Anaerococcus prevotii strain PC1^T (= DSM 20548 = ATCC 9321 = JCM 6508) is the type strain of the species and the type species of the genus [1]. Six strains of the species were characterized by Foubert and Douglas in 1948, originally designated as ‘Micrococcus prevotii’, but subsequently placed in the genus Peptococcus [2]. Based on a comparative study published by Ezaki et al. [3], the type strain of P. prevotii was then transferred to the genus ‘Peptostreptococcus’ and later on assigned to the novel genus Anaerococcus as A. prevotii [1]. The organism is a Gram-positive, anaerobic, indole-negative coccus. The major metabolic end product from metabolism of peptone-yeast-glucose (PYG) is butyric acid. A. prevotii was provisionally assigned to the arranged family ‘Peptostreptococcaceae’ within the order Clostridiales, also designated as Family XI Incertae sedis [4]. Here we present a summary classification and a set of features for A. prevotii strain PC1^T together with the description of the complete genomic sequencing and annotation.

Within the last few years, several changes occurred in the classification of the anaerobic Gram-positive cocci. There are currently five genera of anaerobic Gram-positive cocci which may be isolated from humans (Peptostreptococcus, Peptoniphilus, Parvimonas, Finegoldia, and Anaerococcus). Members of the species A. prevotii are frequently recovered from human clinical specimens such as vaginal discharges and ovarian, peritoneal, sacral or lung abscesses. In particular, A. prevotii was also described as a common isolate of the normal flora of skin, the oral cavity and the gut [3]. Historically the Gram-positive anaerobic cocci were identified mainly by using phenotypic traits, but as shown by Song et al., this often led to the misidentification of A. vaginalis strains, which were mistakenly assigned to A. prevotii or A. tetradius [5]. Currently Genbank does not contain any16S rRNA sequences from cultivated strains that can be clearly linked to the species A. prevotii with over 95% gene sequence similarity. Recently, the temporal diversity of the human skin microbiome was analyzed using 16S rRNA gene phylotyping. It is noteworthy that several clones originated from different skin sites (gluteal crease, occiput, umbilicus, popliteal fossa, volar forearm). These isolates were taken from two patients and showed close relationships to A. prevotii [6]. No closely related isolates or uncultivated clones with more than 84% 16S rRNA gene sequence identity are recorded from global ocean screenings and environmental samples (except for human skin).

Figure 1 shows the phylogenetic neighborhood of A. prevotii strain PC1^T in a 16S rRNA based tree. The four 16S rRNA gene copies in the genome of strain PC1^T differ by up to 15 nucleotides from each other, and by up to 9 nucleotides from the previously published 16S rRNA sequence generated from strain CCUG 41932 (AF542232). The difference between the genome data and the reported 16S rRNA gene sequence is most likely due to sequencing errors in the previously reported sequence data.

Figure 1 Phylogenetic tree highlighting the position of A. prevotii PC1T relative to all type strains of the genus Anaerococcus and the type strains of all other genera within the family ‘Peptostreptococcaceae’ inferred from 1,302 aligned characters [7,8] of the 16S rRNA sequence under the maximum likelihood criterion [9]. Rooting was done with the type species of the genus Clostridium. The branches are scaled in terms of the expected number of substitutions per site. Numbers above branches are support values from 1,000 bootstrap replicates if larger than 60%. Lineages with type strain genome sequencing projects registered in GOLD [10] are shown in blue, published genomes in bold.

A. prevotii PC1^T cells are Gram-positive and non-motile(Table 1). Cells grown in PYG broth are 0.6-0.9 µm in diameter and occur in pairs, tetrads or irregular clumps or short chains (Figure 2). Colonies range from 0.5 to 2 mm in diameter on Columbia blood agar. Optimum temperature for growth is 37°C. Strain PC1^T metabolizes peptones and amino acids and the major metabolic end product from PYG medium is butyric acid. Most species of the genus Anaerococcus ferment carbohydrates weakly. A. prevotii is proteolytic. α-Glucosidase, α –galactosidase, ß-glucuronidase and pyroglutamyl arylamidase activities are detectable [19,20]. Production of urease may vary among strains of the species. Most strains produce ammonia from threonine and serine [3] by deamination of the amino acids to pyruvate. A. prevotii is resistant to sodium polyanethol sulfonate [21], but susceptible to the penicillins [19].

Figure 2 Scanning electron micrograph of A. prevotii PC1T (M. Rohde, HZI Braunschweig)

The genome is 1,998,633 bp long (chromosome and one circular plasmid) with a 35.6% GC content (Table 3). Of the 1,913 genes predicted, 1,852 were protein coding genes, and 61 were RNAs. A total of 46 pseudogenes were also identified, with 73.1% of the genes being assigned a putative function. The remaining genes were annotated as hypothetical proteins. The distribution of genes into COGs functional categories is presented in Figure 3 and Table 4.

Figure 3 Graphical circular map of the genome. 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, sRNAs red, other RNAs black), GC content, GC skew.