Stenotrophomonas acidaminiphila sp nov., a strictly aerobic bacterium isolated from an upflow anaerobic sludge blanket (UASB) reactor

Two of several strictly aerobic, mesophilic bacteria isolated from a lab-scale upflow anaerobic sludge blanket (UASB) reactor treating a petrochemical wastewater, strains AMX 17 and AMX 19(T), were subjected to detailed taxonomic study. Cells were Gram-negative, motile, non-sporulating, straight to curved rods with a polar flagellum. The isolates exhibited phenotypic traits of members of the genus Stenotrophomonas, including cellular fatty acid composition and the limited range of substrates that could be used. Sugars and many amino acids were utilized. Antibiotic susceptibility and physiological characteristics were determined. The DNA base composition was 66.9 mol% G+C. Phylogenetic analysis revealed that the nearest relatives were Stenotrophomonas maltophilia LMG 11114, Stenotrophomonas nitritireducens DSM 12575(T) and Pseudomonas pictorum ATCC 23328(T) (similarity of 98.1-98.8%). Xanthomonas species, S. maltophilia LMG 958(T) and Stenotrophomonas africana CIP 104854(T) showed high 16S rRNA sequence similarities (96.4-97.3%). The high similarity found in cellular fatty acid profiles and identical partial 165 rRNA sequences (500 bp) for strains AMX 17 and AMX 19T indicate that they belong to the same species. DNA-DNA hybridizations revealed respectively 26.7, 31, 65.8 and 43.6% homology between isolate AMX 19T and S. africana CIP 104854(T), S. maltophilia CIP 60.77(T), S. nitritireducens DSM 12575(T) and P. pictorum ATCC 23328T. These results allow the proposal of strain AMX 19(T) (= DSM 13117(T) = ATCC 700916(T) = CIP 106456(T)) as representative of a novel species of the genus Stenotrophomonas, with the name Stenotrophomonas acidaminiphila sp. nov.