ¨mpfer et al., 2006).However, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two aminophosphoglycolipids and an unknown lipid were identified in the strain CW 7 T by Zhou et al., (2008).In this study, the polar lipids of strain CW 7 T comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two aminophosphoglycolipids, five unknown phospholipids, two phosphoglycolipids and one glycolipid (Fig. 1).The differences in the polar lipid profiles found in this study and by Zhou et al., (2008) are attributed to the amounts of lipid material applied to the thin layer plates and the spray reagents used.Based on the significant polar lipid differences found in this study between strain CW 7 T and the type species of the genus Bacillus, Bacillus subtilis, the new isolate described by Zhou et al. (2008) should be reassigned to a new genus as a novel species.Some important phenotypic features of strain CW 7 T compared with the most closely related species currently placed in the genus Bacillus and the type species Bacillus subtilis, based on 16S rRNA gene sequence similarity, are listed in Table 1 and Table 2.According to Principle 6 of the Bacteriological Code (1990 Revision) (Lapage et al., 1992), the correct name of a taxon is based upon valid publication, legitimacy and priority of publication.An illegitimate name may not be used, is not taken into consideration with regards determining priority and cannot be a correct name, and must be replaced.Considering the results discussed above, a new genus name is proposed for the taxon previously published as Bacillus pallidus Zhou et al. 2008, based on the type strain CW 7 T .Based on a consideration of the current Rules of the Code, we consider that only a new genus name is required to avoid homonymy.We therefore propose the new genus name Falsibacillus gen.nov.
There is no indication that the taxon names Falsibacillus and Falsibacillus pallidus have been used previously to designate taxa of prokaryotes, protists, algae, fungi, plants or viruses.The primary resources for searching botanical and zoological names were: Index Nominum Genericorum (ING) Plantarum (http://botany.si.edu/ing/),Names in  ), all of which would affect the way authorship is cited; see also Rule 54.In fact the whole issue of the way illegitimate names are handled needs to be examined carefully in order to avoid potential clashes in the interpretation of the Code (Tindall, 2008;Young, 2009).We have further noted that there are differences in the way the data are presented for the species description of Bacillus pallidus Zhou et al. 2008(Zhou et al., 2008) and the way the data is presented here for the description of the genus Falsibacillus and the species Falsibacillus pallidus.We do not consider it appropriate to refer to the description of Zhou et al. (2008)  Gram-positive, spore-forming, aerobic and rod-shaped cells (0.7-1.061.8-3.5 mm), motile by means of peritrichous flagella.Spores are ellipsoidal and subterminal.Mesophilic and neutrophilic growth requirements.
This name may be linked to the illegitimate name: Bacillus pallidus Zhou et al. 2008.
Cellular morphology, oxygen relationships, colony shape and pigmentation are as given in the genus description above.Growth occurs at 15-42 u C, with an optimum at 30-37 u C. The pH range for growth is pH 6.0-8.5, with an  The type strain, CW 7 T (5KCTC 13200 T 5CCTCC AB 207188 T 5LMG 24451 T ), was isolated from a forest soil in Anhui Province, China.

Fig. 1 .
Fig. 1.Two-dimensional TLC of a polar lipid extract from strain CW 7 T .(a) first stained with ninhydrin and restained using molybdenum blue; (b) stained with a-naphthol.The staining of DPG, PG and PE with a-naphthol is a side reaction caused by overheating of the plates, which causes the fatty acids in these spots to char.DPG, diphosphatidylglycerol; PG, phosphatidylglycerol; PE, phosphatidylethanolamine; NPG1 and NPG2, ninhydrin-positive phosphoglycolipids; PGL1 and PGL2, phosphoglycolipid; PL1-PL5, unknown phospholipids, GL, glycolipid.
is illegitimate or the epithet pallidus in Bacillus pallidus Zhou et al. 2008 is illegitimate.The problem of illegitimate names has been summarized by

Table 1 .
Phenotypic characteristics that differentiate strain CW 7 T from its closest phylogenetic neighbours and the type species of the genus Bacillus, Bacillus subtilis Taxa: 1, strain CW 7 T ; 2, B. flexus DSM 1320 T ; 3, B. simplex DSM 1321 T ; 4, B. cohnii DSM 6307 T ; 5, B. subtilis DSM 10 T .+, Positive; (+), weakly positive; 2, negative; V, variable; NA, not available.The colony colour of B. subtilis was determined in the present study; all other data were obtained from Zhou et al. (2008).Names.asp) and uBio (www.ubio.org).The date of the last search was 9 September 2009.In proposing the name Falsibacillus pallidus, we have taken the following into consideration: While the name Bacillus pallidus Zhou et al. 2008 is a later homonym of Bacillus pallidus Scholz et al. 1988 and the epithet pallidus in Bacillus pallidus Zhou et al. 2008 is also illegitimate, using the epithet pallidus in another combination, Falsibacillus pallidus does not contravene the Code.In fact, Rule 41a states that one must use the earliest validly published and legitimate epithet.It is unclear, however, how this is applied to an epithet that is illegitimate in the position in which it was originally published, but legitimate in another.The question of whether the combination Bacillus pallidus Zhou et al. 2008 is validly published is also another issue and whether the name Falsibacillus pallidus should make reference to that name as its basonym.While it is acceptable to cite the paper by Zhou et al. (2008) as the source of some of the data, the citation of the name Falsibacillus pallidus may either be as a new species name (sp.nov.), a new combination (comb.nov.) or as a new name (nom.nov.