Legionella stuttgartensis sp. nov. and Legionella nigrisilvae sp. nov., two new species isolated from a re-cooling plant and from a drinking water house installation in southern Germany.

The genus Legionella encompasses environmental bacteria frequently present in water samples. Two strains of Legionella isolated from a re-cooling plant and from a drinking water house installation in southern Germany were identified as two different novel species. The isolates were both Gram-stain negative rods, negative to latex agglutination, able to grow at 37 °C on buffered charcoal-yeast extract agar with l-cysteine agar. The phenotypic characterization was complemented by whole-genome sequencing. The genomes of the strains WA2022007384 and WA2024007413 were sequenced and identified as two different novel species with a GC mol% content of 37.92 and 37.91, respectively. Both strains encoded antimicrobial resistance genes against beta-lactams, aminoglycosides and clusters for legioliulin biosynthesis that might confer fluorescence under UV light at 365 nm. The average nucleotide identity percentage between the strain WA2022007384 and its closest related strains was 87.41% to Legionella qingyii km489T and 86.97% to Legionella gormanii NCTC11401T. For the strain WA2024007413, the closest species were 98.28% to Legionella sp. PC997, 85.84% to L. gormanii NCTC11401T and 85.61% to L. qingyii km489T. The phylogenetic tree based on 164 concatenated core genes showed a separated clade neighbouring the strains L. gormanii NCTC11401T and L. qingyii km489T. These results confirm the description of the two novel species Legionella stuttgartensis sp. nov., with WA2022007384T (=DSM 120481T=NCCB 101094T) as its type strain, and Legionella nigrisilvae sp. nov., with WA2024007413T (=DSM 120480T=NCCB 101095T) as its type strain.