A representative genomic 16S rRNA sequence of strain 9751
T was compared using NCBI BLAST under default settings (e.g., considering only the high-scoring segment pairs (HSPs) from the best 250 hits) with the most recent release of the Greengenes database [
14] and the relative frequencies, weighted by BLAST scores, of taxa and keywords (reduced to their stem [
15]) were determined. The five most frequent genera were
Chryseobacterium (45.9%),
Wautersiella (23.2%),
Myroides (7.9%),
Elizabethkingia (7.3%) and
Empedobacter (7.0%) (134 hits in total). Regarding the single hit to sequences from members of the species, the average identity within HSPs was 99.2%, whereas the average coverage by HSPs was 96.8%. Among all other species, the one yielding the highest score was
Empedobacter brevis, which corresponded to an identity of 92.0% and an HSP coverage of 97.0%. Accordingly,
E. brevis groups as the sister genus in trees constructed from 16S rRNA gene sequences [
16-
19] whereas
Bergeyella zoohelcum (family
Flavobacteriaceae) is looked at as the phenotypic sister taxon which may be confused with
W. virosa when applying traditional morphological and physiological tests [
11]. The highest-scoring environmental sequence was GQ383925 ('sewage water isolate XJ109
Flavobacteriaceae str. XJ109'), which showed an identity of 92.5% and a HSP coverage of 98.5%. The five most frequent keywords within the labels of environmental samples which yielded hits were 'skin' (11.2%), 'human' (3.7%), 'fossa' (3.4%), 'microbiom, tempor, topograph' (2.8%) and 'forearm' (2.1%) (116 hits in total). The two most frequent keywords within the labels of environmental samples which yielded hits of a higher score than the highest scoring species were 'sewag, water' (10.1%) and 'aerosol, air, citi, level, microarra, texa, two, urban' (10.0%) (2 hits in total). From these sequence-based observations and the published culture-dependent detections (see above) it can be concluded that
W. virosa occurs mainly as an inhabitant of mucosa of animals and man.
shows the phylogenetic neighborhood of strain 9751T in a 16S rRNA based tree. The sequences of the five 16S rRNA gene copies in the genome differ from each other by up to three nucleotides, and differ by up to two nucleotides from the previously published 16S rRNA sequence (M93152), which contains eleven ambiguous base calls, and differ by up to 314 nucleotides from another previously published 16S rRNA sequence (AF133539) which obviously represents a strain of the genus Bacteroides.
The cells of
W. virosa are rod-shaped (0.6 × 2.0-3.0 µm) with parallel sides and rounded ends (). According to Holmes [
1], the cells stain Gram-negative, are nonmotile and non spore-forming (). No intracellular inclusions such as polyhydroxybutyrate were detected. Colonies on nutrient agar appear circular and low convex with entire edges, smooth, shining and mucoid, reaching 2mm in diameter after 24h [
1]. While the colonies are described as being non-pigmented on nutrient agar by most authors [
1,
37], the production of a nondiffusible yellow pigment was reported during growth on blood agar [
5]. Most strains produce a diffusible dark brown pigment on tyrosine-containing agar [
1]. The strains grow at 42°C but not at 5°C [
1].
W. virosa is a strictly aerobic chemoorganotroph and is not able to reduce nitrate, nitrite or selenite and does not acidify glucose or other sugars under standard conditions [
1,
5]. However, under test conditions developed for fastidious organisms such as
Neisseria (API NH strips, Biomérieux), acid is produced from glucose [IDA] as is observed for the phylogenetic neighbors
E. brevis and
Wautersiella falsenii [
16,
17]. Cytochrome oxidase, catalase and phosphatase are present [
1]. Tolerance to NaCl and pH ranges have not been reported.
W. virosa grows on McConkey agar, indicating tolerance to bile salts [
1] . On the other hand, KCN (75 mg l
-1), cetrimide, colistin [
17], and polymyxin [
5] are not tolerated and inhibit growth. The species is able to utilize β-hydroxybutyrate as a substrate and to hydrolyze casein, gelatin and Tween 20 [
1,
17]. Tryptophan is cleaved to give indole, pyruvate and ammonia when tested with Ehrlich’s reagent, but the reaction can not be detected when Kovacs’ reagent is used [
1] .
W. virosa is inert in most traditional biochemical tests [
1], it does not utilize glucose as a substrate under standard conditions [
16].
W. virosa does not hydrolyze starch, esculin or DNA, and is negative for gluconate oxidation, urease, phenylalanine deaminase, arginine deaminase, arginine dihydrolase, lysine or ornithine decarboxylase, β-D-galactosidase [
1], alkalization of galacturonate [
17]. The following enzymes are present as concluded from tests using API ZYM galleries: acid and alkaline phosphatase, lysine arylamidase, aspartate arylamidase, alanine arylamidase and methionine arylamidase [
1]. In addition, the following substrates were hydrolyzed in the latter galleries by
W. virosa: naphthol-AS-BI-phosphodiamide, bis-(para-nitrophenyl)-phosphate, glycyl-glycyl-β-naphthylamide hydrobromide, glycyl-L-phenylalanyl-β-naphthylamide, glycyl-L-prolyl-β-naphthylamide, L-leucyl-glycyl-β-naphthylamide, α-L-glutamyl-β-naphthylamide, and N-carbobenzoxy-glycyl-glycyl-L-arginine-β-naphthylamide [
1].
W. virosa is susceptible to most β-lactams, tetracycline, chloramphenicol, nalidixic acid, erythromycin and sulfamethoxazole-trimethoprim [
11]. In contrast, the species is resistant to aminoglycosides [
11].
| Table 1Classification and general features of W. virosa 9751T according to the MIGS recommendations [25]. |
Chemotaxonomy
The major respiratory quinone of
W. virosa is menaquinone 6 and the major polyamine is homospermidine, as is the case for all members of the family
Flavobacteriaceae [
11,
38-
40]. No sphingophospholipids were detected [
1]. The polar lipids of
W. virosa have not yet been described. The major whole-cell fatty acids of
W. virosa are
iso-C
15:0 (46%),
iso-C
15:02-OH (10%),
iso-C
17:1ω12t (8%) and
iso-C
17:03-OH (7%) as described for CDC group IIf, the preliminary name given to these strains prior to being formally named
W. virosa [
41]. A comparison of the patterns of
W. virosa and ‘
W. zoohelcum’ obtained at that time [
41] with more recently published patterns of
B. zoohelcum and
E. brevis and phylogenetic neighbors [
17,
19] seems to cast doubts on the comparability of these early patterns. They are the only ones listing the presence of high amounts of
iso-C
15:02-OH and
iso-C
17:1ω12t, which are not listed for phylogenetically related genera later on [
19]. However,
iso-C
15:02-OH and isomers of
iso-heptadecene are included in the summed features of the Microbial Identification System applied in many recent analyses including [
17,
19].