Strain BL78^T (= DSM 18170 = CCUG 54637 = JCM 13657) is the type strain of Bacteroides salanitronis which belongs to the large genus Bacteroides [1,2]. Currently, there are 88 species placed in the genus Bacteroides. The species epithet is derived from the name of Joseph P. Salanitro, an American microbiologist. B. salanitronis strain BL78^T was isolated among other Bacteroides strains from the cecum of a healthy chicken. No other strain belonging to the same species has been identified [2]. Many Bacteroides species are common inhabitants of the intestine where they help to degrade complex molecules such as polysaccharides or transform steroids [3,4]. They also play a role as beneficent protectors of the gut against pathogenic microorganisms [5]. Here we present a summary classification and a set of features for B. salanitronis BL78^T, together with the description of the complete genomic sequencing and annotation.

A representative genomic 16S rRNA sequence of strain BL78^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 [6] and the relative frequencies, weighted by BLAST scores, of taxa and keywords (reduced to their stem [7]) were determined. The single most frequent genus was Bacteroides (100.0%) (1 hit in total). Regarding the single hit to sequences from members of the species, the average identity within HSPs was 99.7%, whereas the average coverage by HSPs was 96.2%. No hits to sequences with (other) species names were found. The highest-scoring environmental sequence was DQ456041 ('pre-adolescent turkey cecum clone CFT112F11'), which showed an identity of 96.8% and an HSP coverage of 63.9%. The five most frequent keywords within the labels of environmental samples which yielded hits were 'fecal' (9.3%), 'microbiota' (7.5%), 'human' (7.1%), 'antibiot, effect, gut, pervas' (7.1%) and 'anim, beef, cattl, coli, escherichia, feedlot, habitat, synecolog' (2.2%) (249 hits in total).

Figure 1 shows the phylogenetic neighborhood of B. salanitronis in a 16S rRNA based tree. The sequences of the six 16S rRNA gene copies in the genome differ from each other by up to 26 nucleotides, and differ by up to 26 nucleotides from the previously published 16S rRNA sequence (AB253731).

Figure 1 Phylogenetic tree highlighting the position of B. salanitronis relative to a selection of other type strains within the genus. The tree was inferred from 1,412 aligned characters [8,9] of the 16S rRNA gene sequence under the maximum likelihood criterion [10] and rooted in accordance with the current taxonomy. The branches are scaled in terms of the expected number of substitutions per site. Numbers to the right of bifurcations are support values from 1,000 bootstrap replicates [11] if larger than 60%. Lineages with type strain genome sequencing projects registered in GOLD [12] but unpublished are labeled with one asterisk, published genomes with two asterisks [13-15].

The cells of B. salanitronis are generally rod-shaped (0.4-0.7 × 0.8-5.6 µm) with rounded ends (Figure 2). The cells are usually arranged singly or in pairs [2]. B. salanitronis is a Gram-negative, non-spore-forming bacterium (Table 1) that is described as non-motile, with only five genes associated with motility having been found in the genome (see below). The temperature optimum for strain BL78^T is 37°C. B. salanitronis is a strictly anaerobic chemoorganotroph and is able to ferment glucose, mannose, sucrose, maltose, arabinose, cellobiose, lactose, xylose and raffinose [2]. The organism hydrolyzes esculin but does not liquefy gelatin, and neither reduces nitrate nor produces indole from tryptophan [2]. B. salanitronis does not utilize trehalose, glycerol, mannitol, sorbitol or melezitose; rhamnose and salicin are fermented weakly [2]. Growth is possible in the presence of bile [2]. Major fermentation products from broth (1% peptone, 1% yeast extract, and 1% glucose each (w/v)) are acetic acid and succinic acid, whereas isovaleric acid is produced in small amounts [2]. B. salanitronis shows activity for alkaline phosphatase, α- and β-galactosidases, α- and β-glucosidases, α-arabinosidase, leucyl glycine arylamidase, alanine arylamidase and glutamyl glutamic acid arylamidase but no activity for urease, catalase, glutamic acid decarboxylase, arginine dihydrolase, β-galactosidase 6-phosphate, β-glucuronidase, N-acetyl-β-glucosaminidase, α-fucosidase and arginine, proline, leucine, phenylalanine, pyroglutamic acid, tyrosine, glycine, histidine and serine arylamidase [2].

Figure 2 Scanning electron micrograph of B. salanitronis BL78T

The genome consists of a 4,242,803 bp long chromosome with a G+C content of 47%, as well as three plasmids of 6,277 bp, 18,280 bp and 40,303 bp length (Table 3 and Figure 3). Of the 3,838 genes predicted, 3,737 were protein-coding genes, and 101 RNAs; 96 pseudogenes were also identified. The majority of the protein-coding genes (57.3%) were assigned with a putative function while the remaining ones were annotated as hypothetical proteins. The distribution of genes into COGs functional categories is presented in Table 4.

Figure 3 Graphical circular map of the chromosome (plasmid maps not shown). From outside to the center: Genes on forward strand (color by COG categories), Genes on reverse strand (color by COG categories), RNA genes (tRNAs green, rRNAs red, other RNAs black), GC content, GC skew.