Novel mycolic acid-containing bacteria in the family Segniliparaceae fam. nov., including the genus Segniliparus gen. nov., with descriptions of Segniliparus rotundus sp. nov. and Segniliparus rugosus sp. nov.

Abstract

Four strains of novel, rapidly growing, acid–alcohol-fast-staining bacteria were characterized with a polyphasic approach. Isolates were received by the Centers for Disease Control and Prevention from domestic health department laboratories for reference testing as unidentifiable, clinical mycobacteria. Bacteria were rod-shaped and produced non-pigmented (white to beige), non-photochromogenic, smooth or wrinkled-rough colonies on Middlebrook 7H10 and 7H11 media at 33 °C. The smooth and wrinkled colony forms were representative of two species with 68·0 and 72·0 mol% DNA G+C content. The cell wall contained meso-diaminopimelic acid and mycolic acids. Species were characterized by cellular fatty acids of C10 : 0, C14 : 0, C16 : 1ω9t, C16 : 0, C18 : 1ω9c and 10-methyl C18 : 0 (tuberculostearic acid). HPLC analysis of mycolic acids produced a novel late-emerging, genus-specific mycolate pattern. TLC analysis demonstrated a novel α +-mycolate. Species were 98·9 % similar by comparison of 16S rRNA gene sequences; however, the DNA–DNA association was <28 %. Phylogenetic analysis of 16S rRNA gene sequences demonstrated an association with Rhodococcus equi, although a DNA–DNA relatedness value of 2 % did not support a close relationship. PCR analysis of a proposed, selected actinomycete-specific 439 bp fragment of the 65 kDa heat-shock protein was negative for three of the four isolates. The creation of Segniliparaceae fam. nov. is proposed to encompass the genus Segniliparus gen. nov., including two novel species, the type species Segniliparus rotundus sp. nov. and Segniliparus rugosus sp. nov., with the respective type strains CDC 1076T (=ATCC BAA-972T=CIP 108378T) and CDC 945T (=ATCC BAA-974T=CIP 108380T).